Cosmological evolution of the Higgs boson's vacuum expectation value

NASA Astrophysics Data System (ADS)

Calmet, Xavier

2017-11-01

We point out that the expansion of the universe leads to a cosmological time evolution of the vacuum expectation of the Higgs boson. Within the standard model of particle physics, the cosmological time evolution of the vacuum expectation of the Higgs leads to a cosmological time evolution of the masses of the fermions and of the electroweak gauge bosons, while the scale of Quantum Chromodynamics (QCD) remains constant. Precise measurements of the cosmological time evolution of μ =m_e/m_p, where m_e and m_p are, respectively, the electron and proton mass (which is essentially determined by the QCD scale), therefore provide a test of the standard models of particle physics and of cosmology. This ratio can be measured using modern atomic clocks.

NLO Hierarchy of Wilson Lines Evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balitsky, Ian

2015-03-01

The high-energy behavior of QCD amplitudes can be described in terms of the rapidity evolution of Wilson lines. I present the hierarchy of evolution equations for Wilson lines in the next-to-leading order.

The Boer-Mulders Transverse Momentum Distribution in the Pion and its Evolution in Lattice QCD

NASA Astrophysics Data System (ADS)

Engelhardt, M.; Musch, B.; Hägler, P.; Schäfer, A.; Negele, J.

2015-02-01

Starting from a definition of transverse momentum-dependent parton distributions (TMDs) in terms of hadronic matrix elements of a quark bilocal operator containing a staple-shaped gauge link, selected TMD observables can be evaluated within Lattice QCD. A TMD ratio describing the Boer-Mulders effect in the pion is investigated, with a particular emphasis on its evolution as a function of a Collins-Soper-type parameter which quantifies the proximity of the staple-shaped gauge links to the light cone.

Light meson gas in the QCD vacuum and oscillating universe

NASA Astrophysics Data System (ADS)

Prokhorov, George; Pasechnik, Roman

2018-01-01

We have developed a phenomenological effective quantum-field theoretical model describing the "hadron gas" of the lightest pseudoscalar mesons, scalar σ-meson and σ-vacuum, i.e. the expectation value of the σ-field, at finite temperatures. The corresponding thermodynamic approach was formulated in terms of the generating functional derived from the effective Lagrangian providing the basic thermodynamic information about the "meson plasma + QCD condensate" system. This formalism enables us to study the QCD transition from the hadron phase with direct implications for cosmological evolution. Using the hypothesis about a positively-definite QCD vacuum contribution stochastically produced in early universe, we show that the universe could undergo a series of oscillations during the QCD epoch before resuming unbounded expansion.

The gluon density of the proton at low x from a QCD analysis of F2

NASA Astrophysics Data System (ADS)

Aid, S.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Baehr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Brasse, F.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Colombo, M.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Delcourt, B.; Del Buono, L.; De Roeck, A.; De Wolf, E. A.; Di Nezza, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Ehrlichmann, H.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gebauer, M.; Gellrich, A.; Genzel, H.; Gerhards, R.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Gonzalez-Pineiro, B.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Hampel, M.; Hanlon, E. M.; Hapke, M.; Haynes, W. J.; Heatherington, J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hildesheim, W.; Hill, P.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Horisberger, R.; Hudgson, V. L.; Huet, Ph.; Hütte, M.; Hufnagel, H.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kant, D.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Krüner-Marquis, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lacour, D.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Lanius, P.; Laporte, J.-F.; Lebedev, A.; Leverenz, C.; Levonian, S.; Ley, Ch.; Lindner, A.; Lindström, G.; Link, J.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lohmander, H.; Lomas, J.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Migliori, A.; Mikocki, S.; Milstead, D.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Newman, P. R.; Newton, D.; Neyret, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Ozerov, D.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Peppel, E.; Perez, E.; Phillips, J. P.; Pichler, Ch.; Pieuchot, A.; Pitzl, D.; Pope, G.; Prell, S.; Prosi, R.; Rabbertz, K.; Rädel, G.; Raupach, F.; Reimer, P.; Reinshagen, S.; Ribarics, P.; Rick, H.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Rylko, R.; Sahlmann, N.; Sanchez, E.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Schwind, A.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Solochenko, V.; Soloviev, Y.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Starosta, R.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stiewe, J.; Stösslein, U.; Stolze, K.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Tchernyshov, V.; Thiebaux, C.; Thompson, G.; Truöl, P.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Van Esch, P.; Van Mechelen, P.; Vartapetian, A.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walker, I. W.; Walther, A.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wellisch, H. P.; West, L. R.; Willard, S.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wright, A. E.; Wünsch, E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zimmer, M.; Zimmermann, W.; Zomer, F.; Zuber, K.; H1 Collaboration

1995-02-01

We present a QCD analysis of the proton structure function F2 measured by the H1 experiment at HERA, combined with data from previous fixed target experiments. The gluon density is extracted from the scaling violations of F2 in the range 2 · 10 -4 < x < 3 · 10 -2 and compared with an approximate solution of the QCD evolution equations. The gluon density is found to rise steeply with decreasing x.

Fragmentation functions at next-to-next-to-leading order accuracy

DOE PAGES

Anderle, Daniele P.; Stratmann, Marco; Ringer, Felix

2015-12-01

We present a first analysis of parton-to-pion fragmentation functions at next-to-next-to-leading order accuracy in QCD based on single-inclusive pion production in electron-positron annihilation. Special emphasis is put on the technical details necessary to perform the QCD scale evolution and cross section calculation in Mellin moment space. Lastly, we demonstrate how the description of the data and the theoretical uncertainties are improved when next-to-next-to-leading order QCD corrections are included.

Unraveling hadron structure with generalized parton distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrei Belitsky; Anatoly Radyushkin

2004-10-01

The recently introduced generalized parton distributions have emerged as a universal tool to describe hadrons in terms of quark and gluonic degrees of freedom. They combine the features of form factors, parton densities and distribution amplitudes - the functions used for a long time in studies of hadronic structure. Generalized parton distributions are analogous to the phase-space Wigner quasi-probability function of non-relativistic quantum mechanics which encodes full information on a quantum-mechanical system. We give an extensive review of main achievements in the development of this formalism. We discuss physical interpretation and basic properties of generalized parton distributions, their modeling andmore » QCD evolution in the leading and next-to-leading orders. We describe how these functions enter a wide class of exclusive reactions, such as electro- and photo-production of photons, lepton pairs, or mesons.« less

QCD for Postgraduates (3/5)

ScienceCinema

Zanderighi, Giulia

2018-04-27

Modern QCD - Lecture 3 We will introduce processes with initial-state hadrons and discuss parton distributions, sum rules, as well as the need for a factorization scale once radiative corrections are taken into account. We will then discuss the DGLAP equation, the evolution of parton densities, as well as ways in which parton densities are extracted from data.

Identifying QCD Transition Using Deep Learning

NASA Astrophysics Data System (ADS)

Zhou, Kai; Pang, Long-gang; Su, Nan; Petersen, Hannah; Stoecker, Horst; Wang, Xin-Nian

2018-02-01

In this proceeding we review our recent work using supervised learning with a deep convolutional neural network (CNN) to identify the QCD equation of state (EoS) employed in hydrodynamic modeling of heavy-ion collisions given only final-state particle spectra ρ(pT, V). We showed that there is a traceable encoder of the dynamical information from phase structure (EoS) that survives the evolution and exists in the final snapshot, which enables the trained CNN to act as an effective "EoS-meter" in detecting the nature of the QCD transition.

Calculation of TMD Evolution for Transverse Single Spin Asymmetry Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mert Aybat, Ted Rogers, Alexey Prokudin

In this letter, we show that it is necessary to include the full treatment of QCD evolution of Transverse Momentum Dependent parton densities to explain discrepancies between HERMES data and recent COMPASS data on a proton target for the Sivers transverse single spin asymmetry in Semi-Inclusive Deep Inelastic Scattering (SIDIS). Calculations based on existing fits to TMDs in SIDIS, and including evolution within the Collins-Soper-Sterman with properly defined TMD PDFs are shown to provide a good explanation for the discrepancy. The non-perturbative input needed for the implementation of evolution is taken from earlier analyses of unpolarized Drell-Yan (DY) scattering atmore » high energy. Its success in describing the Sivers function in SIDIS data at much lower energies is strong evidence in support of the unifying aspect of the QCD TMD-factorization formalism.« less

Linear vs non-linear QCD evolution in the neutrino-nucleon cross section

NASA Astrophysics Data System (ADS)

Albacete, Javier L.; Illana, José I.; Soto-Ontoso, Alba

2016-03-01

Evidence for an extraterrestrial flux of ultra-high-energy neutrinos, in the order of PeV, has opened a new era in Neutrino Astronomy. An essential ingredient for the determination of neutrino fluxes from the number of observed events is the precise knowledge of the neutrino-nucleon cross section. In this work, based on [1], we present a quantitative study of σνN in the neutrino energy range 104 < Eν < 1014 GeV within two transversal QCD approaches: NLO DGLAP evolution using different sets of PDFs and BK small-x evolution with running coupling and kinematical corrections. Further, we translate this theoretical uncertainty into upper bounds for the ultra-high-energy neutrino flux for different experiments.

Effective holographic models for QCD: Glueball spectrum and trace anomaly

NASA Astrophysics Data System (ADS)

Ballon-Bayona, Alfonso; Boschi-Filho, Henrique; Mamani, Luis A. H.; Miranda, Alex S.; Zanchin, Vilson T.

2018-02-01

We investigate effective holographic models for QCD arising from five-dimensional dilaton gravity. The models are characterized by a dilaton with a mass term in the UV, dual to a CFT deformation by a relevant operator, and quadratic in the IR. The UV constraint leads to the explicit breaking of conformal symmetry, whereas the IR constraint guarantees linear confinement. We propose semianalytic interpolations between the UV and the IR and obtain a spectrum for scalar and tensor glueballs consistent with lattice QCD data. We use the glueball spectrum as a physical constraint to find the evolution of the model parameters as the mass term goes to 0. Finally, we reproduce the universal result for the trace anomaly of deformed CFTs and propose a dictionary between this result and the QCD trace anomaly. A nontrivial consequence of this dictionary is the emergence of a β function similar to the two-loop perturbative QCD result.

QCD as a Theory of Hadrons

NASA Astrophysics Data System (ADS)

Narison, Stephan

2004-05-01

About Stephan Narison; Outline of the book; Preface; Acknowledgements; Part I. General Introduction: 1. A short flash on particle physics; 2. The pre-QCD era; 3. The QCD story; 4. Field theory ingredients; Part II. QCD Gauge Theory: 5. Lagrangian and gauge invariance; 6. Quantization using path integral; 7. QCD and its global invariance; Part III. MS scheme for QCD and QED: Introduction; 8. Dimensional regularization; 9. The MS renormalization scheme; 10. Renormalization of operators using the background field method; 11. The renormalization group; 12. Other renormalization schemes; 13. MS scheme for QED; 14. High-precision low-energy QED tests; Part IV. Deep Inelastic Scattering at Hadron Colliders: 15. OPE for deep inelastic scattering; 16. Unpolarized lepton-hadron scattering; 17. The Altarelli-Parisi equation; 18. More on unpolarized deep inelastic scatterings; 19. Polarized deep-inelastic processes; 20. Drell-Yan process; 21. One 'prompt photon' inclusive production; Part V. Hard Processes in e+e- Collisions: Introduction; 22. One hadron inclusive production; 23. gg scatterings and the 'spin' of the photon; 24. QCD jets; 25. Total inclusive hadron productions; Part VI. Summary of QCD Tests and as Measurements; Part VII. Power Corrections in QCD: 26. Introduction; 27. The SVZ expansion; 28. Technologies for evaluating Wilson coefficients; 29. Renormalons; 30. Beyond the SVZ expansion; Part VIII. QCD Two-Point Functions: 31. References guide to original works; 32. (Pseudo)scalar correlators; 33. (Axial-)vector two-point functions; 34. Tensor-quark correlator; 35. Baryonic correlators; 36. Four-quark correlators; 37. Gluonia correlators; 38. Hybrid correlators; 39. Correlators in x-space; Part IX. QCD Non-Perturbative Methods: 40. Introduction; 41. Lattice gauge theory; 42. Chiral perturbation theory; 43. Models of the QCD effective action; 44. Heavy quark effective theory; 45. Potential approaches to quarkonia; 46. On monopole and confinement; Part X. QCD Spectral Sum Rules: 47. Introduction; 48. Theoretical foundations; 49. Survey of QCD spectral sum rules; 50. Weinberg and DMO sum rules; 51. The QCD coupling as; 52. The QCD condensates; 53. Light and heavy quark masses, etc.; 54. Hadron spectroscopy; 55. D, B and Bc exclusive weak decays; 56. B0(s)-B0(s) mixing, kaon CP violation; 57. Thermal behaviour of QCD; 58. More on spectral sum rules; Part XI. Appendix A: physical constants and unites; Appendix B: weight factors for SU(N)c; Appendix C: coordinates and momenta; Appendix D: Dirac equation and matrices; Appendix E: Feynman rules; Appendix F: Feynman integrals; Appendix G: useful formulae for the sum rules; Bibliography; Index.

QCD as a Theory of Hadrons

NASA Astrophysics Data System (ADS)

Narison, Stephan

2007-07-01

About Stephan Narison; Outline of the book; Preface; Acknowledgements; Part I. General Introduction: 1. A short flash on particle physics; 2. The pre-QCD era; 3. The QCD story; 4. Field theory ingredients; Part II. QCD Gauge Theory: 5. Lagrangian and gauge invariance; 6. Quantization using path integral; 7. QCD and its global invariance; Part III. MS scheme for QCD and QED: Introduction; 8. Dimensional regularization; 9. The MS renormalization scheme; 10. Renormalization of operators using the background field method; 11. The renormalization group; 12. Other renormalization schemes; 13. MS scheme for QED; 14. High-precision low-energy QED tests; Part IV. Deep Inelastic Scattering at Hadron Colliders: 15. OPE for deep inelastic scattering; 16. Unpolarized lepton-hadron scattering; 17. The Altarelli-Parisi equation; 18. More on unpolarized deep inelastic scatterings; 19. Polarized deep-inelastic processes; 20. Drell-Yan process; 21. One 'prompt photon' inclusive production; Part V. Hard Processes in e+e- Collisions: Introduction; 22. One hadron inclusive production; 23. gg scatterings and the 'spin' of the photon; 24. QCD jets; 25. Total inclusive hadron productions; Part VI. Summary of QCD Tests and as Measurements; Part VII. Power Corrections in QCD: 26. Introduction; 27. The SVZ expansion; 28. Technologies for evaluating Wilson coefficients; 29. Renormalons; 30. Beyond the SVZ expansion; Part VIII. QCD Two-Point Functions: 31. References guide to original works; 32. (Pseudo)scalar correlators; 33. (Axial-)vector two-point functions; 34. Tensor-quark correlator; 35. Baryonic correlators; 36. Four-quark correlators; 37. Gluonia correlators; 38. Hybrid correlators; 39. Correlators in x-space; Part IX. QCD Non-Perturbative Methods: 40. Introduction; 41. Lattice gauge theory; 42. Chiral perturbation theory; 43. Models of the QCD effective action; 44. Heavy quark effective theory; 45. Potential approaches to quarkonia; 46. On monopole and confinement; Part X. QCD Spectral Sum Rules: 47. Introduction; 48. Theoretical foundations; 49. Survey of QCD spectral sum rules; 50. Weinberg and DMO sum rules; 51. The QCD coupling as; 52. The QCD condensates; 53. Light and heavy quark masses, etc.; 54. Hadron spectroscopy; 55. D, B and Bc exclusive weak decays; 56. B0(s)-B0(s) mixing, kaon CP violation; 57. Thermal behaviour of QCD; 58. More on spectral sum rules; Part XI. Appendix A: physical constants and unites; Appendix B: weight factors for SU(N)c; Appendix C: coordinates and momenta; Appendix D: Dirac equation and matrices; Appendix E: Feynman rules; Appendix F: Feynman integrals; Appendix G: useful formulae for the sum rules; Bibliography; Index.

Real-time evolution of non-Gaussian cumulants in the QCD critical regime

NASA Astrophysics Data System (ADS)

Mukherjee, Swagato; Venugopalan, Raju; Yin, Yi

2015-09-01

We derive a coupled set of equations that describe the nonequilibrium evolution of cumulants of critical fluctuations for spacetime trajectories on the crossover side of the QCD phase diagram. In particular, novel expressions are obtained for the nonequilibrium evolution of non-Gaussian skewness and kurtosis cumulants. UBy utilizing a simple model of the spacetime evolution of a heavy-ion collision, we demonstrate that, depending on the relaxation rate of critical fluctuations, skewness and kurtosis can differ significantly in magnitude as well as in sign from equilibrium expectations. Memory effects are important and shown to persist even for trajectories that skirt the edge of the critical regime. We use phenomenologically motivated parametrizations of freeze-out curves and of the beam-energy dependence of the net baryon chemical potential to explore the implications of our model study for the critical-point search in heavy-ion collisions.

Real time evolution of non-Gaussian cumulants in the QCD critical regime

DOE PAGES

Mukherjee, Swagato; Venugopalan, Raju; Yin, Yi

2015-09-23

In this study, we derive a coupled set of equations that describe the nonequilibrium evolution of cumulants of critical fluctuations for spacetime trajectories on the crossover side of the QCD phase diagram. In particular, novel expressions are obtained for the nonequilibrium evolution of non-Gaussian skewness and kurtosis cumulants. UBy utilizing a simple model of the spacetime evolution of a heavy-ion collision, we demonstrate that, depending on the relaxation rate of critical fluctuations, skewness and kurtosis can differ significantly in magnitude as well as in sign from equilibrium expectations. Memory effects are important and shown to persist even for trajectories thatmore » skirt the edge of the critical regime. We use phenomenologically motivated parametrizations of freeze-out curves and of the beam-energy dependence of the net baryon chemical potential to explore the implications of our model study for the critical-point search in heavy-ion collisions.« less

Neutral Pion Electroproduction in the Δ Resonance Region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villano, Anthony

2007-11-01

The electroproduction of baryon resonances at high Q 2 is examined. Analysis focuses on the Δ(1232) resonance via exclusive pseudoscalar meson production of π 0 particles. Differential cross sections are extracted for exclusive π 0 electroproduction. In the central invariant mass (W) region the cross sections are used to extract resonant multipole amplitudes. In particular, the ratio of the electric quadrupole to magnetic dipole amplitudes (E2/M1) will be discussed for the Δ(1232) resonance. The transition to pQCD is discussed in terms of E2/M1 and other multipoles. The helicity amplitude A 3/2 can be used as a baryon helicity conservation meter in this context and will be discussed. The fast shrinking of the resonant contribution in the Δ region is observed at this high momentum transfer. Apart from the observables related to pQCD scaling, the transition form factor Gmore » $$*\\atop{M}$$ is extracted along with the scalar to magnetic dipole ratio C2/M1.« less

Associated production of a Higgs boson decaying into bottom quarks at the LHC in full NNLO QCD

NASA Astrophysics Data System (ADS)

Ferrera, Giancarlo; Somogyi, Gábor; Tramontano, Francesco

2018-05-01

We consider the production of a Standard Model Higgs boson decaying to bottom quarks in association with a vector boson W± / Z in hadron collisions. We present a fully exclusive calculation of QCD radiative corrections both for the production cross section and for the Higgs boson decay rate up to next-to-next-to-leading order (NNLO) accuracy. Our calculation also includes the leptonic decay of the vector boson with finite-width effects and spin correlations. We consider typical kinematical cuts applied in the experimental analyses at the Large Hadron Collider (LHC) and we find that the full NNLO QCD corrections significantly decrease the accepted cross section and have a substantial impact on the shape of distributions. We point out that these additional effects are essential to obtain precise theoretical predictions to be compared with the LHC data.

New Perspectives for Hadron Phenomenology:The Effects of Final-State Interactions and Near-Conformal Effective QCD Couplings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, S

2003-10-24

The effective QCD charge extracted from {tau} decay is remarkably constant at small momenta, implying the near-conformal behavior of hadronic interactions at small momentum transfer. The correspondence of large-N{sub c} supergravity theory in higher-dimensional anti-de Sitter spaces with gauge theory in physical space-time also has interesting implications for hadron phenomenology in the conformal limit, such as constituent counting rules for hard exclusive processes. The utility of light-front quantization and lightfront Fock wavefunctions for analyzing such phenomena and representing the dynamics of QCD bound states is reviewed. I also discuss the novel effects of initial- and final-state interactions in hard QCDmore » inclusive processes, including Bjorken-scaling single-spin asymmetries and the leading-twist diffractive and shadowing contributions to deep inelastic lepton-proton scattering.« less

Light-cone distribution amplitudes of {xi} and their applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Yonglu; Huang Mingqiu

We present the light-cone distribution amplitudes of the {xi} baryons up to twist six on the basis of QCD conformal partial wave expansion to the leading order conformal spin accuracy. The nonperturbative parameters relevant to the DAs are determined in the framework of the QCD sum rule. The light-cone QCD sum rule approach is used to investigate both the electromagnetic form factors of {xi} and the exclusive semileptonic decay of {xi}{sub c} as applications. Our estimations on the magnetic moments are {mu}{sub {xi}{sup 0}}=-(1.92{+-}0.34){mu}{sub N} and {mu}{sub {xi}{sup -}}=-(1.19{+-}0.03){mu}{sub N}. The decay width of the process {xi}{sub c}{yields}{xi}e{sup +}{nu}{sub e}more » is evaluated to be {gamma}=8.73x10{sup -14} GeV, which is in accordance with the experimental measurements and other theoretical approaches.« less

The Conformal Template and New Perspectives for Quantum Chromodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; /SLAC

2007-03-06

Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, themore » fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. One can also use conformal symmetry as a template for perturbative QCD predictions where the effects of the nonzero beta function can be systematically included in the scale of the QCD coupling. This leads to fixing of the renormalization scale and commensurate scale relations which relate observables without scale or scheme ambiguity. The results are consistent with the renormalization group and the analytic connection of QCD to Abelian theory at N{sub C} {yields} 0. I also discuss a number of novel phenomenological features of QCD. Initial- and .nal-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, di.ractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, nonperturbative antisymmetric sea quark distributions, anomalous heavy quark e.ects, and the unexpected effects of direct higher-twist processes.« less

Deep Exclusive Pseudoscalar Meson Production at Jefferson Lab Hall C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basnet, Samip

2017-09-01

Measurements of exclusive meson production are a useful tool in the study of hadronic structure. In particular, one can discern the relevant degrees of freedom at different distance scales through these studies. In the transition region between low momentum transfer (where a description of hadronic degrees of freedom in terms of effective hadronic Lagrangians is valid) and high momentum transfer (where the degrees of freedom are quarks and gluons), the predictive power of Quantum Chromodynamics (QCD), the theory of the strong interaction, is limited due to the absence of a complete solution. Thus, one has to rely upon experimental datamore » from the non-perturbative intermediate-energy regime to thoroughly understand the onset of perturbative QCD (pQCD) as the momentum transfer is increased. This work involves two deep exclusive meson electroproduction experiments at Jefferson Lab (JLab). The p(e,e'pi+)n reaction is studied at fixed Q^2 and W of 2.5 GeV2 and 2.0 GeV, respectively, while varying the four momentum transfer to the nucleon -t from 0.2 to 2.1 GeV2 . As -t is increased, the hadronic interaction scale is reduced independently of the observation scale of the virtual photon, providing valuable information about the hard- scattering process in general. The data was taken at JLab Hall C in 2003, as a part of the experiment E01-004, Fpi-2, using the High Momentum Spectrometer (HMS) and Short Orbit Spectrometer (SOS), and in this work, the results of the differential cross section analysis are presented and compared to prior data, as well as two theoretical models. Using these results over a wide -t range, the transition from hard to soft QCD is also studied. In addition, the p(e,e'K+)Lambda(Sigma0) reactions are also studied. Despite their importance in elucidating the reaction mechanism underlying strangeness production, we still do not have complete understanding of these reactions above the resonance region. The experiment, E12- 09-011, intends to perform, for the first time, a full Rosenbluth (L/T/LT/TT) separation of p(e,e'K+)Lambda(Sigma0) cross sections above the resonance region using the newly upgraded standard equipment, Super High Momentum Spectrometer (SHMS) at JLab Hall C. The separated data will allow us to better understand the Kaon production reaction mechanism and the hard-soft QCD transition in exclusive processes. The kinematic settings being studied in the experiment ranges from Q^2 of 0.4 to 5.5 GeV2, W of 2.3 to 3.1 GeV, and -t of 0.06 to 0.53 GeV2. Here, the results from some pre-experimental studies with regards to estimations of singles rates as well as real and accidental coincidence rates are presented, using two different models. The implications of these projections on the runplan for the experiment are also discussed.« less

Instanton liquid properties from lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Athenodorou, A.; Boucaud, Philippe; De Soto, F.

Here, we examined the instanton contribution to the QCD configurations generated from lattice QCD for N F = 0, N F = 2 + 1 and N F = 2 + 1 + 1 dynamical quark flavors from two different and complementary approaches. First via the use of Gradient flow, we computed instanton liquid properties using an algorithm to localize instantons in the gauge field configurations and studied their evolution with flow time. Then, the analysis of the running at low momenta of gluon Green's functions serves as an independent confirmation of the instanton density which can also be derivedmore » without the use of the Gradient flow.« less

Instanton liquid properties from lattice QCD

DOE PAGES

Athenodorou, A.; Boucaud, Philippe; De Soto, F.; ...

2018-02-22

Here, we examined the instanton contribution to the QCD configurations generated from lattice QCD for N F = 0, N F = 2 + 1 and N F = 2 + 1 + 1 dynamical quark flavors from two different and complementary approaches. First via the use of Gradient flow, we computed instanton liquid properties using an algorithm to localize instantons in the gauge field configurations and studied their evolution with flow time. Then, the analysis of the running at low momenta of gluon Green's functions serves as an independent confirmation of the instanton density which can also be derivedmore » without the use of the Gradient flow.« less

Nuclear reactions from lattice QCD

DOE PAGES

Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.

2015-01-13

In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculationsmore » of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.« less

Phenomenological consequences of enhanced bulk viscosity near the QCD critical point

DOE PAGES

Monnai, Akihiko; Mukherjee, Swagato; Yin, Yi

2017-03-06

In the proximity of the QCD critical point the bulk viscosity of quark-gluon matter is expected to be proportional to nearly the third power of the critical correlation length, and become significantly enhanced. Here, this work is the first attempt to study the phenomenological consequences of enhanced bulk viscosity near the QCD critical point. For this purpose, we implement the expected critical behavior of the bulk viscosity within a non-boost-invariant, longitudinally expanding 1 + 1 dimensional causal relativistic hydrodynamical evolution at nonzero baryon density. We demonstrate that the critically enhanced bulk viscosity induces a substantial nonequilibrium pressure, effectively softening themore » equation of state, and leads to sizable effects in the flow velocity and single-particle distributions at the freeze-out. In conclusion, the observable effects that may arise due to the enhanced bulk viscosity in the vicinity of the QCD critical point can be used as complementary information to facilitate searches for the QCD critical point.« less

Progress on Complex Langevin simulations of a finite density matrix model for QCD

NASA Astrophysics Data System (ADS)

Bloch, Jacques; Glesaaen, Jonas; Verbaarschot, Jacobus; Zafeiropoulos, Savvas

2018-03-01

We study the Stephanov model, which is an RMT model for QCD at finite density, using the Complex Langevin algorithm. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory rather than to intended theory with dynamical quarks. A detailed analysis of this issue and a potential resolution of the failure of this algorithm are discussed. We study the effect of gauge cooling on the Dirac eigenvalue distribution and time evolution of the norm for various cooling norms, which were specifically designed to remove the pathologies of the complex Langevin evolution. The cooling is further supplemented with a shifted representation for the random matrices. Unfortunately, none of these modifications generate a substantial improvement on the complex Langevin evolution and the final results still do not agree with the analytical predictions.

Transverse momentum dependent parton distribution and fragmentation functions with QCD evolution

NASA Astrophysics Data System (ADS)

Aybat, S. Mert; Rogers, Ted C.

2011-06-01

We assess the current phenomenological status of transverse momentum dependent (TMD) parton distribution functions (PDFs) and fragmentation functions (FFs) and study the effect of consistently including perturbative QCD (pQCD) evolution. Our goal is to initiate the process of establishing reliable, QCD-evolved parametrizations for the TMD PDFs and TMD FFs that can be used both to test TMD factorization and to search for evidence of the breakdown of TMD factorization that is expected for certain processes. In this article, we focus on spin-independent processes because they provide the simplest illustration of the basic steps and can already be used in direct tests of TMD factorization. Our calculations are based on the Collins-Soper-Sterman (CSS) formalism, supplemented by recent theoretical developments which have clarified the precise definitions of the TMD PDFs and TMD FFs needed for a valid TMD-factorization theorem. Starting with these definitions, we numerically generate evolved TMD PDFs and TMD FFs using as input existing parametrizations for the collinear PDFs, collinear FFs, nonperturbative factors in the CSS factorization formalism, and recent fixed-scale fits. We confirm that evolution has important consequences, both qualitatively and quantitatively, and argue that it should be included in future phenomenological studies of TMD functions. Our analysis is also suggestive of extensions to processes that involve spin-dependent functions such as the Boer-Mulders, Sivers, or Collins functions, which we intend to pursue in future publications. At our website [http://projects.hepforge.org/tmd/], we have made available the tables and calculations needed to obtain the TMD parametrizations presented herein.

Quantum Simulation of the Hubbard Model Using Ultra-Cold Atoms

DTIC Science & Technology

2008-11-01

explore phases that do not yet have analogous behavior in QCD . ..,.. Ultracold fennions in optical lattices . The evolution from BCS to BEC...trimer states. The three-component Fermi gas we have created will, when confined in an optical lattice , be an experimental realization of the SU(3...chromodynamics ( QCD ): the color superconducting phase and the formation of baryons. Our initial investigations have focused on understanding three-body

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, C. D.; Schmidt, S. M.; Physics

Continuum strong QCD is the application of models and continuum quantum field theory to the study of phenomena in hadronic physics, which includes; e.g., the spectrum of QCD bound states and their interactions; and the transition to, and properties of, a quark gluon plasma. We provide a contemporary perspective, couched primarily in terms of the Dyson-Schwinger equations but also making comparisons with other approaches and models. Our discourse provides a practitioners' guide to features of the Dyson-Schwinger equations [such as confinement and dynamical chiral symmetry breaking] and canvasses phenomenological applications to light meson and baryon properties in cold, sparse QCD.more » These provide the foundation for an extension to hot, dense QCD, which is probed via the introduction of the intensive thermodynamic variables: chemical potential and temperature. We describe order parameters whose evolution signals deconfinement and chiral symmetry restoration, and chronicle their use in demarcating the quark gluon plasma phase boundary and characterizing the plasma's properties. Hadron traits change in an equilibrated plasma. We exemplify this and discuss putative signals of the effects. Finally, since plasma formation is not an equilibrium process, we discuss recent developments in kinetic theory and its application to describing the evolution from a relativistic heavy ion collision to an equilibrated quark gluon plasma.« less

The heavy quark expansion of QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falk, A.F.

1997-06-01

These lectures contain an elementary introduction to heavy quark symmetry and the heavy quark expansion. Applications such as the expansion of heavy meson decay constants and the treatment of inclusive and exclusive semileptonic B decays are included. Heavy hadron production via nonperturbative fragmentation processes is also discussed. 54 refs., 7 figs.

Resumming double logarithms in the QCD evolution of color dipoles

DOE PAGES

Iancu, E.; Madrigal, J. D.; Mueller, A. H.; ...

2015-05-01

The higher-order perturbative corrections, beyond leading logarithmic accuracy, to the BFKL evolution in QCD at high energy are well known to suffer from a severe lack-of-convergence problem, due to radiative corrections enhanced by double collinear logarithms. Via an explicit calculation of Feynman graphs in light cone (time-ordered) perturbation theory, we show that the corrections enhanced by double logarithms (either energy-collinear, or double collinear) are associated with soft gluon emissions which are strictly ordered in lifetime. These corrections can be resummed to all orders by solving an evolution equation which is non-local in rapidity. This equation can be equivalently rewritten inmore » local form, but with modified kernel and initial conditions, which resum double collinear logs to all orders. We extend this resummation to the next-to-leading order BFKL and BK equations. The first numerical studies of the collinearly-improved BK equation demonstrate the essential role of the resummation in both stabilizing and slowing down the evolution.« less

On the interface between perturbative and nonperturbative QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deur, Alexandre; Brodsky, Stanley J.; de Teramond, Guy F.

2016-04-04

The QCD running couplingmore » $$\\alpha_s(Q^2)$$ sets the strength of the interactions of quarks and gluons as a function of the momentum transfer $Q$. The $Q^2$ dependence of the coupling is required to describe hadronic interactions at both large and short distances. In this article we adopt the light-front holographic approach to strongly-coupled QCD, a formalism which incorporates confinement, predicts the spectroscopy of hadrons composed of light quarks, and describes the low-$Q^2$ analytic behavior of the strong coupling $$\\alpha_s(Q^2)$$. The high-$Q^2$ dependence of the coupling $$\\alpha_s(Q^2)$$ is specified by perturbative QCD and its renormalization group equation. The matching of the high and low $Q^2$ regimes of $$\\alpha_s(Q^2)$$ then determines the scale $$Q_0$$ which sets the interface between perturbative and nonperturbative hadron dynamics. The value of $$Q_0$$ can be used to set the factorization scale for DGLAP evolution of hadronic structure functions and the ERBL evolution of distribution amplitudes. We discuss the scheme-dependence of the value of $$Q_0$$ and the infrared fixed-point of the QCD coupling. Our analysis is carried out for the $$\\bar{MS}$$, $$g_1$$, $MOM$ and $V$ renormalization schemes. Our results show that the discrepancies on the value of $$\\alpha_s$$ at large distance seen in the literature can be explained by different choices of renormalization schemes. Lastly, we also provide the formulae to compute $$\\alpha_s(Q^2)$$ over the entire range of space-like momentum transfer for the different renormalization schemes discussed in this article.« less

Conformal Symmetry as a Template for QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, S

2004-08-04

Conformal symmetry is broken in physical QCD; nevertheless, one can use conformal symmetry as a template, systematically correcting for its nonzero {beta} function as well as higher-twist effects. For example, commensurate scale relations which relate QCD observables to each other, such as the generalized Crewther relation, have no renormalization scale or scheme ambiguity and retain a convergent perturbative structure which reflects the underlying conformal symmetry of the classical theory. The ''conformal correspondence principle'' also dictates the form of the expansion basis for hadronic distribution amplitudes. The AdS/CFT correspondence connecting superstring theory to superconformal gauge theory has important implications for hadronmore » phenomenology in the conformal limit, including an all-orders demonstration of counting rules for hard exclusive processes as well as determining essential aspects of hadronic light-front wavefunctions. Theoretical and phenomenological evidence is now accumulating that QCD couplings based on physical observables such as {tau} decay become constant at small virtuality; i.e., effective charges develop an infrared fixed point in contradiction to the usual assumption of singular growth in the infrared. The near-constant behavior of effective couplings also suggests that QCD can be approximated as a conformal theory even at relatively small momentum transfer. The importance of using an analytic effective charge such as the pinch scheme for unifying the electroweak and strong couplings and forces is also emphasized.« less

Progress on Complex Langevin simulations of a finite density matrix model for QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bloch, Jacques; Glesaan, Jonas; Verbaarschot, Jacobus

We study the Stephanov model, which is an RMT model for QCD at finite density, using the Complex Langevin algorithm. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory rather than to intended theory with dynamical quarks. A detailed analysis of this issue and a potential resolution of the failure of this algorithm are discussed. We study the effect of gauge cooling on the Dirac eigenvalue distribution and time evolution of the norm for various cooling norms, which were specifically designed to remove the pathologies of the complex Langevin evolution. The cooling is further supplementedmore » with a shifted representation for the random matrices. Unfortunately, none of these modifications generate a substantial improvement on the complex Langevin evolution and the final results still do not agree with the analytical predictions.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monnai, Akihiko; Mukherjee, Swagato; Yin, Yi

In the proximity of the QCD critical point the bulk viscosity of quark-gluon matter is expected to be proportional to nearly the third power of the critical correlation length, and become significantly enhanced. Here, this work is the first attempt to study the phenomenological consequences of enhanced bulk viscosity near the QCD critical point. For this purpose, we implement the expected critical behavior of the bulk viscosity within a non-boost-invariant, longitudinally expanding 1 + 1 dimensional causal relativistic hydrodynamical evolution at nonzero baryon density. We demonstrate that the critically enhanced bulk viscosity induces a substantial nonequilibrium pressure, effectively softening themore » equation of state, and leads to sizable effects in the flow velocity and single-particle distributions at the freeze-out. In conclusion, the observable effects that may arise due to the enhanced bulk viscosity in the vicinity of the QCD critical point can be used as complementary information to facilitate searches for the QCD critical point.« less

Cosmological abundance of the QCD axion coupled to hidden photons

NASA Astrophysics Data System (ADS)

Kitajima, Naoya; Sekiguchi, Toyokazu; Takahashi, Fuminobu

2018-06-01

We study the cosmological evolution of the QCD axion coupled to hidden photons. For a moderately strong coupling, the motion of the axion field leads to an explosive production of hidden photons by tachyonic instability. We use lattice simulations to evaluate the cosmological abundance of the QCD axion. In doing so, we incorporate the backreaction of the produced hidden photons on the axion dynamics, which becomes significant in the non-linear regime. We find that the axion abundance is suppressed by at most O (102) for the decay constant fa =1016GeV, compared to the case without the coupling. For a sufficiently large coupling, the motion of the QCD axion becomes strongly damped, and as a result, the axion abundance is enhanced. Our results show that the cosmological upper bound on the axion decay constant can be relaxed by a few hundred for a certain range of the coupling to hidden photons.

The gluon condensation at high energy hadron collisions

NASA Astrophysics Data System (ADS)

Zhu, Wei; Lan, Jiangshan

2017-03-01

We report that the saturation/CGC model of gluon distribution is unstable under action of the chaotic solution in a nonlinear QCD evolution equation, and it evolves to the distribution with a sharp peak at the critical momentum. We find that this gluon condensation is caused by a new kind of shadowing-antishadowing effects, and it leads to a series of unexpected effects in high energy hadron collisions including astrophysical events. For example, the extremely intense fluctuations in the transverse-momentum and rapidity distributions of the gluon jets present the gluon-jet bursts; a sudden increase of the proton-proton cross sections may fill the GZK suppression; the blocking QCD evolution will restrict the maximum available energy of the hadron-hadron colliders.

N3LO corrections to jet production in deep inelastic scattering using the Projection-to-Born method

NASA Astrophysics Data System (ADS)

Currie, J.; Gehrmann, T.; Glover, E. W. N.; Huss, A.; Niehues, J.; Vogt, A.

2018-05-01

Computations of higher-order QCD corrections for processes with exclusive final states require a subtraction method for real-radiation contributions. We present the first-ever generalisation of a subtraction method for third-order (N3LO) QCD corrections. The Projection-to-Born method is used to combine inclusive N3LO coefficient functions with an exclusive second-order (NNLO) calculation for a final state with an extra jet. The input requirements, advantages, and potential applications of the method are discussed, and validations at lower orders are performed. As a test case, we compute the N3LO corrections to kinematical distributions and production rates for single-jet production in deep inelastic scattering in the laboratory frame, and compare them with data from the ZEUS experiment at HERA. The corrections are small in the central rapidity region, where they stabilize the predictions to sub per-cent level. The corrections increase substantially towards forward rapidity where large logarithmic effects are expected, thereby yielding an improved description of the data in this region.

Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS

DOE PAGES

Mokeev, Victor I.

2018-04-06

Studies of the nucleon resonance electroexcitation amplitudes in a wide range of photon virtualities offer unique information on many facets of strong QCD behind the generation of all prominent excited nucleon states of distinctively different structure. Advances in the evaluation of resonance electroexcitation amplitudes from the data measured with the CLAS detector and the future extension of these studies with the CLAS12 detector at Jefferson Lab are presented in this paper. For the first time, analyses ofmore » $$\\pi^0p$$, $$\\pi^+n$$, $$\\eta p$$, and $$\\pi^+\\pi^-p$$ electroproduction off proton channels have provided electroexcitation amplitudes of most resonances in the mass range up to 1.8 GeV and at photon virtualities $Q^2 < 5$ GeV$^2$. Consistent results on resonance electroexcitation amplitudes determined from different exclusive channels validate a credible extraction of these fundamental quantities. Studies of the resonance electroexcitation amplitudes revealed the $N^*$ structure as a complex interplay between the inner core of three dressed quarks and the external meson-baryon cloud. The successful description of the $$\\Delta(1232)3/2^+$$ and $N(1440)1/2^+$ electrocouplings achieved within the Dyson-Schwinger Equation approach under a traceable connection to the QCD Lagrangian and supported by the novel light front quark model demonstrated the relevance of dressed quarks with dynamically generated masses as an active structural component in baryons. Future experiments with the CLAS12 detector will offer insight into the structure of all prominent resonances at the highest photon virtualities, $Q^2 < 12$ GeV$^2$, ever achieved in exclusive reactions, thus addressing the most challenging problems of the Standard Model on the nature of hadron mass, quark-gluon confinement, and the emergence of nucleon resonance structures from QCD. Finally, a search for new states of hadronic matter, the so-called hybrid-baryons with glue as a structural component, will complete the long term efforts on the resonance spectrum exploration.« less

Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mokeev, Victor I.

Studies of the nucleon resonance electroexcitation amplitudes in a wide range of photon virtualities offer unique information on many facets of strong QCD behind the generation of all prominent excited nucleon states of distinctively different structure. Advances in the evaluation of resonance electroexcitation amplitudes from the data measured with the CLAS detector and the future extension of these studies with the CLAS12 detector at Jefferson Lab are presented in this paper. For the first time, analyses ofmore » $$\\pi^0p$$, $$\\pi^+n$$, $$\\eta p$$, and $$\\pi^+\\pi^-p$$ electroproduction off proton channels have provided electroexcitation amplitudes of most resonances in the mass range up to 1.8 GeV and at photon virtualities $Q^2 < 5$ GeV$^2$. Consistent results on resonance electroexcitation amplitudes determined from different exclusive channels validate a credible extraction of these fundamental quantities. Studies of the resonance electroexcitation amplitudes revealed the $N^*$ structure as a complex interplay between the inner core of three dressed quarks and the external meson-baryon cloud. The successful description of the $$\\Delta(1232)3/2^+$$ and $N(1440)1/2^+$ electrocouplings achieved within the Dyson-Schwinger Equation approach under a traceable connection to the QCD Lagrangian and supported by the novel light front quark model demonstrated the relevance of dressed quarks with dynamically generated masses as an active structural component in baryons. Future experiments with the CLAS12 detector will offer insight into the structure of all prominent resonances at the highest photon virtualities, $Q^2 < 12$ GeV$^2$, ever achieved in exclusive reactions, thus addressing the most challenging problems of the Standard Model on the nature of hadron mass, quark-gluon confinement, and the emergence of nucleon resonance structures from QCD. Finally, a search for new states of hadronic matter, the so-called hybrid-baryons with glue as a structural component, will complete the long term efforts on the resonance spectrum exploration.« less

Parton Densities: A Personal Retrospective

NASA Astrophysics Data System (ADS)

Petronzio, R.

The beginning of perturbative QCD and the generalisation of parton evolution probabilities beyond leading order are briefly recalled, together with my personal experience of collaboration and friendships with Gabriele.

Model for nucleon valence structure functions at all x, all p ⊥ and all Q 2 from the correspondence between QCD and DTU

NASA Astrophysics Data System (ADS)

Cohen-Tannoudji, G.; El Hassouni, A.; Mantrach, A.; Oudrhiri-Safiani, E. G.

1982-09-01

We propose a simple parametrization of the nucleon valence structure functions at all x, all p ⊥ and all Q 2. We use the DTU parton model to fix the parametrization at a reference point ( Q {0/2}=3 GeV2) and we mimic the QCD evolution by replacing the dimensioned parameters of the DTU parton model by functions depending on Q 2. Excellent agreement is obtained with existing data.

Weak gauge boson radiation in parton showers

NASA Astrophysics Data System (ADS)

Christiansen, Jesper R.; Sjöstrand, Torbjörn

2014-04-01

The emission of W and Z gauge bosons off quarks is included in a traditional QCD + QED shower. The unitarity of the shower algorithm links the real radiation of the weak gauge bosons to the negative weak virtual corrections. The shower evolution process leads to a competition between QCD, QED and weak radiation, and allows for W and Z boson production inside jets. Various effects on LHC physics are studied, both at low and high transverse momenta, and effects at higher-energy hadron colliders are outlined.

On the small-x behavior of the orbital angular momentum distributions in QCD

NASA Astrophysics Data System (ADS)

Hatta, Yoshitaka; Yang, Dong-Jing

2018-06-01

We present the numerical solution of the leading order QCD evolution equation for the orbital angular momentum distributions of quarks and gluons and discuss its implications for the nucleon spin sum rule. We observe that at small-x, the gluon helicity and orbital angular momentum distributions are roughly of the same magnitude but with opposite signs, indicating a significant cancellation between them. A similar cancellation occurs also in the quark sector. We explain analytically the reason for this cancellation.

Analytic boosted boson discrimination

DOE PAGES

Larkoski, Andrew J.; Moult, Ian; Neill, Duff

2016-05-20

Observables which discriminate boosted topologies from massive QCD jets are of great importance for the success of the jet substructure program at the Large Hadron Collider. Such observables, while both widely and successfully used, have been studied almost exclusively with Monte Carlo simulations. In this paper we present the first all-orders factorization theorem for a two-prong discriminant based on a jet shape variable, D 2, valid for both signal and background jets. Our factorization theorem simultaneously describes the production of both collinear and soft subjets, and we introduce a novel zero-bin procedure to correctly describe the transition region between thesemore » limits. By proving an all orders factorization theorem, we enable a systematically improvable description, and allow for precision comparisons between data, Monte Carlo, and first principles QCD calculations for jet substructure observables. Using our factorization theorem, we present numerical results for the discrimination of a boosted Z boson from massive QCD background jets. We compare our results with Monte Carlo predictions which allows for a detailed understanding of the extent to which these generators accurately describe the formation of two-prong QCD jets, and informs their usage in substructure analyses. In conclusion, our calculation also provides considerable insight into the discrimination power and calculability of jet substructure observables in general.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larkoski, Andrew J.; Moult, Ian; Neill, Duff

Observables which discriminate boosted topologies from massive QCD jets are of great importance for the success of the jet substructure program at the Large Hadron Collider. Such observables, while both widely and successfully used, have been studied almost exclusively with Monte Carlo simulations. In this paper we present the first all-orders factorization theorem for a two-prong discriminant based on a jet shape variable, D 2, valid for both signal and background jets. Our factorization theorem simultaneously describes the production of both collinear and soft subjets, and we introduce a novel zero-bin procedure to correctly describe the transition region between thesemore » limits. By proving an all orders factorization theorem, we enable a systematically improvable description, and allow for precision comparisons between data, Monte Carlo, and first principles QCD calculations for jet substructure observables. Using our factorization theorem, we present numerical results for the discrimination of a boosted Z boson from massive QCD background jets. We compare our results with Monte Carlo predictions which allows for a detailed understanding of the extent to which these generators accurately describe the formation of two-prong QCD jets, and informs their usage in substructure analyses. In conclusion, our calculation also provides considerable insight into the discrimination power and calculability of jet substructure observables in general.« less

Transverse momentum dependent evolution: Matching semi-inclusive deep inelastic scattering processes to Drell-Yan and W/Z boson production

NASA Astrophysics Data System (ADS)

Sun, Peng; Yuan, Feng

2013-12-01

We examine the QCD evolution for the transverse momentum dependent observables in hard processes of semi-inclusive hadron production in deep inelastic scattering and Drell-Yan lepton pair production in pp collisions, including the spin-average cross sections and Sivers single transverse spin asymmetries. We show that the evolution equations derived by a direct integral of the Collins-Soper-Sterman evolution kernel from low to high Q can describe well the transverse momentum distributions of the unpolarized cross sections in the Q2 range from 2 to 100GeV2. In addition, the matching is established between our evolution and the Collins-Soper-Sterman resummation with b* prescription and Konychev-Nodalsky parametrization of the nonperturbative form factors, which are formulated to describe the Drell-Yan lepton pair and W/Z boson production in hadronic collisions. With these results, we present the predictions for the Sivers single transverse spin asymmetries in Drell-Yan lepton pair production and W± boson production in polarized pp and π-p collisions for several proposed experiments. We emphasize that these experiments will not only provide crucial test of the sign change of the Sivers asymmetry but also provide important opportunities to study the QCD evolution effects.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, Nadine; Prestel, S.; Ritzmann, M.

We present the first public implementation of antenna-based QCD initial- and final-state showers. The shower kernels are 2→3 antenna functions, which capture not only the collinear dynamics but also the leading soft (coherent) singularities of QCD matrix elements. We define the evolution measure to be inversely proportional to the leading poles, hence gluon emissions are evolved in a p ⊥ measure inversely proportional to the eikonal, while processes that only contain a single pole (e.g., g → qq¯) are evolved in virtuality. Non-ordered emissions are allowed, suppressed by an additional power of 1/Q 2. Recoils and kinematics are governed bymore » exact on-shell 2 → 3 phase-space factorisations. This first implementation is limited to massless QCD partons and colourless resonances. Tree-level matrix-element corrections are included for QCD up to O(α 4 s) (4 jets), and for Drell–Yan and Higgs production up to O(α 3 s) (V / H + 3 jets). Finally, the resulting algorithm has been made publicly available in Vincia 2.0.« less

Markovian Monte Carlo program EvolFMC v.2 for solving QCD evolution equations

NASA Astrophysics Data System (ADS)

Jadach, S.; Płaczek, W.; Skrzypek, M.; Stokłosa, P.

2010-02-01

We present the program EvolFMC v.2 that solves the evolution equations in QCD for the parton momentum distributions by means of the Monte Carlo technique based on the Markovian process. The program solves the DGLAP-type evolution as well as modified-DGLAP ones. In both cases the evolution can be performed in the LO or NLO approximation. The quarks are treated as massless. The overall technical precision of the code has been established at 5×10. This way, for the first time ever, we demonstrate that with the Monte Carlo method one can solve the evolution equations with precision comparable to the other numerical methods. New version program summaryProgram title: EvolFMC v.2 Catalogue identifier: AEFN_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFN_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including binary test data, etc.: 66 456 (7407 lines of C++ code) No. of bytes in distributed program, including test data, etc.: 412 752 Distribution format: tar.gz Programming language: C++ Computer: PC, Mac Operating system: Linux, Mac OS X RAM: Less than 256 MB Classification: 11.5 External routines: ROOT ( http://root.cern.ch/drupal/) Nature of problem: Solution of the QCD evolution equations for the parton momentum distributions of the DGLAP- and modified-DGLAP-type in the LO and NLO approximations. Solution method: Monte Carlo simulation of the Markovian process of a multiple emission of partons. Restrictions:Limited to the case of massless partons. Implemented in the LO and NLO approximations only. Weighted events only. Unusual features: Modified-DGLAP evolutions included up to the NLO level. Additional comments: Technical precision established at 5×10. Running time: For the 10 6 events at 100 GeV: DGLAP NLO: 27s; C-type modified DGLAP NLO: 150s (MacBook Pro with Mac OS X v.10.5.5, 2.4 GHz Intel Core 2 Duo, gcc 4.2.4, single thread).

Hard quark-quark scattering with exclusive reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barton, D.S.; Bunce, G.M.; Carroll, A.S.

1984-01-01

We present data from ..pi../sup -/p ..-->.. elastic and rho/sup -/p final states for scattering at 90/sup 0/ center of mass, -t = 9 GeV/sup 2//c/sup 2/. A large rho/sup -/p signal is seen and the rho/sup -/ is strongly polarized. This polarization tests a QCD prediction that quarks cannot flip helicity. The test fails dramatically. 9 references, 4 figures.

Forward and small-x QCD physics results from CMS experiment at LHC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cerci, Deniz Sunar, E-mail: deniz.sunar.cerci@cern.ch

2016-03-25

The Compact Muon Solenoid (CMS) is one of the two large, multi-purpose experiments at the Large Hadron Collider (LHC) at CERN. During the Run I Phase a large pp collision dataset has been collected and the CMS collaboration has explored measurements that shed light on a new era. Forward and small-x quantum chromodynamics (QCD) physics measurements with CMS experiment covers a wide range of physics subjects. Some of highlights in terms of testing the very low-x QCD, underlying event and multiple interaction characteristics, photon-mediated processes, jets with large rapidity separation at high pseudo-rapidities and the inelastic proton-proton cross section dominatedmore » by diffractive interactions are presented. Results are compared to Monte Carlo (MC) models with different parameter tunes for the description of the underlying event and to perturbative QCD calculations. The prominent role of multi-parton interactions has been confirmed in the semihard sector but no clear deviation from the standard Dglap parton evolution due to Bfkl has been observed. An outlook to the prospects at 13 TeV is given.« less

VINCIA for hadron colliders

DOE PAGES

Fischer, Nadine; Prestel, S.; Ritzmann, M.; ...

2016-10-28

We present the first public implementation of antenna-based QCD initial- and final-state showers. The shower kernels are 2→3 antenna functions, which capture not only the collinear dynamics but also the leading soft (coherent) singularities of QCD matrix elements. We define the evolution measure to be inversely proportional to the leading poles, hence gluon emissions are evolved in a p ⊥ measure inversely proportional to the eikonal, while processes that only contain a single pole (e.g., g → qq¯) are evolved in virtuality. Non-ordered emissions are allowed, suppressed by an additional power of 1/Q 2. Recoils and kinematics are governed bymore » exact on-shell 2 → 3 phase-space factorisations. This first implementation is limited to massless QCD partons and colourless resonances. Tree-level matrix-element corrections are included for QCD up to O(α 4 s) (4 jets), and for Drell–Yan and Higgs production up to O(α 3 s) (V / H + 3 jets). Finally, the resulting algorithm has been made publicly available in Vincia 2.0.« less

Soft evolution of multi-jet final states

DOE PAGES

Gerwick, Erik; Schumann, Steffen; Höche, Stefan; ...

2015-02-16

We present a new framework for computing resummed and matched distributions in processes with many hard QCD jets. The intricate color structure of soft gluon emission at large angles renders resummed calculations highly non-trivial in this case. We automate all ingredients necessary for the color evolution of the soft function at next-to-leading-logarithmic accuracy, namely the selection of the color bases and the projections of color operators and Born amplitudes onto those bases. Explicit results for all QCD processes with up to 2 → 5 partons are given. We also devise a new tree-level matching scheme for resummed calculations which exploitsmore » a quasi-local subtraction based on the Catani-Seymour dipole formalism. We implement both resummation and matching in the Sherpa event generator. As a proof of concept, we compute the resummed and matched transverse-thrust distribution for hadronic collisions.« less

Double Parton Fragmentation Function and its Evolution in Quarkonium Production

NASA Astrophysics Data System (ADS)

Kang, Zhong-Bo

2014-01-01

We summarize the results of a recent study on a new perturbative QCD factorization formalism for the production of heavy quarkonia of large transverse momentum pT at collider energies. Such a new factorization formalism includes both the leading power (LP) and next-to-leading power (NLP) contributions to the cross section in the mQ2/p_T^2 expansion for heavy quark mass mQ. For the NLP contribution, the so-called double parton fragmentation functions are involved, whose evolution equations have been derived. We estimate fragmentation functions in the non-relativistic QCD formalism, and found that their contribution reproduce the bulk of the large enhancement found in explicit NLO calculations in the color singlet model. Heavy quarkonia produced from NLP channels prefer longitudinal polarization, in contrast to the single parton fragmentation function. This might shed some light on the heavy quarkonium polarization puzzle.

Event-by-event picture for the medium-induced jet evolution

NASA Astrophysics Data System (ADS)

Escobedo, Miguel A.; Iancu, Edmond

2017-08-01

We discuss the evolution of an energetic jet which propagates through a dense quark-gluon plasma and radiates gluons due to its interactions with the medium. Within perturbative QCD, this evolution can be described as a stochastic branching process, that we have managed to solve exactly. We present exact, analytic, results for the gluon spectrum (the average gluon distribution) and for the higher n-point functions, which describe correlations and fluctuations. Using these results, we construct the event-by-event picture of the gluon distribution produced via medium-induced gluon branching. In contrast to what happens in a usual QCD cascade in vacuum, the medium-induced branchings are quasi-democratic, with offspring gluons carrying sizable fractions of the energy of their parent parton. We find large fluctuations in the energy loss and in the multiplicity of soft gluons. The multiplicity distribution is predicted to exhibit KNO (Koba-Nielsen-Olesen) scaling. These predictions can be tested in Pb+Pb collisions at the LHC, via event-by-event measurements of the di-jet asymmetry. Based on [1, 2].

Event-by-event picture for the medium-induced jet evolution

NASA Astrophysics Data System (ADS)

Escobedo, Miguel A.; Iancu, Edmond

2017-03-01

We discuss the evolution of an energetic jet which propagates through a dense quark-gluon plasma and radiates gluons due to its interactions with the medium. Within perturbative QCD, this evolution can be described as a stochastic branching process, that we have managed to solve exactly. We present exact, analytic, results for the gluon spectrum (the average gluon distribution) and for the higher n-point functions, which describe correlations and fluctuations. Using these results, we construct the event-by-event picture of the gluon distribution produced via medium-induced gluon branching. In contrast to what happens in a usual QCD cascade in vacuum, the medium-induced branchings are quasi-democratic, with offspring gluons carrying sizable fractions of the energy of their parent parton. We find large fluctuations in the energy loss and in the multiplicity of soft gluons. The multiplicity distribution is predicted to exhibit KNO (Koba-Nielsen-Olesen) scaling. These predictions can be tested in Pb+Pb collisions at the LHC, via event-by-event measurements of the di-jet asymmetry. Based on [1, 2].

QCD evolution of the Sivers function

NASA Astrophysics Data System (ADS)

Aybat, S. M.; Collins, J. C.; Qiu, J. W.; Rogers, T. C.

2012-02-01

We extend the Collins-Soper-Sterman (CSS) formalism to apply it to the spin dependence governed by the Sivers function. We use it to give a correct numerical QCD evolution of existing fixed-scale fits of the Sivers function. With the aid of approximations useful for the nonperturbative region, we present the results as parametrizations of a Gaussian form in transverse-momentum space, rather than in the Fourier conjugate transverse coordinate space normally used in the CSS formalism. They are specifically valid at small transverse momentum. Since evolution has been applied, our results can be used to make predictions for Drell-Yan and semi-inclusive deep inelastic scattering at energies different from those where the original fits were made. Our evolved functions are of a form that they can be used in the same parton-model factorization formulas as used in the original fits, but now with a predicted scale dependence in the fit parameters. We also present a method by which our evolved functions can be corrected to allow for twist-3 contributions at large parton transverse momentum.

Updates on the Studies of $${\\varvec{N}}^\\mathbf{*}$$ N * Structure with CLAS and the Prospects with CLAS12

DOE PAGES

Mokeev, V. I.

2016-06-16

Here, the recent results onmore » $$\\gamma_vpN^*$$ electrocouplings from analyses of the data on exclusive meson electroproduction off protons measured with the CLAS detector at Jefferson Lab are presented. The impact of these results on the exploration of the excited nucleon state structure and non-perturbative strong interaction dynamics behind its formation is outlined. The future extension of these studies in the experiments with the CLAS12 detector in the upgraded Hall-B at JLab will provide for the first time $$\\gamma_vpN^*$$ electrocouplings of all prominent resonances at the still unexplored distance scales that correspond to extremely low (0.05~GeV$^2 < Q^2 <$ 0.5~GeV$^2$) and the highest photon virtualities (5.0~GeV$^2 < Q^2 <$ 12.0~GeV$^2$) ever achieved in the exclusive electroproduction measurements. The expected results will address the most important open problems of the Standard Model: on the nature of more than 98\\% of hadron mass, quark-gluon confinement and emergence of the excited nucleon state structure from the QCD Lagrangian, as well as allowing a search for the new states of hadron matter predicted from the first principles of QCD, the so-called hybrid baryons.« less

Updates on the Studies of {\\varvec{N}}^* Structure with CLAS and the Prospects with CLAS12

NASA Astrophysics Data System (ADS)

Mokeev, V. I.

2016-10-01

The recent results on γ _vpN^* electrocouplings from analyses of the data on exclusive meson electroproduction off protons measured with the CLAS detector at Jefferson Lab are presented. The impact of these results on the exploration of the excited nucleon state structure and non-perturbative strong interaction dynamics behind its formation is outlined. The future extension of these studies in the experiments with the CLAS12 detector in the upgraded Hall-B at JLab will provide for the first time γ _vpN^* electrocouplings of all prominent resonances at the still unexplored distance scales that correspond to extremely low (0.05 GeV^2 < Q^2< 0.5 GeV^2) and the highest photon virtualities (5.0 GeV^2 < Q^2< 12.0 GeV^2) ever achieved in the exclusive electroproduction measurements. The expected results will address the most important open problems of the Standard Model: on the nature of more than 98 % of hadron mass, quark-gluon confinement and emergence of the excited nucleon state structure from the QCD Lagrangian, as well as allowing a search for the new states of hadron matter predicted from the first principles of QCD, the so-called hybrid baryons.

Assessing the role of the Kelvin-Helmholtz instability at the QCD cosmological transition

NASA Astrophysics Data System (ADS)

Mourão Roque, V. R. C.; Lugones, G.

2018-03-01

We performed numerical simulations with the PLUTO code in order to analyze the non-linear behavior of the Kelvin-Helmholtz instability in non-magnetized relativistic fluids. The relevance of the instability at the cosmological QCD phase transition was explored using an equation of state based on lattice QCD results with the addition of leptons. The results of the simulations were compared with the theoretical predictions of the linearized theory. For small Mach numbers up to Ms ~ 0.1 we find that both results are in good agreement. However, for higher Mach numbers, non-linear effects are significant. In particular, many initial conditions that look stable according to the linear analysis are shown to be unstable according to the full calculation. Since according to lattice calculations the cosmological QCD transition is a smooth crossover, violent fluid motions are not expected. Thus, in order to assess the role of the Kelvin-Helmholtz instability at the QCD epoch, we focus on simulations with low shear velocity and use monochromatic as well as random perturbations to trigger the instability. We find that the Kelvin-Helmholtz instability can strongly amplify turbulence in the primordial plasma and as a consequence it may increase the amount of primordial gravitational radiation. Such turbulence may be relevant for the evolution of the Universe at later stages and may have an impact in the stochastic gravitational wave background.

QCDNUM: Fast QCD evolution and convolution

NASA Astrophysics Data System (ADS)

Botje, M.

2011-02-01

The QCDNUM program numerically solves the evolution equations for parton densities and fragmentation functions in perturbative QCD. Un-polarised parton densities can be evolved up to next-to-next-to-leading order in powers of the strong coupling constant, while polarised densities or fragmentation functions can be evolved up to next-to-leading order. Other types of evolution can be accessed by feeding alternative sets of evolution kernels into the program. A versatile convolution engine provides tools to compute parton luminosities, cross-sections in hadron-hadron scattering, and deep inelastic structure functions in the zero-mass scheme or in generalised mass schemes. Input to these calculations are either the QCDNUM evolved densities, or those read in from an external parton density repository. Included in the software distribution are packages to calculate zero-mass structure functions in un-polarised deep inelastic scattering, and heavy flavour contributions to these structure functions in the fixed flavour number scheme. Program summaryProgram title: QCDNUM version: 17.00 Catalogue identifier: AEHV_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU Public Licence No. of lines in distributed program, including test data, etc.: 45 736 No. of bytes in distributed program, including test data, etc.: 911 569 Distribution format: tar.gz Programming language: Fortran-77 Computer: All Operating system: All RAM: Typically 3 Mbytes Classification: 11.5 Nature of problem: Evolution of the strong coupling constant and parton densities, up to next-to-next-to-leading order in perturbative QCD. Computation of observable quantities by Mellin convolution of the evolved densities with partonic cross-sections. Solution method: Parametrisation of the parton densities as linear or quadratic splines on a discrete grid, and evolution of the spline coefficients by solving (coupled) triangular matrix equations with a forward substitution algorithm. Fast computation of convolution integrals as weighted sums of spline coefficients, with weights derived from user-given convolution kernels. Restrictions: Accuracy and speed are determined by the density of the evolution grid. Running time: Less than 10 ms on a 2 GHz Intel Core 2 Duo processor to evolve the gluon density and 12 quark densities at next-to-next-to-leading order over a large kinematic range.

Lattice QCD inputs to the CKM unitarity triangle analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laiho, Jack; Department of Physics and Astronomy, University of Glasgow, Glasgow, G128 QQ; Lunghi, E.

2010-02-01

We perform a global fit to the Cabibbo-Kobayashi-Maskawa unitarity triangle using the latest experimental and theoretical constraints. Our emphasis is on the hadronic weak matrix elements that enter the analysis, which must be computed using lattice QCD or other nonperturbative methods. Realistic lattice QCD calculations which include the effects of the dynamical up, down, and strange quarks are now available for all of the standard inputs to the global fit. We therefore present lattice averages for all of the necessary hadronic weak matrix elements. We attempt to account for correlations between lattice QCD results in a reasonable but conservative manner:more » whenever there are reasons to believe that an error is correlated between two lattice calculations, we take the degree of correlation to be 100%. These averages are suitable for use as inputs both in the global Cabibbo-Kobayashi-Maskawa unitarity triangle fit and other phenomenological analyses. In order to illustrate the impact of the lattice averages, we make standard model predictions for the parameters B-circumflex{sub K}, |V{sub cb}|, and |V{sub ub}|/|V{sub cb}|. We find a (2-3){sigma} tension in the unitarity triangle, depending upon whether we use the inclusive or exclusive determination of |V{sub cb}|. If we interpret the tension as a sign of new physics in either neutral kaon or B mixing, we find that the scenario with new physics in kaon mixing is preferred by present data.« less

Lattice QCD Inputs to the CKM Unitarity Triangle Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van de Water, R.; Lunghi, E; Laiho, J

2010-02-02

We perform a global fit to the Cabibbo-Kobayashi-Maskawa unitarity triangle using the latest experimental and theoretical constraints. Our emphasis is on the hadronic weak matrix elements that enter the analysis, which must be computed using lattice QCD or other nonperturbative methods. Realistic lattice QCD calculations which include the effects of the dynamical up, down, and strange quarks are now available for all of the standard inputs to the global fit. We therefore present lattice averages for all of the necessary hadronic weak matrix elements. We attempt to account for correlations between lattice QCD results in a reasonable but conservative manner:more » whenever there are reasons to believe that an error is correlated between two lattice calculations, we take the degree of correlation to be 100%. These averages are suitable for use as inputs both in the global Cabibbo-Kobayashi-Maskawa unitarity triangle fit and other phenomenological analyses. In order to illustrate the impact of the lattice averages, we make standard model predictions for the parameters B{sub K}, |V{sub cb}|, and |V{sub ub}|/|Vcb|. We find a (2-3){sigma} tension in the unitarity triangle, depending upon whether we use the inclusive or exclusive determination of |V{sub cb}|. If we interpret the tension as a sign of new physics in either neutral kaon or B mixing, we find that the scenario with new physics in kaon mixing is preferred by present data.« less

Lattice QCD Studies of Transverse Momentum-Dependent Parton Distribution Functions

NASA Astrophysics Data System (ADS)

Engelhardt, M.; Musch, B.; Hägler, P.; Negele, J.; Schäfer, A.

2015-09-01

Transverse momentum-dependent parton distributions (TMDs) relevant for semi-inclusive deep inelastic scattering and the Drell-Yan process can be defined in terms of matrix elements of a quark bilocal operator containing a staple-shaped gauge link. Such a definition opens the possibility of evaluating TMDs within lattice QCD. By parametrizing the aforementioned matrix elements in terms of invariant amplitudes, the problem can be cast in a Lorentz frame suited for the lattice calculation. Results for selected TMD observables are presented, including a particular focus on their dependence on a Collins-Soper-type evolution parameter, which quantifies proximity of the staple-shaped gauge links to the light cone.

Transverse Momentum-Dependent Parton Distributions from Lattice QCD

NASA Astrophysics Data System (ADS)

Engelhardt, M.; Musch, B.; Hägler, P.; Negele, J.; Schäfer, A.

Starting from a definition of transverse momentum-dependent parton distributions for semi-inclusive deep inelastic scattering and the Drell-Yan process, given in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection, a scheme to determine such observables in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are presented, focusing in particular on their dependence on the staple extent and the Collins-Soper evolution parameter.

Transverse Momentum-Dependent Parton Distributions From Lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael Engelhardt, Bernhard Musch, Philipp Haegler, Andreas Schaefer

Starting from a definition of transverse momentum-dependent parton distributions for semi-inclusive deep inelastic scattering and the Drell-Yan process, given in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection, a scheme to determine such observables in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are presented, focusing in particular on their dependence on the staple extent and the Collins-Soper evolution parameter.

Exclusive Electroproduction of meson rho on the nucleon Virtualite Intermediate With the CLAS Detector at Jlab; Electroproduction Exclusive de meson rho sur le nucleon Virtualite Intermediaire Avec le Detecteur CLAS at Jlab (in French)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hadjidakis, Cynthia

2002-12-17

This report presents the exclusive rho0 meson electroproduction on the nucleon at intermediate square momentum transfers Q 2 (1.5 < Q 2 < 3 GeV 2) and above the resonance region. The experiment has been taken place at the Jefferson laboratory with the CLAS detector, with a 4.2 GeV beam energy on a hydrogen target in the February-March 1999 period. They present the results and in particular the L/T separated cross sections. This experimentally unexplored domain experimentally is at the intersection between traditional ''soft'' hadronic physics models (VDM and Regge inspired models) and ''hard'' pQCD inspired approaches (recently introduced Generalizedmore » Parton Distribution). They discuss both approaches and their domain of validity.« less

Quasi-two-body decays B → Kρ → Kππ in perturbative QCD approach

NASA Astrophysics Data System (ADS)

Wang, Wen-Fei; Li, Hsiang-nan

2016-12-01

We analyze the quasi-two-body decays B → Kρ → Kππ in the perturbative QCD (PQCD) approach, in which final-state interactions between the pions in the resonant regions associated with the P-wave states ρ (770) and ρ‧ (1450) are factorized into two-pion distribution amplitudes. Adopting experimental inputs for the time-like pion form factors involved in two-pion distribution amplitudes, we calculate branching ratios and direct CP asymmetries of the B → Kρ (770) , Kρ‧ (1450) → Kππ modes. It is shown that agreement of theoretical results with data can be achieved, through which Gegenbauer moments of the P-wave two-pion distribution amplitudes are determined. The consistency between the three-body and two-body analyses of the B → Kρ (770) → Kππ decays supports the PQCD factorization framework for exclusive hadronic B meson decays.

Heavy quarkonium suppression in a fireball

NASA Astrophysics Data System (ADS)

Brambilla, Nora; Escobedo, Miguel A.; Soto, Joan; Vairo, Antonio

2018-04-01

We perform a comprehensive study of the time evolution of heavy-quarkonium states in an expanding hot QCD medium by implementing effective field theory techniques in the framework of open quantum systems. The formalism incorporates quarkonium production and its subsequent evolution in the fireball including quarkonium dissociation and recombination. We consider a fireball with a local temperature that is much smaller than the inverse size of the quarkonium and much larger than its binding energy. The calculation is performed at an accuracy that is leading order in the heavy-quark density expansion and next-to-leading order in the multipole expansion. Within this accuracy, for a smooth variation of the temperature and large times, the evolution equation can be written as a Lindblad equation. We solve the Lindblad equation numerically both for a weakly coupled quark-gluon plasma and a strongly coupled medium. As an application, we compute the nuclear modification factor for the ϒ (1 S ) and ϒ (2 S ) states. We also consider the case of static quarks, which can be solved analytically. Our study fulfills three essential conditions: it conserves the total number of heavy quarks, it accounts for the non-Abelian nature of QCD, and it avoids classical approximations.

Partonic quasidistributions of the proton and pion from transverse-momentum distributions

NASA Astrophysics Data System (ADS)

Broniowski, Wojciech; Arriola, Enrique Ruiz

2018-02-01

The parton quasidistribution functions (QDFs) of Ji have been found by Radyushkin to be directly related to the transverse momentum distributions (TMDs), to the pseudodistributions, and to the Ioffe-time distributions (ITDs). This makes the QDF results at finite longitudinal momentum of the hadron interesting in their own right. Moreover, the QDF-TMD relation provides a gateway to the pertinent QCD evolution, with respect to the resolution scale Q , for the QDFs. Using the Kwieciński evolution equations and well established parametrizations at a low initial scale, we analyze the QCD evolution of quark and gluon QDF components of the proton and the pion. We discuss the resulting breaking of the longitudinal-transverse factorization and show that it has little impact on QDFs at the relatively low scales presently accessible on the lattice, but the effect is visible in reduced ITDs at sufficiently large values of the Ioffe time. Sum rules involving derivatives of ITDs and moments of the parton distribution functions (PDFs) are applied to the European Twisted Mass Collaboration lattice data. This allows us for a lattice determination of the transverse-momentum width of the TMDs from QDF studies.

Forward jet and particle production at HERA

NASA Astrophysics Data System (ADS)

Adloff, C.; Anderson, M.; Andreev, V.; Andrieu, B.; Arkadov, V.; Arndt, C.; Ayyaz, I.; Babaev, A.; Bähr, J.; Bán, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Bate, P.; Beck, M.; Beglarian, A.; Behnke, O.; Behrend, H.-J.; Beier, C.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bertrand-Coremans, G.; Biddulph, P.; Bizot, J. C.; Boudry, V.; Braunschweig, W.; Brisson, V.; Brown, D. P.; Brückner, W.; Bruel, P.; Bruncko, D.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Buschhorn, G.; Calvet, D.; Campbell, A. J.; Carli, T.; Chabert, E.; Charlet, M.; Clarke, D.; Clerbaux, B.; Cocks, S.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Cousinou, M.-C.; Cox, B. E.; Cozzika, G.; Cvach, J.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Davidsson, M.; De Roeck, A.; De Wolf, E. A.; Delcourt, B.; Demirchyan, R.; Diaconu, C.; Dirkmann, M.; Dixon, P.; Dlugosz, W.; Donovan, K. T.; Dowell, J. D.; Droutskoi, A.; Ebert, J.; Eckerlin, G.; Eckstein, D.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Elsen, E.; Enzenberger, M.; Erdmann, M.; Fahr, A. B.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Fleischer, M.; Flügge, G.; Fomenko, A.; Formánek, J.; Foster, J. M.; Franke, G.; Gabathuler, E.; Gabathuler, K.; Gaede, F.; Garvey, J.; Gayler, J.; Gerhards, R.; Ghazaryan, S.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Gorelov, I.; Grab, C.; Grässler, H.; Greenshaw, T.; Griffiths, R. K.; Grindhammer, G.; Hadig, T.; Haidt, D.; Hajduk, L.; Haller, T.; Hampel, M.; Haustein, V.; Haynes, W. J.; Heinemann, B.; Heinzelmann, G.; Henderson, R. C. W.; Hengstmann, S.; Henschel, H.; Heremans, R.; Herynek, I.; Hewitt, K.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoffmann, D.; Holtom, T.; Horisberger, R.; Hudgson, V. L.; Hurling, S.; Ibbotson, M.; İşsever, Ç.; Itterbeck, H.; Jacquet, M.; Jaffre, M.; Jansen, D. M.; Jönsson, L.; Johnson, D. P.; Jung, H.; Kästli, H. K.; Kander, M.; Kant, D.; Kapichine, M.; Karlsson, M.; Karschnik, O.; Katzy, J.; Kaufmann, O.; Kausch, M.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhne, J. H.; Kolanoski, H.; Kolya, S. D.; Korbel, V.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, K.; Küpper, A.; Küster, H.; Kuhlen, M.; Kurča, T.; Laforge, B.; Lahmann, R.; Landon, M. P. J.; Lange, W.; Langenegger, U.; Lebedev, A.; Lehner, F.; Lemaitre, V.; Lendermann, V.; Levonian, S.; Lindstroem, M.; List, B.; Lobo, G.; Lobodzinska, E.; Lubimov, V.; Lüke, D.; Lytkin, L.; Magnussen, N.; Mahlke-Krüger, H.; Malinovski, E.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martin, G.; Martyn, H.-U.; Martyniak, J.; Maxfield, S. J.; McMahon, S. J.; McMahon, T. R.; Mehta, A.; Meier, K.; Merkel, P.; Metlica, F.; Meyer, A.; Meyer, A.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Mikochi, S.; Milstead, D.; Moeck, J.; Mohr, R.; Mohrdieck, S.; Moreau, F.; Morris, J. V.; Müller, D.; Müller, K.; Murín, P.; Nagovizin, V.; Naroska, B.; Naumann, Th.; Négri, I.; Newman, P. R.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Niggli, H.; Nikitin, D.; Nix, O.; Nowak, G.; Nunnemann, T.; Oberlack, H.; Olsson, J. E.; Ozerov, D.; Palmen, P.; Panassik, V.; Pascaud, C.; Passaggio, S.; Patel, G. D.; Pawletta, H.; Perez, E.; Phillips, J. P.; Pieuchot, A.; Pitzl, D.; Pöschl, R.; Pope, G.; Povh, B.; Rabbertz, K.; Rauschenberger, J.; Reimer, P.; Reisert, B.; Rick, H.; Riess, S.; Rizvi, E.; Robmann, P.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rusakov, S.; Rybicki, K.; Sankey, D. P. C.; Schacht, P.; Scheins, J.; Schleif, S.; Schleper, P.; Schmidt, D.; Schmidt, D.; Schoeffel, L.; Schröder, V.; Schultz-Coulon, H.-C.; Schwab, B.; Sefkow, F.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Sirois, Y.; Sloan, T.; Smirnov, P.; Smith, M.; Solochenko, V.; Soloviev, Y.; Spaskov, V.; Specka, A.; Spiekermann, J.; Spitzer, H.; Squinabol, F.; Steffen, P.; Steinberg, R.; Steinhart, J.; Stella, B.; Stellberger, A.; Stiewe, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Swart, M.; Tapprogge, S.; Taševský, M.; Tchernyshov, V.; Tchetchelnitski, S.; Theissen, J.; Thompson, G.; Thompson, P. D.; Tobien, N.; Todenhagen, R.; Truöl, P.; Tsipolitis, G.; Turnau, J.; Tzamariudaki, E.; Udluft, S.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Van Esch, P.; Van Haecke, A.; Van Mechelen, P.; Vazdik, Y.; Villet, G.; Wacker, K.; Wallny, R.; Walter, T.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wengler, T.; Werner, M.; West, L. R.; Wiesand, S.; Wilksen, T.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wittmann, E.; Wobisch, M.; Wollatz, H.; Wünsch, E.; Žáček, J.; Zálešák, J.; Zhang, Z.; Zhokin, A.; Zini, P.; Zomer, F.; Zsembery, J.; zurNedden, M.; H1 Collaboration

1999-01-01

Single particles and jets in deeply inelastic scattering at low x are measured with the H1 detector in the region away from the current jet and towards the proton remnant, known as the forward region. Hadronic final state measurements in this region are expected to be particularly sensitive to QCD evolution effects. Jet cross sections are presented as a function of Bjorken- x for forward jets produced with a polar angle to the proton direction, θjet, in the range 7° < θjet < 20°. Azimuthal correlations are studied between the forward jet and the scattered lepton. Charged and neutral single particle production in the forward region are measured as a function of Bjorken- x, in the range 5° < θ < 25°, for particle transverse momenta larger than 1 GeV. QCD based Monte Carlo predictions and analytical calculations based on BFKL, CCFM and DGLAP evolution are compared to the data. Predictions based on the DGLAP approach fail to describe the data, except for those which allow for a resolved photon contribution.

The order of the quantum chromodynamics transition predicted by the standard model of particle physics.

PubMed

Aoki, Y; Endrodi, G; Fodor, Z; Katz, S D; Szabó, K K

2006-10-12

Quantum chromodynamics (QCD) is the theory of the strong interaction, explaining (for example) the binding of three almost massless quarks into a much heavier proton or neutron--and thus most of the mass of the visible Universe. The standard model of particle physics predicts a QCD-related transition that is relevant for the evolution of the early Universe. At low temperatures, the dominant degrees of freedom are colourless bound states of hadrons (such as protons and pions). However, QCD is asymptotically free, meaning that at high energies or temperatures the interaction gets weaker and weaker, causing hadrons to break up. This behaviour underlies the predicted cosmological transition between the low-temperature hadronic phase and a high-temperature quark-gluon plasma phase (for simplicity, we use the word 'phase' to characterize regions with different dominant degrees of freedom). Despite enormous theoretical effort, the nature of this finite-temperature QCD transition (that is, first-order, second-order or analytic crossover) remains ambiguous. Here we determine the nature of the QCD transition using computationally demanding lattice calculations for physical quark masses. Susceptibilities are extrapolated to vanishing lattice spacing for three physical volumes, the smallest and largest of which differ by a factor of five. This ensures that a true transition should result in a dramatic increase of the susceptibilities. No such behaviour is observed: our finite-size scaling analysis shows that the finite-temperature QCD transition in the hot early Universe was not a real phase transition, but an analytic crossover (involving a rapid change, as opposed to a jump, as the temperature varied). As such, it will be difficult to find experimental evidence of this transition from astronomical observations.

Study of exclusive charmless semileptonic B decays and |Vub|.

PubMed

Adam, N E; Alexander, J P; Berkelman, K; Cassel, D G; Duboscq, J E; Ehrlich, R; Fields, L; Gibbons, L; Gray, R; Gray, S W; Hartill, D L; Heltsley, B K; Hertz, D; Jones, C D; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Mahlke-Krüger, H; Meyer, T O; Onyisi, P U E; Patterson, J R; Peterson, D; Pivarski, J; Riley, D; Ryd, A; Sadoff, A J; Schwarthoff, H; Shi, X; Stroiney, S; Sun, W M; Wilksen, T; Weinberger, M; Athar, S B; Patel, R; Potlia, V; Yelton, J; Rubin, P; Cawlfield, C; Eisenstein, B I; Karliner, I; Kim, D; Lowrey, N; Naik, P; Selen, M; White, E J; Wiss, J; Mitchell, R E; Shepherd, M R; Besson, D; Pedlar, T K; Cronin-Hennessy, D; Gao, K Y; Hietala, J; Kubota, Y; Klein, T; Lang, B W; Poling, R; Scott, A W; Smith, A; Zweber, P; Dobbs, S; Metreveli, Z; Seth, K K; Tomaradze, A; Ernst, J; Ecklund, K M; Severini, H; Love, W; Savinov, V; Aquines, O; Li, Z; Lopez, A; Mehrabyan, S; Mendez, H; Ramirez, J; Huang, G S; Miller, D H; Pavlunin, V; Sanghi, B; Shipsey, I P J; Xin, B; Adams, G S; Anderson, M; Cummings, J P; Danko, I; Hu, D; Moziak, B; Napolitano, J; He, Q; Insler, J; Muramatsu, H; Park, C S; Thorndike, E H; Yang, F; Coan, T E; Gao, Y S; Artuso, M; Blusk, S; Butt, J; Li, J; Menaa, N; Mountain, R; Nisar, S; Randrianarivony, K; Sia, R; Skwarnicki, T; Stone, S; Wang, J C; Zhang, K; Bonvicini, G; Cinabro, D; Dubrovin, M; Lincoln, A; Asner, D M; Edwards, K W; Briere, R A; Ferguson, T; Tatishvili, G; Vogel, H; Watkins, M E; Rosner, J L

2007-07-27

We study semileptonic B decay to the exclusive charmless states pi, rho/omega, eta, and eta;{'} using the 16 fb(-1) CLEO Upsilon(4S) data sample. We find B(B0-->pi-l+nu)=(1.37+/-0.15stat+/-0.11sys)x10(-4) and B(B0-->rho-l+nu)=(2.93+/-0.37stat+/-0.37sys)x10(-4) and find evidence for B+-->eta'l+nu, with B(B+-->eta'l+nu)=(2.66+/-0.80stat+/-0.56sys)x10(-4). From our B-->pilnu rate for q2>16 GeV2 and lattice QCD, we find |Vub|=(3.6+/0.4stat+/0.2syst-0.4thy+0.6)x10(-3) [corrected

Exclusive vector meson photoproduction with a leading baryon in photon-hadron interactions at hadronic colliders

NASA Astrophysics Data System (ADS)

Carvalho, F.; Gonçalves, V. P.; Navarra, F. S.; Spiering, D.

2018-04-01

Exclusive vector meson photoproduction associated with a leading baryon (B =n ,Δ+,Δ0 ) in p p and p A collisions at RHIC and LHC energies is investigated using the color dipole formalism and taking into account nonlinear effects in the QCD dynamics. In particular, we compute the cross sections for ρ , ϕ and J /Ψ production together with a Δ and compare the predictions with those obtained for a leading neutron. Our results show that the V +Δ cross section is almost 30% of the V +n one. Our results also show that a future experimental analysis of these processes is, in principle, feasible and can be useful to study leading particle production.

Quantum Yang-Mills Dark Energy

NASA Astrophysics Data System (ADS)

Pasechnik, Roman

2016-02-01

In this short review, I discuss basic qualitative characteristics of quantum non-Abelian gauge dynamics in the non-stationary background of the expanding Universe in the framework of the standard Einstein--Yang--Mills formulation. A brief outlook of existing studies of cosmological Yang--Mills fields and their properties will be given. Quantum effects have a profound impact on the gauge field-driven cosmological evolution. In particular, a dynamical formation of the spatially-homogeneous and isotropic gauge field condensate may be responsible for both early and late-time acceleration, as well as for dynamical compensation of non-perturbative quantum vacua contributions to the ground state of the Universe. The main properties of such a condensate in the effective QCD theory at the flat Friedmann--Lema\\'itre--Robertson--Walker (FLRW) background will be discussed within and beyond perturbation theory. Finally, a phenomenologically consistent dark energy can be induced dynamically as a remnant of the QCD vacua compensation arising from leading-order graviton-mediated corrections to the QCD ground state.

Bsrightarrowtau+tau- decay in the general two Higgs doublet

NASA Astrophysics Data System (ADS)

Iltan, Erhan Onur; Turan, Gursevil

2002-11-01

We study the exclusive decay Bsrightarrowtau+tau- in the general two Higgs doublet model. We analyse the dependencies of the branching ratio on the model parameters, including the leading order QCD corrections. We found that there is an enhancement in the branching ratio, especially for rtb = bar xiN,ttU/bar xiN,bbD > 1 case. Further, the neutral Higgs effects are detectable for large values of the parameter bar xiN,tautauD.

Beam Spin Asymmetry in Exclusive ω Photoproduction off the Bound Proton

NASA Astrophysics Data System (ADS)

Cortes, Olga; Cole, Philip; CLAS Collaboration

2016-03-01

In this talk, we present preliminary results for the polarization observable beam-spin asymmetry, Σ, of the γ --> d --> ωp (n) reaction, where the ω meson was identified through its ω -->π+π-π0 decay. The data were taken during the E06-103 experiment with the CLAS detector in Hall B at Jefferson Laboratory. The experiment used the Hall-B Coherent Bremsstrahlung Facility to provide a high quality beam of linearly-polarized photons in the energy range from 1 . 1 to 2 . 3 GeV. We determined the beam-spin asymmetry of the ω's photoproduced off quasi-free protons in deuterium. We studied the evolution of Σ with photon energy and center-of-mass angle. This observable provides information on the underlying mechanisms responsible for s- and t-channel processes. Further, since the ω meson is an isoscalar (Iω = 0), the reaction of interest serves as an ideal isospin filter, as only N* states may contribute to the production process. Our results, together with studies of other reaction channels, serve to constrain the missing resonances predicted by QCD-inspired models of the nucleon's internal structure. This work is funded in part by NSF Grant PHY-1307340.

The cosmic QCD phase transition with dense matter and its gravitational waves from holography

NASA Astrophysics Data System (ADS)

Ahmadvand, M.; Bitaghsir Fadafan, K.

2018-04-01

Consistent with cosmological constraints, there are scenarios with the large lepton asymmetry which can lead to the finite baryochemical potential at the cosmic QCD phase transition scale. In this paper, we investigate this possibility in the holographic models. Using the holographic renormalization method, we find the first order Hawking-Page phase transition, between the Reissner-Nordström AdS black hole and thermal charged AdS space, corresponding to the de/confinement phase transition. We obtain the gravitational wave spectra generated during the evolution of bubbles for a range of the bubble wall velocity and examine the reliability of the scenarios and consequent calculations by gravitational wave experiments.

Exclusive Reactions at High Momentum Transfer

NASA Astrophysics Data System (ADS)

Radyushkin, Anatoly; Stoler, Paul

2008-03-01

Hard exclusive scattering at JLab / P. Kroll -- AdS/CFT and exclusive processes in QCD / S. J. Brodsky and G. F. de Téramond -- Hadron structure matters in collisions at high energy and momentum / A. W. Thomas -- Inclusive perspectives / P. Hoyer -- Fitting DVCS at NLO and beyond / K. Kumericki, D. Müller and K. Passek-Kumericki -- Spin-orbit correlations and single-spin asymmetries / M. Burkardt -- Electroproduction of soft pions at large momentum transfers / V. M. Braun, D. Yu. Ivanov and A. Peters -- Color transparency: 33 years and still running / M. Strikman -- Meson clouds and nucleon electromagnetic form factors / G. A. Miller -- Covariance, dynamics and symmetries, and hadron form factors / M. S. Bhagwat, I. C. Cloët and C. D. Roberts -- N to [symbol] electromagnetic and axial form factors in full QCD / C. Alexandrou -- Real and virtual compton scattering in perturbative QCD / C.-R. Ji and R. Thomson -- Deeply virtual compton scattering at Jefferson Lab / F. Sabatie -- DVCS at HERMES: recent results / F. Ellinghaus -- Deeply virtual compton scattering with CLAS / F. X. Girod -- Deeply virtual compton scattering off the neutron at JLab Hall A / M. Mazouz -- The future DVCS experiments in Hall A at JLab / J. Roche -- Deeply virtual compton scattering with CLAS12 / L. Elouadrhiri -- Quark helicity flip and the transverse spin dependence of inclusive DIS / A. Afanasev, M. Strikman and C. Weiss -- Deeply virtual pseudoscalar meson production / V. Kubarovsky and P. Stoler -- Exclusive p[symbol] electroproduction on the proton: GPDs or not GPDs? / M. Guidal and S. Morrow -- p[symbol] transverse target spin asymmetry at HERMES / A. Airapetian -- Electroproduction of ø(1020) mesons / J. P. Santoro and E. S. Smith -- Generalized parton distributions from hadronic observables / S. Ahmad ... [et al.] -- Imaging the proton via hard exclusive production in diffractive pp scattering / G. E. Hyde ... [et al.] -- Regge contributions to exclusive electro-production / A. P. Szczepaniak and J. T. Londergan -- High energy break-up of few-nucleon systems / M. Sargsian -- Photodisintegration of the deuteron, and [symbol]He / R. Gilman -- A review of the few-body form factors / G. G. Petratos -- Nucleon form factor measurements and interpretation / C. F. Perdrisat -- Implications of G[symbol](Q[symbol])/G[symbol](Q[symbol]) / S. Dubnicka and A. Z. Dubnickova -- High Q[symbol] large acceptance G[symbol]/G[symbol] measurements using polarization transfer / L. Pentchev, C. F. Perdrisat and B. Wojtsekhowski -- A precise measurement of the neutron magnetic form factor G[symbol] in the few-GeV[symbol] region / G. P. Gilfoyle et al. (the CLAS collaboration) -- Magnetic form factor of the neutron up to 8 (GeV/c)[symbol] / B. Quinn -- Timelike form factors / K. K. Seth -- Polarization phenomena in e[symbol]e[symbol] [symbol] pp¯ revisited / A. Z. Dubnickova and S. Dubnicka -- Light-cone sum rules for form factors of the N[symbol] transition at Q[symbol] = 0 / J. Rohrwild -- Exclusive electroproduction of [symbol] mesons / A. N. Villano (for the JLab E01-002 collaboration) -- Exclusive electroproduction of [symbol] mesons in the S[symbol](1535) resonance region at high momentum transfer / M. M. Dalton (for the JLab E01-002 collaboration) -- Two-photon exchange in electron-proton elastic scattering: theory update / A. V. Afanasev -- Two-photon exchange contributions to elastic ep scattering in the non-local field formalism / P. Jain, S. D. Joglekar and S. Mitra -- Beyond the born approximation: a precise comparison of positron-proton and electron-proton elastic scattering in CLAS / J. Lachniet et al. -- Meson form factors in the space-like region / D. Gaskell -- Pion-nucleon distribution amplitudes / A. Peters -- [symbol] scattering in the 1/N[symbol] expansion / H. J. Kwee -- [symbol] annihilations into quasi-two-body final states at 10.58 GeV / Kai Yi -- Transition distribution amplitudes / J. P. Lansberg, B. Pire and L. Szymanowski -- Novel QCD effects from initial and final state interactions / S. J. Brodsky -- Parton distributions and spin-orbital correlations / F. Yuan -- Transverse momentum dependences of distribution and fragmentation functions / D. S. Hwang and D. S. Kim -- Flavor dependence of the Boer-Mulders function and its influence on Azimuthal and single-spin asymmetries in semi-inclusive DIS / L. P. Gamberg, G. R. Goldstein and M. Schlegel -- Symmetric spin-dependent structure function in deep inelastic processes / D. S. Hwang, J. H. Kim and S. Kim -- HERMES recoil detector / R. Perez-Benito -- Inner calorimeter in CLAS/DVCS experiment / R. Niyazov -- Frozen-spin HD as a possible target for electro-production experiments / A. M. Sandorfi et al.

NLO evolution of color dipoles in N=4 SYM

DOE PAGES

Chirilli, Giovanni A.; Balitsky, Ian

2009-07-04

Here, high-energy behavior of amplitudes in a gauge theory can be reformulated in terms of the evolution of Wilson-line operators. In the leading logarithmic approximation it is given by the conformally invariant BK equation for the evolution of color dipoles. In QCD, the next-to-leading order BK equation has both conformal and non-conformal parts, the latter providing the running of the coupling constant. To separate the conformally invariant effects from the running-coupling effects, we calculate the NLO evolution of the color dipoles in the conformalmore » $${\\cal N}$$=4 SYM theory. We define the "composite dipole operator" with the rapidity cutoff preserving conformal invariance.« less

Exclusive photoproduction of J/ψ and ψ(2S) in pp and AA collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cisek, Anna; Schäfer, Wolfgang; Szczurek, Antoni

2015-04-10

The amplitude for γp → J/ψp(γp → ψ'p) is calculated in a pQCD k{sub ⊥}-factorization approach. The total cross section for this process is calculated for different unintegrated gluon distributions and compared with the HERA data and the data extracted recently by the LHCb collaboration. The amplitude for γp → J/ψp(γp → ψ'p) is used to predict the cross section for exclusive photoproduction of the J/ψ(ψ') meson in proton-proton and nucleus-nucleus collisions. In the pp case, compared to earlier calculations we include both Dirac and Pauli electromagnetic form factors. We also discuss the dependence of nuclear shadowing on the charmoniummore » state.« less

Scaling behavior in exclusive meson photoproduction from Jefferson Lab at large momentum transfers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dey, Biplab

2014-07-01

With the availability of new high-statistics and wide-angle measurements for several exclusive non-πN meson photoproduction channels from Jefferson Lab, we examine the fundamental scaling law of 90° scattering in QCD that was originally derived in the high-energy perturbative limit. The data show scaling to be prominently visible even in the medium-energy domain of 2.5 GeV ≲√s≲2.84 GeV, where √s is the center-of-mass energy. While constituent quark exchange suffices for pseudoscalar mesons, additional gluon exchanges from higher Fock states of the hadronic wave functions appear be needed for vector-meson production. Finally, the case of the Φ(1020), where two-gluon exchanges are knownmore » to dominate, is especially illuminating.« less

Peccei-Quinn relaxion

NASA Astrophysics Data System (ADS)

Jeong, Kwang Sik; Shin, Chang Sub

2018-01-01

The relaxation mechanism, which solves the electroweak hierarchy problem without relying on TeV scale new physics, crucially depends on how a Higgs-dependent back-reaction potential is generated. In this paper, we suggest a new scenario in which the scalar potential induced by the QCD anomaly is responsible both for the relaxation mechanism and the Peccei-Quinn mechanism to solve the strong CP problem. The key idea is to introduce the relaxion and the QCD axion whose cosmic evolutions become quite different depending on an inflaton-dependent scalar potential. Our scheme raises the cutoff scale of the Higgs mass up to 107 GeV, and allows reheating temperature higher than the electroweak scale as would be required for viable cosmology. In addition, the QCD axion can account for the observed dark matter of the universe as produced by the conventional misalignment mechanism. We also consider the possibility that the couplings of the Standard Model depend on the inflaton and become stronger during inflation. In this case, the relaxation can be implemented with a sub-Planckian field excursion of the relaxion for a cutoff scale below 10 TeV.

Continuous Advances in QCD 2008

NASA Astrophysics Data System (ADS)

Peloso, Marco M.

2008-12-01

1. High-order calculations in QCD and in general gauge theories. NLO evolution of color dipoles / I. Balitsky. Recent perturbative results on heavy quark decays / J. H. Piclum, M. Dowling, A. Pak. Leading and non-leading singularities in gauge theory hard scattering / G. Sterman. The space-cone gauge, Lorentz invariance and on-shell recursion for one-loop Yang-Mills amplitudes / D. Vaman, Y.-P. Yao -- 2. Heavy flavor physics. Exotic cc¯ mesons / E. Braaten. Search for new physics in B[symbol]-mixing / A. J. Lenz. Implications of D[symbol]-D[symbol] mixing for new physics / A. A. Petrov. Precise determinations of the charm quark mass / M. Steinhauser -- 3. Quark-gluon dynamics at high density and/or high temperature. Crystalline condensate in the chiral Gross-Neveu model / G. V. Dunne, G. Basar. The strong coupling constant at low and high energies / J. H. Kühn. Quarkyonic matter and the phase diagram of QCD / L. McLerran. Statistical QCD with non-positive measure / J. C. Osborn, K. Splittorff, J. J. M. Verbaarschot. From equilibrium to transport properties of strongly correlated fermi liquids / T. Schäfer. Lessons from random matrix theory for QCD at finite density / K. Splittorff, J. J. M. Verbaarschot -- 4. Methods and models of holographic correspondence. Soft-wall dynamics in AdS/QCD / B. Batell. Holographic QCD / N. Evans, E. Threlfall. QCD glueball sum rules and vacuum topology / H. Forkel. The pion form factor in AdS/QCD / H. J. Kwee, R. F. Lebed. The fast life of holographic mesons / R. C. Myers, A. Sinha. Properties of Baryons from D-branes and instantons / S. Sugimoto. The master space of N = 1 quiver gauge theories: counting BPS operators / A. Zaffaroni. Topological field congurations. Skyrmions in theories with massless adjoint quarks / R. Auzzi. Domain walls, localization and confinement: what binds strings inside walls / S. Bolognesi. Static interactions of non-abelian vortices / M. Eto. Vortices which do not abelianize dynamically: semi-classical origin of non-abelian monopoles / K. Konishi. A generalized construction for lumps and non-abelian vortices / W. Vinci -- 6. Dynamics in supersymmetric theories. Cusp anomalous dimension in planar maximally supersymmetric Yang-Mills theory / B. Basso. SO(2M) and USp(2M) (hyper)Kähler quotients and lumps / S. B. Gudnason -- 7. Other developments. Gluinos condensing at the CCNI: 4096 CPUs weigh in / J. Giedt ... [et al.]. Baryon Regge trajectories and the 1/N[symbol] expansion / J. L. Goity, N. Matagne. Infrared behavior of the fermion propagator in unquenched QED[symbol] with finite threshold effects / Y. Hoshino. Gauge fields in accelerated frames / F. Lenz. QCD at complex coupling, large order in perturbation theory and the gluon condensate / Y. Meurice. 511 KeV line and other diffuse emissions as a trace of the dark matter / A. R. Zhitnitsky -- 8. Glimpses of the conference.

Flavour symmetry breaking in the kaon parton distribution amplitude

DOE PAGES

none,

2014-11-01

We compute the kaon's valence-quark (twist-two parton) distribution amplitude (PDA) by projecting its Poincaré-covariant Bethe–Salpeter wave-function onto the light-front. At a scale ζ = 2 GeV, the PDA is a broad, concave and asymmetric function, whose peak is shifted 12–16% away from its position in QCD's conformal limit. These features are a clear expression of SU(3)-flavour-symmetry breaking. They show that the heavier quark in the kaon carries more of the bound-state's momentum than the lighter quark and also that emergent phenomena in QCD modulate the magnitude of flavour-symmetry breaking: it is markedly smaller than one might expect based on themore » difference between light-quark current masses. Our results add to a body of evidence which indicates that at any energy scale accessible with existing or foreseeable facilities, a reliable guide to the interpretation of experiment requires the use of such nonperturbatively broadened PDAs in leading-order, leading-twist formulae for hard exclusive processes instead of the asymptotic PDA associated with QCD's conformal limit. We illustrate this via the ratio of kaon and pion electromagnetic form factors: using our nonperturbative PDAs in the appropriate formulae, F K/F π=1.23 at spacelike-Q 2=17 GeV 2, which compares satisfactorily with the value of 0.92(5) inferred in e +e - annihilation at s=17 GeV 2.« less

Computer Simulation of Electron Positron Annihilation Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, y

2003-10-02

With the launching of the Next Linear Collider coming closer and closer, there is a pressing need for physicists to develop a fully-integrated computer simulation of e{sup +}e{sup -} annihilation process at center-of-mass energy of 1TeV. A simulation program acts as the template for future experiments. Either new physics will be discovered, or current theoretical uncertainties will shrink due to more accurate higher-order radiative correction calculations. The existence of an efficient and accurate simulation will help us understand the new data and validate (or veto) some of the theoretical models developed to explain new physics. It should handle well interfacesmore » between different sectors of physics, e.g., interactions happening at parton levels well above the QCD scale which are described by perturbative QCD, and interactions happening at much lower energy scale, which combine partons into hadrons. Also it should achieve competitive speed in real time when the complexity of the simulation increases. This thesis contributes some tools that will be useful for the development of such simulation programs. We begin our study by the development of a new Monte Carlo algorithm intended to perform efficiently in selecting weight-1 events when multiple parameter dimensions are strongly correlated. The algorithm first seeks to model the peaks of the distribution by features, adapting these features to the function using the EM algorithm. The representation of the distribution provided by these features is then improved using the VEGAS algorithm for the Monte Carlo integration. The two strategies mesh neatly into an effective multi-channel adaptive representation. We then present a new algorithm for the simulation of parton shower processes in high energy QCD. We want to find an algorithm which is free of negative weights, produces its output as a set of exclusive events, and whose total rate exactly matches the full Feynman amplitude calculation. Our strategy is to create the whole QCD shower as a tree structure generated by a multiple Poisson process. Working with the whole shower allows us to include correlations between gluon emissions from different sources. QCD destructive interference is controlled by the implementation of ''angular-ordering,'' as in the HERWIG Monte Carlo program. We discuss methods for systematic improvement of the approach to include higher order QCD effects.« less

Study of Exclusive Charmless Semileptonic B Decays and |Vub|

NASA Astrophysics Data System (ADS)

Adam, N. E.; Alexander, J. P.; Berkelman, K.; Cassel, D. G.; Duboscq, J. E.; Ehrlich, R.; Fields, L.; Gibbons, L.; Gray, R.; Gray, S. W.; Hartill, D. L.; Heltsley, B. K.; Hertz, D.; Jones, C. D.; Kandaswamy, J.; Kreinick, D. L.; Kuznetsov, V. E.; Mahlke-Krüger, H.; Meyer, T. O.; Onyisi, P. U. E.; Patterson, J. R.; Peterson, D.; Pivarski, J.; Riley, D.; Ryd, A.; Sadoff, A. J.; Schwarthoff, H.; Shi, X.; Stroiney, S.; Sun, W. M.; Wilksen, T.; Weinberger, M.; Athar, S. B.; Patel, R.; Potlia, V.; Yelton, J.; Rubin, P.; Cawlfield, C.; Eisenstein, B. I.; Karliner, I.; Kim, D.; Lowrey, N.; Naik, P.; Selen, M.; White, E. J.; Wiss, J.; Mitchell, R. E.; Shepherd, M. R.; Besson, D.; Pedlar, T. K.; Cronin-Hennessy, D.; Gao, K. Y.; Hietala, J.; Kubota, Y.; Klein, T.; Lang, B. W.; Poling, R.; Scott, A. W.; Smith, A.; Zweber, P.; Dobbs, S.; Metreveli, Z.; Seth, K. K.; Tomaradze, A.; Ernst, J.; Ecklund, K. M.; Severini, H.; Love, W.; Savinov, V.; Aquines, O.; Li, Z.; Lopez, A.; Mehrabyan, S.; Mendez, H.; Ramirez, J.; Huang, G. S.; Miller, D. H.; Pavlunin, V.; Sanghi, B.; Shipsey, I. P. J.; Xin, B.; Adams, G. S.; Anderson, M.; Cummings, J. P.; Danko, I.; Hu, D.; Moziak, B.; Napolitano, J.; He, Q.; Insler, J.; Muramatsu, H.; Park, C. S.; Thorndike, E. H.; Yang, F.; Coan, T. E.; Gao, Y. S.; Artuso, M.; Blusk, S.; Butt, J.; Li, J.; Menaa, N.; Mountain, R.; Nisar, S.; Randrianarivony, K.; Sia, R.; Skwarnicki, T.; Stone, S.; Wang, J. C.; Zhang, K.; Bonvicini, G.; Cinabro, D.; Dubrovin, M.; Lincoln, A.; Asner, D. M.; Edwards, K. W.; Briere, R. A.; Ferguson, T.; Tatishvili, G.; Vogel, H.; Watkins, M. E.; Rosner, J. L.

2007-07-01

We study semileptonic B decay to the exclusive charmless states π, ρ/ω, η, and η' using the 16fb-1 CLEO Υ(4S) data sample. We find B(B0→π-ℓ+ν)=(1.37±0.15stat±0.11sys)×10-4 and B(B0→ρ-ℓ+ν)=(2.93±0.37stat±0.37sys)×10-4 and find evidence for B+→η'ℓ+ν, with B(B+→η'ℓ+ν)=(2.66±0.80stat±0.56sys)×10-4. From our B→πℓν rate for q2>16GeV2 and lattice QCD, we find |Vub|=(3.6±0.4stat±0.2syst-0.4thy+0.6)×10-3.

Role and convergent evolution of competing RNA secondary structures in mutually exclusive splicing

PubMed Central

Yue, Yuan; Hou, Shouqing; Wang, Xiu; Zhan, Leilei; Cao, Guozheng; Li, Guoli; Shi, Yang; Zhang, Peng; Hong, Weiling; Lin, Hao; Liu, Baoping; Shi, Feng; Yang, Yun; Jin, Yongfeng

2017-01-01

ABSTRACT Exon or cassette duplication is an important means of expanding protein and functional diversity through mutually exclusive splicing. However, the mechanistic basis of this process in non-arthropod species remains poorly understood. Here, we demonstrate that MRP1 genes underwent tandem exon duplication in Nematoda, Platyhelminthes, Annelida, Mollusca, Arthropoda, Echinodermata, and early-diverging Chordata but not in late-diverging vertebrates. Interestingly, these events were of independent origin in different phyla, suggesting convergent evolution of alternative splicing. Furthermore, we showed that multiple sets of clade-conserved RNA pairings evolved to guide species-specific mutually exclusive splicing in Arthropoda. Importantly, we also identified a similar structural code in MRP exon clusters of the annelid, Capitella teleta, and chordate, Branchiostoma belcheri, suggesting an evolutionarily conserved competing pairing-guided mechanism in bilaterians. Taken together, these data reveal the molecular determinants and RNA pairing-guided evolution of species-specific mutually exclusive splicing spanning more than 600 million years of bilaterian evolution. These findings have a significant impact on our understanding of the evolution of and mechanism underpinning isoform diversity and complex gene structure. PMID:28277933

Role and convergent evolution of competing RNA secondary structures in mutually exclusive splicing.

PubMed

Yue, Yuan; Hou, Shouqing; Wang, Xiu; Zhan, Leilei; Cao, Guozheng; Li, Guoli; Shi, Yang; Zhang, Peng; Hong, Weiling; Lin, Hao; Liu, Baoping; Shi, Feng; Yang, Yun; Jin, Yongfeng

2017-10-03

Exon or cassette duplication is an important means of expanding protein and functional diversity through mutually exclusive splicing. However, the mechanistic basis of this process in non-arthropod species remains poorly understood. Here, we demonstrate that MRP1 genes underwent tandem exon duplication in Nematoda, Platyhelminthes, Annelida, Mollusca, Arthropoda, Echinodermata, and early-diverging Chordata but not in late-diverging vertebrates. Interestingly, these events were of independent origin in different phyla, suggesting convergent evolution of alternative splicing. Furthermore, we showed that multiple sets of clade-conserved RNA pairings evolved to guide species-specific mutually exclusive splicing in Arthropoda. Importantly, we also identified a similar structural code in MRP exon clusters of the annelid, Capitella teleta, and chordate, Branchiostoma belcheri, suggesting an evolutionarily conserved competing pairing-guided mechanism in bilaterians. Taken together, these data reveal the molecular determinants and RNA pairing-guided evolution of species-specific mutually exclusive splicing spanning more than 600 million years of bilaterian evolution. These findings have a significant impact on our understanding of the evolution of and mechanism underpinning isoform diversity and complex gene structure.

Transverse energy and forward jet production in the low x regime at HERA

NASA Astrophysics Data System (ADS)

Aid, S.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Bähr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Brasse, F.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M. J.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Colombo, M.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Coutures, Ch; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Delcourt, B.; Del Buono, L.; De Roeck, A.; De Wolf, E. A.; Di Nezza, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Ehrlichmann, H.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Garvey, J.; Gayler, J.; Gebauer, M.; Gellrich, A.; Genzel, H.; Gerhards, R.; Glazov, A.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Gonzalez-Pineiro, B.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Hampel, M.; Hapke, M.; Haynes, W. J.; Heatherington, J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hildesheim, W.; Hill, P.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Horisberger, R.; Hudgson, V. L.; Huet, Ph; Hütte, M.; Hufnagel, H.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kant, D.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Krüner-Marquis, U.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lacour, D.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Lanius, P.; Laporte, J.-F.; Lebedev, A.; Lehner, F.; Leverenz, C.; Levonian, S.; Ley, Ch; Lindner, A.; Lindström, G.; Link, J.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lohmander, H.; Lomas, J. W.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, G.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, A.; Meyer, C. A.; Meyer, H.; Meyer, J.; Migliori, A.; Mikocki, S.; Milstead, D.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th; Newman, P. R.; Newton, D.; Neyret, D.; Nguyen, H. K.; Nicholls, T. C.; Nieberball, F.; Niebuhr, C.; Niedzballa, Ch; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Ozerov, D.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Peppel, E.; Perez, E.; Phillips, J. P.; Pichler, Ch; Pieuchot, A.; Pitzl, D.; Pope, G.; Prell, S.; Prosi, R.; Rabbertz, K.; Rädel, G.; Raupach, F.; Reimer, P.; Reinshagen, S.; Ribarics, P.; Rick, H.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Rylko, R.; Sahlmann, N.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleif, S.; Schleper, P.; von Schlippe, W.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Sciacca, G.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Solochenko, V.; Soloviev, Y.; Spiekermann, J.; Spitzer, H.; Starosta, R.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stiewe, J.; Stößlein, U.; Stolze, K.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Tchernyshov, V.; Thiebaux, C.; Thompson, G.; Truöl, P.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Vandenplas, D.; Van Esch, P.; Van Mechelen, P.; Vartapetian, A.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walther, A.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wellisch, H. P.; West, L. R.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wright, A. E.; Wünsch, E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zimmer, M.; Zimmermann, W.; Zomer, F.; Zuber, K.; zur Nedden, M.; H1 Collaboration

1995-02-01

The production of transverse energy in deep inelastic scattering is measured as a function of the kinematic variables x and Q2 using the H1 detector at the ep collider HERA. The results are compared to the different predictions based upon two alternative QCD evolution equations, namely the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) and the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equations. In a pseudorapidity interval which is central in the hadronic centre of mass system between the current and the proton remnant fragmentation region the produced transverse energy increases with decreasing x for constant Q2. Such a behaviour can be explained with a QCD calculation based upon the BFKL ansatz. The rate of forward jets, proposed as a signature for BFKL dynamics, has been measured.

JEWEL 2.0.0: directions for use

NASA Astrophysics Data System (ADS)

Zapp, Korinna

2014-02-01

In this publication the first official release of the Jewel 2.0.0 code [The first version Jewel 1 (Zapp et al. in Eur Phys J C 60:617, 2009) could only treat elastic scattering explicitly and the code was never published, The code can be downloaded from the official Jewel homepage http://jewel.hepforge.org] is presented. Jewel is a Monte Carlo event generator simulating QCD jet evolution in heavy-ion collisions. It treats the interplay of QCD radiation and re-scattering in a medium with fully microscopic dynamics in a consistent perturbative framework with minimal assumptions. After a qualitative introduction into the physics of Jewel detailed information about the practical aspects of using the code is given. The code is available from the official Jewel homepage http://jewel.hepforge.org.

PEGASYS---A proposed internal target facility for the PEP storage ring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Biber, K.

A proposal for an integral gas-jet target and forward spectrometer for the PEP storage ring is described. The beam structure, allowable, luminosity (L = 10/sup 33/ cm/sup /minus/2/s/sup /minus/1/ for H/sub 2/, D/sub 2/) and energy (E/sub e/ less than or equal to 15 GeV) make the ring ideal for multiparticle coincidence studies in the scaling regime, and where perturbative QCD may be an apt description of some exclusive and semi-inclusive reactions. 14 refs., 7 figs.

Open charm production in double parton scattering processes in the forward kinematics

DOE PAGES

Blok, B.; Strikman, M.

2016-12-18

We calculate the rate of double open charm production in the forward kinematics studied recently in the LHCb experiment.We find that the mean field approximation for the double partonGPD (generalized parton distributions), which neglects parton–parton correlations, underestimates the rate by a factor of 2. The enhancement due to the perturbative QCD correlation 1Ⓧ2 mechanism which explains the rate of double parton interactions at the central rapidities is found to explain 60 ÷ 80% of the discrepancy. We argue that the nonperturbative fluctuations leading to nonfactorized (correlated) contributions to the initial conditions for the DGLAP collinear evolution of the double partonmore » GPD play an important role in this kinematics. Combined, the two correlation mechanisms provide a good description of the rate of double charm production reported by the LHCb. We also give predictions for the variation of the σeff (i.e. the ratio of double and square of single inclusive rates) in the discussed kinematics as a function of pt . The account for two correlation mechanisms strongly reduces the sensitivity of the results to the starting point of the QCD evolution.« less

Thermal behavior of Charmonium in the vector channel from QCD sum rules

NASA Astrophysics Data System (ADS)

Dominguez, C. A.; Loewe, M.; Rojas, J. C.; Zhang, Y.

2010-11-01

The thermal evolution of the hadronic parameters of charmonium in the vector channel, i.e. the J/Ψ resonance mass, coupling (leptonic decay constant), total width, and continuum threshold are analyzed in the framework of thermal Hilbert moment QCD sum rules. The continuum threshold s0 has the same behavior as in all other hadronic channels, i.e. it decreases with increasing temperature until the PQCD threshold s0 = 4mQ2 is reached at T≃1.22Tc (mQ is the charm quark mass). The other hadronic parameters behave in a very different way from those of light-light and heavy-light quark systems. The J/Ψ mass is essentially constant in a wide range of temperatures, while the total width grows with temperature up to T≃1.04Tc beyond which it decreases sharply with increasing T. The resonance coupling is also initially constant beginning to increase monotonically around T≃Tc. This behavior of the total width and of the leptonic decay constant is a strong indication that the J/Ψ resonance might survive beyond the critical temperature for deconfinement, in agreement with some recent lattice QCD results.

Refining new-physics searches in B→Dτν with lattice QCD.

PubMed

Bailey, Jon A; Bazavov, A; Bernard, C; Bouchard, C M; Detar, C; Du, Daping; El-Khadra, A X; Foley, J; Freeland, E D; Gámiz, E; Gottlieb, Steven; Heller, U M; Kim, Jongjeong; Kronfeld, A S; Laiho, J; Levkova, L; Mackenzie, P B; Meurice, Y; Neil, E T; Oktay, M B; Qiu, Si-Wei; Simone, J N; Sugar, R; Toussaint, D; Van de Water, R S; Zhou, Ran

2012-08-17

The semileptonic decay channel B→Dτν is sensitive to the presence of a scalar current, such as that mediated by a charged-Higgs boson. Recently, the BABAR experiment reported the first observation of the exclusive semileptonic decay B→Dτ(-)ν, finding an approximately 2σ disagreement with the standard-model prediction for the ratio R(D)=BR(B→Dτν)/BR(B→Dℓν), where ℓ = e,μ. We compute this ratio of branching fractions using hadronic form factors computed in unquenched lattice QCD and obtain R(D)=0.316(12)(7), where the errors are statistical and total systematic, respectively. This result is the first standard-model calculation of R(D) from ab initio full QCD. Its error is smaller than that of previous estimates, primarily due to the reduced uncertainty in the scalar form factor f(0)(q(2)). Our determination of R(D) is approximately 1σ higher than previous estimates and, thus, reduces the tension with experiment. We also compute R(D) in models with electrically charged scalar exchange, such as the type-II two-Higgs-doublet model. Once again, our result is consistent with, but approximately 1σ higher than, previous estimates for phenomenologically relevant values of the scalar coupling in the type-II model. As a by-product of our calculation, we also present the standard-model prediction for the longitudinal-polarization ratio P(L)(D)=0.325(4)(3).

Exclusive ϱ0 production in deep inelastic electron-proton scattering at HERA

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Mikunas, D.; Musgrave, B.; Repond, J.; Stanek, R.; Talaga, R. L.; Zhang, H.; Ayad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Cara Romeo, G.; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Contin, A.; Corradi, M.; Gialas, I.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Zamora Garcia, Y.; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Eckert, M.; Feld, L.; Frey, A.; Geerts, M.; Grothe, M.; Hartmann, H.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mari, S. M.; Mengel, S.; Mollen, J.; Paul, E.; Pfeiffer, M.; Rembser, Ch.; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Llewellyn, T. J.; Morgado, C. J. S.; Norman, D. J. P.; O'Mara, J. A.; Tapper, R. J.; Wilson, S. S.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Capua, M.; Garfagnini, A.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Cartiglia, N.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Zhu, Q.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Beier, H.; Bienlein, J. K.; Coldewey, C.; Deppe, O.; Desler, K.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Glasman, C.; Göttlicher, P.; Große-Knetter, J.; Gutjahr, B.; Haas, T.; Hain, W.; Hasell, D.; Heßling, H.; Iga, Y.; Johnson, K.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mainusch, J.; Mańczak, O.; Monteiro, T.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schulz, W.; Selonke, F.; Stiliaris, E.; Surrow, B.; Voß, T.; Westphal, D.; Wolf, G.; Youngman, C.; Zeuner, W.; Zhou, J. F.; Grabosch, H. J.; Kharchilava, A.; Leich, A.; Mattingly, M. C. K.; Meyer, A.; Schlenstedt, S.; Wulff, N.; Barbagli, G.; Pelfer, P.; Anzivino, G.; Maccarrone, G.; De Pasquale, S.; Votano, L.; Bamberger, A.; Eisenhardt, S.; Freidhof, A.; Söldner-Rembold, S.; Schroeder, J.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Fleck, J. I.; Saxon, D. H.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Hagge, L.; Lohrmann, E.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Zetsche, F.; Bacon, T. C.; Bruemmer, N.; Butterworth, I.; Gallo, E.; Harris, V. L.; Hung, B. Y. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Nam, S. W.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Fernandez, J. P.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; Martinez, M.; del Peso, J.; Puga, J.; Terron, J.; de Trocóniz, J. F.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; St. Laurent, M.; Ullmann, R.; Zacek, G.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Yu. A.; Kobrin, V. D.; Korzhavina, I. A.; Kurzhavina, V. A.; Kuzmin, V. A.; Lukina, O. Yu.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. 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L.; Barberis, E.; Dubbs, T.; Heusch, C.; Van Hook, M.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Williams, D. C.; Biltzinger, J.; Seifert, R. J.; Schwarzer, O.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nakamitsu, Y.; Yamauchi, K.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Polenz, S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Blankenship, K.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchuła, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Karshon, U.; Revel, D.; Zer-Zion, D.; Ali, I.; Badgett, W. F.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Vaiciulis, A.; Wodarczyk, M.; Tsurugai, T.; Bhadra, S.; Cardy, M. L.; Fagerstroem, C.-P.; Frisken, W. R.; Furutani, K. M.; Khakzad, M.; Schmidke, W. B.; ZEUS Collaboration

1995-02-01

The exclusive production of ϱ0 mesons in deep inelastic electron-proton scattering has been studied using the ZEUS detector. Cross sections have been measured in the range 7 < Q2 < 25 GeV 2 for λ ∗p centre of mass (c.m.) energies 40 to 130 GeV. The λ ∗p → ϱ 0p cross section exhibits a Q-(4.2±0.8 -0.5+1.4) dependence and both longitudinally and transversely polarised ϱ0's are observed. The λ ∗p → ϱ 0p cross section rises strongly with increasing c.m. energy, when compared with NMC data at lower energy, which cannot be explained by production through soft pomeron exchange. The data are compared with perturbative QCD calculations where the rise in the cross section reflects the increase in the gluon density at low x.

Study of B Meson Production in p+Pb Collisions at √[S(NN)]=5.02 TeV Using Exclusive Hadronic Decays.

PubMed

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Swartz, M; Xiao, M; Xin, Y; You, C; Baringer, P; Bean, A; Benelli, G; Bruner, C; Kenny, R P; Majumder, D; Malek, M; Murray, M; Sanders, S; Stringer, R; Wang, Q; Ivanov, A; Kaadze, K; Khalil, S; Makouski, M; Maravin, Y; Mohammadi, A; Saini, L K; Skhirtladze, N; Toda, S; Lange, D; Rebassoo, F; Wright, D; Anelli, C; Baden, A; Baron, O; Belloni, A; Calvert, B; Eno, S C; Ferraioli, C; Gomez, J A; Hadley, N J; Jabeen, S; Kellogg, R G; Kolberg, T; Kunkle, J; Lu, Y; Mignerey, A C; Shin, Y H; Skuja, A; Tonjes, M B; Tonwar, S C; Apyan, A; Barbieri, R; Baty, A; Bierwagen, K; Brandt, S; Busza, W; Cali, I A; Demiragli, Z; Di Matteo, L; Gomez Ceballos, G; Goncharov, M; Gulhan, D; Iiyama, Y; Innocenti, G M; Klute, M; Kovalskyi, D; Lai, Y S; Lee, Y-J; Levin, A; Luckey, P D; Marini, A C; Mcginn, C; Mironov, C; Niu, X; Paus, C; Ralph, D; Roland, C; Roland, G; Salfeld-Nebgen, J; Stephans, G S F; Sumorok, K; Varma, M; Velicanu, D; Veverka, J; Wang, J; Wang, T W; Wyslouch, B; Yang, M; Zhukova, V; Dahmes, B; Finkel, A; Gude, A; Hansen, P; Kalafut, S; Kao, S C; Klapoetke, K; Kubota, Y; Lesko, Z; Mans, J; Nourbakhsh, S; Ruckstuhl, N; Rusack, R; Tambe, N; Turkewitz, J; Acosta, J G; Oliveros, S; Avdeeva, E; Bloom, K; Bose, S; Claes, D R; Dominguez, A; Fangmeier, C; Gonzalez Suarez, R; Kamalieddin, R; Keller, J; Knowlton, D; Kravchenko, I; Lazo-Flores, J; Meier, F; Monroy, J; Ratnikov, F; Siado, J E; Snow, G R; Alyari, M; Dolen, J; George, J; Godshalk, A; Harrington, C; Iashvili, I; Kaisen, J; Kharchilava, A; Kumar, A; Rappoccio, S; Alverson, G; Barberis, E; Baumgartel, D; Chasco, M; Hortiangtham, A; Massironi, A; Morse, D M; Nash, D; Orimoto, T; Teixeira De Lima, R; Trocino, D; Wang, R-J; Wood, D; Zhang, J; Hahn, K A; Kubik, A; Mucia, N; Odell, N; Pollack, B; Pozdnyakov, A; Schmitt, M; Stoynev, S; Sung, K; Trovato, M; Velasco, M; Brinkerhoff, A; Dev, N; Hildreth, M; Jessop, C; Karmgard, D J; Kellams, N; Lannon, K; Lynch, S; Marinelli, N; Meng, F; Mueller, C; Musienko, Y; Pearson, T; Planer, M; Reinsvold, A; Ruchti, R; Smith, G; Taroni, S; Valls, N; Wayne, M; Wolf, M; Woodard, A; Antonelli, L; Brinson, J; Bylsma, B; Durkin, L S; Flowers, S; Hart, A; Hill, C; Hughes, R; Ji, W; Kotov, K; Ling, T Y; Liu, B; Luo, W; Puigh, D; Rodenburg, M; Winer, B L; Wulsin, H W; Driga, O; Elmer, P; Hardenbrook, J; Hebda, P; Koay, S A; Lujan, P; Marlow, D; Medvedeva, T; Mooney, M; Olsen, J; Palmer, C; Piroué, P; Quan, X; Saka, H; Stickland, D; Tully, C; Werner, J S; Zuranski, A; Malik, S; Barnes, V E; Benedetti, D; Bortoletto, D; Gutay, L; Jha, M K; Jones, M; Jung, K; Kress, M; Miller, D H; Neumeister, N; Radburn-Smith, B C; Shi, X; Shipsey, I; Silvers, D; Sun, J; Svyatkovskiy, A; Wang, F; Xie, W; Xu, L; Parashar, N; Stupak, J; Adair, A; Akgun, B; Chen, Z; Ecklund, K M; Geurts, F J M; Guilbaud, M; Li, W; Michlin, B; Northup, M; Padley, B P; Redjimi, R; Roberts, J; Rorie, J; Tu, Z; Zabel, J; Betchart, B; Bodek, A; de Barbaro, P; Demina, R; Eshaq, Y; Ferbel, T; Galanti, M; Garcia-Bellido, A; Han, J; Harel, A; Hindrichs, O; Khukhunaishvili, A; Petrillo, G; Verzetti, M; Demortier, L; Arora, S; Barker, A; Chou, J P; Contreras-Campana, C; Contreras-Campana, E; Duggan, D; Ferencek, D; Gershtein, Y; Gray, R; Halkiadakis, E; Hidas, D; Hughes, E; Kaplan, S; Kunnawalkam Elayavalli, R; Lath, A; Nash, K; Panwalkar, S; Park, M; Salur, S; Schnetzer, S; Sheffield, D; Somalwar, S; Stone, R; Thomas, S; Thomassen, P; Walker, M; Foerster, M; Riley, G; Rose, K; Spanier, S; York, A; Bouhali, O; Castaneda Hernandez, A; Dalchenko, M; De Mattia, M; Delgado, A; Dildick, S; Eusebi, R; Flanagan, W; Gilmore, J; Kamon, T; Krutelyov, V; Montalvo, R; Mueller, R; Osipenkov, I; Pakhotin, Y; Patel, R; Perloff, A; Roe, J; Rose, A; Safonov, A; Tatarinov, A; Ulmer, K A; Akchurin, N; Cowden, C; Damgov, J; Dragoiu, C; Dudero, P R; Faulkner, J; Kunori, S; Lamichhane, K; Lee, S W; Libeiro, T; Undleeb, S; Volobouev, I; Appelt, E; Delannoy, A G; Greene, S; Gurrola, A; Janjam, R; Johns, W; Maguire, C; Mao, Y; Melo, A; Ni, H; Sheldon, P; Snook, B; Tuo, S; Velkovska, J; Xu, Q; Arenton, M W; Boutle, S; Cox, B; Francis, B; Goodell, J; Hirosky, R; Ledovskoy, A; Li, H; Lin, C; Neu, C; Wolfe, E; Wood, J; Xia, F; Clarke, C; Harr, R; Karchin, P E; Kottachchi Kankanamge Don, C; Lamichhane, P; Sturdy, J; Belknap, D A; Carlsmith, D; Cepeda, M; Christian, A; Dasu, S; Dodd, L; Duric, S; Friis, E; Gomber, B; Hall-Wilton, R; Herndon, M; Hervé, A; Klabbers, P; Lanaro, A; Levine, A; Long, K; Loveless, R; Mohapatra, A; Ojalvo, I; Perry, T; Pierro, G A; Polese, G; Ross, I; Ruggles, T; Sarangi, T; Savin, A; Sharma, A; Smith, N; Smith, W H; Taylor, D; Woods, N

2016-01-22

The production cross sections of the B^{+}, B^{0}, and B_{s}^{0} mesons, and of their charge conjugates, are measured via exclusive hadronic decays in p+Pb collisions at the center-of-mass energy sqrt[s_{NN}]=5.02  TeV with the CMS detector at the CERN LHC. The data set used for this analysis corresponds to an integrated luminosity of 34.6  nb^{-1}. The production cross sections are measured in the transverse momentum range between 10 and 60  GeV/c. No significant modification is observed compared to proton-proton perturbative QCD calculations scaled by the number of incoherent nucleon-nucleon collisions. These results provide a baseline for the study of in-medium b quark energy loss in Pb+Pb collisions.

A first determination of the unpolarized quark TMDs from a global analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bacchetta, Alessandro; Delcarro, Filippo; Pisano, Cristian

Transverse momentum dependent distribution and fragmentation functions of unpolarized quarks inside unpolarized protons are extracted, for the first time, through a simultaneous analysis of semi-inclusive deep-inelastic scattering, Drell-Yan and Z boson hadroproduction processes. This study is performed at leading order in perturbative QCD, with energy scale evolution at the next-to-leading logarithmic accuracy. Moreover, some specific choices are made to deal with low scale evolution around 1 GeV2. Since only data in the low transverse momentum region are considered, no matching to fixed-order calculations at high transverse momentum is needed.

Studying the Puzzle of the Pion Nucleon Sigma Term

NASA Astrophysics Data System (ADS)

Kane, Christopher; Lin, Huey-Wen

2017-09-01

The pion nucleon sigma term (σπN) is a fundamental parameter of QCD and is integral in the experimental search for dark matter particles as it is used to calculate the cross section of interactions between potential dark matter candidates and nucleons. Recent calculations of this term from lattice-QCD data disagree with calculations done using phenomenological data. This disparity is large enough to cause concern in the dark matter community as it would change the constraints on their experiments. We investigate one potential source of this disparity by studying the flavor dependence on LQCD data used to calculate σπN. To calculate σπN, we study the nucleon mass dependence on the pion mass and implement the Hellmann-Feynman Theorem. Previous calculations only consider LQCD data that accounted for 2 and 3 of the lightest quarks in the quark sea. We extend this study by using new high statistic data that considers 2, 3, and 4 quarks in the quark sea to see if the exclusion of the heavier quarks can account for this disparity. National Science Foundation.

Next-to-leading order QCD corrections to the decay of Higgs to vector meson and Z boson

NASA Astrophysics Data System (ADS)

Sun, Qing-Feng; Wang, An-Min

2018-02-01

The exclusive decay of the Higgs boson to a vector meson (J/ψ or Υ(1S)) and Z boson is studied in this work. The decay amplitudes are separated into two parts in a gauge invariant manner. The first part comes from the direct coupling of the Higgs boson to the charm (bottom) quark and the other from the HZZ* or the loop-induced HZ γ* vertexes in the standard model. While the branching ratios from the direct channel are much smaller than those of the indirect channel, their interference terms give nontrivial contributions. We further calculate the QCD radiative corrections to both channels, which reduce the total branching ratios by around 20% for both (J/ψ or Υ(1S)) production. Our results provide a possible chance to check the SM predictions of the {{Hc}}\\bar{{{c}}}({{Hb}}\\bar{{{b}}}) coupling and to seek for hints of new physics at the High Luminosity LHC or future hadron colliders. Supported by National Natural Science Foundation of China (11375168)

Perturbative QCD analysis of exclusive processes e+e-→V P and e+e-→T P

NASA Astrophysics Data System (ADS)

Lü, Cai-Dian; Wang, Wei; Xing, Ye; Zhang, Qi-An

2018-06-01

We study the e+e-→V P and e+e-→T P processes in the perturbative QCD approach based on kT factorization, where the P , V and T denotes a light pseudoscalar, vector, and tensor meson, respectively. We point out in the case of e+e-→T P transition due to charge conjugation invariance, only three channels are allowed: e+e-→a2±π∓ , e+e-→K2*±K∓ and the V-spin suppressed e+e-→K2*0K¯ 0+K¯2 *0K0 . Cross sections of e+e-→V P and e+e-→T P at √{s }=3.67 GeV and √{s }=10.58 GeV are calculated and the invariant mass dependence is found to favor the 1 /s4 power law. Most of our theoretical results are consistent with the available experimental data and other predictions can be tested at the ongoing BESIII and forthcoming Belle-II experiments.

QCD-Electroweak First-Order Phase Transition in a Supercooled Universe.

PubMed

Iso, Satoshi; Serpico, Pasquale D; Shimada, Kengo

2017-10-06

If the electroweak sector of the standard model is described by classically conformal dynamics, the early Universe evolution can be substantially altered. It is already known that-contrarily to the standard model case-a first-order electroweak phase transition may occur. Here we show that, depending on the model parameters, a dramatically different scenario may happen: A first-order, six massless quark QCD phase transition occurs first, which then triggers the electroweak symmetry breaking. We derive the necessary conditions for this dynamics to occur, using the specific example of the classically conformal B-L model. In particular, relatively light weakly coupled particles are predicted, with implications for collider searches. This scenario is also potentially rich in cosmological consequences, such as renewed possibilities for electroweak baryogenesis, altered dark matter production, and gravitational wave production, as we briefly comment upon.

The Evolution of Soft Collinear Effective Theory

DOE PAGES

Lee, Christopher

2015-02-25

Soft Collinear Effective Theory (SCET) is an effective field theory of Quantum Chromodynamics (QCD) for processes where there are energetic, nearly lightlike degrees of freedom interacting with one another via soft radiation. SCET has found many applications in high-energy and nuclear physics, especially in recent years the physics of hadronic jets in e +e -, lepton-hadron, hadron-hadron, and heavy-ion collisions. SCET can be used to factorize multi-scale cross sections in these processes into single-scale hard, collinear, and soft functions, and to evolve these through the renormalization group to resum large logarithms of ratios of the scales that appear in themore » QCD perturbative expansion, as well as to study properties of nonperturbative effects. We overview the elementary concepts of SCET and describe how they can be applied in high-energy and nuclear physics.« less

QCD-Electroweak First-Order Phase Transition in a Supercooled Universe

NASA Astrophysics Data System (ADS)

Iso, Satoshi; Serpico, Pasquale D.; Shimada, Kengo

2017-10-01

If the electroweak sector of the standard model is described by classically conformal dynamics, the early Universe evolution can be substantially altered. It is already known that—contrarily to the standard model case—a first-order electroweak phase transition may occur. Here we show that, depending on the model parameters, a dramatically different scenario may happen: A first-order, six massless quark QCD phase transition occurs first, which then triggers the electroweak symmetry breaking. We derive the necessary conditions for this dynamics to occur, using the specific example of the classically conformal B -L model. In particular, relatively light weakly coupled particles are predicted, with implications for collider searches. This scenario is also potentially rich in cosmological consequences, such as renewed possibilities for electroweak baryogenesis, altered dark matter production, and gravitational wave production, as we briefly comment upon.

Transverse momentum-dependent parton distribution functions from lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael Engelhardt, Philipp Haegler, Bernhard Musch, John Negele, Andreas Schaefer

Transverse momentum-dependent parton distributions (TMDs) relevant for semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process can be defined in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection. Starting from such a definition, a scheme to determine TMDs in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are obtained using ensembles at the pion masses 369MeV and 518MeV, focusing in particularmore » on the dependence of these shifts on the staple extent and a Collins-Soper-type evolution parameter quantifying proximity of the staples to the light cone.« less

Hard QCD processes in the nuclear medium

NASA Astrophysics Data System (ADS)

Freese, Adam

The environment inside the atomic nucleus is one of the most fascinating arenas for the study of quantum chromodynamics (QCD). The strongly-interacting nature of the nuclear medium a?ects the nature of both QCD processes and the quark-gluon structure of hadrons, allowing several unique aspects of the strong nuclear force to be investigated in reactions involving nuclear targets. The research presented in this dissertation explores two aspects of nuclear QCD: firstly, the partonic structure of the nucleus itself; and secondly, the use of the nucleus as a micro-laboratory in which QCD processes can be studied. The partonic structure of the nucleus is calculated in this work by deriving and utilizing a convolution formula. The hadronic structure of the nucleus and the quark-gluon structure of its constituent nucleons are taken together to determine the nuclear partonic structure. Light cone descriptions of short range correlations, in terms of both hadronic and partonic structure, are derived and taken into account. Medium modifications of the bound nucleons are accounted for using the color screening model, and QCD evolution is used to connect nuclear partonic structure at vastly di?erent energy scales. The formalism developed for calculating nuclear partonic structure is applied to inclusive dijet production from proton-nucleus collisions at LHC kinematics, and novel predictions are calculated and presented for the dijet cross section. The nucleus is investigated as a micro-laboratory in vector meson photoproduction reactions. In particular, the deuteron is studied in the break-up reaction gammad → Vpn, for both the φ(1020) and J/v vector mesons. The generalized eikonal approximation is utilized, allowing unambiguous separation of the impulse approximation and final state interactions (FSIs). Two peaks or valleys are seen in the angular distribution of the reaction cross section, each of which is due to an FSI between either the proton and neutron, or the produced vector meson and the spectator nucleon. The presence and size of the latter FSI valley/peak contains information about the meson-nucleon interaction, and it is shown that several models of this interaction can be distinguished by measuring the angular distribution for the deuteron breakup reaction.

PEGASYS: A proposed internal target-spectrometer facility for the PEP storage ring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Bibber, K.

A proposal for an internal gas-jet target and forward spectrometer for the PEP storage ring is described. The beam structure, allowable luminosity (L=10/sup 33/ cm/sup /minus/2/s/sup /minus/1/ for H/sub 2/, D/sub 2/ decreasing as Z/sup /minus/1.75/ for nuclear targets) and energy (E/sub e/less than or equal to 15 GeV) make the ring ideal for multiparticle coincidence studies in the scaling regime, and where perturbative QCD may be an apt description of some exclusive and semi-inclusive reactions. 17 refs., 5 figs.

The Light-Front Schrödinger Equation and Determination of the Perturbative QCD Scale from Color Confinement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; de Teramond, Guy F.; Deur, Alexandre P.

2015-09-01

The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a relativistic equation of motion with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. If one requires that the effective action which underlies the QCD Lagrangian remains conformally invariant and extends the formalism of de Alfaro, Fubini and Furlan to light front Hamiltonian theory, the potential U has a unique form of a harmonic oscillator potential, and a mass gap arises. The result is a nonperturbative relativistic light-front quantum mechanical wave equation which incorporates color confinement and other essential spectroscopic andmore » dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the same slope in the radial quantum number n and orbital angular momentum L. Only one mass parameter κ appears. Light-front holography thus provides a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. We also show how the mass scale κ underlying confinement and hadron masses determines the scale Λ {ovr MS} controlling the evolution of the perturbative QCD coupling. The relation between scales is obtained by matching the nonperturbative dynamics, as described by an effective conformal theory mapped to the light-front and its embedding in AdS space, to the perturbative QCD regime computed to four-loop order. The result is an effective coupling defined at all momenta. The predicted value Λ {ovr MS}=0.328±0.034 GeV is in agreement with the world average 0.339±0.010 GeV. The analysis applies to any renormalization scheme.« less

Exclusive and Semi-Exclusive Reactions at a Higher Energy CEBAF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carl Carlson

More energy at CEBAF provides more opportunity for studies of hadron and nuclear properties. Many of the experiments that could be done are extensions of things already done at lower energies. Others represent new initiatives that could not work or could not theoretically be interpreted at lower energies. The author concentrates on the new initiatives, but do not wish our thinking to neglect what can be learned from continuations of lower energy work. The author begins with a list of some things that should be continued into a new energy regime. (1) Baryon and meson spectroscopy of higher mass states.more » With 4 GeV incoming electron energy, strange mesons are limited to 1.8 GeV in mass and charm is not producible. (2) Exclusive reactions, including meson and baryon form factors and reactions on few nucleon systems. The latter includes deuteron photodisintegration, the A and B form factors of the deuteron, and the deuteron tensor polarization T{sub 20}. (And we should not forget T{sub 20} in inclusive scattering.) (3) Hadrons in the nuclear medium, with such topics as color transparency, electroproduction of {rho} mesons, virtual Compton scattering off nuclei, and backward hadrons from e-d reactions. The very last must be especially important, since it gives the logo used in the advertizing for this conference. In addition, there are new initiatives that this talk will call attention to, in particular: (1) semi-exclusive meson production; (2) duality in semi-exclusive reactions; and (3) new views of exclusive reactions and perturbative QCD (leading to ''off-forward parton distributions'').« less

Naturalizing supersymmetry with a two-field relaxion mechanism

DOE PAGES

Evans, Jason L.; Gherghetta, Tony; Nagata, Natsumi; ...

2016-09-26

We present a supersymmetric version of a two-field relaxion model that naturalizes tuned versions of supersymmetry. This arises from a relaxion mechanism that does not depend on QCD dynamics and where the relaxion potential barrier height is controlled by a second axion-like field. During the cosmological evolution, the relaxion rolls with a nonzero value that breaks supersymmetry and scans the soft supersymmetric mass terms. Electroweak symmetry is broken after the soft masses become of order the supersymmetric Higgs mass term and causes the relaxion to stop rolling for superpartner masses up to ~10 9 GeV. This can explain the tuningmore » in supersymmetric models, including split-SUSY models, while preserving the QCD axion solution to the strong CP problem. Furthermore, besides predicting two very weakly-coupled axion-like particles, the supersymmetric spectrum may contain an extra Goldstino, which could be a viable dark matter candidate.« less

Pion distribution amplitude from lattice QCD.

PubMed

Cloët, I C; Chang, L; Roberts, C D; Schmidt, S M; Tandy, P C

2013-08-30

A method is explained through which a pointwise accurate approximation to the pion's valence-quark distribution amplitude (PDA) may be obtained from a limited number of moments. In connection with the single nontrivial moment accessible in contemporary simulations of lattice-regularized QCD, the method yields a PDA that is a broad concave function whose pointwise form agrees with that predicted by Dyson-Schwinger equation analyses of the pion. Under leading-order evolution, the PDA remains broad to energy scales in excess of 100 GeV, a feature which signals persistence of the influence of dynamical chiral symmetry breaking. Consequently, the asymptotic distribution φπ(asy)(x) is a poor approximation to the pion's PDA at all such scales that are either currently accessible or foreseeable in experiments on pion elastic and transition form factors. Thus, related expectations based on φ φπ(asy)(x) should be revised.

Parton distribution functions with QED corrections in the valon model

NASA Astrophysics Data System (ADS)

Mottaghizadeh, Marzieh; Taghavi Shahri, Fatemeh; Eslami, Parvin

2017-10-01

The parton distribution functions (PDFs) with QED corrections are obtained by solving the QCD ⊗QED DGLAP evolution equations in the framework of the "valon" model at the next-to-leading-order QCD and the leading-order QED approximations. Our results for the PDFs with QED corrections in this phenomenological model are in good agreement with the newly related CT14QED global fits code [Phys. Rev. D 93, 114015 (2016), 10.1103/PhysRevD.93.114015] and APFEL (NNPDF2.3QED) program [Comput. Phys. Commun. 185, 1647 (2014), 10.1016/j.cpc.2014.03.007] in a wide range of x =[10-5,1 ] and Q2=[0.283 ,108] GeV2 . The model calculations agree rather well with those codes. In the latter, we proposed a new method for studying the symmetry breaking of the sea quark distribution functions inside the proton.

Leading-twist parton distribution amplitudes of S-wave heavy-quarkonia

DOE PAGES

Ding, Minghui; Gao, Fei; Chang, Lei; ...

2015-12-08

Here, the leading-twist parton distribution amplitudes (PDAs) of ground-state 1S 0 and 3S 1 cc¯- and bb¯quarkonia are calculated using a symmetry-preserving continuum treatment of the meson bound-state problem which unifies the properties of these heavy-quark systems with those of light-quark bound-states, including QCD's Goldstone modes. Analysing the evolution of 1S 0 and 3S 1 PDAs with current-quark mass, m^ q, increasing away from the chiral limit, it is found that in all cases there is a value of m^ q for which the PDA matches the asymptotic form appropriate to QCD's conformal limit and hence is insensitive to changesmore » in renormalisation scale, ζ. This mass lies just above that associated with the s-quark. At current-quark masses associated with heavy-quarkonia, on the other hand, the PDAs are piecewise convex–concave–convex.« less

Selected inversion as key to a stable Langevin evolution across the QCD phase boundary

NASA Astrophysics Data System (ADS)

Bloch, Jacques; Schenk, Olaf

2018-03-01

We present new results of full QCD at nonzero chemical potential. In PRD 92, 094516 (2015) the complex Langevin method was shown to break down when the inverse coupling decreases and enters the transition region from the deconfined to the confined phase. We found that the stochastic technique used to estimate the drift term can be very unstable for indefinite matrices. This may be avoided by using the full inverse of the Dirac operator, which is, however, too costly for four-dimensional lattices. The major breakthrough in this work was achieved by realizing that the inverse elements necessary for the drift term can be computed efficiently using the selected inversion technique provided by the parallel sparse direct solver package PARDISO. In our new study we show that no breakdown of the complex Langevin method is encountered and that simulations can be performed across the phase boundary.

Bottomonium suppression using a lattice QCD vetted potential

NASA Astrophysics Data System (ADS)

Krouppa, Brandon; Rothkopf, Alexander; Strickland, Michael

2018-01-01

We estimate bottomonium yields in relativistic heavy-ion collisions using a lattice QCD vetted, complex-valued, heavy-quark potential embedded in a realistic, hydrodynamically evolving medium background. We find that the lattice-vetted functional form and temperature dependence of the proper heavy-quark potential dramatically reduces the dependence of the yields on parameters other than the temperature evolution, strengthening the picture of bottomonium as QGP thermometer. Our results also show improved agreement between computed yields and experimental data produced in RHIC 200 GeV /nucleon collisions. For LHC 2.76 TeV /nucleon collisions, the excited states, whose suppression has been used as a vital sign for quark-gluon-plasma production in a heavy-ion collision, are reproduced better than previous perturbatively-motivated potential models; however, at the highest LHC energies our estimates for bottomonium suppression begin to underestimate the data. Possible paths to remedy this situation are discussed.

Sivers and Boer-Mulders observables from lattice QCD

NASA Astrophysics Data System (ADS)

Musch, B. U.; Hägler, Ph.; Engelhardt, M.; Negele, J. W.; Schäfer, A.

2012-05-01

We present a first calculation of transverse momentum-dependent nucleon observables in dynamical lattice QCD employing nonlocal operators with staple-shaped, “process-dependent” Wilson lines. The use of staple-shaped Wilson lines allows us to link lattice simulations to TMD effects determined from experiment, and, in particular, to access nonuniversal, naively time-reversal odd TMD observables. We present and discuss results for the generalized Sivers and Boer-Mulders transverse momentum shifts for the SIDIS and DY cases. The effect of staple-shaped Wilson lines on T-even observables is studied for the generalized tensor charge and a generalized transverse shift related to the worm-gear function g1T. We emphasize the dependence of these observables on the staple extent and the Collins-Soper evolution parameter. Our numerical calculations use an nf=2+1 mixed action scheme with domain wall valence fermions on an Asqtad sea and pion masses 369 MeV as well as 518 MeV.

Next-to-leading order weighted Sivers asymmetry in semi-inclusive deep inelastic scattering: three-gluon correlator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Lingyun; Prokudin, Alexei; Kang, Zhong-Bo

2015-09-01

We study the three-gluon correlation function contribution to the Sivers asymmetry in semi-inclusive deep inelastic scattering. We first establish the matching between the usual twist-3 collinear factorization approach and transverse momentum dependent factorization formalism for the moderate transverse momentum region. We then derive the so-called coefficient functions used in the usual TMD evolution formalism. Finally, we perform the next-to-leading order calculation for the transverse-momentum-weighted spin-dependent differential cross section, from which we identify the QCD collinear evolution of the twist-3 Qiu-Sterman function: the off-diagonal contribution from the three-gluon correlation functions.

Evolution equation in the field theory of strings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marui, M.; Sugamoto, A.; Oda, I.

This paper reports on a stringy version of the Altarelli-Parisi equation given within the field theory of bosonic strings formulated in the light-cone gauge. Using this equation, the authors study the behavior of the decay function of strings under the change of reference scale, especially imposing an assumption of large transverse momentum. In some cases the n-th moment of the decay function behaves very differently from QCD.

Multiscale Monte Carlo equilibration: Two-color QCD with two fermion flavors

DOE PAGES

Detmold, William; Endres, Michael G.

2016-12-02

In this study, we demonstrate the applicability of a recently proposed multiscale thermalization algorithm to two-color quantum chromodynamics (QCD) with two mass-degenerate fermion flavors. The algorithm involves refining an ensemble of gauge configurations that had been generated using a renormalization group (RG) matched coarse action, thereby producing a fine ensemble that is close to the thermalized distribution of a target fine action; the refined ensemble is subsequently rethermalized using conventional algorithms. Although the generalization of this algorithm from pure Yang-Mills theory to QCD with dynamical fermions is straightforward, we find that in the latter case, the method is susceptible tomore » numerical instabilities during the initial stages of rethermalization when using the hybrid Monte Carlo algorithm. We find that these instabilities arise from large fermion forces in the evolution, which are attributed to an accumulation of spurious near-zero modes of the Dirac operator. We propose a simple strategy for curing this problem, and demonstrate that rapid thermalization--as probed by a variety of gluonic and fermionic operators--is possible with the use of this solution. Also, we study the sensitivity of rethermalization rates to the RG matching of the coarse and fine actions, and identify effective matching conditions based on a variety of measured scales.« less

The Emergence of Hadrons from QCD Color

NASA Astrophysics Data System (ADS)

Brooks, William; Color Dynamics in Cold Matter (CDCM) Collaboration

2015-10-01

The formation of hadrons from energetic quarks, the dynamical enforcement of QCD confinement, is not well understood at a fundamental level. In Deep Inelastic Scattering, modifications of the distributions of identified hadrons emerging from nuclei of different sizes reveal a rich variety of spatial and temporal characteristics of the hadronization process, including its dependence on spin, flavor, energy, and hadron mass and structure. The EIC will feature a wide range of kinematics, allowing a complete investigation of medium-induced gluon bremsstrahlung by the propagating quarks, leading to partonic energy loss. This fundamental process, which is also at the heart of jet quenching in heavy ion collisions, can be studied for light and heavy quarks at the EIC through observables quantifying hadron ``attenuation'' for a variety of hadron species. Transverse momentum broadening of hadrons, which is sensitive to the nuclear gluonic field, will also be accessible, and can be used to test our understanding from pQCD of how this quantity evolves with pathlength, as well as its connection to partonic energy loss. The evolution of the forming hadrons in the medium will shed new light on the dynamical origins of the forces between hadrons, and thus ultimately on the nuclear force. Supported by the Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) of Chile.

Examination of the relevance of hydrodynamics for data measured at the BNL relativistic heavy ion collider

NASA Astrophysics Data System (ADS)

Trainor, Thomas A.

2010-08-01

Hydrodynamic (hydro) models applied to heavy ion data from the relativistic heavy ion collider (RHIC) suggest that a dense QCD medium nearly opaque to partons—a strongly coupled quark-gluon plasma—is formed in more-central Au-Au collisions and may have a small viscosity ('perfect liquid'). Claimed evidence for radial and elliptic flows and possible coalescence of 'constituent quarks' seems to support the conclusion. But other measurements provide contradictory evidence. Unbiased angular correlations indicate that most back-to-back jets from initial-state scattered partons with energies as low as 3 GeV survive as 'minijet' hadron correlations even in central Au-Au collisions, suggesting near transparency. Two-component analysis of single-particle spectra reveals a spectrum hard component (parton fragment distribution) which can be mistaken for 'radial flow' in some forms of analysis. Based on recent results, reinterpretation of 'elliptic flow' as a QCD quadrupole scattering process including fragmentation may be possible. In this paper we review conventional analysis methods in the context of two paradigms: a hydrodynamics/hard-probes paradigm and a quadrupole/minijets paradigm. Re-examination of fiducial data suggests that hydrodynamics may not be relevant to RHIC collisions. Collision evolution may be dominated by QCD scattering and fragmentation, albeit strongly modified in more-central A-A collisions.

Constraining the physics of jet quenching

NASA Astrophysics Data System (ADS)

Renk, Thorsten

2012-04-01

Hard probes in the context of ultrarelativistic heavy-ion collisions represent a key class of observables studied to gain information about the QCD medium created in such collisions. However, in practice, the so-called jet tomography has turned out to be more difficult than expected initially. One of the major obstacles in extracting reliable tomographic information from the data is that neither the parton-medium interaction nor the medium geometry are known with great precision, and thus a difference in model assumptions in the hard perturbative Quantum Choromdynamics (pQCD) modeling can usually be compensated by a corresponding change of assumptions in the soft bulk medium sector and vice versa. The only way to overcome this problem is to study the full systematics of combinations of parton-medium interaction and bulk medium evolution models. This work presents a meta-analysis summarizing results from a number of such systematical studies and discusses in detail how certain data sets provide specific constraints for models. Combining all available information, only a small group of models exhibiting certain characteristic features consistent with a pQCD picture of parton-medium interaction is found to be viable given the data. In this picture, the dominant mechanism is medium-induced radiation combined with a surprisingly small component of elastic energy transfer into the medium.

QCD constituent counting rules for neutral vector mesons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; Lebed, Richard F.; Lyubovitskij, Valery E.

QCD constituent counting rules define the scaling behavior of exclusive hadronic scattering and electromagnetic scattering amplitudes at high momentum transfer in terms of the total number of fundamental constituents in the initial and final states participating in the hard subprocess. The scaling laws reflect the twist of the leading Fock state for each hadron and hence the leading operator that creates the composite state from the vacuum. Thus, the constituent counting scaling laws can be used to identify the twist of exotic hadronic candidates such as tetraquarks and pentaquarks. Effective field theories must consistently implement the scaling rules in ordermore » to be consistent with the fundamental theory. Here in this paper, we examine how one can apply constituent counting rules for the exclusive production of one or two neutral vector mesons V 0 in e + e - annihilation, processes in which the V 0 can couple via intermediate photons. In the case of a (narrow) real V 0, the photon virtuality is fixed to a precise value s 1 = m2V 0, thus treating the V 0 as a single fundamental particle. Each real V 0 thus contributes to the constituent counting rules with NV0 = 1 . In effect, the leading operator underlying the V 0 has twist 1. Thus, in the specific physical case of single or double on-shell V 0 production via intermediate photons, the predicted scaling from counting rules coincides with vector-meson dominance (VMD), an effective theory that treats V 0 as an elementary field. However, the VMD prediction fails in the general case where the V 0 is not coupled through an elementary photon field, and then the leading-twist interpolating operator has twist NV 0 = 2 . Analogous effects appear in pp scattering processes.« less

QCD constituent counting rules for neutral vector mesons

NASA Astrophysics Data System (ADS)

Brodsky, Stanley J.; Lebed, Richard F.; Lyubovitskij, Valery E.

2018-02-01

QCD constituent counting rules define the scaling behavior of exclusive hadronic scattering and electromagnetic scattering amplitudes at high momentum transfer in terms of the total number of fundamental constituents in the initial and final states participating in the hard subprocess. The scaling laws reflect the twist of the leading Fock state for each hadron and hence the leading operator that creates the composite state from the vacuum. Thus, the constituent counting scaling laws can be used to identify the twist of exotic hadronic candidates such as tetraquarks and pentaquarks. Effective field theories must consistently implement the scaling rules in order to be consistent with the fundamental theory. Here, we examine how one can apply constituent counting rules for the exclusive production of one or two neutral vector mesons V0 in e+e- annihilation, processes in which the V0 can couple via intermediate photons. In the case of a (narrow) real V0, the photon virtuality is fixed to a precise value s1=mV02, thus treating the V0 as a single fundamental particle. Each real V0 thus contributes to the constituent counting rules with NV0=1. In effect, the leading operator underlying the V0 has twist 1. Thus, in the specific physical case of single or double on-shell V0 production via intermediate photons, the predicted scaling from counting rules coincides with vector-meson dominance (VMD), an effective theory that treats V0 as an elementary field. However, the VMD prediction fails in the general case where the V0 is not coupled through an elementary photon field, and then the leading-twist interpolating operator has twist NV 0=2 . Analogous effects appear in p p scattering processes.

QCD constituent counting rules for neutral vector mesons

DOE PAGES

Brodsky, Stanley J.; Lebed, Richard F.; Lyubovitskij, Valery E.

2018-02-08

QCD constituent counting rules define the scaling behavior of exclusive hadronic scattering and electromagnetic scattering amplitudes at high momentum transfer in terms of the total number of fundamental constituents in the initial and final states participating in the hard subprocess. The scaling laws reflect the twist of the leading Fock state for each hadron and hence the leading operator that creates the composite state from the vacuum. Thus, the constituent counting scaling laws can be used to identify the twist of exotic hadronic candidates such as tetraquarks and pentaquarks. Effective field theories must consistently implement the scaling rules in ordermore » to be consistent with the fundamental theory. Here in this paper, we examine how one can apply constituent counting rules for the exclusive production of one or two neutral vector mesons V 0 in e + e - annihilation, processes in which the V 0 can couple via intermediate photons. In the case of a (narrow) real V 0, the photon virtuality is fixed to a precise value s 1 = m2V 0, thus treating the V 0 as a single fundamental particle. Each real V 0 thus contributes to the constituent counting rules with NV0 = 1 . In effect, the leading operator underlying the V 0 has twist 1. Thus, in the specific physical case of single or double on-shell V 0 production via intermediate photons, the predicted scaling from counting rules coincides with vector-meson dominance (VMD), an effective theory that treats V 0 as an elementary field. However, the VMD prediction fails in the general case where the V 0 is not coupled through an elementary photon field, and then the leading-twist interpolating operator has twist NV 0 = 2 . Analogous effects appear in pp scattering processes.« less

Emergence of homeostasis and “noise imprinting” in an evolution model

PubMed Central

Stern, Michael D.

1999-01-01

Homeostasis, the creation of a stabilized internal milieu, is ubiquitous in biological evolution, despite the entropic cost of excluding noise information from a region. The advantages of stability seem self evident, but the alternatives are not so clear. This issue was studied by means of numerical experiments on a simple evolution model: a population of Boolean network “organisms” selected for performance of a curve-fitting task while subjected to noise. During evolution, noise sensitivity increased with fitness. Noise exclusion evolved spontaneously, but only if the noise was sufficiently unpredictable. Noise that was limited to one or a few stereotyped patterns caused symmetry breaking that prevented noise exclusion. Instead, the organisms incorporated the noise into their function at little cost in ultimate fitness and became totally noise dependent. This “noise imprinting” suggests caution when interpreting apparent adaptations seen in nature. If the noise was totally random from generation to generation, noise exclusion evolved reliably and irreversibly, but if the noise was correlated over several generations, maladaptive selection of noise-dependent traits could reverse noise exclusion, with catastrophic effect on population fitness. Noise entering the selection process rather than the organism had a different effect: adaptive evolution was totally abolished above a critical noise amplitude, in a manner resembling a thermodynamic phase transition. Evolutionary adaptation to noise involves the creation of a subsystem screened from noise information but increasingly vulnerable to its effects. Similar considerations may apply to information channeling in human cultural evolution. PMID:10485897

Deeply Virtual Exclusive Processes and Generalized Parton Distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

,

2011-06-01

The goal of the comprehensive program in Deeply Virtual Exclusive Scattering at Jefferson Laboratory is to create transverse spatial images of quarks and gluons as a function of their longitudinal momentum fraction in the proton, the neutron, and in nuclei. These functions are the Generalized Parton Distributions (GPDs) of the target nucleus. Cross section measurements of the Deeply Virtual Compton Scattering (DVCS) reaction ep {yields} ep{gamma} in Hall A support the QCD factorization of the scattering amplitude for Q^2 {>=} 2 GeV^2. Quasi-free neutron-DVCS measurements on the Deuteron indicate sensitivity to the quark angular momentum sum rule. Fully exclusive H(e,more » e'p{gamma} ) measurements have been made in a wide kinematic range in CLAS with polarized beam, and with both unpolarized and longitudinally polarized targets. Existing models are qualitatively consistent with the JLab data, but there is a clear need for less constrained models. Deeply virtual vector meson production is studied in CLAS. The 12 GeV upgrade will be essential for for these channels. The {rho} and {omega} channels reactions offer the prospect of flavor sensitivity to the quark GPDs, while the {phi}-production channel is dominated by the gluon distribution.« less

Experimental access to Transition Distribution Amplitudes with the P¯ANDA experiment at FAIR

NASA Astrophysics Data System (ADS)

Singh, B. P.; Erni, W.; Keshelashvili, I.; Krusche, B.; Steinacher, M.; Liu, B.; Liu, H.; Liu, Z.; Shen, X.; Wang, C.; Zhao, J.; Albrecht, M.; Fink, M.; Heinsius, F. H.; Held, T.; Holtmann, T.; Koch, H.; Kopf, B.; Kümmel, M.; Kuhl, G.; Kuhlmann, M.; Leyhe, M.; Mikirtychyants, M.; Musiol, P.; Mustafa, A.; Pelizäus, M.; Pychy, J.; Richter, M.; Schnier, C.; Schröder, T.; Sowa, C.; Steinke, M.; Triffterer, T.; Wiedner, U.; Beck, R.; Hammann, C.; Kaiser, D.; Ketzer, B.; Kube, M.; Mahlberg, P.; Rossbach, M.; Schmidt, C.; Schmitz, R.; Thoma, U.; Walther, D.; Wendel, C.; Wilson, A.; Bianconi, A.; Bragadireanu, M.; Caprini, M.; Pantea, D.; Pietreanu, D.; Vasile, M. E.; Patel, B.; Kaplan, D.; Brandys, P.; Czyzewski, T.; Czyzycki, W.; Domagala, M.; Hawryluk, M.; Filo, G.; Krawczyk, M.; Kwiatkowski, D.; Lisowski, E.; Lisowski, F.; Fiutowski, T.; Idzik, M.; Mindur, B.; Przyborowski, D.; Swientek, K.; Czech, B.; Kliczewski, S.; Korcyl, K.; Kozela, A.; Kulessa, P.; Lebiedowicz, P.; Malgorzata, K.; Pysz, K.; Schäfer, W.; Siudak, R.; Szczurek, A.; Biernat, J.; Jowzaee, S.; Kamys, B.; Kistryn, S.; Korcyl, G.; Krzemien, W.; Magiera, A.; Moskal, P.; Palka, M.; Psyzniak, A.; Rudy, Z.; Salabura, P.; Smyrski, J.; Strzempek, P.; Wrońska, A.; Augustin, I.; Lehmann, I.; Nicmorus, D.; Schepers, G.; Schmitt, L.; Al-Turany, M.; Cahit, U.; Capozza, L.; Dbeyssi, A.; Deppe, H.; Dzhygadlo, R.; Ehret, A.; Flemming, H.; Gerhardt, A.; Götzen, K.; Karabowicz, R.; Kliemt, R.; Kunkel, J.; Kurilla, U.; Lehmann, D.; Lühning, J.; Maas, F.; Morales Morales, C.; Mora Espí, M. C.; Nerling, F.; Orth, H.; Peters, K.; Rodríguez Piñeiro, D.; Saito, N.; Saito, T.; Sánchez Lorente, A.; Schmidt, C. J.; Schwarz, C.; Schwiening, J.; Traxler, M.; Valente, R.; Voss, B.; Wieczorek, P.; Wilms, A.; Zühlsdorf, M.; Abazov, V. M.; Alexeev, G.; Arefiev, A.; Astakhov, V. I.; Barabanov, M. Yu.; Batyunya, B. V.; Davydov, Yu. I.; Dodokhov, V. Kh.; Efremov, A. A.; Fedunov, A. G.; Festchenko, A. A.; Galoyan, A. S.; Grigoryan, S.; Karmokov, A.; Koshurnikov, E. K.; Lobanov, V. I.; Lobanov, Yu. Yu.; Makarov, A. F.; Malinina, L. V.; Malyshev, V. L.; Mustafaev, G. A.; Olshevskiy, A.; Pasyuk, M. A.; Perevalova, E. A.; Piskun, A. A.; Pocheptsov, T. A.; Pontecorvo, G.; Rodionov, V. K.; Rogov, Yu. N.; Salmin, R. A.; Samartsev, A. G.; Sapozhnikov, M. G.; Shabratova, G. S.; Skachkov, N. B.; Skachkova, A. N.; Strokovsky, E. A.; Suleimanov, M. K.; Teshev, R. Sh.; Tokmenin, V. V.; Uzhinsky, V. V.; Vodopyanov, A. S.; Zaporozhets, S. A.; Zhuravlev, N. I.; Zorin, A. G.; Branford, D.; Glazier, D.; Watts, D.; Woods, P.; Britting, A.; Eyrich, W.; Lehmann, A.; Uhlig, F.; Dobbs, S.; Seth, K.; Tomaradze, A.; Xiao, T.; Bettoni, D.; Carassiti, V.; Cotta Ramusino, A.; Dalpiaz, P.; Drago, A.; Fioravanti, E.; Garzia, I.; Savriè, M.; Stancari, G.; Akishina, V.; Kisel, I.; Kulakov, I.; Zyzak, M.; Arora, R.; Bel, T.; Gromliuk, A.; Kalicy, G.; Krebs, M.; Patsyuk, M.; Zuehlsdorf, M.; Bianchi, N.; Gianotti, P.; Guaraldo, C.; Lucherini, V.; Pace, E.; Bersani, A.; Bracco, G.; Macri, M.; Parodi, R. F.; Bianco, S.; Bremer, D.; Brinkmann, K. T.; Diehl, S.; Dormenev, V.; Drexler, P.; Düren, M.; Eissner, T.; Etzelmüller, E.; Föhl, K.; Galuska, M.; Gessler, T.; Gutz, E.; Hayrapetyan, A.; Hu, J.; Kröck, B.; Kühn, W.; Kuske, T.; Lange, S.; Liang, Y.; Merle, O.; Metag, V.; Mülhheim, D.; Münchow, D.; Nanova, M.; Novotny, R.; Pitka, A.; Quagli, T.; Rieke, J.; Rosenbaum, C.; Schnell, R.; Spruck, B.; Stenzel, H.; Thöring, U.; Ullrich, M.; Wasem, T.; Werner, M.; Zaunick, H. G.; Ireland, D.; Rosner, G.; Seitz, B.; Deepak, P. N.; Kulkarni, A. V.; Apostolou, A.; Babai, M.; Kavatsyuk, M.; Lemmens, P.; Lindemulder, M.; Löhner, H.; Messchendorp, J.; Schakel, P.; Smit, H.; van der Weele, J. C.; Tiemens, M.; Veenstra, R.; Vejdani, S.; Kalita, K.; Mohanta, D. P.; Kumar, A.; Roy, A.; Sahoo, R.; Sohlbach, H.; Büscher, M.; Cao, L.; Cebulla, A.; Deermann, D.; Dosdall, R.; Esch, S.; Georgadze, I.; Gillitzer, A.; Goerres, A.; Goldenbaum, F.; Grunwald, D.; Herten, A.; Hu, Q.; Kemmerling, G.; Kleines, H.; Kozlov, V.; Lehrach, A.; Leiber, S.; Maier, R.; Nellen, R.; Ohm, H.; Orfanitski, S.; Prasuhn, D.; Prencipe, E.; Ritman, J.; Schadmand, S.; Schumann, J.; Sefzick, T.; Serdyuk, V.; Sterzenbach, G.; Stockmanns, T.; Wintz, P.; Wüstner, P.; Xu, H.; Li, S.; Li, Z.; Sun, Z.; Xu, H.; Rigato, V.; Fissum, S.; Hansen, K.; Isaksson, L.; Lundin, M.; Schröder, B.; Achenbach, P.; Bleser, S.; Cardinali, M.; Corell, O.; Deiseroth, M.; Denig, A.; Distler, M.; Feldbauer, F.; Fritsch, M.; Jasinski, P.; Hoek, M.; Kangh, D.; Karavdina, A.; Lauth, W.; Leithoff, H.; Merkel, H.; Michel, M.; Motzko, C.; Müller, U.; Noll, O.; Plueger, S.; Pochodzalla, J.; Sanchez, S.; Schlimme, S.; Sfienti, C.; Steinen, M.; Thiel, M.; Weber, T.; Zambrana, M.; Dormenev, V. I.; Fedorov, A. A.; Korzihik, M. V.; Missevitch, O. V.; Balanutsa, P.; Balanutsa, V.; Chernetsky, V.; Demekhin, A.; Dolgolenko, A.; Fedorets, P.; Gerasimov, A.; Goryachev, V.; Varentsov, V.; Boukharov, A.; Malyshev, O.; Marishev, I.; Semenov, A.; Konorov, I.; Paul, S.; Grieser, S.; Hergemöller, A. K.; Khoukaz, A.; Köhler, E.; Täschner, A.; Wessels, J.; Dash, S.; Jadhav, M.; Kumar, S.; Sarin, P.; Varma, R.; Chandratre, V. B.; Datar, V.; Dutta, D.; Jha, V.; Kumawat, H.; Mohanty, A. K.; Roy, B.; Yan, Y.; Chinorat, K.; Khanchai, K.; Ayut, L.; Pornrad, S.; Barnyakov, A. Y.; Blinov, A. E.; Blinov, V. E.; Bobrovnikov, V. S.; Kononov, S. A.; Kravchenko, E. A.; Kuyanov, I. A.; Onuchin, A. P.; Sokolov, A. A.; Tikhonov, Y. A.; Atomssa, E.; Hennino, T.; Imre, M.; Kunne, R.; Le Galliard, C.; Ma, B.; Marchand, D.; Ong, S.; Ramstein, B.; Rosier, P.; Tomasi-Gustafsson, E.; Van de Wiele, J.; Boca, G.; Costanza, S.; Genova, P.; Lavezzi, L.; Montagna, P.; Rotondi, A.; Abramov, V.; Belikov, N.; Bukreeva, S.; Davidenko, A.; Derevschikov, A.; Goncharenko, Y.; Grishin, V.; Kachanov, V.; Kormilitsin, V.; Melnik, Y.; Levin, A.; Minaev, N.; Mochalov, V.; Morozov, D.; Nogach, L.; Poslavskiy, S.; Ryazantsev, A.; Ryzhikov, S.; Semenov, P.; Shein, I.; Uzunian, A.; Vasiliev, A.; Yakutin, A.; Yabsley, B.; Bäck, T.; Cederwall, B.; Makónyi, K.; Tegnér, P. E.; von Würtemberg, K. M.; Belostotski, S.; Gavrilov, G.; Izotov, A.; Kashchuk, A.; Levitskaya, O.; Manaenkov, S.; Miklukho, O.; Naryshkin, Y.; Suvorov, K.; Veretennikov, D.; Zhadanov, A.; Rai, A. K.; Godre, S. S.; Duchat, R.; Amoroso, A.; Bussa, M. P.; Busso, L.; De Mori, F.; Destefanis, M.; Fava, L.; Ferrero, L.; Greco, M.; Maggiora, M.; Maniscalco, G.; Marcello, S.; Sosio, S.; Spataro, S.; Zotti, L.; Calvo, D.; Coli, S.; De Remigis, P.; Filippi, A.; Giraudo, G.; Lusso, S.; Mazza, G.; Mingnore, M.; Rivetti, A.; Wheadon, R.; Balestra, F.; Iazzi, F.; Introzzi, R.; Lavagno, A.; Younis, H.; Birsa, R.; Bradamante, F.; Bressan, A.; Martin, A.; Clement, H.; Gålnander, B.; Caldeira Balkeståhl, L.; Calén, H.; Fransson, K.; Johansson, T.; Kupsc, A.; Marciniewski, P.; Pettersson, J.; Schönning, K.; Wolke, M.; Zlomanczuk, J.; Díaz, J.; Ortiz, A.; Vinodkumar, P. C.; Parmar, A.; Chlopik, A.; Melnychuk, D.; Slowinski, B.; Trzcinski, A.; Wojciechowski, M.; Wronka, S.; Zwieglinski, B.; Bühler, P.; Marton, J.; Suzuki, K.; Widmann, E.; Zmeskal, J.; Fröhlich, B.; Khaneft, D.; Lin, D.; Zimmermann, I.; Semenov-Tian-Shansky, K.

2015-08-01

Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion ( πN) TDAs from reaction with the future P¯ANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q 2, the amplitude of the signal channel admits a QCD factorized description in terms of πN TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring with the P¯ANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q 2 < 4.3 GeV2 and 5 < q 2 GeV2, respectively, with a neutral pion scattered in the forward or backward cone in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the P¯ANDA detector will allow to achieve a background rejection factor of 5 · 107 (1 · 107) at low (high) q 2 for s = 5 GeV2, and of 1 · 108 (6 · 106) at low (high) q 2 for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 fb-1 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with P¯ANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing π TDAs.

Proceedings of the Ringberg Workshop New Trends in HERA Physics 2005

NASA Astrophysics Data System (ADS)

Grindhammer, G.; Ochs, W.; Kniehl, B. A.; Kramer, G.

2006-04-01

1. Proton structure. Proton structure measurements at high Q2 and large x / Katarzyna Wichmann. Electroweak physics at HERA / Joachim Meyer. Inclusive low Q2 measurements at HERA / Victor Lendermann. Resummed perturbative evolution at high energy / Richard Ball. Colour dipole phenomenology / Graham Shaw -- 2. Spin physics. Exclusive reactions at HERMES / Frank Ellinghaus. Transverse spin effects in single and double hadron electroproduction at HERMES / Benedikt Zihlmann. Present understanding of the nucleon spin structure in view of recent experiments / Andreas Metz -- 3. Production of Hadrons and Jets. Measurements of [symbol] and parton distribution functions using HERA jet data / Amanda Cooper-Sarkar. A new parton shower algorithm: shower evolution, matching at leading and next-to-leading order level / Zóltan Nagy. Jet production at HERA / Dan Traynor. Multi-jet production in lepton-proton scattering with next-to-leading order accuracy / Zóltan Trócsányi. Dijet rates with symmetric [symbol] cuts / Andrea Banfi. QCD dynamics from forward hadron and jet measurements / Lidia Goerlich. Light-hadron electroproduction at next-to-leading order and implications / Bernd Kniehl. Particle production and fragmentation / David Saxon. Soft gluon logarithmic resummation and hadron mass effects in single hadron inclusive production / Simon Albino -- 4. Heavy-flavour production. Heavy-flavour photo- and electroproduction at NLO / Ingo Schienbein. Physics with charm quarks at HERA / John Loizides. Beauty production at HERA / Olaf Behnke. J/[symbol] photoproduction at next-to-leading order / Luminita Mihaila. J/[symbol] photoproduction at large z in soft collinear effective theory / Sean Fleming -- 5. Diffractive ep Scattering. Exclusive and inclusive diffraction at HERA / Henri Kowalski. Diffractive production of vector mesons and the gluon at small x / Thomas Teubner. Inclusive diffraction / Laurent Favart. From factorization to its breaking in diffractive dijet production / Michael Klasen. Diffractive parton density functions / Graeme Watt -- 6. Beyond the standard model. Beyond the standard model at HERA: status and prospects / Emmanuelle Perez -- 7. Resonances and diquarks. New resonances in the hadronic final state at HERA / Katsuo Tokushuku. Hadron systematics and emergent diquarks / Frank Wilczek -- 8. Future projects. Importance of a measurement of [symbol] at HERA / Robert Thorne. Measurement of the longitudinal proton structure function at low x at HERA / Joël Feltesse. HERA and the LHC / Albert De Roeck -- List of participants.

Cosmological QCD phase transition in steady non-equilibrium dissipative Hořava–Lifshitz early universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khodadi, M., E-mail: M.Khodadi@sbu.ac.ir; Sepangi, H.R., E-mail: hr-sepangi@sbu.ac.ir

We study the phase transition from quark–gluon plasma to hadrons in the early universe in the context of non-equilibrium thermodynamics. According to the standard model of cosmology, a phase transition associated with chiral symmetry breaking after the electro-weak transition has occurred when the universe was about 1–10 μs old. We focus attention on such a phase transition in the presence of a viscous relativistic cosmological background fluid in the framework of non-detailed balance Hořava–Lifshitz cosmology within an effective model of QCD. We consider a flat Friedmann–Robertson–Walker universe filled with a non-causal and a causal bulk viscous cosmological fluid respectively and investigatemore » the effects of the running coupling constants of Hořava–Lifshitz gravity, λ, on the evolution of the physical quantities relevant to a description of the early universe, namely, the temperature T, scale factor a, deceleration parameter q and dimensionless ratio of the bulk viscosity coefficient to entropy density (ξ)/s . We assume that the bulk viscosity cosmological background fluid obeys the evolution equation of the steady truncated (Eckart) and full version of the Israel–Stewart fluid, respectively. -- Highlights: •In this paper we have studied quark–hadron phase transition in the early universe in the context of the Hořava–Lifshitz model. •We use a flat FRW universe with the bulk viscosity cosmological background fluid obeying the evolution equation of the steady truncated (Eckart) and full version of the Israel–Stewart fluid, respectively.« less

Extraction of partonic transverse momentum distributions from semi-inclusive deep inelastic scattering and Drell-Yan data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pisano, Cristian; Bacchetta, Alessandro; Delcarro, Filippo

We present a first attempt at a global fit of unpolarized quark transverse momentum dependent distribution and fragmentation functions from available data on semi-inclusive deep-inelastic scattering, Drell-Yan and $Z$ boson production processes. This analysis is performed in the low transverse momentum region, at leading order in perturbative QCD and with the inclusion of energy scale evolution effects at the next-to-leading logarithmic accuracy.

Modelling exclusive meson pair production at hadron colliders

NASA Astrophysics Data System (ADS)

Harland-Lang, L. A.; Khoze, V. A.; Ryskin, M. G.

2014-04-01

We present a study of the central exclusive production of light meson pairs, concentrating on the region of lower invariant masses of the central system and/or meson transverse momentum, where perturbative QCD cannot be reliably applied. We describe in detail a phenomenological model, using the tools of Regge theory, that may be applied with some success in this regime, and we present the new, publicly available, Dime Monte Carlo (MC) implementation of this for , and production. The MC implementation includes a fully differential treatment of the survival factor, which in general depends on all kinematic variables, as well as allows for the so far reasonably unconstrained model parameters to be set by the user. We present predictions for the Tevatron and LHC, discuss and estimate the size of the proton-dissociative background, and show how future measurements may further test this Regge-based approach, as well as the soft hadronic model required to calculate the survival factor, in particular in the presence of tagged protons.

Constraining the double gluon distribution by the single gluon distribution

DOE PAGES

Golec-Biernat, Krzysztof; Lewandowska, Emilia; Serino, Mirko; ...

2015-10-03

We show how to consistently construct initial conditions for the QCD evolution equations for double parton distribution functions in the pure gluon case. We use to momentum sum rule for this purpose and a specific form of the known single gluon distribution function in the MSTW parameterization. The resulting double gluon distribution satisfies exactly the momentum sum rule and is parameter free. Furthermore, we study numerically its evolution with a hard scale and show the approximate factorization into product of two single gluon distributions at small values of x, whereas at large values of x the factorization is always violatedmore » in agreement with the sum rule.« less

B → Dℓν form factors at nonzero recoil and |V cb| from 2+1-flavor lattice QCD

DOE PAGES

Bailey, Jon A.

2015-08-10

We present the first unquenched lattice-QCD calculation of the hadronic form factors for the exclusive decay B¯→Dℓν¯ at nonzero recoil. We carry out numerical simulations on 14 ensembles of gauge-field configurations generated with 2+1 flavors of asqtad-improved staggered sea quarks. The ensembles encompass a wide range of lattice spacings (approximately 0.045 to 0.12 fm) and ratios of light (up and down) to strange sea-quark masses ranging from 0.05 to 0.4. For the b and c valence quarks we use improved Wilson fermions with the Fermilab interpretation, while for the light valence quarks we use asqtad-improved staggered fermions. We extrapolate ourmore » results to the physical point using rooted staggered heavy-light meson chiral perturbation theory. We then parametrize the form factors and extend them to the full kinematic range using model-independent functions based on analyticity and unitarity. We present our final results for f +(q 2) and f 0(q 2), including statistical and systematic errors, as coefficients of a series in the variable z and the covariance matrix between these coefficients. We then fit the lattice form-factor data jointly with the experimentally measured differential decay rate from BABAR to determine the CKM matrix element, |V cb|=(39.6 ± 1.7 QCD+exp ± 0.2 QED) × 10 –3. As a byproduct of the joint fit we obtain the form factors with improved precision at large recoil. In conclusion, we use them to update our calculation of the ratio R(D) in the Standard Model, which yields R(D)=0.299(11).« less

Mapping the QCD Phase Transition with Accreting Compact Stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blaschke, D.; Bogoliubov Laboratory for Theoretical Physics, JINR Dubna, Joliot-Curie str. 6, 141980 Dubna; Poghosyan, G.

2008-10-29

We discuss an idea for how accreting millisecond pulsars could contribute to the understanding of the QCD phase transition in the high-density nuclear matter equation of state (EoS). It is based on two ingredients, the first one being a ''phase diagram'' of rapidly rotating compact star configurations in the plane of spin frequency and mass, determined with state-of-the-art hybrid equations of state, allowing for a transition to color superconducting quark matter. The second is the study of spin-up and accretion evolution in this phase diagram. We show that the quark matter phase transition leads to a characteristic line in themore » {omega}-M plane, the phase border between neutron stars and hybrid stars with a quark matter core. Along this line a drop in the pulsar's moment of inertia entails a waiting point phenomenon in the accreting millisecond pulsar (AMXP) evolution: most of these objects should therefore be found along the phase border in the {omega}-M plane, which may be viewed as the AMXP analog of the main sequence in the Hertzsprung-Russell diagram for normal stars. In order to prove the existence of a high-density phase transition in the cores of compact stars we need population statistics for AMXPs with sufficiently accurate determination of their masses, spin frequencies and magnetic fields.« less

The asymptotic form of non-global logarithms, black disc saturation, and gluonic deserts

NASA Astrophysics Data System (ADS)

Neill, Duff

2017-01-01

We develop an asymptotic perturbation theory for the large logarithmic behavior of the non-linear integro-differential equation describing the soft correlations of QCD jet measurements, the Banfi-Marchesini-Smye (BMS) equation. This equation captures the late-time evolution of radiating color dipoles after a hard collision. This allows us to prove that at large values of the control variable (the non-global logarithm, a function of the infra-red energy scales associated with distinct hard jets in an event), the distribution has a gaussian tail. We compute the decay width analytically, giving a closed form expression, and find it to be jet geometry independent, up to the number of legs of the dipole in the active jet. Enabling the asymptotic expansion is the correct perturbative seed, where we perturb around an anzats encoding formally no real emissions, an intuition motivated by the buffer region found in jet dynamics. This must be supplemented with the correct application of the BFKL approximation to the BMS equation in collinear limits. Comparing to the asymptotics of the conformally related evolution equation encountered in small-x physics, the Balitisky-Kovchegov (BK) equation, we find that the asymptotic form of the non-global logarithms directly maps to the black-disc unitarity limit of the BK equation, despite the contrasting physical pictures. Indeed, we recover the equations of saturation physics in the final state dynamics of QCD.

Lattice QCD in rotating frames.

PubMed

Yamamoto, Arata; Hirono, Yuji

2013-08-23

We formulate lattice QCD in rotating frames to study the physics of QCD matter under rotation. We construct the lattice QCD action with the rotational metric and apply it to the Monte Carlo simulation. As the first application, we calculate the angular momenta of gluons and quarks in the rotating QCD vacuum. This new framework is useful to analyze various rotation-related phenomena in QCD.

Energy dependence of Kπ, pπ and Kp fluctuations in Au+Au collisions from √s NN=7.7 to 200 GeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamczyk, L.

A search for the quantum chromodynamics (QCD) critical point was performed by the STAR experiment at the Relativistic Heavy Ion Collider, using dynamical fluctuations of unlike particle pairs. Heavy ion collisions were studied over a large range of collision energies with homogeneous acceptance and excellent particle identification, covering a significant range in the QCD phase diagram where a critical point may be located. Dynamical Kπ, pπ, and Kp fluctuations as measured by the STAR experiment in central 0–5% Au+Au collisions from center-of-mass collision energies √s NN=7.7 to 200 GeV are presented. The observable νdyn was used to quantify the magnitudemore » of the dynamical fluctuations in event-by-event measurements of the Kπ, pπ, and Kp pairs. The energy dependences of these fluctuations from central 0–5% Au+Au collisions all demonstrate a smooth evolution with collision energy.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boroun, G. R., E-mail: boroun@razi.ac.ir; Rezaie, B.

We present a set of formulas using the solution of the QCD Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equation to extract of the exponents of the gluon distribution, {lambda}{sub g}, and structure function, {lambda}{sub S}, from the Regge-like behavior at low x. The exponents are found to be independent of x and to increase linearly with lnQ{sup 2} and are compared with the most data from the H1 Collaboration. We also calculated the structure function F{sub 2}(x,Q{sup 2}) and the gluon distribution G(x,Q{sup 2}) at low x assuming the Regge-like behavior of the gluon distribution function at this limit and compared them withmore » an NLO-QCD fit to theH1 data, two-Pomeron fit, multipole Pomeron exchange fit, and MRST (A.D. Martin, R.G. Roberts, W.J. Stirling, and R.S. Thorne), DL (A. Donnachie and P.V. Landshoff), and NLO GRV (M. Gluek, E. Reya, and A. Vogt) fit results.« less

Sivers and Boer-Mulders observables from lattice QCD.

DOE Office of Scientific and Technical Information (OSTI.GOV)

B.U. Musch, Ph. Hagler, M. Engelhardt, J.W. Negele, A. Schafer

We present a first calculation of transverse momentum dependent nucleon observables in dynamical lattice QCD employing non-local operators with staple-shaped, 'process-dependent' Wilson lines. The use of staple-shaped Wilson lines allows us to link lattice simulations to TMD effects determined from experiment, and in particular to access non-universal, naively time-reversal odd TMD observables. We present and discuss results for the generalized Sivers and Boer-Mulders transverse momentum shifts for the SIDIS and DY cases. The effect of staple-shaped Wilson lines on T-even observables is studied for the generalized tensor charge and a generalized transverse shift related to the worm gear function g{submore » 1}T. We emphasize the dependence of these observables on the staple extent and the Collins-Soper evolution parameter. Our numerical calculations use an n{sub f} = 2+1 mixed action scheme with domain wall valence fermions on an Asqtad sea and pion masses 369 MeV as well as 518 MeV.« less

Lattice QCD study of the Boer-Mulders effect in a pion

NASA Astrophysics Data System (ADS)

Engelhardt, M.; Hägler, P.; Musch, B.; Negele, J.; Schäfer, A.

2016-03-01

The three-dimensional momenta of quarks inside a hadron are encoded in transverse momentum-dependent parton distribution functions (TMDs). This work presents an exploratory lattice QCD study of a TMD observable in the pion describing the Boer-Mulders effect, which is related to polarized quark transverse momentum in an unpolarized hadron. The primary goal is to gain insight into the behavior of TMDs as a function of a Collins-Soper evolution parameter, ζ ^, which quantifies the rapidity difference between the hadron momentum and a vector describing the trajectory of the struck quark, e.g., in a semi-inclusive deep-inelastic scattering (SIDIS) process. The lattice calculation, performed at the pion mass mπ=518 MeV , utilizes a definition of TMDs via hadronic matrix elements of a quark bilocal operator with a staple-shaped gauge connection; in this context, the evolution parameter is related to the staple direction. By parametrizing the aforementioned matrix elements in terms of invariant amplitudes, the problem can be cast in a Lorentz frame suited for the lattice calculation. Aided by the lower mass of the pion, compared to the nucleon studied previously, the present investigation of pion TMD observables constitutes an important step towards the quantitative study of the physically important regime of large relative rapidity where the dependence on ζ ^ appears to approach a limit. Although matching to perturbative evolution equations in ζ ^ is not yet available, extrapolations based on Ansätze containing inverse powers of ζ ^ yield stable results with an uncertainty as low as 20%, and both upper and lower bounds for the asymptotics are obtained. In passing, the similarity between the Boer-Mulders effects extracted in the pion and the nucleon is noted.

Electroproduction of Eta Mesons in the S11(1535) Resonance Region at High Momentum Transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalton, Mark; Adams, Gary; Ahmidouch, Abdellah

2009-01-01

The differential cross-section for the process p(e,e'p)eta has been measured at Q2 ~ 5.7 and 7.0 (GeV/c)2 for centre-of-mass energies from threshold to 1.8 GeV, encompassing the S11(1535) resonance, which dominates the channel. This is the highest momentum transfer measurement of this exclusive process to date. The helicity-conserving transition amplitude A_1/2, for the production of the S11(1535) resonance, is extracted from the data. This quantity appears to begin scaling as 1/Q3, a predicted signal of the dominance of perturbative QCD, at Q2 ~ 5 (GeV/c)2.

Large $N$ approach to kaon decays and mixing 28 years later: $$\\Delta I = 1/2$$ rule, $$\\hat B_K$$ and $$\\Delta M_K$$

DOE PAGES

Buras, Andrzej J.; Gérard, Jean -Marc; Bardeen, William A.

2014-05-20

We review and update our results for K → π π decays and K⁰- K¯⁰ mixing obtained by us in the 1980s within an approach based on the dual representation of QCD as a theory of weakly interacting mesons for large N colours. In our analytic approach the dynamics behind the enhancement of ReA 0 and suppression of ReA 2, the so-called ΔI = 1/2 rule for K → π π decays, has a simple structure: the usual octet enhancement through quark-gluon renormalization group evolution down to the scales O(1 GeV) is continued as a meson evolution down to zeromore » momentum scales at which the factorization of hadronic matrix elements is at work. The inclusion of lowest-lying vector meson contributions in addition to the pseudoscalar ones and of Wilson coefficients in a momentum scheme improves significantly the matching between quark-gluon and meson evolutions. In particular, the anomalous dimension matrix governing the meson evolution exhibits the structure of the known anomalous dimension matrix in the quark-gluon evolution. The recent results on ReA 2 and ReA 0 from the RBC-UKQC collaboration give support for our approach. In particular, the signs of the two main contractions found numerically by these authors follow uniquely from our analytic approach. At NLO in 1/N we obtain R = ReA 0/ReA 2= 16.0±1.5 which amounts to an order of magnitude enhancement over the strict large N limit value √2. QCD penguins contribute at 15% level to this result. We also find B^ K = 0.73± 0.02, with the smallness of 1/N corrections to the large N value B^ K = 3/4 resulting within our approach from an approximate cancellation between pseudoscalar and vector meson one-loop contributions. We summarize the status of ΔM K in this approach.« less

Higher order corrections to mixed QCD-EW contributions to Higgs boson production in gluon fusion

NASA Astrophysics Data System (ADS)

Bonetti, Marco; Melnikov, Kirill; Tancredi, Lorenzo

2018-03-01

We present an estimate of the next-to-leading-order (NLO) QCD corrections to mixed QCD-electroweak contributions to the Higgs boson production cross section in gluon fusion, combining the recently computed three-loop virtual corrections and the approximate treatment of real emission in the soft approximation. We find that the NLO QCD corrections to the mixed QCD-electroweak contributions are nearly identical to NLO QCD corrections to QCD Higgs production. Our result confirms an earlier estimate of these O (α αs2) effects by Anastasiou et al. [J. High Energy Phys. 04 (2009) 003, 10.1088/1126-6708/2009/04/003] and provides further support for the factorization approximation of QCD and electroweak corrections.

Heavy quarkonium production at collider energies: Factorization and evolution

NASA Astrophysics Data System (ADS)

Kang, Zhong-Bo; Ma, Yan-Qing; Qiu, Jian-Wei; Sterman, George

2014-08-01

We present a perturbative QCD factorization formalism for inclusive production of heavy quarkonia of large transverse momentum, pT at collider energies, including both leading power (LP) and next-to-leading power (NLP) behavior in pT. We demonstrate that both LP and NLP contributions can be factorized in terms of perturbatively calculable short-distance partonic coefficient functions and universal nonperturbative fragmentation functions, and derive the evolution equations that are implied by the factorization. We identify projection operators for all channels of the factorized LP and NLP infrared safe short-distance partonic hard parts, and corresponding operator definitions of fragmentation functions. For the NLP, we focus on the contributions involving the production of a heavy quark pair, a necessary condition for producing a heavy quarkonium. We evaluate the first nontrivial order of evolution kernels for all relevant fragmentation functions, and discuss the role of NLP contributions.

Calculating TMDs of a large nucleus: Quasi-classical approximation and quantum evolution

DOE PAGES

Kovchegov, Yuri V.; Sievert, Matthew D.

2015-12-24

We set up a formalism for calculating transverse-momentum-dependent parton distribution functions (TMDs) of a large nucleus using the tools of saturation physics. By generalizing the quasi-classical Glauber–Gribov–Mueller/McLerran–Venugopalan approximation to allow for the possibility of spin–orbit coupling, we show how any TMD can be calculated in the saturation framework. This can also be applied to the TMDs of a proton by modeling it as a large “nucleus.” To illustrate our technique, we calculate the quark TMDs of an unpolarized nucleus at large-x: the unpolarized quark distribution and the quark Boer–Mulders distribution. Here, we observe that spin–orbit coupling leads to mixing betweenmore » different TMDs of the nucleus and of the nucleons. We then consider the evolution of TMDs: at large-x, in the double-logarithmic approximation, we obtain the Sudakov form factor. At small-x the evolution of unpolarized-target quark TMDs is governed by BK/JIMWLK evolution, while the small-x evolution of polarized-target quark TMDs appears to be dominated by the QCD Reggeon.« less

Scale influence on the energy dependence of photon-proton cross sections

NASA Astrophysics Data System (ADS)

Aid, S.; Anderson, M.; Andreev, V.; Andrieu, B.; Babaev, A.; Bähr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Beck, M.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Boudry, V.; Braemer, A.; Braunschweig, W.; Brisson, V.; Brückner, W.; Bruel, P.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M. J.; Calvet, D.; Campbell, A. J.; Carli, T.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Cocks, S.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Cousinou, M.-C.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Davis, C. L.; Delcourt, B.; de Roeck, A.; de Wolf, E. A.; Dirkmann, M.; Dixon, P.; di Nezza, P.; Dlugosz, W.; Dollfus, C.; Donovan, K. T.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Elsen, E.; Erdmann, M.; Erdmann, W.; Fahr, A. B.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gaede, F.; Garvey, J.; Gayler, J.; Gebauer, M.; Genzel, H.; Gerhards, R.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Golec-Biernat, K.; Gonzalez-Pineiro, B.; Gorelov, I.; Grab, C.; Grässler, H.; Greenshaw, T.; Griffiths, R. K.; Grindhammer, G.; Gruber, A.; Gruber, C.; Hadig, T.; Haidt, D.; Hajduk, L.; Haller, T.; Hampel, M.; Haynes, W. J.; Heinemann, B.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hewitt, K.; Hildesheim, W.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Höppner, M.; Hoffmann, D.; Holtom, T.; Horisberger, R.; Hudgson, V. L.; Hütte, M.; Ibbotson, M.; Itterbeck, H.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, D. M.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Jung, H.; Kalmus, P. I. P.; Kander, M.; Kant, D.; Kaschowitz, R.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kaufmann, O.; Kausch, M.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kolya, S. D.; Korbel, V.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Lacour, D.; Laforge, B.; Landon, M. P. J.; Lange, W.; Langenegger, U.; Lebedev, A.; Lehner, F.; Levonian, S.; Lindström, G.; Lindstroem, M.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lomas, J. W.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Lytkin, L.; Magnussen, N.; Malinovski, E.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, G.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Metlica, F.; Meyer, A.; Meyer, A.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Migliori, A.; Mikocki, S.; Milstead, D.; Moeck, J.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, D.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Négri, I.; Newman, P. R.; Newton, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Niggli, H.; Nowak, G.; Noyes, G. W.; Nunnemann, T.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Olsson, J. E.; Ozerov, D.; Palmen, P.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Pawletta, H.; Peppel, E.; Perez, E.; Phillips, J. P.; Pieuchot, A.; Pitzl, D.; Pope, G.; Povh, B.; Prell, S.; Rabbertz, K.; Rädel, G.; Reimer, P.; Reinshagen, S.; Rick, H.; Riepenhausen, F.; Riess, S.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleif, S.; Schleper, P.; von Schlippe, W.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Sefkow, F.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Solochenko, V.; Soloviev, Y.; Specka, A.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Squinabol, F.; Steffen, P.; Steinberg, R.; Steiner, H.; Steinhart, J.; Stella, B.; Stellberger, A.; Stier, J.; Stiewe, J.; Stößlein, U.; Stolze, K.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Taševský, M.; Tchernyshov, V.; Tchetchelnitski, S.; Theissen, J.; Thiebaux, C.; Thompson, G.; Todenhagen, R.; Truöl, P.; Tsipolitis, G.; Turnau, J.; Tutas, J.; Tzamariudaki, E.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Vandenplas, D.; van Esch, P.; van Mechelen, P.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wengler, T.; Werner, M.; West, L. R.; Wilksen, T.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wobisch, M.; Wünsch, E.; ŽáČek, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zini, P.; Zomer, F.; Zsembery, J.; Zuber, K.; Zurnedden, M.

1997-02-01

The scale dependence of the evolution of photoproduction cross sections with the photon-proton centre of mass energyW is studied using low Q2 < 0.01 GeV2 e+p interactions collected by the H1 experiment at HERA. The value of the largest transverse momentum of a charged particle in the photon fragmentation region is used to define the hard scale. The slope of the W dependence of the cross section is observed to increase steeply with increasing transverse momentum. The result is compared to measurements of the Q2 evolution of the W dependence of the virtual photon-proton cross section. Interpretations in terms of QCD and in terms of Regge phenomenology are discussed.

Nonperturbative evolution of parton quasi-distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radyushkin, A. V.

2017-02-14

Using the formalism of parton virtuality distribution functions (VDFs) we establish a connection between the transverse momentum dependent distributions (TMDs) F(x,k ⊥ 2) and quasi-distributions (PQDs) Q(y,p 3) introduced recently by X. Ji for lattice QCD extraction of parton distributions f(x). We build models for PQDs from the VDF-based models for soft TMDs, and analyze the p 3 dependence of the resulting PQDs. We observe a strong nonperturbative evolution of PQDs for small and moderately large values of p 3 reflecting the transverse momentum dependence of TMDs. Furthermore, the study of PQDs on the lattice in the domain of strongmore » nonperturbative effects opens a new perspective for investigation of the 3-dimensional hadron structure.« less

QCD for Postgraduates (1/5)

ScienceCinema

Zanderighi, Giulia

2018-04-26

Modern QCD - Lecture 1 Starting from the QCD Lagrangian we will revisit some basic QCD concepts and derive fundamental properties like gauge invariance and isospin symmetry and will discuss the Feynman rules of the theory. We will then focus on the gauge group of QCD and derive the Casimirs CF and CA and some useful color identities.

Measurement of the underlying event in jet events from 7 proton-proton collisions with the ATLAS detector

NASA Astrophysics Data System (ADS)

Aad, G.; Abajyan, T.; Abbott, B.; Abdallah, J.; Khalek, S. Abdel; Abdinov, O.; Aben, R.; Abi, B.; Abolins, M.; AbouZeid, O. S.; Abramowicz, H.; Abreu, H.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Addy, T. N.; Adelman, J.; Adomeit, S.; Adye, T.; Agatonovic-Jovin, T.; Aguilar-Saavedra, J. A.; Agustoni, M.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Åkesson, T. P. A.; Akimoto, G.; Akimov, A. V.; Albert, J.; Albrand, S.; Verzini, M. J. Alconada; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexandre, G.; Alexopoulos, T.; Alhroob, M.; Alimonti, G.; Alio, L.; Alison, J.; Allbrooke, B. M. M.; Allison, L. J.; Allport, P. P.; Allwood-Spiers, S. E.; Almond, J.; Aloisio, A.; Alon, R.; Alonso, A.; Alonso, F.; Alpigiani, C.; Altheimer, A.; Gonzalez, B. Alvarez; Alviggi, M. G.; Amako, K.; Coutinho, Y. Amaral; Amelung, C.; Amidei, D.; Ammosov, V. V.; Santos, S. P. Amor Dos; Amorim, A.; Amoroso, S.; Amram, N.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Anduaga, X. S.; Angelidakis, S.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonaki, A.; Antonelli, M.; Antonov, A.; Antos, J.; Anulli, F.; Aoki, M.; Bella, L. Aperio; Apolle, R.; Arabidze, G.; Aracena, I.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arguin, J.-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Arnaez, O.; Arnal, V.; Arslan, O.; Artamonov, A.; Artoni, G.; Asai, S.; Asbah, N.; Ashkenazi, A.; Ask, S.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Auerbach, B.; Auge, E.; Augsten, K.; Aurousseau, M.; Avolio, G.; Azuelos, G.; Azuma, Y.; Baak, M. A.; Bacci, C.; Bach, A. M.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Mayes, J. Backus; Badescu, E.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Bailey, D. C.; Bain, T.; Baines, J. T.; Baker, O. 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T.; Shapiro, M.; Shatalov, P. B.; Shaw, K.; Sherwood, P.; Shimizu, S.; Shimmin, C. O.; Shimojima, M.; Shiyakova, M.; Shmeleva, A.; Shochet, M. J.; Short, D.; Shrestha, S.; Shulga, E.; Shupe, M. A.; Shushkevich, S.; Sicho, P.; Sidorov, D.; Sidoti, A.; Siegert, F.; Sijacki, Dj.; Silbert, O.; Silva, J.; Silver, Y.; Silverstein, D.; Silverstein, S. B.; Simak, V.; Simard, O.; Simic, Lj.; Simion, S.; Simioni, E.; Simmons, B.; Simoniello, R.; Simonyan, M.; Sinervo, P.; Sinev, N. B.; Sipica, V.; Siragusa, G.; Sircar, A.; Sisakyan, A. N.; Sivoklokov, S. Yu.; Sjölin, J.; Sjursen, T. B.; Skinnari, L. A.; Skottowe, H. P.; Skovpen, K. Yu.; Skubic, P.; Slater, M.; Slavicek, T.; Sliwa, K.; Smakhtin, V.; Smart, B. H.; Smestad, L.; Smirnov, S. Yu.; Smirnov, Y.; Smirnova, L. N.; Smirnova, O.; Smith, K. M.; Smizanska, M.; Smolek, K.; Snesarev, A. A.; Snidero, G.; Snyder, S.; Sobie, R.; Socher, F.; Soffer, A.; Soh, D. A.; Solans, C. A.; Solar, M.; Solc, J.; Soldatov, E. Yu.; Soldevila, U.; Camillocci, E. Solfaroli; Solodkov, A. A.; Solovyanov, O. V.; Solovyev, V.; Sommer, P.; Song, H. Y.; Soni, N.; Sood, A.; Sopko, B.; Sopko, V.; Sorin, V.; Sosebee, M.; Soualah, R.; Soueid, P.; Soukharev, A. M.; South, D.; Spagnolo, S.; Spanò, F.; Spearman, W. R.; Spighi, R.; Spigo, G.; Spousta, M.; Spreitzer, T.; Spurlock, B.; St. Denis, R. D.; Staerz, S.; Stahlman, J.; Stamen, R.; Stanecka, E.; Stanek, R. W.; Stanescu, C.; Stanescu-Bellu, M.; Stanitzki, M. M.; Stapnes, S.; Starchenko, E. A.; Stark, J.; Staroba, P.; Starovoitov, P.; Staszewski, R.; Stavina, P.; Steele, G.; Steinberg, P.; Stelzer, B.; Stelzer, H. J.; Stelzer-Chilton, O.; Stenzel, H.; Stern, S.; Stewart, G. A.; Stillings, J. A.; Stockton, M. C.; Stoebe, M.; Stoerig, K.; Stoicea, G.; Stolte, P.; Stonjek, S.; Stradling, A. R.; Straessner, A.; Strandberg, J.; Strandberg, S.; Strandlie, A.; Strauss, E.; Strauss, M.; Strizenec, P.; Ströhmer, R.; Strom, D. M.; Stroynowski, R.; Stucci, S. A.; Stugu, B.; Styles, N. A.; Su, D.; Su, J.; Subramania, H. S.; Subramaniam, R.; Succurro, A.; Sugaya, Y.; Suhr, C.; Suk, M.; Sulin, V. V.; Sultansoy, S.; Sumida, T.; Sun, X.; Sundermann, J. E.; Suruliz, K.; Susinno, G.; Sutton, M. R.; Suzuki, Y.; Svatos, M.; Swedish, S.; Swiatlowski, M.; Sykora, I.; Sykora, T.; Ta, D.; Tackmann, K.; Taenzer, J.; Taffard, A.; Tafirout, R.; Taiblum, N.; Takahashi, Y.; Takai, H.; Takashima, R.; Takeda, H.; Takeshita, T.; Takubo, Y.; Talby, M.; Talyshev, A. A.; Tam, J. Y. C.; Tamsett, M. C.; Tan, K. G.; Tanaka, J.; Tanaka, R.; Tanaka, S.; Tanaka, S.; Tanasijczuk, A. J.; Tani, K.; Tannoury, N.; Tapprogge, S.; Tarem, S.; Tarrade, F.; Tartarelli, G. F.; Tas, P.; Tasevsky, M.; Tashiro, T.; Tassi, E.; Delgado, A. Tavares; Tayalati, Y.; Taylor, C.; Taylor, F. E.; Taylor, G. N.; Taylor, W.; Teischinger, F. A.; Castanheira, M. Teixeira Dias; Teixeira-Dias, P.; Temming, K. K.; Kate, H. Ten; Teng, P. K.; Terada, S.; Terashi, K.; Terron, J.; Terzo, S.; Testa, M.; Teuscher, R. J.; Therhaag, J.; Theveneaux-Pelzer, T.; Thoma, S.; Thomas, J. P.; Thomas-Wilsker, J.; Thompson, E. N.; Thompson, P. D.; Thompson, P. D.; Thompson, A. S.; Thomsen, L. A.; Thomson, E.; Thomson, M.; Thong, W. M.; Thun, R. P.; Tian, F.; Tibbetts, M. J.; Tikhomirov, V. O.; Tikhonov, Yu. A.; Timoshenko, S.; Tiouchichine, E.; Tipton, P.; Tisserant, S.; Todorov, T.; Todorova-Nova, S.; Toggerson, B.; Tojo, J.; Tokár, S.; Tokushuku, K.; Tollefson, K.; Tomlinson, L.; Tomoto, M.; Tompkins, L.; Toms, K.; Topilin, N. D.; Torrence, E.; Torres, H.; Pastor, E. Torró; Toth, J.; Touchard, F.; Tovey, D. R.; Tran, H. L.; Trefzger, T.; Tremblet, L.; Tricoli, A.; Trigger, I. M.; Trincaz-Duvoid, S.; Tripiana, M. F.; Triplett, N.; Trischuk, W.; Trocmé, B.; Troncon, C.; Trottier-McDonald, M.; Trovatelli, M.; True, P.; Trzebinski, M.; Trzupek, A.; Tsarouchas, C.; Tseng, J. C.-L.; Tsiareshka, P. V.; Tsionou, D.; Tsipolitis, G.; Tsirintanis, N.; Tsiskaridze, S.; Tsiskaridze, V.; Tskhadadze, E. G.; Tsukerman, I. I.; Tsulaia, V.; Tsuno, S.; Tsybychev, D.; Tua, A.; Tudorache, A.; Tudorache, V.; Tuna, A. N.; Tupputi, S. A.; Turchikhin, S.; Turecek, D.; Cakir, I. Turk; Turra, R.; Tuts, P. M.; Tykhonov, A.; Tylmad, M.; Tyndel, M.; Uchida, K.; Ueda, I.; Ueno, R.; Ughetto, M.; Ugland, M.; Uhlenbrock, M.; Ukegawa, F.; Unal, G.; Undrus, A.; Unel, G.; Ungaro, F. C.; Unno, Y.; Urbaniec, D.; Urquijo, P.; Usai, G.; Usanova, A.; Vacavant, L.; Vacek, V.; Vachon, B.; Valencic, N.; Valentinetti, S.; Valero, A.; Valery, L.; Valkar, S.; Gallego, E. Valladolid; Vallecorsa, S.; Ferrer, J. A. Valls; Van Der Deijl, P. C.; van der Geer, R.; van der Graaf, H.; Van Der Leeuw, R.; van der Ster, D.; Eldik, N. van; van Gemmeren, P.; Van Nieuwkoop, J.; van Vulpen, I.; van Woerden, M. C.; Vanadia, M.; Vandelli, W.; Vaniachine, A.; Vankov, P.; Vannucci, F.; Vardanyan, G.; Vari, R.; Varnes, E. W.; Varol, T.; Varouchas, D.; Vartapetian, A.; Varvell, K. E.; Vazeille, F.; Schroeder, T. Vazquez; Veatch, J.; Veloso, F.; Veneziano, S.; Ventura, A.; Ventura, D.; Venturi, M.; Venturi, N.; Venturini, A.; Vercesi, V.; Verducci, M.; Verkerke, W.; Vermeulen, J. C.; Vest, A.; Vetterli, M. C.; Viazlo, O.; Vichou, I.; Vickey, T.; Boeriu, O. E. Vickey; Viehhauser, G. H. A.; Viel, S.; Vigne, R.; Villa, M.; Perez, M. Villaplana; Vilucchi, E.; Vincter, M. G.; Vinogradov, V. B.; Virzi, J.; Vitells, O.; Vivarelli, I.; Vaque, F. Vives; Vlachos, S.; Vladoiu, D.; Vlasak, M.; Vogel, A.; Vokac, P.; Volpi, G.; Volpi, M.; von der Schmitt, H.; Radziewski, H. von; von Toerne, E.; Vorobel, V.; Vos, M.; Voss, R.; Vossebeld, J. H.; Vranjes, N.; Milosavljevic, M. Vranjes; Vrba, V.; Vreeswijk, M.; Anh, T. Vu; Vuillermet, R.; Vukotic, I.; Vykydal, Z.; Wagner, P.; Wagner, W.; Wahrmund, S.; Wakabayashi, J.; Walder, J.; Walker, R.; Walkowiak, W.; Wall, R.; Waller, P.; Walsh, B.; Wang, C.; Wang, C.; Wang, F.; Wang, H.; Wang, H.; Wang, J.; Wang, J.; Wang, K.; Wang, R.; Wang, S. M.; Wang, T.; Wang, X.; Warburton, A.; Ward, C. P.; Wardrope, D. R.; Warsinsky, M.; Washbrook, A.; Wasicki, C.; Watanabe, I.; Watkins, P. M.; Watson, A. T.; Watson, I. J.; Watson, M. F.; Watts, G.; Watts, S.; Waugh, B. M.; Webb, S.; Weber, M. S.; Weber, S. W.; Webster, J. S.; Weidberg, A. R.; Weigell, P.; Weinert, B.; Weingarten, J.; Weiser, C.; Weits, H.; Wells, P. S.; Wenaus, T.; Wendland, D.; Weng, Z.; Wengler, T.; Wenig, S.; Wermes, N.; Werner, M.; Werner, P.; Wessels, M.; Wetter, J.; Whalen, K.; White, A.; White, M. J.; White, R.; White, S.; Whiteson, D.; Wicke, D.; Wickens, F. J.; Wiedenmann, W.; Wielers, M.; Wienemann, P.; Wiglesworth, C.; Wiik-Fuchs, L. A. M.; Wijeratne, P. A.; Wildauer, A.; Wildt, M. A.; Wilkens, H. G.; Will, J. Z.; Williams, H. H.; Williams, S.; Willis, C.; Willocq, S.; Wilson, A.; Wilson, J. A.; Wingerter-Seez, I.; Winkelmann, S.; Winklmeier, F.; Wittgen, M.; Wittig, T.; Wittkowski, J.; Wollstadt, S. J.; Wolter, M. W.; Wolters, H.; Wosiek, B. K.; Wotschack, J.; Woudstra, M. J.; Wozniak, K. W.; Wright, M.; Wu, S. L.; Wu, X.; Wu, Y.; Wulf, E.; Wyatt, T. R.; Wynne, B. M.; Xella, S.; Xiao, M.; Xu, D.; Xu, L.; Yabsley, B.; Yacoob, S.; Yamada, M.; Yamaguchi, H.; Yamaguchi, Y.; Yamamoto, A.; Yamamoto, K.; Yamamoto, S.; Yamamura, T.; Yamanaka, T.; Yamauchi, K.; Yamazaki, Y.; Yan, Z.; Yang, H.; Yang, H.; Yang, U. K.; Yang, Y.; Yanush, S.; Yao, L.; Yao, W.-M.; Yasu, Y.; Yatsenko, E.; Wong, K. H. Yau; Ye, J.; Ye, S.; Yen, A. L.; Yildirim, E.; Yilmaz, M.; Yoosoofmiya, R.; Yorita, K.; Yoshida, R.; Yoshihara, K.; Young, C.; Young, C. J. S.; Youssef, S.; Yu, D. R.; Yu, J.; Yu, J. M.; Yu, J.; Yuan, L.; Yurkewicz, A.; Zabinski, B.; Zaidan, R.; Zaitsev, A. M.; Zaman, A.; Zambito, S.; Zanello, L.; Zanzi, D.; Zaytsev, A.; Zeitnitz, C.; Zeman, M.; Zemla, A.; Zengel, K.; Zenin, O.; Ženiš, T.; Zerwas, D.; della Porta, G. Zevi; Zhang, D.; Zhang, F.; Zhang, H.; Zhang, J.; Zhang, L.; Zhang, X.; Zhang, Z.; Zhao, Z.; Zhemchugov, A.; Zhong, J.; Zhou, B.; Zhou, L.; Zhou, N.; Zhu, C. G.; Zhu, H.; Zhu, J.; Zhu, Y.; Zhuang, X.; Zibell, A.; Zieminska, D.; Zimine, N. I.; Zimmermann, C.; Zimmermann, R.; Zimmermann, S.; Zimmermann, S.; Zinonos, Z.; Ziolkowski, M.; Zitoun, R.; Zobernig, G.; Zoccoli, A.; zur Nedden, M.; Zurzolo, G.; Zutshi, V.; Zwalinski, L.

2014-08-01

Distributions sensitive to the underlying event in QCD jet events have been measured with the ATLAS detector at the LHC, based on of proton-proton collision data collected at a centre-of-mass energy of 7 . Charged-particle mean and densities of all-particle and charged-particle multiplicity and have been measured in regions azimuthally transverse to the hardest jet in each event. These are presented both as one-dimensional distributions and with their mean values as functions of the leading-jet transverse momentum from 20 to 800 . The correlation of charged-particle mean with charged-particle multiplicity is also studied, and the densities include the forward rapidity region; these features provide extra data constraints for Monte Carlo modelling of colour reconnection and beam-remnant effects respectively. For the first time, underlying event observables have been computed separately for inclusive jet and exclusive dijet event selections, allowing more detailed study of the interplay of multiple partonic scattering and QCD radiation contributions to the underlying event. Comparisons to the predictions of different Monte Carlo models show a need for further model tuning, but the standard approach is found to generally reproduce the features of the underlying event in both types of event selection.

Towards an alternative evolution model.

PubMed

van Waesberghe, H

1982-01-01

Lamarck and Darwin agreed on the inconstancy of species and on the exclusive gradualism of evolution (nature does not jump). Darwinism, revived as neo-Darwinism, was almost generally accepted from about 1930 till 1960. In the sixties the evolutionary importance of selection has been called in question by the neutralists. The traditional conception of the gene is disarranged by recent molecular-biological findings. Owing to the increasing confusion about the concept of genotype, this concept is reconsidered. The idea of the genotype as a cluster of genes is replaced by a cybernetical interpretation of the genotype. As nature does jump, exclusive gradualism is dismissed. Saltatory evolution is a natural phenomenon, provided by a sudden collapse of the thresholds which resist against evolution. The fossil record and the taxonomic system call for a macromutational interpretation. As Lamarck and Darwin overlooked the resistance of evolutionary thresholds, an alternative evolution model is needed, the first to be constructed on a palaeontological and taxonomic basis.

Quantum Chromodynamics and Color Confinement (confinement 2000) - Proceedings of the International Symposium

NASA Astrophysics Data System (ADS)

Suganuma, H.; Fukushima, M.; Toki, H.

The Table of Contents for the book is as follows: * Preface * Opening Address * Monopole Condensation and Quark Confinement * Dual QCD, Effective String Theory, and Regge Trajectories * Abelian Dominance and Monopole Condensation * Non-Abelian Stokes Theorem and Quark Confinement in QCD * Infrared Region of QCD and Confining Configurations * BRS Quartet Mechanism for Color Confinement * Color Confinement and Quartet Mechanism * Numerical Tests of the Kugo-Ojima Color Confinement Criterion * Monopoles and Confinement in Lattice QCD * SU(2) Lattice Gauge Theory at T > 0 in a Finite Box with Fixed Holonomy * Confining and Dirac Strings in Gluodynamics * Cooling, Monopoles, and Vortices in SU(2) Lattice Gauge Theory * Quark Confinement Physics from Lattice QCD * An (Almost) Perfect Lattice Action for SU(2) and SU(3) Gluodynamics * Vortices and Confinement in Lattice QCD * P-Vortices, Nexuses and Effects of Gribov Copies in the Center Gauges * Laplacian Center Vortices * Center Vortices at Strong Couplings and All Couplings * Simulations in SO(3) × Z(2) Lattice Gauge Theory * Exciting a Vortex - the Cost of Confinement * Instantons in QCD * Deformation of Instanton in External Color Fields * Field Strength Correlators in the Instanton Liquid * Instanton and Meron Physics in Lattice QCD * The Dual Ginzburg-Landau Theory for Confinement and the Role of Instantons * Lattice QCD for Quarks, Gluons and Hadrons * Hadronic Spectral Functions in QCD * Universality and Chaos in Quantum Field Theories * Lattice QCD Study of Three Quark Potential * Probing the QCD Vacuum with Flavour Singlet Objects : η' on the Lattice * Lattice Studies of Quarks and Gluons * Quarks and Hadrons in QCD * Supersymmetric Nonlinear Sigma Models * Chiral Transition and Baryon-number Susceptibility * Light Quark Masses in QCD * Chiral Symmetry of Baryons and Baryon Resonances * Confinement and Bound States in QCD * Parallel Session * Off-diagonal Gluon Mass Generation and Strong Randomness of Off-diagonal Gluon Phase in the Maximally Abelian Gauge * On the Colour Confinement and the Minimal Surface * Glueball Mass and String Tension of SU(2) Gluodynamics from Abelian Monopoles and Strings * Application of the Non-Perturbative Renormalization Group to the Nambu-Jona-Lasinio Model at Finite Temperature and Density * Confining Flux-Tube and Hadrons in QCD * Gauge Symmetry Breakdown due to Dynamical Higgs Scalar * Spatial Structure of Quark Cooper Pairs * New Approach to Axial Coupling Constants in the QCD Sum Rule and Instanton Effects * String Breaking on a Lattice * Bethe-Salpeter Approach for Mesons within the Dual Ginzburg-Landau Theory * Gauge Dependence and Matching Procedure of a Nonrelativistic QCD Boundstate Formalism * A Mathematical Approach to the SU(2)-Quark Confinement * Simulations of Odd Flavors QCD by Hybrid Monte Carlo * Non-Perturbative Renormalization Group Analysis of Dynamical Chiral Symmetry Breaking with Beyond Ladder Contributions * Charmonium Physics in Finite Temperature Lattice QCD * From Meson-Nucleon Scattering to Vector Mesons in Nuclear Matter * Symposium Program * List of Participants

Exploring Partonic Structure of Hadrons Using ab initio Lattice QCD Calculations.

PubMed

Ma, Yan-Qing; Qiu, Jian-Wei

2018-01-12

Following our previous proposal, we construct a class of good "lattice cross sections" (LCSs), from which we can study the partonic structure of hadrons from ab initio lattice QCD calculations. These good LCSs, on the one hand, can be calculated directly in lattice QCD, and on the other hand, can be factorized into parton distribution functions (PDFs) with calculable coefficients, in the same way as QCD factorization for factorizable hadronic cross sections. PDFs could be extracted from QCD global analysis of the lattice QCD generated data of LCSs. We also show that the proposed functions for lattice QCD calculation of PDFs in the literature are special cases of these good LCSs.

Topological susceptibility in finite temperature (2 +1 )-flavor QCD using gradient flow

NASA Astrophysics Data System (ADS)

Taniguchi, Yusuke; Kanaya, Kazuyuki; Suzuki, Hiroshi; Umeda, Takashi; WHOT-QCD Collaboration

2017-03-01

We compute the topological charge and its susceptibility in finite temperature (2 +1 )-flavor QCD on the lattice applying a gradient flow method. With the Iwasaki gauge action and nonperturbatively O (a ) -improved Wilson quarks, we perform simulations on a fine lattice with a ≃0.07 fm at a heavy u , d quark mass with mπ/mρ≃0.63 , but approximately physical s quark mass with mηss/mϕ≃0.74 . In a temperature range from T ≃174 MeV (Nt=16 ) to 697 MeV (Nt=4 ), we study two topics on the topological susceptibility. One is a comparison of gluonic and fermionic definitions of the topological susceptibility. Because the two definitions are related by chiral Ward-Takahashi identities, their equivalence is not trivial for lattice quarks which violate the chiral symmetry explicitly at finite lattice spacings. The gradient flow method enables us to compute them without being bothered by the chiral violation. We find a good agreement between the two definitions with Wilson quarks. The other is a comparison with a prediction of the dilute instanton gas approximation, which is relevant in a study of axions as a candidate of the dark matter in the evolution of the Universe. We find that the topological susceptibility shows a decrease in T which is consistent with the predicted χt(T )∝(T /Tpc)-8 for three-flavor QCD even at low temperature Tpc

Light-front holography and superconformal quantum mechanics: A new approach to hadron structure and color confinement

NASA Astrophysics Data System (ADS)

Brodsky, Stanley J.; Deur, Alexandre; de Téramond, Guy F.; Dosch, Hans Günter

2015-11-01

A primary question in hadron physics is how the mass scale for hadrons consisting of light quarks, such as the proton, emerges from the QCD Lagrangian even in the limit of zero quark mass. If one requires the effective action which underlies the QCD Lagrangian to remain conformally invariant and extends the formalism of de Alfaro, Fubini and Furlan to light-front Hamiltonian theory, then a unique, color-confining potential with a mass parameter κ emerges. The actual value of the parameter κ is not set by the model - only ratios of hadron masses and other hadronic mass scales are predicted. The result is a nonperturbative, relativistic light-front quantum mechanical wave equation, the Light-Front Schrödinger Equation which incorporates color confinement and other essential spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the identical slope in the radial quantum number n and orbital angular momentum L. The same light-front equations for mesons with spin J also can be derived from the holographic mapping to QCD (3+1) at fixed light-front time from the soft-wall model modification of AdS5 space with a specific dilaton profile. Light-front holography thus provides a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. One can also extend the analysis to baryons using superconformal algebra - 2 × 2 supersymmetric representations of the conformal group. The resulting fermionic LF bound-state equations predict striking similarities between the meson and baryon spectra. In fact, the holographic QCD light-front Hamiltonians for the states on the meson and baryon trajectories are identical if one shifts the internal angular momenta of the meson (LM) and baryon (LB) by one unit: LM = LB + 1. We also show how the mass scale κ underlying confinement and the masses of light-quark hadrons determines the scale ΛMS¯ controlling the evolution of the perturbative QCD coupling. The relation between scales is obtained by matching the nonperturbative dynamics, as described by an effective conformal theory mapped to the light-front and its embedding in AdS space, to the perturbative QCD regime. The data for the effective coupling defined from the Bjorken sum rule αg1(Q2) are remarkably consistent with the Gaussian form predicted by LF holographic QCD. The result is an effective coupling defined at all momenta. The predicted value ΛMS¯(NF=3)=0.440mρ=0.341±0.024GeV is in agreement with the world average 0.339±0.010GeV. We thus can connect ΛMS¯ to hadron masses. The analysis applies to any renormalization scheme.

The asymptotic form of non-global logarithms, black disc saturation, and gluonic deserts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neill, Duff

Here, we develop an asymptotic perturbation theory for the large logarithmic behavior of the non-linear integro-differential equation describing the soft correlations of QCD jet measurements, the Banfi-Marchesini-Smye (BMS) equation. Furthermore, this equation captures the late-time evolution of radiating color dipoles after a hard collision. This allows us to prove that at large values of the control variable (the non-global logarithm, a function of the infra-red energy scales associated with distinct hard jets in an event), the distribution has a gaussian tail. We also compute the decay width analytically, giving a closed form expression, and find it to be jet geometrymore » independent, up to the number of legs of the dipole in the active jet. By enabling the asymptotic expansion we find that the perturbative seed is correct; we perturb around an anzats encoding formally no real emissions, an intuition motivated by the buffer region found in jet dynamics. This must be supplemented with the correct application of the BFKL approximation to the BMS equation in collinear limits. Comparing to the asymptotics of the conformally related evolution equation encountered in small-x physics, the Balitisky-Kovchegov (BK) equation, we find that the asymptotic form of the non-global logarithms directly maps to the black-disc unitarity limit of the BK equation, despite the contrasting physical pictures. Indeed, we recover the equations of saturation physics in the final state dynamics of QCD.« less

The asymptotic form of non-global logarithms, black disc saturation, and gluonic deserts

DOE PAGES

Neill, Duff

2017-01-25

Here, we develop an asymptotic perturbation theory for the large logarithmic behavior of the non-linear integro-differential equation describing the soft correlations of QCD jet measurements, the Banfi-Marchesini-Smye (BMS) equation. Furthermore, this equation captures the late-time evolution of radiating color dipoles after a hard collision. This allows us to prove that at large values of the control variable (the non-global logarithm, a function of the infra-red energy scales associated with distinct hard jets in an event), the distribution has a gaussian tail. We also compute the decay width analytically, giving a closed form expression, and find it to be jet geometrymore » independent, up to the number of legs of the dipole in the active jet. By enabling the asymptotic expansion we find that the perturbative seed is correct; we perturb around an anzats encoding formally no real emissions, an intuition motivated by the buffer region found in jet dynamics. This must be supplemented with the correct application of the BFKL approximation to the BMS equation in collinear limits. Comparing to the asymptotics of the conformally related evolution equation encountered in small-x physics, the Balitisky-Kovchegov (BK) equation, we find that the asymptotic form of the non-global logarithms directly maps to the black-disc unitarity limit of the BK equation, despite the contrasting physical pictures. Indeed, we recover the equations of saturation physics in the final state dynamics of QCD.« less

Two-color QCD at high density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boz, Tamer; Skullerud, Jon-Ivar; Centre for the Subatomic Structure of Matter, Adelaide University, Adelaide, SA 5005

2016-01-22

QCD at high chemical potential has interesting properties such as deconfinement of quarks. Two-color QCD, which enables numerical simulations on the lattice, constitutes a laboratory to study QCD at high chemical potential. Among the interesting properties of two-color QCD at high density is the diquark condensation, for which we present recent results obtained on a finer lattice compared to previous studies. The quark propagator in two-color QCD at non-zero chemical potential is referred to as the Gor’kov propagator. We express the Gor’kov propagator in terms of form factors and present recent lattice simulation results.

Progress in vacuum susceptibilities and their applications to the chiral phase transition of QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Zhu-Fang, E-mail: phycui@nju.edu.cn; State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing, 100190; Hou, Feng-Yao

2015-07-15

The QCD vacuum condensates and various vacuum susceptibilities are all important parameters which characterize the nonperturbative properties of the QCD vacuum. In the QCD sum rules external field formula, various QCD vacuum susceptibilities play important roles in determining the properties of hadrons. In this paper, we review the recent progress in studies of vacuum susceptibilities together with their applications to the chiral phase transition of QCD. The results of the tensor, the vector, the axial–vector, the scalar, and the pseudo-scalar vacuum susceptibilities are shown in detail in the framework of Dyson–Schwinger equations.

The tempo and mode of evolution: body sizes of island mammals.

PubMed

Raia, Pasquale; Meiri, Shai

2011-07-01

The tempo and mode of body size evolution on islands are believed to be well known. It is thought that body size evolves relatively quickly on islands toward the mammalian modal value, thus generating extreme cases of size evolution and the island rule. Here, we tested both theories in a phylogenetically explicit context, by using two different species-level mammalian phylogenetic hypotheses limited to sister clades dichotomizing into an exclusively insular and an exclusively mainland daughter nodes. Taken as a whole, mammals were found to show a largely punctuational mode of size evolution. We found that, accounting for this, and regardless of the phylogeny used, size evolution on islands is no faster than on the continents. We compared different selection regimes using a set of Ornstein-Uhlenbeck models to examine the effects of insularity of the mode of evolution. The models strongly supported clade-specific selection regimes. Under this regime, however, an evolutionary model allowing insular species to evolve differently from their mainland relatives performs worse than a model that ignores insularity as a factor. Thus, insular taxa do not experience statistically different selection from their mainland relatives. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

QCD In Extreme Conditions

NASA Astrophysics Data System (ADS)

Wilczek, Frank

Introduction Symmetry and the Phenomena of QCD Apparent and Actual Symmetries Asymptotic Freedom Confinement Chiral Symmetry Breaking Chiral Anomalies and Instantons High Temperature QCD: Asymptotic Properties Significance of High Temperature QCD Numerical Indications for Quasi-Free Behavior Ideas About Quark-Gluon Plasma Screening Versus Confinement Models of Chiral Symmetry Breaking More Refined Numerical Experiments High-Temperature QCD: Phase Transitions Yoga of Phase Transitions and Order Parameters Application to Glue Theories Application to Chiral Transitions Close Up on Two Flavors A Genuine Critical Point! (?) High-Density QCD: Methods Hopes, Doubts, and Fruition Another Renormalization Group Pairing Theory Taming the Magnetic Singularity High-Density QCD: Color-Flavor Locking and Quark-Hadron Continuity Gauge Symmetry (Non)Breaking Symmetry Accounting Elementary Excitations A Modified Photon Quark-Hadron Continuity Remembrance of Things Past More Quarks Fewer Quarks and Reality

Semileptonic B-meson decays to light pseudoscalar mesons on the HISQ ensembles

NASA Astrophysics Data System (ADS)

Gelzer, Zechariah; Bernard, C.; Tar, C. De; El-Khadra, AX; Gámiz, E.; Gottlieb, Steven; Kronfeld, Andreas S.; Liu, Yuzhi; Meurice, Y.; Simone, J. N.; Toussaint, D.; Water, R. S. Van de; Zhou, R.

2018-03-01

We report the status of an ongoing lattice-QCD calculation of form factors for exclusive semileptonic decays of B mesons with both charged currents (B → πlv, Bs → Klv) and neutral currents (B → πl+l-, B → Kl+l-). The results are important for constraining or revealing physics beyond the Standard Model. This work uses MILC's (2+1 + 1)-flavor ensembles with the HISQ action for the sea and light valence quarks and the clover action in the Fermilab interpretation for the b quark. Simulations are carried out at three lattice spacings down to 0.088 fm, with both physical and unphysical sea-quark masses. We present preliminary results for correlation-function fits.

Exclusive decay of P-wave bottomonium into double J/{psi}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Juan; Institute of Theoretical Physics, Shanxi University, Taiyuan, Shanxi 030006; Dong Hairong

2011-11-01

We calculate the relativistic corrections of J/{psi}, including electromagnetic corrections, to {chi}{sub b}J{yields}J/{psi}J/{psi} in the framework of nonrelativistic QCD factorization. The relativistic effects are found to increase the lower-order prediction for the decay width by about 10%, while the electromagnetism contribution is very small, about 0.2% for {chi}{sub b0} and {chi}{sub b2}. The total branching ratios are predicted to be of order 10{sup -5} for {chi}{sub b0,b2}{yields}J/{psi}J/{psi}, but 10{sup -11} for {chi}{sub b1}{yields}J/{psi}J/{psi}, since there is only electromagnetism contribution in this channel. We predict it is possible to observe these reactions in LHC.

Recent development in lattice QCD studies for three-nucleon forces

NASA Astrophysics Data System (ADS)

Doi, Takumi; HAL QCD Collaboration

2014-09-01

The direct determination of nuclear forces from QCD has been one of the most desirable challenges in nuclear physics. Recently, a first-principles lattice QCD determination is becoming possible by a novel theoretical method, HAL QCD method, in which Nambu-Bethe-Salpeter (NBS) wave functions are utilized. In this talk, I will focus on the study of three-nucleon forces in HAL QCD method by presenting the recent theoretical/numerical development.

Extraction of quark transversity distribution and Collins fragmentation functions with QCD evolution

DOE PAGES

Kang, Zhong-Bo; Prokudin, Alexei; Sun, Peng; ...

2016-01-13

In this paper, we study the transverse momentum dependent (TMD) evolution of the Collins azimuthal asymmetries in e +e - annihilations and semi-inclusive hadron production in deep inelastic scattering (SIDIS) processes. All the relevant coefficients are calculated up to the next-to-leading logarithmic (NLL) order accuracy. By applying the TMD evolution at the approximate NLL order in the Collins- Soper-Sterman (CSS) formalism, we extract transversity distributions for u and d quarks and Collins fragmentation functions from current experimental data by a global analysis of the Collins asymmetries in back-to-back di-hadron productions in e +e - annihilations measured by BELLE and BABARmore » Collaborations and SIDIS data from HERMES, COMPASS, and JLab HALL A experiments. The impact of the evolution effects and the relevant theoretical uncertainties are discussed. We further discuss the TMD interpretation for our results, and illustrate the unpolarized quark distribution, transversity distribution, unpolarized quark fragmentation and Collins fragmentation functions depending on the transverse momentum and the hard momentum scale. Finally, we give predictions and discuss impact of future experiments.« less

Extraction of quark transversity distribution and Collins fragmentation functions with QCD evolution

NASA Astrophysics Data System (ADS)

Kang, Zhong-Bo; Prokudin, Alexei; Sun, Peng; Yuan, Feng

2016-01-01

We study the transverse-momentum-dependent (TMD) evolution of the Collins azimuthal asymmetries in e+e- annihilations and semi-inclusive hadron production in deep inelastic scattering processes. All the relevant coefficients are calculated up to the next-to-leading-logarithmic-order accuracy. By applying the TMD evolution at the approximate next-to-leading-logarithmic order in the Collins-Soper-Sterman formalism, we extract transversity distributions for u and d quarks and Collins fragmentation functions from current experimental data by a global analysis of the Collins asymmetries in back-to-back dihadron productions in e+e- annihilations measured by BELLE and BABAR collaborations and semi-inclusive hadron production in deep inelastic scattering data from HERMES, COMPASS, and JLab HALL A experiments. The impact of the evolution effects and the relevant theoretical uncertainties are discussed. We further discuss the TMD interpretation for our results and illustrate the unpolarized quark distribution, transversity distribution, unpolarized quark fragmentation, and Collins fragmentation functions depending on the transverse momentum and the hard momentum scale. We make detailed predictions for future experiments and discuss their impact.

Extraction of quark transversity distribution and Collins fragmentation functions with QCD evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Zhong-Bo; Prokudin, Alexei; Sun, Peng

In this paper, we study the transverse momentum dependent (TMD) evolution of the Collins azimuthal asymmetries in e +e - annihilations and semi-inclusive hadron production in deep inelastic scattering (SIDIS) processes. All the relevant coefficients are calculated up to the next-to-leading logarithmic (NLL) order accuracy. By applying the TMD evolution at the approximate NLL order in the Collins- Soper-Sterman (CSS) formalism, we extract transversity distributions for u and d quarks and Collins fragmentation functions from current experimental data by a global analysis of the Collins asymmetries in back-to-back di-hadron productions in e +e - annihilations measured by BELLE and BABARmore » Collaborations and SIDIS data from HERMES, COMPASS, and JLab HALL A experiments. The impact of the evolution effects and the relevant theoretical uncertainties are discussed. We further discuss the TMD interpretation for our results, and illustrate the unpolarized quark distribution, transversity distribution, unpolarized quark fragmentation and Collins fragmentation functions depending on the transverse momentum and the hard momentum scale. Finally, we give predictions and discuss impact of future experiments.« less

Phenomenological constraints on the bulk viscosity of QCD

NASA Astrophysics Data System (ADS)

Paquet, Jean-François; Shen, Chun; Denicol, Gabriel; Jeon, Sangyong; Gale, Charles

2017-11-01

While small at very high temperature, the bulk viscosity of Quantum Chromodynamics is expected to grow in the confinement region. Although its precise magnitude and temperature-dependence in the cross-over region is not fully understood, recent theoretical and phenomenological studies provided evidence that the bulk viscosity can be sufficiently large to have measurable consequences on the evolution of the quark-gluon plasma. In this work, a Bayesian statistical analysis is used to establish probabilistic constraints on the temperature-dependence of bulk viscosity using hadronic measurements from RHIC and LHC.

Measurement of multiplicity and momentum spectra in the current fragmentation region of the Breit frame at HERA

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Mikunas, D.; Musgrave, B.; Repond, J.; Stanek, R.; Talaga, R. L.; Zhang, H.; Avad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Romeo, G. Cara; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Contin, A.; Gialas, I.; Giusti, P.; Lacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Garcia, Y. Zamora; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Eckert, M.; Feld, L.; Frey, A.; Geerts, M.; Geitz, G.; Grothe, M.; Haas, T.; Hartmann, H.; Haun, D.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mari, S. M.; Mass, A.; Mengel, S.; Mollen, J.; Paul, E.; Rembser, Ch.; Schattevoy, R.; Schramm, D.; Stamm, V.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Llewellyn, T. J.; Morgado, C. J. S.; Norman, D. J. P.; O'Mara, J. A.; Tapper, R. J.; Wilson, S. S.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Zhu, Q.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Eskreys, K.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarębska, E.; Suszycki, L.; Zając, J.; Kotański, A.; Przybycień, M.; Bauerdick, I. A. T.; Behrens, U.; Beier, H.; Bienlein, J. K.; Coldewey, C.; Deppe, O.; Desler, K.; Drews, G.; Flasińki, M.; Gilkinson, D. J.; Glasman, C.; Göttlicher, P.; Große-Knetter, J.; Gutjahr, B.; Hain, W.; Hasell, D.; Heßling, H.; Hultschig, H.; Iga, Y.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Kopke, L.; Kötz, U.; Kowalski, H.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mańczak, O.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneckloth, U.; Schulz, W.; Selonke, F.; Stiliaris, E.; Surrow, B.; Voß, T.; Westphal, D.; Wolf, G.; Youngman, C.; Zhou, J. F.; Grabosch, H. J.; Kharchilava, A.; Leich, A.; Mattingly, M.; Meyer, A.; Schlenstedt, S.; Barbagli, G.; Pelfer, P.; Anzivino, G.; Maccarrone, G.; de Pasquale, S.; Votano, L.; Bamberger, A.; Eisenhardt, S.; Freidhof, A.; Söldner-Rembold, S.; Schroeder, J.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Fleck, I.; Jamieson, V. A.; Saxon, D. H.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Hagge, L.; Lohrmann, E.; Mainusch, J.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Zetsche, F.; Bacon, T. C.; Butterworth, I.; Gallo, E.; Harris, V. L.; Hung, B. Y. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Zhang, Y.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Nam, S. W.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-I.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; Del Peso, J.; Puga, J.; Terron, J.; de Trocóniz, I. F.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; St. Laurent, M.; Ullmann, R.; Zacek, G.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Y. A.; Kobrin, V. D.; Kuzmin, V. A.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Botje, M.; Chlebana, F.; Dake, A.; Engelen, J.; de Kamps, M.; Kooijman, P.; Kruse, A.; Tiecke, H.; Verkerke, W.; Vreeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Bailey, D. S.; Blair, G. A.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Daniels, D.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Luffman, P. E.; Lindemann, L.; McFall, J. D.; Nath, C.; Quadt, A.; Uijterwaal, H.; Walczak, R.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; de Giorgi, M.; Dosselli, U.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Field, R. G.; Oh, B. Y.; Whitmore, J. J.; D'Agostini, G.; Marini, G.; Nigro, A.; Tassi, E.; Hart, J. C.; McCubbin, N. A.; Prytz, K.; Shah, T. P.; Short, T. L.; Barberis, E.; Cartiglia, N.; Dubbs, T.; Heusch, C.; van Hook, M.; Hubbard, B.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Biltzinger, J.; Seifert, R. J.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nakamitsu, Y.; Yamauchi, K.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Crombie, M. B.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Blankenship, K.; Kochocki, J.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchuła, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Karshon, U.; Revel, D.; Zer-Zion, D.; Ali, I.; Badgett, W. F.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Vaiciulis, A.; Wodarczyk, M.; Tsurugai, T.; Bhadra, S.; Cardy, M. L.; Fagerstroem, C.-P.; Frisken, W. R.; Furutani, K. M.; Khakzad, M.; Schmidke, W. B.

1995-03-01

Charged particle production has been measured in Deep Inelastic Scattering (DIS) events using the ZEUS detector over a large range of Q 2 from 10 to 1280 GeV2. The evolution with Q of the charged multiplicity and scaled momentum has been investigated in the current fragmentation region of the Breit frame. The data are used to study QCD coherence effects in DIS and are compared with corresponding e + e - data in order to test the universality of quark fragmentation.

Isocurvature constraints and anharmonic effects on QCD axion dark matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Takeshi; Kurematsu, Ryosuke; Takahashi, Fuminobu, E-mail: takeshi@cita.utoronto.ca, E-mail: rkurematsu@tuhep.phys.tohoku.ac.jp, E-mail: fumi@tuhep.phys.tohoku.ac.jp

2013-09-01

We revisit the isocurvature density perturbations induced by quantum fluctuations of the axion field by extending a recently developed analytic method and approximations to a time-dependent scalar potential, which enables us to follow the evolution of the axion until it starts to oscillate. We find that, as the initial misalignment angle approaches the hilltop of the potential, the isocurvature perturbations become significantly enhanced, while the non-Gaussianity parameter increases slowly but surely. As a result, the isocurvature constraint on the inflation scale is tightened as H{sub inf}∼

The current matrix elements from HAL QCD method

NASA Astrophysics Data System (ADS)

Watanabe, Kai; Ishii, Noriyoshi

2018-03-01

HAL QCD method is a method to construct a potential (HAL QCD potential) that reproduces the NN scattering phase shift faithful to the QCD. The HAL QCD potential is obtained from QCD by eliminating the degrees of freedom of quarks and gluons and leaving only two particular hadrons. Therefor, in the effective quantum mechanics of two nucleons defined by HAL QCD potential, the conserved current consists not only of the nucleon current but also an extra current originating from the potential (two-body current). Though the form of the two-body current is closely related to the potential, it is not straight forward to extract the former from the latter. In this work, we derive the the current matrix element formula in the quantum mechanics defined by the HAL QCD potential. As a first step, we focus on the non-relativistic case. To give an explicit example, we consider a second quantized non-relativistic two-channel coupling model which we refer to as the original model. From the original model, the HAL QCD potential for the open channel is constructed by eliminating the closed channel in the elastic two-particle scattering region. The current matrix element formula is derived by demanding the effective quantum mechanics defined by the HAL QCD potential to respond to the external field in the same way as the original two-channel coupling model.

Lattice analysis for the energy scale of QCD phenomena.

PubMed

Yamamoto, Arata; Suganuma, Hideo

2008-12-12

We formulate a new framework in lattice QCD to study the relevant energy scale of QCD phenomena. By considering the Fourier transformation of link variable, we can investigate the intrinsic energy scale of a physical quantity nonperturbatively. This framework is broadly available for all lattice QCD calculations. We apply this framework for the quark-antiquark potential and meson masses in quenched lattice QCD. The gluonic energy scale relevant for the confinement is found to be less than 1 GeV in the Landau or Coulomb gauge.

QCD dirac operator at nonzero chemical potential: lattice data and matrix model.

PubMed

Akemann, Gernot; Wettig, Tilo

2004-03-12

Recently, a non-Hermitian chiral random matrix model was proposed to describe the eigenvalues of the QCD Dirac operator at nonzero chemical potential. This matrix model can be constructed from QCD by mapping it to an equivalent matrix model which has the same symmetries as QCD with chemical potential. Its microscopic spectral correlations are conjectured to be identical to those of the QCD Dirac operator. We investigate this conjecture by comparing large ensembles of Dirac eigenvalues in quenched SU(3) lattice QCD at a nonzero chemical potential to the analytical predictions of the matrix model. Excellent agreement is found in the two regimes of weak and strong non-Hermiticity, for several different lattice volumes.

First Measurement of the E Double-polarization Observable for the γη to Κ +Σ - with CLAS & a New Forward Tagger Hodoscope for CLAS12

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleming, Jamie

Establishing the excitation spectrum of the nucleon would be a key advance to further our understanding of nucleon structure and Quantum Chromodynamics (QCD). Recent theoretical advances allow predictions of the excitation spectrum of the nucleon and other nucleon properties directly from QCD in the nonperturbative regime, via numerical methods (such as Lattice QCD), complementing existing constituent quark models. There is an ongoing world programme in meson photoproduction from the nucleon, which has already led to a number of nucleon resonances being discovered and established. This advance has largely been made possible by the first accurate measurement of polarisation observables. Availablemore » data has been obtained for proton targets, whereas for a complete picture of meson photoproduction, data from the neutron must also be obtained. This is important, as nucleon resonances can have very different photo-couplings to the proton and neutron. This thesis presents the rst measurement of the E double-polarisation observable for the exclusive γη -> Κ +Σ - reaction using a polarised hydrogendeuterium target from the g14 run period at CLAS. Circularly polarised photons of energies between 1:1 and 2:3 GeV were used, with results shown in 200 MeV bins in E and bins of 0:4 in cosθ C.M./ Κ+ . Further to this, CLAS has undergone a detector upgrade in order to facilitate electrons of up to 12 GeV from Jefferson Lab's upgraded accelerator. Essential to this, is a new system for tagging quasi-real photons by detecting electrons scattered at very small angles. My work includes signi cant contributions to the design, realisation and construction of a hodoscope for this forward photon tagging apparatus. Presented in this thesis is a comprehensive overview of my work in developing and constructing the scintillating hodoscope for the CLAS12 Forward Tagger.« less

On the impact of power corrections in the prediction of B → K *μ+μ- observables

NASA Astrophysics Data System (ADS)

Descotes-Genon, Sébastien; Hofer, Lars; Matias, Joaquim; Virto, Javier

2014-12-01

The recent LHCb angular analysis of the exclusive decay B → K * μ + μ - has indicated significant deviations from the Standard Model expectations. Accurate predictions can be achieved at large K *-meson recoil for an optimised set of observables designed to have no sensitivity to hadronic input in the heavy-quark limit at leading order in α s . However, hadronic uncertainties reappear through non-perturbative ΛQCD /m b power corrections, which must be assessed precisely. In the framework of QCD factorisation we present a systematic method to include factorisable power corrections and point out that their impact on angular observables depends on the scheme chosen to define the soft form factors. Associated uncertainties are found to be under control, contrary to earlier claims in the literature. We also discuss the impact of possible non-factorisable power corrections, including an estimate of charm-loop effects. We provide results for angular observables at large recoil for two different sets of inputs for the form factors, spelling out the different sources of theoretical uncertainties. Finally, we comment on a recent proposal to explain the anomaly in B → K * μ + μ - observables through charm-resonance effects, and we propose strategies to test this proposal identifying observables and kinematic regions where either the charm-loop model can be disentangled from New Physics effects or the two options leave different imprints.

Measurement of the underlying event in jet events from 7 TeV proton–proton collisions with the ATLAS detector

DOE PAGES

Aad, G.; Abajyan, T.; Abbott, B.; ...

2014-08-12

Distributions sensitive to the underlying event in QCD jet events have been measured with the ATLAS detector at the LHC, based on 37 pb -1 of proton–proton collision data collected at a centre-of-mass energy of 7 TeV. Charged-particle mean p T and densities of all-particle E T and charged-particle multiplicity and p T have been measured in regions azimuthally transverse to the hardest jet in each event. These are presented both as one-dimensional distributions and with their mean values as functions of the leading-jet transverse momentum from 20 to 800 GeV. The correlation of charged-particle mean p T with charged-particlemore » multiplicity is also studied, and the E T densities include the forward rapidity region; these features provide extra data constraints for Monte Carlo modelling of colour reconnection and beam-remnant effects respectively. For the first time, underlying event observables have been computed separately for inclusive jet and exclusive dijet event selections, allowing more detailed study of the interplay of multiple partonic scattering and QCD radiation contributions to the underlying event. Comparisons to the predictions of different Monte Carlo models show a need for further model tuning, but the standard approach is found to generally reproduce the features of the underlying event in both types of event selection.« less

Recent progress on the understanding of the medium-induced jet evolution and energy loss in pQCD

NASA Astrophysics Data System (ADS)

Apolinário, Liliana

2017-03-01

Motivated by the striking modifications of jets observed both at RHIC and the LHC, significant progress towards the understanding of jet dynamics within QGP has occurred over the last few years. In this talk, I review the recent theoretical developments in the study of medium-induced jet evolution and energy loss within a perturbative framework. The main mechanisms of energy loss and broadening will be firstly addressed with focus on leading particle calculations beyond the eikonal approximation. Then, I will provide an overview of the modifications of the interference pattern between the different parton emitters that build up the parton shower when propagating through an extended coloured medium. I will show that the interplay between color coherence/decoherence that arises from such effects is the main mechanism for the modification of the jet core angular structure. Finally, I discuss the possibility of a probabilistic picture of the parton shower evolution in the limit of a very dense or infinite medium.

Recurrent abnormalities in conifer cones and the evolutionary origins of flower-like structures.

PubMed

Rudall, Paula J; Hilton, Jason; Vergara-Silva, Francisco; Bateman, Richard M

2011-03-01

Conifer cones are reproductive structures that are typically of restricted growth and either exclusively pollen-bearing (male) or exclusively ovule-bearing (female). Here, we review two common spontaneous developmental abnormalities of conifer cones: proliferated cones, in which the apex grows vegetatively, and bisexual cones, which possess both male and female structures. Emerging developmental genetic data, combined with evidence from comparative morphology, ontogeny and palaeobotany, provide new insights into the evolution of both cones and flowers, and prompt novel strategies for understanding seed-plant evolution. Copyright © 2010 Elsevier Ltd. All rights reserved.

QCD for Postgraduates (2/5)

ScienceCinema

Zanderighi, Giulia

2018-05-21

Modern QCD - Lecture 2 We will start discussing the matter content of the theory and revisit the experimental measurements that led to the discovery of quarks. We will then consider a classic QCD observable, the R-ratio, and use it to illustrate the appearance of UV divergences and the need to renormalize the coupling constant of QCD. We will then discuss asymptotic freedom and confinement. Finally, we will examine a case where soft and collinear infrared divergences appear, will discuss the soft approximation in QCD and will introduce the concept of infrared safe jets.

Nucleon-nucleon interactions via Lattice QCD: Methodology. HAL QCD approach to extract hadronic interactions in lattice QCD

NASA Astrophysics Data System (ADS)

Aoki, Sinya

2013-07-01

We review the potential method in lattice QCD, which has recently been proposed to extract nucleon-nucleon interactions via numerical simulations. We focus on the methodology of this approach by emphasizing the strategy of the potential method, the theoretical foundation behind it, and special numerical techniques. We compare the potential method with the standard finite volume method in lattice QCD, in order to make pros and cons of the approach clear. We also present several numerical results for nucleon-nucleon potentials.

Renormalization of Extended QCD2

NASA Astrophysics Data System (ADS)

Fukaya, Hidenori; Yamamura, Ryo

2015-10-01

Extended QCD (XQCD), proposed by Kaplan [D. B. Kaplan, arXiv:1306.5818], is an interesting reformulation of QCD with additional bosonic auxiliary fields. While its partition function is kept exactly the same as that of original QCD, XQCD naturally contains properties of low-energy hadronic models. We analyze the renormalization group flow of 2D (X)QCD, which is solvable in the limit of a large number of colors N_c, to understand what kind of roles the auxiliary degrees of freedom play and how the hadronic picture emerges in the low-energy region.

θ and the η ' in large N supersymmetric QCD

DOE PAGES

Dine, Michael; Draper, Patrick; Stephenson-Haskins, Laurel; ...

2017-05-22

Here, we study the large N θ dependence and the η' potential in supersymmetric QCD with small soft SUSY-breaking terms. Known exact results in SUSY QCD are found to reflect a variety of expectations from large N perturbation theory, including the presence of branches and the behavior of theories with matter (both with N f << N and N f ~ N ). But, there are also striking departures from ordinary QCD and the conventional large N description: instanton effects, when under control, are not exponentially suppressed at large N , and branched structure in supersymmetric QCD is always associatedmore » with approximate discrete symmetries. We suggest that these differences motivate further study of large N QCD on the lattice.« less

Matrix theory for baryons: an overview of holographic QCD for nuclear physics.

PubMed

Aoki, Sinya; Hashimoto, Koji; Iizuka, Norihiro

2013-10-01

We provide, for non-experts, a brief overview of holographic QCD (quantum chromodynamics) and a review of the recent proposal (Hashimoto et al 2010 (arXiv:1003.4988[hep-th])) of a matrix-like description of multi-baryon systems in holographic QCD. Based on the matrix model, we derive the baryon interaction at short distances in multi-flavor holographic QCD. We show that there is a very universal repulsive core of inter-baryon forces for a generic number of flavors. This is consistent with a recent lattice QCD analysis for Nf = 2, 3 where the repulsive core looks universal. We also provide a comparison of our results with the lattice QCD and the operator product expansion analysis.

Exploring Partonic Structure of Hadrons Using ab initio Lattice QCD Calculations

DOE PAGES

Ma, Yan-Qing; Qiu, Jian-Wei

2018-01-10

Following our previous proposal, we construct a class of good "lattice cross sections" (LCSs), from which we can study the partonic structure of hadrons from ab initio lattice QCD calculations. These good LCSs, on the one hand, can be calculated directly in lattice QCD, and on the other hand, can be factorized into parton distribution functions (PDFs) with calculable coefficients, in the same way as QCD factorization for factorizable hadronic cross sections. PDFs could be extracted from QCD global analysis of the lattice QCD generated data of LCSs. In conclusion, we also show that the proposed functions for lattice QCDmore » calculation of PDFs in the literature are special cases of these good LCSs.« less

Nonperturbative Transverse Momentum Effects in p +p and p +A Collisions at PHENIX

NASA Astrophysics Data System (ADS)

Skoby, Michael; Phenix Collaboration

2017-09-01

Due to the non-Abelian nature of QCD, there is a prediction that quarks can become correlated across colliding protons in hadron production processes sensitive to nonperturbative transverse momentum effects. Measuring the evolution of nonperturbative transverse momentum widths as a function of the hard interaction scale can help distinguish these effects from other possibilities. Collins-Soper-Sterman evolution comes directly from the proof of transverse-momentum-dependent (TMD) factorization for processes such as Drell-Yan, semi-inclusive deep-inelastic scattering, and e +e- annihilation and predicts nonperturbative momentum widths to increase with hard scale. Experimental results from proton-proton and proton-nucleus collisions, in which TMD factorization is predicted to be broken, will be presented. The results show that these widths decrease with hard scale, suggesting possible effects from TMD factorization breaking.

Two-baryon systems from HAL QCD method and the mirage in the temporal correlation of the direct method

NASA Astrophysics Data System (ADS)

Iritani, Takumi

2018-03-01

Both direct and HAL QCD methods are currently used to study the hadron interactions in lattice QCD. In the direct method, the eigen-energy of two-particle is measured from the temporal correlation. Due to the contamination of excited states, however, the direct method suffers from the fake eigen-energy problem, which we call the "mirage problem," while the HAL QCD method can extract information from all elastic states by using the spatial correlation. In this work, we further investigate systematic uncertainties of the HAL QCD method such as the quark source operator dependence, the convergence of the derivative expansion of the non-local interaction kernel, and the single baryon saturation, which are found to be well controlled. We also confirm the consistency between the HAL QCD method and the Lüscher's finite volume formula. Based on the HAL QCD potential, we quantitatively confirm that the mirage plateau in the direct method is indeed caused by the contamination of excited states.

Nucleon QCD sum rules in the instanton medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryskin, M. G.; Drukarev, E. G., E-mail: drukarev@pnpi.spb.ru; Sadovnikova, V. A.

2015-09-15

We try to find grounds for the standard nucleon QCD sum rules, based on a more detailed description of the QCD vacuum. We calculate the polarization operator of the nucleon current in the instanton medium. The medium (QCD vacuum) is assumed to be a composition of the small-size instantons and some long-wave gluon fluctuations. We solve the corresponding QCD sum rule equations and demonstrate that there is a solution with the value of the nucleon mass close to the physical one if the fraction of the small-size instantons contribution is w{sub s} ≈ 2/3.

A case-control study of the difficulties in daily functioning experienced by children with depressive disorder.

PubMed

Usami, Masahide; Iwadare, Yoshitaka; Watanabe, Kyota; Ushijima, Hirokage; Kodaira, Masaki; Okada, Takashi; Sasayama, Daimei; Sugiyama, Nobuhiro; Saito, Kazuhiko

2015-07-01

The parent-assessed children-with-difficulties questionnaire (Questionnaire-Children with Difficulties; QCD) is designed to evaluate a child׳s difficulties in functioning during specific periods of the day. This study aimed to use the QCD to evaluate the difficulties in daily functioning experienced by children with depressive disorders. A case-control design was used. The cases comprised 90 junior high school students with depressive disorder, whereas a community sample of 363 junior high school students was enrolled as controls. Behaviors were assessed using the QCD, Depression Self-Rating Scale (DSRS), Tokyo Autistic Behavior Scale (TABS), attention deficit hyperactivity disorder-rating scale (ADHD-RS), and Oppositional Defiant Behavior Inventory (ODBI). We then analyzed the effects of sex and diagnosis on the QCD scores as well as the correlation coefficients between the QCD and the other questionnaires. We included 90 cases (33 boys, 57 girls) with depressive disorders and 363 controls (180 boys, 183 girls). The QCD scores for the children with depressive disorders were significantly lower compared with those from the community sample (P<0.001). The morning, school-time, and night subscores of the QCD were lower for the children with both depressive disorders and truancy problems than for those with depressive disorders alone (P<0.001). Significant correlations were observed between the following: the night QCD subscore and the DSRS scores among boys, the morning QCD subscore and ADHD-RS inattention scores for all groups, and the evening QCD subscore and the TABS score. Parents reported that children with depressive disorders experienced greater difficulties in completing basic daily activities compared with community controls. These difficulties were dependent on sex, symptoms, and the time of day. The use of QCD to assess children with depressive disorders enables clinicians to clarify the time periods at which the children face difficulties. Copyright © 2015 Elsevier B.V. All rights reserved.

Separated Response Function Ratios in Exclusive, Forward π ± Electroproduction

DOE PAGES

Huber, G. M.; Blok, H. P.; Butuceanu, C.; ...

2014-05-05

The study of exclusive π ± electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio R L = σ π- L / σ π+ L is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of R T = σ π- T / σ π+ T from unity at small –t, to 1/4 at large –t, would suggest a transition from coupling to a (virtual)more » pion to coupling to individual quarks. Furthermore, the mentioned ratios may show an earlier approach to perturbative QCD than the individual cross sections. We have performed the first complete separation of the four unpolarized electromagnetic structure functions above the dominant resonances in forward, exclusive π ± electroproduction on the deuteron at central Q 2 values of 0.6, 1.0, 1.6 GeV 2 at W = 1.95 GeV, and Q 2 = 2.45 GeV 2 at W = 2.22 GeV. In this paper, we present the L and T cross sections, with emphasis on R L and R T, and compare them with theoretical calculations. Finally, results for the separated ratio R L indicate dominance of the pion-pole diagram at low –t, while results for R T are consistent with a transition between pion knockout and quark knockout mechanisms.« less

Additional strange hadrons from QCD thermodynamics and strangeness freezeout in heavy ion collisions.

PubMed

Bazavov, A; Ding, H-T; Hegde, P; Kaczmarek, O; Karsch, F; Laermann, E; Maezawa, Y; Mukherjee, Swagato; Ohno, H; Petreczky, P; Schmidt, C; Sharma, S; Soeldner, W; Wagner, M

2014-08-15

We compare lattice QCD results for appropriate combinations of net strangeness fluctuations and their correlations with net baryon number fluctuations with predictions from two hadron resonance gas (HRG) models having different strange hadron content. The conventionally used HRG model based on experimentally established strange hadrons fails to describe the lattice QCD results in the hadronic phase close to the QCD crossover. Supplementing the conventional HRG with additional, experimentally uncharted strange hadrons predicted by quark model calculations and observed in lattice QCD spectrum calculations leads to good descriptions of strange hadron thermodynamics below the QCD crossover. We show that the thermodynamic presence of these additional states gets imprinted in the yields of the ground-state strange hadrons leading to a systematic 5-8 MeV decrease of the chemical freeze-out temperatures of ground-state strange baryons.

Limits on transverse momentum dependent evolution from semi-inclusive deep inelastic scattering at moderate Q

NASA Astrophysics Data System (ADS)

Aidala, C. A.; Field, B.; Gamberg, L. P.; Rogers, T. C.

2014-05-01

In the QCD evolution of transverse momentum dependent parton distribution and fragmentation functions, the Collins-Soper evolution kernel includes both a perturbative short-distance contribution and a large-distance nonperturbative, but strongly universal, contribution. In the past, global fits, based mainly on larger Q Drell-Yan-like processes, have found substantial contributions from nonperturbative regions in the Collins-Soper evolution kernel. In this article, we investigate semi-inclusive deep inelastic scattering measurements in the region of relatively small Q, of the order of a few GeV, where sensitivity to nonperturbative transverse momentum dependence may become more important or even dominate the evolution. Using recently available deep inelastic scattering data from the COMPASS experiment, we provide estimates of the regions of coordinate space that dominate in transverse momentum dependent (TMD) processes when the hard scale is of the order of only a few GeV. We find that distance scales that are much larger than those commonly probed in large Q measurements become important, suggesting that the details of nonperturbative effects in TMD evolution are especially significant in the region of intermediate Q. We highlight the strongly universal nature of the nonperturbative component of evolution and its potential to be tightly constrained by fits from a wide variety of observables that include both large and moderate Q. On this basis, we recommend detailed treatments of the nonperturbative component of the Collins-Soper evolution kernel for future TMD studies.

Charged particle multiplicities in deep inelastic scattering at HERA

NASA Astrophysics Data System (ADS)

Aid, S.; Anderson, M.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Babaev, A.; Bähr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Braunschweig, W.; Brisson, V.; Bruel, P.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M. J.; Calvet, D.; Campbell, A. J.; Carli, T.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Cocks, S.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Cousinou, M.-C.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Davis, C. L.; Delcourt, B.; de Roeck, A.; de Wolf, E. A.; Dirkmann, M.; Dixon, P.; di Nezza, P.; Dlugosz, W.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Fahr, A. B.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gaede, F.; Garvey, J.; Gayler, J.; Gebauer, M.; Genzel, H.; Gerhards, R.; Glazov, A.; Goerlach, U.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Golec-Biernat, K.; Gonzalez-Pineiro, B.; Gorelov, I.; Grab, C.; Grässler, H.; Greenshaw, T.; Griffiths, R. K.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Hadig, T.; Haidt, D.; Hajduk, L.; Hampel, M.; Haynes, W. J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hewitt, K.; Hildesheim, W.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Hoffmann, D.; Holtom, T.; Horisberger, R.; Hudgson, V. L.; Hütte, M.; Ibbotson, M.; Itterbeck, H.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Jung, H.; Kalmus, P. I. P.; Kander, M.; Kant, D.; Kaschowitz, R.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kaufmann, O.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Lacour, D.; Laforge, B.; Lander, R.; Landon, M. P. J.; Lange, W.; Langenegger, U.; Laporte, J.-F.; Lebedev, A.; Lehner, F.; Levonian, S.; Lindström, G.; Lindstroem, M.; Link, J.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Lomas, J. W.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, G.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Meyer, A.; Meyer, A.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Migliori, A.; Mikocki, S.; Milstead, D.; Moeck, J.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, D.; Müller, G.; Müller, K.; Müller, M.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Négri, I.; Newman, P. R.; Newton, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Niggli, H.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Olsson, J. E.; Ozerov, D.; Palmen, P.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Pawletta, H.; Peppel, E.; Perez, E.; Phillips, J. P.; Pieuchot, A.; Pitzl, D.; Pope, G.; Prell, S.; Rabbertz, K.; Rädel, G.; Reimer, P.; Reinshagen, S.; Rick, H.; Riech, V.; Riedlberger, J.; Riepenhausen, F.; Riess, S.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleif, S.; Schleper, P.; von Schlippe, W.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Solochenko, V.; Soloviev, Y.; Specka, A.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Squinabol, F.; Steenbock, M.; Steffen, P.; Steinberg, R.; Steiner, H.; Steinhart, J.; Stella, B.; Stellberger, A.; Stier, J.; Stiewe, J.; Stößlein, U.; Stolze, K.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Taševský, M.; Tchernyshov, V.; Tchetchelnitski, S.; Theissen, J.; Thiebaux, C.; Thompson, G.; Truöl, P.; Tsipolitis, G.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Vandenplas, D.; van Esch, P.; van Mechelen, P.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walther, A.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wengler, T.; Werner, M.; West, L. R.; Wilksen, T.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wobisch, M.; Wünsch, E.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zini, P.; Zomer, F.; Zsembery, J.; Zuber, K.; Zurnedden, M.

1996-12-01

Using the H1 detector at HERA, charged particle multiplicity distributions in deep inelastic e + p scattering have been measured over a large kinematical region. The evolution with W and Q 2 of the multiplicity distribution and of the multiplicity moments in pseudorapidity domains of varying size is studied in the current fragmentation region of the hadronic centre-of-mass frame. The results are compared with data from fixed target lepton-nucleon interactions, e + e - annihilations and hadron-hadron collisions as well as with expectations from QCD based parton models. Fits to the Negative Binomial and Lognormal distributions are presented.

Leading-Color Fully Differential Two-Loop Soft Corrections to QCD Dipole Showers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dulat, Falko; Höche, Stefan; Prestel, Stefan

We compute the next-to-leading order corrections to soft-gluon radiation differentially in the one-emission phase space. We show that their contribution to the evolution of color dipoles can be obtained in a modified subtraction scheme, such that both one- and two-emission terms are amenable to Monte-Carlo integration. The two-loop cusp anomalous dimension is recovered naturally upon integration over the full phase space. We present two independent implementations of the new algorithm in the two event generators Pythia and Sherpa, and we compare the resulting fully differential simulation to the CMW scheme.

Critical end point in the presence of a chiral chemical potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Z. -F.; Cloët, I. C.; Lu, Y.

A class of Polyakov-loop-modified Nambu-Jona-Lasinio models has been used to support a conjecture that numerical simulations of lattice-regularized QCD defined with a chiral chemical potential can provide information about the existence and location of a critical end point in the QCD phase diagram drawn in the plane spanned by baryon chemical potential and temperature. That conjecture is challenged by conflicts between the model results and analyses of the same problem using simulations of lattice-regularized QCD (lQCD) and well-constrained Dyson-Schwinger equation (DSE) studies. We find the conflict is resolved in favor of the lQCD and DSE predictions when both a physicallymore » motivated regularization is employed to suppress the contribution of high-momentum quark modes in the definition of the effective potential connected with the Polyakov-loop-modified Nambu-Jona-Lasinio models and the four-fermion coupling in those models does not react strongly to changes in the mean field that is assumed to mock-up Polyakov-loop dynamics. With the lQCD and DSE predictions thus confirmed, it seems unlikely that simulations of lQCD with mu(5) > 0 can shed any light on a critical end point in the regular QCD phase diagram.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Yan-Qing; Qiu, Jian-Wei

Following our previous proposal, we construct a class of good "lattice cross sections" (LCSs), from which we can study the partonic structure of hadrons from ab initio lattice QCD calculations. These good LCSs, on the one hand, can be calculated directly in lattice QCD, and on the other hand, can be factorized into parton distribution functions (PDFs) with calculable coefficients, in the same way as QCD factorization for factorizable hadronic cross sections. PDFs could be extracted from QCD global analysis of the lattice QCD generated data of LCSs. In conclusion, we also show that the proposed functions for lattice QCDmore » calculation of PDFs in the literature are special cases of these good LCSs.« less

The quark condensate in multi-flavour QCD – planar equivalence confronting lattice simulations

DOE PAGES

Armoni, Adi; Shifman, Mikhail; Shore, Graham; ...

2015-02-01

Planar equivalence between the large N limits of N=1 Super Yang–Mills (SYM) theory and a variant of QCD with fermions in the antisymmetric representation is a powerful tool to obtain analytic non-perturbative results in QCD itself. In particular, it allows the quark condensate for N=3 QCD with quarks in the fundamental representation to be inferred from exact calculations of the gluino condensate in N=1 SYM. In this paper, we review and refine our earlier predictions for the quark condensate in QCD with a general number nf of flavours and confront these with lattice results.

QCD tests in $$p\\bar{p}$$ collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huth, John E.; Mangano, Michelangelo L.

1993-02-01

We review the status of QCD tests in high energy p-pbar collisions. Contents: i) Introduction ii) QCD in Hadronic Collisions iii) Jet Production iv) Heavy Flavour Production v) W and Z Production vi) Direct Photons.

Parton distributions and lattice QCD calculations: A community white paper

NASA Astrophysics Data System (ADS)

Lin, Huey-Wen; Nocera, Emanuele R.; Olness, Fred; Orginos, Kostas; Rojo, Juan; Accardi, Alberto; Alexandrou, Constantia; Bacchetta, Alessandro; Bozzi, Giuseppe; Chen, Jiunn-Wei; Collins, Sara; Cooper-Sarkar, Amanda; Constantinou, Martha; Del Debbio, Luigi; Engelhardt, Michael; Green, Jeremy; Gupta, Rajan; Harland-Lang, Lucian A.; Ishikawa, Tomomi; Kusina, Aleksander; Liu, Keh-Fei; Liuti, Simonetta; Monahan, Christopher; Nadolsky, Pavel; Qiu, Jian-Wei; Schienbein, Ingo; Schierholz, Gerrit; Thorne, Robert S.; Vogelsang, Werner; Wittig, Hartmut; Yuan, C.-P.; Zanotti, James

2018-05-01

In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this document we present an overview of lattice-QCD and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. This document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.

Strangeness S =-1 hyperon-nucleon interactions: Chiral effective field theory versus lattice QCD

NASA Astrophysics Data System (ADS)

Song, Jing; Li, Kai-Wen; Geng, Li-Sheng

2018-06-01

Hyperon-nucleon interactions serve as basic inputs to studies of hypernuclear physics and dense (neutron) stars. Unfortunately, a precise understanding of these important quantities has lagged far behind that of the nucleon-nucleon interaction due to lack of high-precision experimental data. Historically, hyperon-nucleon interactions are either formulated in quark models or meson exchange models. In recent years, lattice QCD simulations and chiral effective field theory approaches start to offer new insights from first principles. In the present work, we contrast the state-of-the-art lattice QCD simulations with the latest chiral hyperon-nucleon forces and show that the leading order relativistic chiral results can already describe the lattice QCD data reasonably well. Given the fact that the lattice QCD simulations are performed with pion masses ranging from the (almost) physical point to 700 MeV, such studies provide a useful check on both the chiral effective field theory approaches as well as lattice QCD simulations. Nevertheless more precise lattice QCD simulations are eagerly needed to refine our understanding of hyperon-nucleon interactions.

Extension of the HAL QCD approach to inelastic and multi-particle scatterings in lattice QCD

NASA Astrophysics Data System (ADS)

Aoki, S.

We extend the HAL QCD approach, with which potentials between two hadrons can be obtained in QCD at energy below inelastic thresholds, to inelastic and multi-particle scatterings. We first derive asymptotic behaviors of the Nambu-Bethe-Salpeter (NBS) wave function at large space separations for systems with more than 2 particles, in terms of the one-shell $T$-matrix consrainted by the unitarity of quantum field theories. We show that its asymptotic behavior contains phase shifts and mixing angles of $n$ particle scatterings. This property is one of the essential ingredients of the HAL QCD scheme to define "potential" from the NBS wave function in quantum field theories such as QCD. We next construct energy independent but non-local potentials above inelastic thresholds, in terms of these NBS wave functions. We demonstrate an existence of energy-independent coupled channel potentials with a non-relativistic approximation, where momenta of all particles are small compared with their own masses. Combining these two results, we can employ the HAL QCD approach also to investigate inelastic and multi-particle scatterings.

Scale dependencies of proton spin constituents with a nonperturbative αs

NASA Astrophysics Data System (ADS)

Jia, Shaoyang; Huang, Feng

2012-11-01

By introducing the contribution from dynamically generated gluon mass, we present a brand new parametrized form of QCD beta function to get an inferred limited running behavior of QCD coupling constant αs. This parametrized form is regarded as an essential factor to determine the scale dependencies of the proton spin constituents at the very low scale. In order to compare with experimental results directly, we work within the gauge-invariant framework to decompose the proton spin. Utilizing the updated next-to-next-leading-order evolution equations for angular momentum observables within a modified minimal subtraction scheme, we indicate that gluon contribution to proton spin cannot be ignored. Specifically, by assuming asymptotic limits of the total quark/gluon angular momentum valid, respectively, the scale dependencies of quark angular momentum Jq and gluon angular momentum Jg down to Q2˜1GeV2 are presented, which are comparable with the preliminary analysis of deeply virtual Compton scattering experiments by HERMES and JLab. After solving scale dependencies of quark spin ΔΣq, orbital angular momenta of quarks Lq are given by subtraction, presenting a holistic picture of proton spin partition within up and down quarks at a low scale.

pT spectra in pp and AA collisions at RHIC and LHC energies using the Tsallis-Weibull approach

NASA Astrophysics Data System (ADS)

Dash, Sadhana; Mahapatra, D. P.

2018-04-01

The Tsallis q -statistics have been incorporated in the Weibull model of particle production, in the form of q-Weibull distribution, to describe the transverse momentum (pT) distribution of charged hadrons at mid-rapidity, measured at RHIC and LHC energies. The q-Weibull distribution is found to describe the observed pT distributions over all ranges of measured pT. Below 2.2 GeV/c, while going from peripheral to central collisions, the parameter q is found to decrease systematically towards unity, indicating an evolution from a non-equilibrated system in peripheral collisions, towards a more thermalized system in central collisions. However, the trend is reversed in the all inclusive pT regime. This can be attributed to an increase in relative contribution of hard pQCD processes in central collisions. The λ-parameter is found to be associated with the mean pT or the collective expansion velocity of the produced hadrons, which shows an expected increase with centrality of collisions. The k parameter is observed to increase with the onset of hard QCD scatterings, initial fluctuations, and other processes leading to non-equilibrium conditions.

Resonant conversions of QCD axions into hidden axions and suppressed isocurvature perturbations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitajima, Naoya; Takahashi, Fuminobu, E-mail: kitajima@tuhep.phys.tohoku.ac.jp, E-mail: fumi@tuhep.phys.tohoku.ac.jp

2015-01-01

We study in detail MSW-like resonant conversions of QCD axions into hidden axions, including cases where the adiabaticity condition is only marginally satisfied, and where anharmonic effects are non-negligible. When the resonant conversion is efficient, the QCD axion abundance is suppressed by the hidden and QCD axion mass ratio. We find that, when the resonant conversion is incomplete due to a weak violation of the adiabaticity, the CDM isocurvature perturbations can be significantly suppressed, while non-Gaussianity of the isocurvature perturbations generically remain unsuppressed. The isocurvature bounds on the inflation scale can therefore be relaxed by the partial resonant conversion ofmore » the QCD axions into hidden axions.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dine, Michael; Draper, Patrick; Stephenson-Haskins, Laurel

Here, we study the large N θ dependence and the η' potential in supersymmetric QCD with small soft SUSY-breaking terms. Known exact results in SUSY QCD are found to reflect a variety of expectations from large N perturbation theory, including the presence of branches and the behavior of theories with matter (both with N f << N and N f ~ N ). But, there are also striking departures from ordinary QCD and the conventional large N description: instanton effects, when under control, are not exponentially suppressed at large N , and branched structure in supersymmetric QCD is always associatedmore » with approximate discrete symmetries. We suggest that these differences motivate further study of large N QCD on the lattice.« less

Scheme Variations of the QCD Coupling and Hadronic τ Decays

NASA Astrophysics Data System (ADS)

Boito, Diogo; Jamin, Matthias; Miravitllas, Ramon

2016-10-01

The quantum chromodynamics (QCD) coupling αs is not a physical observable of the theory, since it depends on conventions related to the renormalization procedure. We introduce a definition of the QCD coupling, denoted by α^s, whose running is explicitly renormalization scheme invariant. The scheme dependence of the new coupling α^s is parametrized by a single parameter C , related to transformations of the QCD scale Λ . It is demonstrated that appropriate choices of C can lead to substantial improvements in the perturbative prediction of physical observables. As phenomenological applications, we study e+e- scattering and decays of the τ lepton into hadrons, both being governed by the QCD Adler function.

Scattering processes and resonances from lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briceno, Raul A.; Dudek, Jozef J.; Young, Ross D.

The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lightermore » hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This paper reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. Finally, the challenges which currently limit the field are discussed along with the steps being taken to resolve them.« less

Scattering processes and resonances from lattice QCD

NASA Astrophysics Data System (ADS)

Briceño, Raúl A.; Dudek, Jozef J.; Young, Ross D.

2018-04-01

The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This article reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. The challenges which currently limit the field are discussed along with the steps being taken to resolve them.

Scattering processes and resonances from lattice QCD

DOE PAGES

Briceno, Raul A.; Dudek, Jozef J.; Young, Ross D.

2018-04-18

The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lightermore » hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This paper reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. Finally, the challenges which currently limit the field are discussed along with the steps being taken to resolve them.« less

Darwin's Missing Link--A Novel Paradigm for Evolution Education

ERIC Educational Resources Information Center

Catley, Kefyn M.

2006-01-01

Microevolutionary mechanisms are taught almost exclusively in our schools, to the detriment of those mechanisms that allow us to understand the larger picture--macroevolution. The results are demonstrable; as a result of the strong emphasis on micro processes in evolution education, students and teachers still have poor understanding of the…

Primordial gravitational waves, precisely: the role of thermodynamics in the Standard Model

NASA Astrophysics Data System (ADS)

Saikawa, Ken'ichi; Shirai, Satoshi

2018-05-01

In this paper, we revisit the estimation of the spectrum of primordial gravitational waves originated from inflation, particularly focusing on the effect of thermodynamics in the Standard Model of particle physics. By collecting recent results of perturbative and non-perturbative analysis of thermodynamic quantities in the Standard Model, we obtain the effective degrees of freedom including the corrections due to non-trivial interaction properties of particles in the Standard Model for a wide temperature interval. The impact of such corrections on the spectrum of primordial gravitational waves as well as the damping effect due to free-streaming particles is investigated by numerically solving the evolution equation of tensor perturbations in the expanding universe. It is shown that the reevaluation of the effects of free-streaming photons and neutrinos gives rise to some additional damping features overlooked in previous studies. We also observe that the continuous nature of the QCD crossover results in a smooth spectrum for modes that reenter the horizon at around the epoch of the QCD phase transition. Furthermore, we explicitly show that the values of the effective degrees of freedom remain smaller than the commonly used value 106.75 even at temperature much higher than the critical temperature of the electroweak crossover, and that the amplitude of primordial gravitational waves at a frequency range relevant to direct detection experiments becomes Script O(1) % larger than previous estimates that do not include such corrections. This effect can be relevant to future high-sensitivity gravitational wave experiments such as ultimate DECIGO. Our results on the temperature evolution of the effective degrees of freedom are made available as tabulated data and fitting functions, which can also be used in the analysis of other cosmological relics.

The generalized scheme-independent Crewther relation in QCD

NASA Astrophysics Data System (ADS)

Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang; Brodsky, Stanley J.

2017-07-01

The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton-nucleon scattering times the Adler function, defined from the cross section for electron-positron annihilation into hadrons, has no pQCD radiative corrections. The ;Generalized Crewther Relation; relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (Dns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (CBjp) at leading twist. A scheme-dependent ΔCSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both Dns and the inverse coefficient CBjp-1 have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, αˆd (Q) =∑i≥1 αˆg1 i (Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Similar scale-fixed commensurate scale relations also connect other physical observables at their physical momentum scales, thus providing convention-independent, fundamental precision tests of QCD.

Dyonic Flux Tube Structure of Nonperturbative QCD Vacuum

NASA Astrophysics Data System (ADS)

Chandola, H. C.; Pandey, H. C.

We study the flux tube structure of the nonperturbative QCD vacuum in terms of its dyonic excitations by using an infrared effective Lagrangian and show that the dyonic condensation of QCD vacuum has a close connection with the process of color confinement. Using the fiber bundle formulation of QCD, the magnetic symmetry condition is presented in a gauge covariant form and the gauge potential has been constructed in terms of the magnetic vectors on global sections. The dynamical breaking of the magnetic symmetry has been shown to lead the dyonic condensation of QCD vacuum in the infrared energy sector. Deriving the asymptotic solutions of the field equations in the dynamically broken phase, the dyonic flux tube structure of QCD vacuum is explored which has been shown to lead the confinement parameters in terms of the vector and scalar mass modes of the condensed vacuum. Evaluating the charge quantum numbers and energy associated with the dyonic flux tube solutions, the effect of electric excitation of monopole is analyzed using the Regge slope parameter (as an input parameter) and an enhancement in the dyonic pair correlations and the confining properties of QCD vacuum in its dyonically condensed mode has been demonstrated.

Symmetric and anti-symmetric LS hyperon potentials from lattice QCD

NASA Astrophysics Data System (ADS)

Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji; Inoue, Takashi; HAL QCD Collaboration

2014-09-01

We present recent results of odd-parity hyperon-hyperon potentials from lattice QCD. By using HAL QCD method, we generate hyperon-hyperon potentials from Nambu-Bethe-Salpeter (NBS) wave functions generated by lattice QCD simulation in the flavor SU(3) limit. Potentials in the irreducible flavor SU(3) representations are combined to make a Lambda-N potential which has a strong symmetric LS potential and a weak anti-symmetric LS potential. We discuss a possible cancellation between symmetric and anti-symmetric LS (Lambda-N) potentials after the coupled Sigma-N sector is integrated out. We present recent results of odd-parity hyperon-hyperon potentials from lattice QCD. By using HAL QCD method, we generate hyperon-hyperon potentials from Nambu-Bethe-Salpeter (NBS) wave functions generated by lattice QCD simulation in the flavor SU(3) limit. Potentials in the irreducible flavor SU(3) representations are combined to make a Lambda-N potential which has a strong symmetric LS potential and a weak anti-symmetric LS potential. We discuss a possible cancellation between symmetric and anti-symmetric LS (Lambda-N) potentials after the coupled Sigma-N sector is integrated out. This work is supported by JSPS KAKENHI Grant Number 25400244.

QCD on the BlueGene/L Supercomputer

NASA Astrophysics Data System (ADS)

Bhanot, G.; Chen, D.; Gara, A.; Sexton, J.; Vranas, P.

2005-03-01

In June 2004 QCD was simulated for the first time at sustained speed exceeding 1 TeraFlops in the BlueGene/L supercomputer at the IBM T.J. Watson Research Lab. The implementation and performance of QCD in the BlueGene/L is presented.

Vortical susceptibility of finite-density QCD matter

DOE PAGES

Aristova, A.; Frenklakh, D.; Gorsky, A.; ...

2016-10-07

Here, the susceptibility of finite-density QCD matter to vorticity is introduced, as an analog of magnetic susceptibility. It describes the spin polarization of quarks and antiquarks in finite-density QCD matter induced by rotation. We estimate this quantity in the chirally broken phase using the mixed gauge-gravity anomaly at finite baryon density. It is proposed that the vortical susceptibility of QCD matter is responsible for the polarization of Λ and Λ¯ hyperons observed recently in heavy ion collisions at RHIC by the STAR collaboration.

Polyakov loop modeling for hot QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukushima, Kenji; Skokov, Vladimir

Here, we review theoretical aspects of quantum chromodynamics (QCD) at finite temperature. The most important physical variable to characterize hot QCD is the Polyakov loop, which is an approximate order parameter for quark deconfinement in a hot gluonic medium. Additionally to its role as an order parameter, the Polyakov loop has rich physical contents in both perturbative and non-perturbative sectors. This review covers a wide range of subjects associated with the Polyakov loop from topological defects in hot QCD to model building with coupling to the Polyakov loop.

Polyakov loop modeling for hot QCD

DOE PAGES

Fukushima, Kenji; Skokov, Vladimir

2017-06-19

Here, we review theoretical aspects of quantum chromodynamics (QCD) at finite temperature. The most important physical variable to characterize hot QCD is the Polyakov loop, which is an approximate order parameter for quark deconfinement in a hot gluonic medium. Additionally to its role as an order parameter, the Polyakov loop has rich physical contents in both perturbative and non-perturbative sectors. This review covers a wide range of subjects associated with the Polyakov loop from topological defects in hot QCD to model building with coupling to the Polyakov loop.

Relativistic corrections to the form factors of Bc into P-wave orbitally excited charmonium

NASA Astrophysics Data System (ADS)

Zhu, Ruilin

2018-06-01

We investigated the form factors of the Bc meson into P-wave orbitally excited charmonium using the nonrelativistic QCD effective theory. Through the analytic computation, the next-to-leading order relativistic corrections to the form factors were obtained, and the asymptotic expressions were studied in the infinite bottom quark mass limit. Employing the general form factors, we discussed the exclusive decays of the Bc meson into P-wave orbitally excited charmonium and a light meson. We found that the relativistic corrections lead to a large correction for the form factors, which makes the branching ratios of the decay channels B (Bc ± →χcJ (hc) +π± (K±)) larger. These results are useful for the phenomenological analysis of the Bc meson decays into P-wave charmonium, which shall be tested in the LHCb experiments.

Lattice Gauge Theories Within and Beyond the Standard Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gelzer, Zechariah John

The Standard Model of particle physics has been very successful in describing fundamental interactions up to the highest energies currently probed in particle accelerator experiments. However, the Standard Model is incomplete and currently exhibits tension with experimental data for interactions involvingmore » $B$~mesons. Consequently, $B$-meson physics is of great interest to both experimentalists and theorists. Experimentalists worldwide are studying the decay and mixing processes of $B$~mesons in particle accelerators. Theorists are working to understand the data by employing lattice gauge theories within and beyond the Standard Model. This work addresses the theoretical effort and is divided into two main parts. In the first part, I present a lattice-QCD calculation of form factors for exclusive semileptonic decays of $B$~mesons that are mediated by both charged currents ($$B \\to \\pi \\ell \

Neutrino-nucleon cross sections at energies of Megaton-scale detectors

NASA Astrophysics Data System (ADS)

Gazizov, A.; Kowalski, M.; Kuzmin, K. S.; Naumov, V. A.; Spiering, Ch.

2016-04-01

An updated set of (anti)neutrino-nucleon charged and neutral current cross sections at 3 GeV ≲ Eν ≲100 GeV is presented. These cross sections are of particular interest for the detector optimization and data processing and interpretation in the future Megaton-scale experiments like PINGU, ORCA, and Hyper-Kamiokande. Finite masses of charged leptons and target mass corrections in exclusive and deep inelastic (ν̅)νN interactions are taken into account. A new set of QCD NNLO parton density functions, ABMP15, is used for calculation of the DIS cross sections. The sensitivity of the cross sections to phenomenological parameters and to extrapolations of the nucleon structure functions to small x and Q2 is studied. An agreement within the uncertainties of our calculations with experimental data is demonstrated.

Electroproduction of {eta} mesons in the S{sub 11}(1535) resonance region at high momentum transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalton, M. M.; Adams, G. S.; Moziak, B.

2009-07-15

The differential cross section for the process p(e,e{sup '}p){eta} has been measured at Q{sup 2}{approx}5.7 and 7.0(GeV/c){sup 2} for center-of-mass energies from threshold to 1.8 GeV, encompassing the S{sub 11}(1535) resonance, which dominates the channel. This is the highest momentum-transfer measurement of this exclusive process to date. The helicity-conserving transition amplitude A{sub 1/2}, for the production of the S{sub 11}(1535) resonance, is extracted from the data. Within the limited Q{sup 2} now measured, this quantity appears to begin scaling as Q{sup -3}--a predicted, but not definitive, signal of the dominance of perturbative QCD at Q{sup 2}{approx}5 (GeV/c){sup 2}.

Some New/Old Approaches to QCD

DOE R&D Accomplishments Database

Gross, D. J.

1992-11-01

In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anand, Sampurn; Mohanty, Subhendra; Dey, Ujjal Kumar, E-mail: sampurn@prl.res.in, E-mail: ujjal@cts.iitkgp.ernet.in, E-mail: mohanty@prl.res.in

Cosmological phase transitions can be a source of Stochastic Gravitational Wave (SGW) background. Apart from the dynamics of the phase transition, the characteristic frequency and the fractional energy density Ω{sub gw} of the SGW depends upon the temperature of the transition. In this article, we compute the SGW spectrum in the light of QCD equation of state provided by the lattice results. We find that the inclusion of trace anomaly from lattice QCD, enhances the SGW signal generated during QCD phase transition by ∼ 50% and the peak frequency of the QCD era SGW are shifted higher by ∼ 25%more » as compared to the earlier estimates without trace anomaly. This result is extremely significant for testing the phase transition dynamics near QCD epoch.« less

Scheme variations of the QCD coupling

NASA Astrophysics Data System (ADS)

Boito, Diogo; Jamin, Matthias; Miravitllas, Ramon

2017-03-01

The Quantum Chromodynamics (QCD) coupling αs is a central parameter in the Standard Model of particle physics. However, it depends on theoretical conventions related to renormalisation and hence is not an observable quantity. In order to capture this dependence in a transparent way, a novel definition of the QCD coupling, denoted by â, is introduced, whose running is explicitly renormalisation scheme invariant. The remaining renormalisation scheme dependence is related to transformations of the QCD scale Λ, and can be parametrised by a single parameter C. Hence, we call â the C-scheme coupling. The dependence on C can be exploited to study and improve perturbative predictions of physical observables. This is demonstrated for the QCD Adler function and hadronic decays of the τ lepton.

Symmetry Transition Preserving Chirality in QCD: A Versatile Random Matrix Model

NASA Astrophysics Data System (ADS)

Kanazawa, Takuya; Kieburg, Mario

2018-06-01

We consider a random matrix model which interpolates between the chiral Gaussian unitary ensemble and the Gaussian unitary ensemble while preserving chiral symmetry. This ensemble describes flavor symmetry breaking for staggered fermions in 3D QCD as well as in 4D QCD at high temperature or in 3D QCD at a finite isospin chemical potential. Our model is an Osborn-type two-matrix model which is equivalent to the elliptic ensemble but we consider the singular value statistics rather than the complex eigenvalue statistics. We report on exact results for the partition function and the microscopic level density of the Dirac operator in the ɛ regime of QCD. We compare these analytical results with Monte Carlo simulations of the matrix model.

The QCD running coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

Here, we review present knowledge onmore » $$\\alpha_{s}$$, the Quantum Chromodynamics (QCD) running coupling. The dependence of $$\\alpha_s(Q^2)$$ on momentum transfer $Q$ encodes the underlying dynamics of hadron physics --from color confinement in the infrared domain to asymptotic freedom at short distances. We will survey our present theoretical and empirical knowledge of $$\\alpha_s(Q^2)$$, including constraints at high $Q^2$ predicted by perturbative QCD, and constraints at small $Q^2$ based on models of nonperturbative dynamics. In the first, introductory, part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain. In the second, more technical, part of the review, we discuss $$\\alpha_s(Q^2)$$ in the high momentum transfer domain of QCD. We review how $$\\alpha_s$$ is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as `` Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization scale ambiguity. We also report recent important experimental measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the ``Principle of Maximum Conformality" which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of the gauge and renormalization scheme. In last part of the review, we discuss $$\\alpha_s(Q^2)$$ in the low momentum transfer domain, where there has been no consensus on how to define $$\\alpha_s(Q^2)$$ or its analytic behavior. We will discuss the various approaches used for low energy calculations. Among them, we will discuss the light-front holographic approach to QCD in the strongly coupled regime and its prediction for the analytic form of $$\\alpha_s(Q^2)$$. The AdS/QCD light-front holographic analysis predicts the color confinement potential underlying hadron spectroscopy and dynamics, and it gives a remarkable connection between the perturbative QCD scale $$\\Lambda$$ and hadron masses. One can also identify a specific scale $$Q_0$$ which demarcates the division between perturbative and nonperturbative QCD. We also review other important methods for computing the QCD coupling, including Lattice QCD, Schwinger-Dyson equations and the Gribov-Zwanziger analysis. After describing these approaches and enumerating conflicting results, we provide a partial discussion on the origin of these discrepancies and how to remedy them. Our aim is not only to review the advances on this difficult subject, but also to suggest what could be the best definition of $$\\alpha_s(Q^2)$$ in order to bring better unity to the subject.« less

The QCD running coupling

DOE PAGES

Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

2016-05-09

Here, we review present knowledge onmore » $$\\alpha_{s}$$, the Quantum Chromodynamics (QCD) running coupling. The dependence of $$\\alpha_s(Q^2)$$ on momentum transfer $Q$ encodes the underlying dynamics of hadron physics --from color confinement in the infrared domain to asymptotic freedom at short distances. We will survey our present theoretical and empirical knowledge of $$\\alpha_s(Q^2)$$, including constraints at high $Q^2$ predicted by perturbative QCD, and constraints at small $Q^2$ based on models of nonperturbative dynamics. In the first, introductory, part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain. In the second, more technical, part of the review, we discuss $$\\alpha_s(Q^2)$$ in the high momentum transfer domain of QCD. We review how $$\\alpha_s$$ is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as `` Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization scale ambiguity. We also report recent important experimental measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the ``Principle of Maximum Conformality" which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of the gauge and renormalization scheme. In last part of the review, we discuss $$\\alpha_s(Q^2)$$ in the low momentum transfer domain, where there has been no consensus on how to define $$\\alpha_s(Q^2)$$ or its analytic behavior. We will discuss the various approaches used for low energy calculations. Among them, we will discuss the light-front holographic approach to QCD in the strongly coupled regime and its prediction for the analytic form of $$\\alpha_s(Q^2)$$. The AdS/QCD light-front holographic analysis predicts the color confinement potential underlying hadron spectroscopy and dynamics, and it gives a remarkable connection between the perturbative QCD scale $$\\Lambda$$ and hadron masses. One can also identify a specific scale $$Q_0$$ which demarcates the division between perturbative and nonperturbative QCD. We also review other important methods for computing the QCD coupling, including Lattice QCD, Schwinger-Dyson equations and the Gribov-Zwanziger analysis. After describing these approaches and enumerating conflicting results, we provide a partial discussion on the origin of these discrepancies and how to remedy them. Our aim is not only to review the advances on this difficult subject, but also to suggest what could be the best definition of $$\\alpha_s(Q^2)$$ in order to bring better unity to the subject.« less

Baryon interactions in lattice QCD: the direct method vs. the HAL QCD potential method

NASA Astrophysics Data System (ADS)

Iritani, T.; HAL QCD Collaboration

We make a detailed comparison between the direct method and the HAL QCD potential method for the baryon-baryon interactions, taking the $\\Xi\\Xi$ system at $m_\\pi= 0.51$ GeV in 2+1 flavor QCD and using both smeared and wall quark sources. The energy shift $\\Delta E_\\mathrm{eff}(t)$ in the direct method shows the strong dependence on the choice of quark source operators, which means that the results with either (or both) source are false. The time-dependent HAL QCD method, on the other hand, gives the quark source independent $\\Xi\\Xi$ potential, thanks to the derivative expansion of the potential, which absorbs the source dependence to the next leading order correction. The HAL QCD potential predicts the absence of the bound state in the $\\Xi\\Xi$($^1$S$_0$) channel at $m_\\pi= 0.51$ GeV, which is also confirmed by the volume dependence of finite volume energy from the potential. We also demonstrate that the origin of the fake plateau in the effective energy shift $\\Delta E_\\mathrm{eff}(t)$ at $t \\sim 1$ fm can be clarified by a few low-lying eigenfunctions and eigenvalues on the finite volume derived from the HAL QCD potential, which implies that the ground state saturation of $\\Xi\\Xi$($^1$S$_0$) requires $t \\sim 10$ fm in the direct method for the smeared source on $(4.3 \\ \\mathrm{fm})^3$ lattice, while the HAL QCD method does not suffer from such a problem.

The QCD running coupling

NASA Astrophysics Data System (ADS)

Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

2016-09-01

We review the present theoretical and empirical knowledge for αs, the fundamental coupling underlying the interactions of quarks and gluons in Quantum Chromodynamics (QCD). The dependence of αs(Q2) on momentum transfer Q encodes the underlying dynamics of hadron physics-from color confinement in the infrared domain to asymptotic freedom at short distances. We review constraints on αs(Q2) at high Q2, as predicted by perturbative QCD, and its analytic behavior at small Q2, based on models of nonperturbative dynamics. In the introductory part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain. In the second, more technical, part of the review, we discuss the behavior of αs(Q2) in the high momentum transfer domain of QCD. We review how αs is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as "Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization-scale ambiguity. We also report recent significant measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the "Principle of Maximum Conformality", which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of theoretical conventions such as the renormalization scheme. In the last part of the review, we discuss the challenge of understanding the analytic behavior αs(Q2) in the low momentum transfer domain. We survey various theoretical models for the nonperturbative strongly coupled regime, such as the light-front holographic approach to QCD. This new framework predicts the form of the quark-confinement potential underlying hadron spectroscopy and dynamics, and it gives a remarkable connection between the perturbative QCD scale Λ and hadron masses. One can also identify a specific scale Q0 which demarcates the division between perturbative and nonperturbative QCD. We also review other important methods for computing the QCD coupling, including lattice QCD, the Schwinger-Dyson equations and the Gribov-Zwanziger analysis. After describing these approaches and enumerating their conflicting predictions, we discuss the origin of these discrepancies and how to remedy them. Our aim is not only to review the advances in this difficult area, but also to suggest what could be an optimal definition of αs(Q2) in order to bring better unity to the subject.

Rationality alters the rank between peer punishment and social exclusion

NASA Astrophysics Data System (ADS)

Sui, Xiukai; Wu, Bin; Wang, Long

2018-02-01

Peer punishment and social exclusion are two ways to punish free-riders. Previous work usually focuses on how their presence, either peer punishment or social exclusion, shapes the evolution of cooperation. Little attention has been given to which of these two strategies is favored by natural selection when they are both present. Here we investigate how rationality alters the ranking of these two strategies. Under weak rationality, for compulsory public goods games, peer punishment has an evolutionary advantage over social exclusion if the efficiency of punishment or the cost of exclusion is high. Furthermore, this rank is preserved for voluntary public goods games where loners are involved. Under strong rationality, however, peer punishment cannot prevail over social exclusion for both compulsory and voluntary public goods games. This indicates that rationality greatly alters the rank between peer punishment and social exclusion. Moreover, we find that this ranking is sensitive to the rationality. Our work thus gives an insight into how different types of punishment evolve.

First Renormalized Parton Distribution Functions from Lattice QCD

NASA Astrophysics Data System (ADS)

Lin, Huey-Wen; LP3 Collaboration

2017-09-01

We present the first lattice-QCD results on the nonperturbatively renormalized parton distribution functions (PDFs). Using X.D. Ji's large-momentum effective theory (LaMET) framework, lattice-QCD hadron structure calculations are able to overcome the longstanding problem of determining the Bjorken- x dependence of PDFs. This has led to numerous additional theoretical works and exciting progress. In this talk, we will address a recent development that implements a step missing from prior lattice-QCD calculations: renormalization, its effects on the nucleon matrix elements, and the resultant changes to the calculated distributions.

The CP-PACS Project and Lattice QCD Results

NASA Astrophysics Data System (ADS)

Iwasaki, Y.

The aim of the CP-PACS project was to develop a massively parallel computer for performing numerical research in computational physics with primary emphasis on lattice QCD. The CP-PACS computer with a peak speed of 614 GFLOPS with 2048 processors was completed in September 1996, and has been in full operation since October 1996. We present an overview of the CP-PACS project and describe characteristics of the CP-PACS computer. The CP-PACS has been mainly used for hadron spectroscopy studies in lattice QCD. Main results in lattice QCD simulations are given.

Remarks on the Phase Transition in QCD

NASA Astrophysics Data System (ADS)

Wilczek, Frank

The significance of the question of the order of the phase transition in QCD, and recent evidence that real-world QCD is probably close to having a single second order transition as a function of temperature, is reviewed. Although this circumstance seems to remove the possibility that the QCD transition during the big bang might have had spectacular cosmological consequences, there is some good news: it allows highly non-trivial yet reliable quantitative predictions to be made for the behavior near the transition. These predictions can be tested in numerical simulations and perhaps even eventually in heavy ion collisions. The present paper is a very elementary discussion of the relevant concepts, meant to be an accessible introduction for those innocent of the renormalization group approach to critical phenomena and/or the details of QCD.

Towards understanding Regge trajectories in holographic QCD

NASA Astrophysics Data System (ADS)

Catà, Oscar

2007-05-01

We reassess a work done by Migdal on the spectrum of low-energy vector mesons in QCD in the light of the anti-de Sitter (AdS)-QCD correspondence. Recently, a tantalizing parallelism was suggested between Migdal’s work and a family of holographic duals of QCD. Despite the intriguing similarities, both approaches face a major drawback: the spectrum is in conflict with well-tested Regge scaling. However, it has recently been shown that holographic duals can be modified to accommodate Regge behavior. Therefore, it is interesting to understand whether Regge behavior can also be achieved in Migdal’s approach. In this paper we investigate this issue. We find that Migdal’s approach, which is based on a modified Padé approximant, is closely related to the issue of quark-hadron duality breakdown in QCD.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dudek, Jozef

Highlights of the research include: the determination of the form of the lowest energy gluonic excitation within QCD and the spectrum of hybrid hadrons which follows; the first calculation of the spectrum of hybrid baryons within a first-principles approach to QCD; a detailed mapping out of the phase-shift of elastic ππ scattering featuring the ρ resonance at two values of the light quark mass within lattice QCD; the first (and to date, only) determinations of coupled-channel meson-meson scattering within first-principles QCD; the first (and to date, only) determinations of the radiative coupling of a resonant state, the ρ appearing inmore » πγ→ππ; the first (and to date, only) determination of the properties of the broad σ resonance in elastic ππ scattering within QCD without unjustified approximations.« less

Transverse momentum dependent (TMD) parton distribution functions: Status and prospects*

DOE PAGES

Angeles-Martinez, R.; Bacchetta, A.; Balitsky, Ian I.; ...

2015-01-01

In this study, we review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum q T spectra of Higgs and vector bosons for low q T, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present the application of a new tool, TMD LIB, to parton density fits andmore » parameterizations.« less

Highlights in light-baryon spectroscopy and searches for gluonic excitations

NASA Astrophysics Data System (ADS)

Crede, Volker

2016-01-01

The spectrum of excited hadrons - mesons and baryons - serves as an excellent probe of quantum chromodynamics (QCD), the fundamental theory of the strong interaction. The strong coupling however makes QCD challenging. It confines quarks and breaks chiral symmetry, thus providing us with the world of light hadrons. Highly-excited hadronic states are sensitive to the details of quark confinement, which is only poorly understood within QCD. This is the regime of non-perturbative QCD and it is one of the key issues in hadronic physics to identify the corresponding internal degrees of freedom and how they relate to strong coupling QCD. The quark model suggests mesons are made of a constituent quark and an antiquark and baryons consist of three such quarks. QCD predicts other forms of matter. What is the role of glue? Resonances with large gluonic components are predicted as bound states by QCD. The lightest hybrid mesons with exotic quantum numbers are estimated to have masses in the range from 1 to 2 GeV/c2 and are well in reach of current experimental programs. At Jefferson Laboratory (JLab) and other facilities worldwide, the high-energy electron and photon beams present a remarkably clean probe of hadronic matter, providing an excellent microscope for examining atomic nuclei and the strong nuclear force.

Social exclusion in finite populations

NASA Astrophysics Data System (ADS)

Li, Kun; Cong, Rui; Wu, Te; Wang, Long

2015-04-01

Social exclusion, keeping free riders from benefit sharing, plays an important role in sustaining cooperation in our world. Here we propose two different exclusion regimes, namely, peer exclusion and pool exclusion, to investigate the evolution of social exclusion in finite populations. In the peer exclusion regime, each excluder expels all the defectors independently, and thus bears the total cost on his own, while in the pool exclusion regime, excluders spontaneously form an institution to carry out rejection of the free riders, and each excluder shares the cost equally. In a public goods game containing only excluders and defectors, it is found that peer excluders outperform pool excluders if the exclusion costs are small, and the situation is converse once the exclusion costs exceed some critical points, which holds true for all the selection intensities and different update rules. Moreover, excluders can dominate the whole population under a suitable parameters range in the presence of second-order free riders (cooperators), showing that exclusion has prominent advantages over common costly punishment. More importantly, our finding indicates that the group exclusion mechanism helps the cooperative union to survive under unfavorable conditions. Our results may give some insights into better understanding the prevalence of such a strategy in the real world and its significance in sustaining cooperation.

Pulling out all the stops: searching for RPV SUSY with stop-jets

NASA Astrophysics Data System (ADS)

Bai, Yang; Katz, Andrey; Tweedie, Brock

2014-01-01

If the lighter stop eigenstate decays directly to two jets via baryonic R-parity violation, it could have escaped existing LHC and Tevatron searches in four-jet events, even for masses as small as 100 GeV. In order to recover sensitivity in the face of increasingly harsh trigger requirements at the LHC, we propose a search for stop pairs in the highly-boosted regime, using the approaches of jet substructure. We demonstrate that the four-jet triggers can be completely bypassed by using inclusive jet- H T triggers, and that the resulting QCD continuum background can be processed by substructure methods into a featureless spectrum suitable for a data-driven bump-hunt down to 100 GeV. We estimate that the LHC 8 TeV run is sensitive to 100 GeV stops with decays of any flavor at better than 5σ-level, and could place exclusions up to 300 GeV or higher. Assuming Minimal Flavor Violation and running a b-tagged analysis, exclusion reach may extend up to nearly 400 GeV. Longer-term, the 14 TeV LHC at 300 fb-1 could extend these mass limits by a factor of two, while continuing to improve sensitivity in the 100 GeV region.

Setting the renormalization scale in pQCD: Comparisons of the principle of maximum conformality with the sequential extended Brodsky-Lepage-Mackenzie approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Hong -Hao; Wu, Xing -Gang; Ma, Yang

A key problem in making precise perturbative QCD (pQCD) predictions is how to set the renormalization scale of the running coupling unambiguously at each finite order. The elimination of the uncertainty in setting the renormalization scale in pQCD will greatly increase the precision of collider tests of the Standard Model and the sensitivity to new phenomena. Renormalization group invariance requires that predictions for observables must also be independent on the choice of the renormalization scheme. The well-known Brodsky-Lepage-Mackenzie (BLM) approach cannot be easily extended beyond next-to-next-to-leading order of pQCD. Several suggestions have been proposed to extend the BLM approach tomore » all orders. In this paper we discuss two distinct methods. One is based on the “Principle of Maximum Conformality” (PMC), which provides a systematic all-orders method to eliminate the scale and scheme ambiguities of pQCD. The PMC extends the BLM procedure to all orders using renormalization group methods; as an outcome, it significantly improves the pQCD convergence by eliminating renormalon divergences. An alternative method is the “sequential extended BLM” (seBLM) approach, which has been primarily designed to improve the convergence of pQCD series. The seBLM, as originally proposed, introduces auxiliary fields and follows the pattern of the β0-expansion to fix the renormalization scale. However, the seBLM requires a recomputation of pQCD amplitudes including the auxiliary fields; due to the limited availability of calculations using these auxiliary fields, the seBLM has only been applied to a few processes at low orders. In order to avoid the complications of adding extra fields, we propose a modified version of seBLM which allows us to apply this method to higher orders. As a result, we then perform detailed numerical comparisons of the two alternative scale-setting approaches by investigating their predictions for the annihilation cross section ratio R e+e– at four-loop order in pQCD.« less

The generalized scheme-independent Crewther relation in QCD

DOE PAGES

Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang; ...

2017-05-10

The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton–nucleon scattering times the Adler function, defined from the cross section for electron–positron annihilation into hadrons, has no pQCD radiative corrections. The “Generalized Crewther Relation” relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (D ns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (C Bjp) at leading twist. A scheme-dependent Δ CSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both D ns and the inverse coefficient Cmore » $$-1\\atop{Bjp}$$ have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, $$\\hat{α}$$ d(Q)=Σ i≥1$$\\hat{α}^i\\atop{g1}$$(Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Lastly, similar scale-fixed commensurate scale relations also connect other physical observables at their physical momentum scales, thus providing convention-independent, fundamental precision tests of QCD.« less

The generalized scheme-independent Crewther relation in QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang

The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton–nucleon scattering times the Adler function, defined from the cross section for electron–positron annihilation into hadrons, has no pQCD radiative corrections. The “Generalized Crewther Relation” relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (D ns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (C Bjp) at leading twist. A scheme-dependent Δ CSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both D ns and the inverse coefficient Cmore » $$-1\\atop{Bjp}$$ have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, $$\\hat{α}$$ d(Q)=Σ i≥1$$\\hat{α}^i\\atop{g1}$$(Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Lastly, similar scale-fixed commensurate scale relations also connect other physical observables at their physical momentum scales, thus providing convention-independent, fundamental precision tests of QCD.« less

Hadronic and nuclear interactions in QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

Despite the evidence that QCD - or something close to it - gives a correct description of the structure of hadrons and their interactions, it seems paradoxical that the theory has thus far had very little impact in nuclear physics. One reason for this is that the application of QCD to distances larger than 1 fm involves coherent, non-perturbative dynamics which is beyond present calculational techniques. For example, in QCD the nuclear force can evidently be ascribed to quark interchange and gluon exchange processes. These, however, are as complicated to analyze from a fundamental point of view as is themore » analogous covalent bond in molecular physics. Since a detailed description of quark-quark interactions and the structure of hadronic wavefunctions is not yet well-understood in QCD, it is evident that a quantitative first-principle description of the nuclear force will require a great deal of theoretical effort. Another reason for the limited impact of QCD in nuclear physics has been the conventional assumption that nuclear interactions can for the most part be analyzed in terms of an effective meson-nucleon field theory or potential model in isolation from the details of short distance quark and gluon structure of hadrons. These lectures, argue that this view is untenable: in fact, there is no correspondence principle which yields traditional nuclear physics as a rigorous large-distance or non-relativistic limit of QCD dynamics. On the other hand, the distinctions between standard nuclear physics dynamics and QCD at nuclear dimensions are extremely interesting and illuminating for both particle and nuclear physics.« less

Parton distributions and lattice QCD calculations: A community white paper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Huey-Wen; Nocera, Emanuele R.; Olness, Fred

In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this paper we present an overview of lattice-QCDmore » and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. Finally, this document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.« less

Gravitation waves from QCD and electroweak phase transitions

NASA Astrophysics Data System (ADS)

Chen, Yidian; Huang, Mei; Yan, Qi-Shu

2018-05-01

We investigate the gravitation waves produced from QCD and electroweak phase transitions in the early universe by using a 5-dimension holographic QCD model and a holographic technicolor model. The dynamical holographic QCD model is to describe the pure gluon system, where a first order confinement-deconfinement phase transition can happen at the critical temperature around 250 MeV. The minimal holographic technicolor model is introduced to model the strong dynamics of electroweak, it can give a first order electroweak phase transition at the critical temperature around 100-360 GeV. We find that for both GW signals produced from QCD and EW phase transitions, in the peak frequency region, the dominant contribution comes from the sound waves, while away from the peak frequency region the contribution from the bubble collision is dominant. The peak frequency of gravitation wave determined by the QCD phase transition is located around 10-7 Hz which is within the detectability of FAST and SKA, and the peak frequency of gravitational wave predicted by EW phase transition is located at 0.002 - 0.007 Hz, which might be detectable by BBO, DECIGO, LISA and ELISA.

Twin Higgs Asymmetric Dark Matter.

PubMed

García García, Isabel; Lasenby, Robert; March-Russell, John

2015-09-18

We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

Parton distributions and lattice QCD calculations: A community white paper

DOE PAGES

Lin, Huey-Wen; Nocera, Emanuele R.; Olness, Fred; ...

2018-01-31

In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this paper we present an overview of lattice-QCDmore » and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. Finally, this document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.« less

Flavor-singlet baryons in the graded symmetry approach to partially quenched QCD

NASA Astrophysics Data System (ADS)

Hall, Jonathan M. M.; Leinweber, Derek B.

2016-11-01

Progress in the calculation of the electromagnetic properties of baryon excitations in lattice QCD presents new challenges in the determination of sea-quark loop contributions to matrix elements. A reliable estimation of the sea-quark loop contributions represents a pressing issue in the accurate comparison of lattice QCD results with experiment. In this article, an extension of the graded symmetry approach to partially quenched QCD is presented, which builds on previous theory by explicitly including flavor-singlet baryons in its construction. The formalism takes into account the interactions among both octet and singlet baryons, octet mesons, and their ghost counterparts; the latter enables the isolation of the quark-flow disconnected sea-quark loop contributions. The introduction of flavor-singlet states enables systematic studies of the internal structure of Λ -baryon excitations in lattice QCD, including the topical Λ (1405 ).

Hamiltonian Effective Field Theory Study of the N^{*}(1535) Resonance in Lattice QCD.

PubMed

Liu, Zhan-Wei; Kamleh, Waseem; Leinweber, Derek B; Stokes, Finn M; Thomas, Anthony W; Wu, Jia-Jun

2016-02-26

Drawing on experimental data for baryon resonances, Hamiltonian effective field theory (HEFT) is used to predict the positions of the finite-volume energy levels to be observed in lattice QCD simulations of the lowest-lying J^{P}=1/2^{-} nucleon excitation. In the initial analysis, the phenomenological parameters of the Hamiltonian model are constrained by experiment and the finite-volume eigenstate energies are a prediction of the model. The agreement between HEFT predictions and lattice QCD results obtained on volumes with spatial lengths of 2 and 3 fm is excellent. These lattice results also admit a more conventional analysis where the low-energy coefficients are constrained by lattice QCD results, enabling a determination of resonance properties from lattice QCD itself. Finally, the role and importance of various components of the Hamiltonian model are examined.

Recombination algorithms and jet substructure: Pruning as a tool for heavy particle searches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ellis, Stephen D.; Vermilion, Christopher K.; Walsh, Jonathan R.

2010-05-01

We discuss jet substructure in recombination algorithms for QCD jets and single jets from heavy particle decays. We demonstrate that the jet algorithm can introduce significant systematic effects into the substructure. By characterizing these systematic effects and the substructure from QCD, splash-in, and heavy particle decays, we identify a technique, pruning, to better identify heavy particle decays into single jets and distinguish them from QCD jets. Pruning removes protojets typical of soft, wide-angle radiation, improves the mass resolution of jets reconstructing heavy particle decays, and decreases the QCD background to these decays. We show that pruning provides significant improvements overmore » unpruned jets in identifying top quarks and W bosons and separating them from a QCD background, and may be useful in a search for heavy particles.« less

Classical evolution of fractal measures on the lattice

NASA Astrophysics Data System (ADS)

Antoniou, N. G.; Diakonos, F. K.; Saridakis, E. N.; Tsolias, G. A.

2007-04-01

We consider the classical evolution of a lattice of nonlinear coupled oscillators for a special case of initial conditions resembling the equilibrium state of a macroscopic thermal system at the critical point. The displacements of the oscillators define initially a fractal measure on the lattice associated with the scaling properties of the order parameter fluctuations in the corresponding critical system. Assuming a sudden symmetry breaking (quench), leading to a change in the equilibrium position of each oscillator, we investigate in some detail the deformation of the initial fractal geometry as time evolves. In particular, we show that traces of the critical fractal measure can be sustained for large times, and we extract the properties of the chain that determine the associated time scales. Our analysis applies generally to critical systems for which, after a slow developing phase where equilibrium conditions are justified, a rapid evolution, induced by a sudden symmetry breaking, emerges on time scales much shorter than the corresponding relaxation or observation time. In particular, it can be used in the fireball evolution in a heavy-ion collision experiment, where the QCD critical point emerges, or in the study of evolving fractals of astrophysical and cosmological scales, and may lead to determination of the initial critical properties of the Universe through observations in the symmetry-broken phase.

Resumming double non-global logarithms in the evolution of a jet

NASA Astrophysics Data System (ADS)

Hatta, Y.; Iancu, E.; Mueller, A. H.; Triantafyllopoulos, D. N.

2018-02-01

We consider the Banfi-Marchesini-Smye (BMS) equation which resums `non-global' energy logarithms in the QCD evolution of the energy lost by a pair of jets via soft radiation at large angles. We identify a new physical regime where, besides the energy logarithms, one has to also resum (anti)collinear logarithms. Such a regime occurs when the jets are highly collimated (boosted) and the relative angles between successive soft gluon emissions are strongly increasing. These anti-collinear emissions can violate the correct time-ordering for time-like cascades and result in large radiative corrections enhanced by double collinear logs, making the BMS evolution unstable beyond leading order. We isolate the first such a correction in a recent calculation of the BMS equation to next-to-leading order by Caron-Huot. To overcome this difficulty, we construct a `collinearly-improved' version of the leading-order BMS equation which resums the double collinear logarithms to all orders. Our construction is inspired by a recent treatment of the Balitsky-Kovchegov (BK) equation for the high-energy evolution of a space-like wavefunction, where similar time-ordering issues occur. We show that the conformal mapping relating the leading-order BMS and BK equations correctly predicts the physical time-ordering, but it fails to predict the detailed structure of the collinear improvement.

The large-N Yang-Mills S matrix is ultraviolet finite, but the large-N QCD S matrix is only renormalizable

NASA Astrophysics Data System (ADS)

Bochicchio, Marco

2017-03-01

Yang-Mills (YM) theory and QCD are known to be renormalizable, but not ultraviolet (UV) finite, order by order, in perturbation theory. It is a fundamental question whether YM theory or QCD is UV finite, or only renormalizable, order by order, in the large-N 't Hooft or Veneziano expansions. We demonstrate that the renormalization group (RG) and asymptotic freedom imply that in 't Hooft large-N expansion the S matrix in YM theory is UV finite, while in both 't Hooft and Veneziano large-N expansions, the S matrix in confining massless QCD is renormalizable but not UV finite. By the same argument, the large-N N =1 supersymmetry (SUSY) YM S matrix is UV finite as well. Besides, we demonstrate that, in both 't Hooft and Veneziano large-N expansions, the correlators of local gauge-invariant operators, as opposed to the S matrix, are renormalizable but, in general, not UV finite, either in YM theory and N =1 SUSY YM theory or a fortiori in massless QCD. Moreover, we compute explicitly the counterterms that arise from renormalizing the 't Hooft and Veneziano expansions by deriving in confining massless QCD-like theories a low-energy theorem of the Novikov-Shifman-Vainshtein-Zakharov type that relates the log derivative with respect to the gauge coupling of a k -point correlator, or the log derivative with respect to the RG-invariant scale, to a (k +1 )-point correlator with the insertion of Tr F2 at zero momentum. Finally, we argue that similar results hold in the large-N limit of a vast class of confining massive QCD-like theories, provided a renormalization scheme exists—as, for example, MS ¯ —in which the beta function is not dependent on the masses. Specifically, in both 't Hooft and Veneziano large-N expansions, the S matrix in confining massive QCD and massive N =1 SUSY QCD is renormalizable but not UV finite.

Collinearly-improved BK evolution meets the HERA data

DOE PAGES

Iancu, E.; Madrigal, J. D.; Mueller, A. H.; ...

2015-10-03

In a previous publication, we have established a collinearly-improved version of the Balitsky–Kovchegov (BK) equation, which resums to all orders the radiative corrections enhanced by large double transverse logarithms. Here, we study the relevance of this equation as a tool for phenomenology, by confronting it to the HERA data. To that aim, we first improve the perturbative accuracy of our resummation, by including two classes of single-logarithmic corrections: those generated by the first non-singular terms in the DGLAP splitting functions and those expressing the one-loop running of the QCD coupling. The equation thus obtained includes all the next-to-leading order correctionsmore » to the BK equation which are enhanced by (single or double) collinear logarithms. Furthermore, we then use numerical solutions to this equation to fit the HERA data for the electron–proton reduced cross-section at small Bjorken x. We obtain good quality fits for physically acceptable initial conditions. Our best fit, which shows a good stability up to virtualities as large as Q 2 = 400 GeV 2 for the exchanged photon, uses as an initial condition the running-coupling version of the McLerran–Venugopalan model, with the QCD coupling running according to the smallest dipole prescription.« less

Strings with a confining core in a quark-gluon plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Layek, Biswanath; Mishra, Ananta P.; Srivastava, Ajit M.

2005-04-01

We consider the intersection of N different interfaces interpolating between different Z{sub N} vacua of an SU(N) gauge theory using the Polyakov loop order parameter. Topological arguments show that at such a stringlike junction, the order parameter should vanish, implying that the core of this string (i.e. the junction region of all the interfaces) is in the confining phase. Using the effective potential for the Polyakov loop proposed by Pisarski for QCD, we use numerical minimization technique and estimate the energy per unit length of the core of this string to be about 2.7 GeV/fm at a temperature about twicemore » the critical temperature. For the parameters used, the interface tension is obtained to be about 7 GeV/fm{sup 2}. Lattice simulation of pure gauge theories should be able to investigate properties of these strings. For QCD with quarks, it has been discussed in the literature that this Z{sub N} symmetry may still be meaningful, with quark contributions leading to explicit breaking of this Z{sub N} symmetry. With this interpretation, such quark-gluon plasma strings may play important role in the evolution of the quark-gluon plasma phase and in the dynamics of quark-hadron transition.« less

Accurate determinations of alpha(s) from realistic lattice QCD.

PubMed

Mason, Q; Trottier, H D; Davies, C T H; Foley, K; Gray, A; Lepage, G P; Nobes, M; Shigemitsu, J

2005-07-29

We obtain a new value for the QCD coupling constant by combining lattice QCD simulations with experimental data for hadron masses. Our lattice analysis is the first to (1) include vacuum polarization effects from all three light-quark flavors (using MILC configurations), (2) include third-order terms in perturbation theory, (3) systematically estimate fourth and higher-order terms, (4) use an unambiguous lattice spacing, and (5) use an [symbol: see text](a2)-accurate QCD action. We use 28 different (but related) short-distance quantities to obtain alpha((5)/(MS))(M(Z)) = 0.1170(12).

Dimensional Transmutation by Monopole Condensation in QCD

NASA Astrophysics Data System (ADS)

Cho, Y. M.

2015-01-01

The dimensional transmutation by the monopole condensation in QCD is reviewed. Using Abelian projection of the gauge potential which projects out the monopole potential gauge independently, we we show that there are two types of gluons: the color neutral binding gluons which plays the role of the confining agent and the colored valence gluons which become confined prisoners. With this we calculate the one-loop QCD effective potential and show the monopole condensation becomes the true vacuum of QCD. We propose to test the existence of two types of gluons experimentally by re-analyzing the existing gluon jets data.

QCD and Multiparticle Production - Proceedings of the XXIX International Symposium on Multiparticle Dynamics

NASA Astrophysics Data System (ADS)

Sarcevic, Ina; Tan, Chung-I.

2000-07-01

The Table of Contents for the full book PDF is as follows: * Preface * Monday morning session: Hadronic Final States - Conveners: E. de Wolf and J. W. Gary * Session Chairman: J. W. Gary * Inclusive Jets at the Tevatron * Forward Jets, Dijets, and Subjets at the Tevatron * Inclusive Hadron Production and Dijets at HERA * Recent Opal Results on Photon Structure and Interactions * Review of Two-Photon Physics at LEP * Session Chairman: E. de Wolf * An Intriguing Area-Law-Based Hadron Production Scheme in e+e- Annihilation and Its Possible Extensions * Hyperfine Splitting in Hadron Production at High Energies * Event Selection Effects on Multiplicities in Quark and Gluon Jets * Quark and Gluon Jet Properties at LEP * Rapidity Gaps in Quark and Gluon Jets -- A Perturbative Approach * Monday afternoon session: Diffractive and Small-x - Conveners: M. Derrick and A. White * Session Chairman: A. White * Structure Functions: Low x, High y, Low Q2 * The Next-to-Leading Dynamics of the BFKL Pomeron * Renormalization Group Improved BFKL Equation * Session Chairman: G. Briskin * New Experimental Results on Diffraction at HERA * Diffractive Parton Distributions in Light-Cone QCD * The Logarithmic Derivative of the F2 Structure Function and Saturation * Spin Dependence of Diffractive DIS * Monday evening session * Session Chairman: M. Braun * Tests of QCD with Particle Production at HERA: Review and Outlook * Double Parton Scattering and Hadron Structure in Transverse Space * The High Density Parton Dynamics from Eikonal and Dipole Pictures * Hints of Higher Twist Effects in the Slope of the Proton Structure Function * Tuesday morning session: Correlations and Fluctuations - Conveners: R. Hwa and M. Tannenbaum * Session Chairman: A. Giovannini -- Fluctuations and Correlations * Bose-Einstein Results from L3 * Short-Range and Long-Range Correlations in DIS at HERA * Coior Mutation Model, Intermittency, and Erraticity * QCD Queuing and Hadron Multiplicity * Soft and Semi-hard Components in Multiplicity Distributions in the TeV Region * Qualitative Difference Between Particle Production Dynamics in Soft and Hard Processes * Session Chairman: M. Tannenbaum -- Bose-Einstein Correlations * Questions in Bose-Einstein Correlations * The Source Size Dependence on the mhadron Applying Fermi and Bose Statistics and I-Spin Invariance * Signal of Partial UA(1) Symmetry Restoration from Two-Pion Bose-Einstein Correlations * Multiparticle Bose-Einstein Correlations in Heavy-Ion Collisions * Tuesday afternoon session: Heavy Ion Collisions - Conveners: B. Müller and J. Statchel * Session Chairman: J. Stachel * Probing Baryon Freeze-out Density at the AGS with Proton Correlations * Centrality Dependence of Hadronic Observables at CERN SPS * Study of Transverse Momentum Spectra in pp Collisions with a Statistical Model of Hadronisation * Session Chairman: B. Brower * Production of Light (Anti-)Nuclei with E864 at the AGS * QCD Critical Point in Heavy-Ion Collision Experiments * Tuesday evening session * Session Chairman: H. M. Fried * Oscillating Hq, Event Shapes, and QCD * Critical Behavior of Quark-Hadron Phase Transition * Shadowing of Gluons at RHIC and LHC * Parton Distributions in Nuclei at Small x * Wednesday morning session: Diffraction and Small x - Conveners: M. Derrick and A. White * Session Chairman: C. Pajares * High-Energy Effective Action from Scattering of Shock Waves in QCD * The Triangle Anomaly in the Triple-Regge Limit * CDF Results on Hard Diffraction and Rapidity Gap Physics * DØ Results on Hard Diffraction * Interjet Rapidity Gaps in Perturbative QCD * Pomeron: Beyond the Standard Approach * Factorization and Diffractive Production at Collider Energies * Thursday morning session: Heavy Ion Collisions - Conveners: B. Müller and J. B. Stachel * Session Chairman: N. Schmitz * Summary of J/ψ Suppression Data and Preliminary Results on Multiplicity Distributions in PB-PB Collisions from the NA50 Experiment * Duality and Chiral Restoration from Dilepton Production in Relativistic Heavy-Ion Collisions * Session Chairman: I. Sarcevic * Transport-Theoretical Analysis of Reaction Dynamics, Particle Production and Freeze-out at RHIC * Inclusive Particle Spectra and Exotic Particle Searches Using STAR * The First Fermi in a High Energy Nuclear Collision * Probing the Space-Time Evolution of Heavy Ion Collisions with Bremsstrahlung * Thursday afternoon session: Hadronic Final States - Conveners: E. de Wolf and J. Gary * Session Chairman: F. Verbeure * QCD with SLD * QCD at LEP II * Multidimensional Analysis of the Bose-Einstein Correlations at DELPHI * Study of Color Singlet with Gluonic Subsinglet by Color Effective Hamiltonian * Correlations and Fluctuations - Conveners: R. Hwa and M. Tannenbaum * Session Chairman: R. C. Hwa -- Fluctuations in Heavy-Ion Collisions * Scale-Local Statistical Measures and the Multiparticle Final State * Centrality and ET Fluctuations from p + Be to Au + Au at AGS Energies * Order Parameter of Single Event * Multiplicities, Transverse Momenta and Their Correlations from Percolating Colour Strings * Probing the QCD Critical Point in Nuclear Collisions * Event-by-Event Fluctuations in Pb + Pb Collisions at the CERN SPS * Friday morning session: High Energy Collisions and Cosmic-Ray/Astrophysics - Conveners: F. Halzen and T. Stanev * Session Chairman: U. Sukhatme * Rethinking the Eikonal Approximation * QCD and Total Cross-Sections * The Role of Multiple Parton Collisions in Hadron Collisions * Effective Cross Sections and Spatial Structure of the Hadrons * Looking for the Odderon * QCD in Embedded Coordinates * Session Chairman: F. Bopp * Extensive Air Sbowers and Hadronic Interaction Models * Penetration of the Earth by Ultrahigh Energy Neutrinos and the Parton Distributions Inside the Nucleon * Comparison of Prompt Muon Observations to Charm Expectations * Friday afternoon session: Recent Developments - Conveners: R. Brower and I. Sarcevic * Session Chairman: G. Guralnik * The Relation Between Gauge Theories and Gravity * From Black Holes to Pomeron: Tensor Glueball and Pomeron Intercept at Strong Coupling * Summary Talks * Summary of Results of the Ultrarelativistic Heavy Ion Fixed Target Program * Review of Theory Talks * Summary of Experimental Talks * List of Participants

Resonance production in. gamma gamma. collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renard, F.M.

1983-04-01

The processes ..gamma gamma.. ..-->.. hadrons can be depicted as follows. One photon creates a q anti q pair which starts to evolve; the other photon can either (A) make its own q anti q pair and the (q anti q q anti q) system continue to evolve or (B) interact with the quarks of the first pair and lead to a modified (q anti q) system in interaction with C = +1 quantum numbers. A review of the recent theoretical activity concerning resonance production and related problems is given under the following headings: hadronic C = +1 spectroscopy (qmore » anti q, qq anti q anti q, q anti q g, gg, ggg bound states and mixing effects); exclusive ..gamma gamma.. processes (generalities, unitarized Born method, VDM and QCD); total cross section (soft and hard contributions); q/sup 2/ dependence of soft processes (soft/hard separation, 1/sup +- +/ resonances); and polarization effects. (WHK)« less

Search for microscopic black holes in pp collisions at $$ \\sqrt{s}=8 $$ TeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.

2013-07-01

A search for microscopic black holes and string balls is presented, based on a data sample of pp collisions at sqrt(s) = 8 TeV recorded by the CMS experiment at the Large Hadron Collider and corresponding to an integrated luminosity of 12 inverse femtobarns. No excess of events with energetic multiparticle final states, typical of black hole production or of similar new physics processes, is observed. Given the agreement of the observations with the expected standard model background, which is dominated by QCD multijet production, 95% confidence limits are set on the production of semiclassical or quantum black holes, ormore » of string balls, corresponding to the exclusions of masses below 4.3 to 6.2 TeV, depending on model assumptions. In addition, model-independent limits are set on new physics processes resulting in energetic multiparticle final states.« less

LHC forward physics

DOE PAGES

Akiba, K.; Akbiyik, M.; Albrow, M.; ...

2016-10-17

The goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the LHC. The report starts presenting a selection of the Monte Carlo simulation tools currently available, chapter 2, then enters the rich phenomenology of QCD at low, chapter 3, and high, chapter 4, momentum transfer, while the unique scattering conditions of central exclusive production are analyzed in chapter 5. The last two experimental topics, Cosmic Ray and Heavy Ion physics are presented in the chapter 6 and 7 respectively. Chaptermore » 8 is dedicated to the BFKL dynamics, multiparton interactions, and saturation. Here, the report ends with an overview of the forward detectors at LHC. Each chapter is correlated with a comprehensive bibliography, attempting to provide to the interested reader with a wide opportunity for further studies.« less

Electroproduction of {eta} mesons in the S{sub 11} (1535) resonance region at high momentum transfer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalton, M. M.; Adams, G. S.; Ahmidouch, A.

2009-07-01

The differential cross section for the process p(e,e{prime}p) {eta} has been measured at Q{sup 2} {approx} 5.7 and 7.0(GeV/c){sup 2} for center-of-mass energies from threshold to 1.8 GeV, encompassing the S{sub 11}(1535) resonance, which dominates the channel. This is the highest momentum-transfer measurement of this exclusive process to date. The helicity-conserving transition amplitude A{sub 1/2}, for the production of the S{sub 11}(1535) resonance, is extracted from the data. Within the limited Q{sup 2} now measured, this quantity appears to begin scaling as Q{sup -3} - a predicted, but not definitive, signal of the dominance of perturbative QCD at Q{sup 2}more » {approx} 5 (GeV/c){sup 2}.« less

LHC forward physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cartiglia, N.; Royon, C.

The goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the LHC. The report starts presenting a selection of the Monte Carlo simulation tools currently available, chapter 2, then enters the rich phenomenology of QCD at low, chapter 3, and high, chapter 4, momentum transfer, while the unique scattering conditions of central exclusive production are analyzed in chapter 5. The last two experimental topics, Cosmic Ray and Heavy Ion physics are presented in the chapter 6 and 7 respectively. Chaptermore » 8 is dedicated to the BFKL dynamics, multiparton interactions, and saturation. The report ends with an overview of the forward detectors at LHC. Each chapter is correlated with a comprehensive bibliography, attempting to provide to the interested reader with a wide opportunity for further studies.« less

Scaling Phenomenology in Meson Photoproduction from CLAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biplab Dey, Curtis A. Meyer

2010-08-01

In the high energy limit, perturbative QCD predicts that hard scattering amplitudes should follow simple scaling laws. For hard scattering at 90°, we show that experiments support this prediction even in the “medium energy” regime of 2.3 GeV<=sqrt(s)<=2.84 GeV, as long as there are no s-channel resonances present. Our data consists of high statistics measurements for five different exclusive meson photoproduction channels (pomega, peta, peta[prime], K+Lambdaand K+[summation]0) recently obtained from CLAS at Jefferson Lab. The same power-law scaling also leads to “saturated” Regge trajectories at high energies. That is, at large -t and -u, Regge trajectories must approach constant negativemore » integers. We demonstrate the application of saturated Regge phenomenology by performing a partial wave analysis fit to the gammayp-->peta[prime]differential cross sections.« less

Disentangling the Correlated Evolution of Monogamy and Cooperation.

PubMed

Dillard, Jacqueline R; Westneat, David F

2016-07-01

Lifetime genetic monogamy, by increasing sibling relatedness, has been proposed as an important causal factor in the evolution of altruism. Monogamy, however, could influence the subsequent evolution of cooperation in other ways. We present several alternative, non-mutually exclusive, evolutionary processes that could explain the correlated evolution of monogamy and cooperation. Our analysis of these possibilities reveals that many ecological or social factors can affect all three variables of Hamilton's Rule simultaneously, thus calling for a more holistic, systems-level approach to studying the evolution of social traits. This perspective reveals novel dimensions to coevolutionary relationships and provides solutions for assigning causality in complex cases of correlated social trait evolution, such as the sequential evolution of monogamy and cooperation. Copyright © 2016 Elsevier Ltd. All rights reserved.

QCD inequalities for the nucleon mass and the free energy of baryonic matter.

PubMed

Cohen, Thomas D

2003-07-18

The positivity of the integrand of certain Euclidean space functional integrals for two flavor QCD with degenerate quark masses implies that the free energy per unit volume for QCD with a baryon chemical potential mu(B) (and zero isospin chemical potential) is greater than the free energy with an isospin chemical potential mu(I)=(2 mu(B)/N(c)) (and zero baryon chemical potential). The same result applies to QCD with any number of heavy flavors in addition to the two light flavors so long as the chemical potential is understood as applying to the light quark contributions to the baryon number. This relation implies a bound on the nucleon mass: there exists a particle X in QCD (presumably the pion) such that M(N)> or =(N(c) m(X)/2 I(X)) where m(X) is the mass of the particle and I(X) is its isospin.

Phenomenology of Semileptonic B-Meson Decays with Form Factors from Lattice QCD

DOE PAGES

Du, Daping; El-Khadra, A. X.; Gottlieb, Steven; ...

2016-02-03

We study the exclusive semileptonic B-meson decays B→K(π)ℓ +ℓ -, B→K(π)νν¯, and B→πτν, computing observables in the Standard model using the recent lattice-QCD results for the underlying form factors from the Fermilab Lattice and MILC Collaborations. These processes provide theoretically clean windows into physics beyond the Standard Model because the hadronic uncertainties are now under good control. The resulting partially-integrated branching fractions for B→πμ +μ - and B→Kμ +μ - outside the charmonium resonance region are 1-2σ higher than the LHCb Collaboration's recent measurements, where the theoretical and experimental errors are commensurate. The combined tension is 1.7σ. Combining the Standard-Modelmore » rates with LHCb's measurements yields values for the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |V td|=7.45(69)×10 -3, |V ts|=35.7(1.5)×10 -3, and |V td/V ts|=0.201(20), which are compatible with the values obtained from neutral B (s)-meson oscillations and have competitive uncertainties. Alternatively, taking the CKM matrix elements from unitarity, we constrain new-physics contributions at the electroweak scale. Furthermore, the constraints on the Wilson coefficients Re(C 9) and Re(C 10) from B→πμ +μ - and B→Kμ +μ - are competitive with those from B→K*μ +μ -, and display a 2.0σ tension with the Standard Model. Our predictions for B→K(π)νν¯ and B→πτν are close to the current experimental limits.« less

Polarization phenomena in quantum chromodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, S.J.

1994-12-01

The author discusses a number of interrelated hadronic spin effects which test fundamental features of perturbative and nonperturbative QCD. For example, the anomalous magnetic moment of the proton and the axial coupling g{sub A} on the nucleon are shown to be related to each other for fixed proton radius, independent of the form of the underlying three-quark relativistic quark wavefunction. The renormalization scale and scheme ambiguities for the radiative corrections to the Bjorken sum rule for the polarized structure functions can be eliminated by using commensurate scale relations with other observables. Other examples include (a) new constraints on the shapemore » and normalization of the polarized quark and gluon structure functions of the proton at large and small x{sub bj}; (b) consequences of the principle of hadron retention in high x{sub F} inclusive reactions; (c) applications of hadron helicity conservation to high momentum transfer exclusive reactions; and (d) the dependence of nuclear structure functions and shadowing on virtual photon polarization. The author also discusses the implications of a number of measurements which are in striking conflict with leading-twist perturbative QCD predictions, such as the extraordinarily large spin correlation A{sub NN} observed in large angle proton-proton scattering, the anomalously large {rho}{pi} branching ratio of the J/{psi}, and the rapidly changing polarization dependence of both J/{psi} and continuum lepton pair hadroproduction observed at large x{sub F}. The azimuthal angular dependence of the Drell-Yan process is shown to be highly sensitive to the projectile distribution amplitude, the fundamental valence light-cone wavefunction of the hadron.« less

Studies of L-T Separated Kaon Electroproduction

NASA Astrophysics Data System (ADS)

Trotta, Richard; Horn, Tanja; Vargas, Andres

2017-09-01

QCD is characterized by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB). Pion and kaon form factors are of particular interest as they are connected to the Goldstone modes of DCSB. The flavor degrees of freedom of the produced meson selectively probe aspects of the reaction mechanism and the transition from hadronic to partonic degrees of freedom. There has been significant progress in the theoretical description of the nucleon structure in terms of QCD degrees of freedom, in particular through Generalized Parton Distributions (GPDs).The last decade saw a dramatic improvement in precision of charged pion form factor data and new results have become available on the pion transition form factor. The kaon provides an interesting way to expand these studies, opening the possibility to access the production mechanism involving strangeness. Kaon data at larger virtual photon mass allow one to search for the onset of the partonic picture. In this regime, hard and soft physics have been shown to factorize and GPDs provide the most complete description of the non-perturbative physics. The lack of necessary experimental facilities has left a gap in L-T separated data for exclusive K + production from the proton above the resonance region.The newly upgraded 12 GeV beam energy at Jlab, in addition to the recently built SHMS spectrometer for Hall C, has provided an opportunity to expand the kaon data. Recent kaon form factor and cross section results will be discussed showing the impact of E12-09-011, the running Jlab 12 GeV kaon experiment. NSF Grants PHY1306227, PHY1306418 and PHY1530874.

Recent QCD Studies at the Tevatron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Group, Robert Craig

2008-04-01

Since the beginning of Run II at the Fermilab Tevatron the QCD physics groups of the CDF and D0 experiments have worked to reach unprecedented levels of precision for many QCD observables. Thanks to the large dataset--over 3 fb{sup -1} of integrated luminosity recorded by each experiment--important new measurements have recently been made public and will be summarized in this paper.

Lattice quantum chromodynamical approach to nuclear physics

NASA Astrophysics Data System (ADS)

Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji; HAL QCD Collaboration

2012-09-01

We review recent progress in the HAL QCD method, which was recently proposed to investigate hadron interactions in lattice quantum chromodynamics (QCD). The strategy to extract the energy-independent non-local potential in lattice QCD is explained in detail. The method is applied to study nucleon-nucleon, nucleon-hyperon, hyperon-hyperon, and meson-baryon interactions. Several extensions of the method are also discussed.

On microscopic structure of the QCD vacuum

NASA Astrophysics Data System (ADS)

Pak, D. G.; Lee, Bum-Hoon; Kim, Youngman; Tsukioka, Takuya; Zhang, P. M.

2018-05-01

We propose a new class of regular stationary axially symmetric solutions in a pure QCD which correspond to monopole-antimonopole pairs at macroscopic scale. The solutions represent vacuum field configurations which are locally stable against quantum gluon fluctuations in any small space-time vicinity. This implies that the monopole-antimonopole pair can serve as a structural element in microscopic description of QCD vacuum formation.

Equivalence of the AdS-metric and the QCD running coupling

NASA Astrophysics Data System (ADS)

Pirner, H. J.; Galow, B.

2009-08-01

We use the functional form of the QCD running coupling to modify the conformal metric in AdS/CFT mapping the fifth-dimensional z-coordinate to the energy scale in the four-dimensional QCD. The resulting type-0 string theory in five dimensions is solved with the Nambu-Goto action giving good agreement with the Coulombic and confinement QQbar potential.

Renormalizability of quasiparton distribution functions

DOE PAGES

Ishikawa, Tomomi; Ma, Yan-Qing; Qiu, Jian-Wei; ...

2017-11-21

Quasi-parton distribution functions have received a lot of attentions in both perturbative QCD and lattice QCD communities in recent years because they not only carry good information on the parton distribution functions, but also could be evaluated by lattice QCD simulations. However, unlike the parton distribution functions, the quasi-parton distribution functions have perturbative ultraviolet power divergences because they are not defined by twist-2 operators. Here in this article, we identify all sources of ultraviolet divergences for the quasi-parton distribution functions in coordinate-space, and demonstrated that power divergences, as well as all logarithmic divergences can be renormalized multiplicatively to all ordersmore » in QCD perturbation theory.« less

Susceptibility of the QCD vacuum to CP-odd electromagnetic background fields.

PubMed

D'Elia, Massimo; Mariti, Marco; Negro, Francesco

2013-02-22

We investigate two flavor quantum chromodynamics (QCD) in the presence of CP-odd electromagnetic background fields and determine, by means of lattice QCD simulations, the induced effective θ term to first order in E[over →] · B[over →]. We employ a rooted staggered discretization and study lattice spacings down to 0.1 fm and Goldstone pion masses around 480 MeV. In order to deal with a positive measure, we consider purely imaginary electric fields and real magnetic fields, and then exploit the analytic continuation. Our results are relevant to a description of the effective pseudoscalar quantum electrodynamics-QCD interactions.

Renormalizability of quasiparton distribution functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishikawa, Tomomi; Ma, Yan-Qing; Qiu, Jian-Wei

Quasi-parton distribution functions have received a lot of attentions in both perturbative QCD and lattice QCD communities in recent years because they not only carry good information on the parton distribution functions, but also could be evaluated by lattice QCD simulations. However, unlike the parton distribution functions, the quasi-parton distribution functions have perturbative ultraviolet power divergences because they are not defined by twist-2 operators. Here in this article, we identify all sources of ultraviolet divergences for the quasi-parton distribution functions in coordinate-space, and demonstrated that power divergences, as well as all logarithmic divergences can be renormalized multiplicatively to all ordersmore » in QCD perturbation theory.« less

Quark–hadron phase structure, thermodynamics, and magnetization of QCD matter

NASA Astrophysics Data System (ADS)

Nasser Tawfik, Abdel; Magied Diab, Abdel; Hussein, M. T.

2018-05-01

The SU(3) Polyakov linear-sigma model (PLSM) is systematically implemented to characterize the quark-hadron phase structure and to determine various thermodynamic quantities and the magnetization of quantum chromodynamic (QCD) matter. Using mean-field approximation, the dependence of the chiral order parameter on a finite magnetic field is also calculated. Under a wide range of temperatures and magnetic field strengths, various thermodynamic quantities including trace anomaly, speed of sound squared, entropy density, and specific heat are presented, and some magnetic properties are described as well. Where available these results are compared to recent lattice QCD calculations. The temperature dependence of these quantities confirms our previous finding that the transition temperature is reduced with the increase in the magnetic field strength, i.e. QCD matter is characterized by an inverse magnetic catalysis. Furthermore, the temperature dependence of the magnetization showing that QCD matter has paramagnetic properties slightly below and far above the pseudo-critical temperature is confirmed as well. The excellent agreement with recent lattice calculations proves that our QCD-like approach (PLSM) seems to possess the correct degrees of freedom in both the hadronic and partonic phases and describes well the dynamics deriving confined hadrons to deconfined quark-gluon plasma.

Matter density perturbation and power spectrum in running vacuum model

NASA Astrophysics Data System (ADS)

Geng, Chao-Qiang; Lee, Chung-Chi

2017-01-01

We investigate the matter density perturbation δm and power spectrum P(k) in the running vacuum model, with the cosmological constant being a function of the Hubble parameter, given by Λ = Λ0 + 6σHH0 + 3νH2, in which the linear and quadratic terms of H would originate from the QCD vacuum condensation and cosmological renormalization group, respectively. Taking the dark energy perturbation into consideration, we derive the evolution equation for δm and find a specific scale dcr = 2π/kcr, which divides the evolution of the universe into the sub-interaction and super-interaction regimes, corresponding to k ≪ kcr and k ≫ kcr, respectively. For the former, the evolution of δm has the same behaviour as that in the Λ cold dark model, while for the latter, the growth of δm is frozen (greatly enhanced) when ν + σ > (<)0 due to the couplings between radiation, matter and dark energy. It is clear that the observational data rule out the cases with ν < 0 and ν + σ < 0, while the allowed window for the model parameters is extremely narrow with ν , |σ | ≲ O(10^{-7}).

MARTINI: An event generator for relativistic heavy-ion collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schenke, Bjoern; Gale, Charles; Jeon, Sangyong

2009-11-15

We introduce the modular algorithm for relativistic treatment of heavy ion interactions (MARTINI), a comprehensive event generator for the hard and penetrating probes in high-energy nucleus-nucleus collisions. Its main components are a time-evolution model for the soft background, PYTHIA 8.1, and the McGill-Arnold, Moore, and Yaffe (AMY) parton-evolution scheme, including radiative as well as elastic processes. This allows us to generate full event configurations in the high p{sub T} region that take into account thermal quantum chromodynamic (QCD) and quantum electrodynamic (QED) effects as well as effects of the evolving medium. We present results for the neutral pion nuclear modificationmore » factor in Au+Au collisions at the BNL Relativistic Heavy Ion Collider as a function of p{sub T} for different centralities and also as a function of the angle with respect to the reaction plane for noncentral collisions. Furthermore, we study the production of high-transverse-momentum photons, incorporating a complete set of photon-production channels.« less

Next-to-leading order transverse momentum-weighted Sivers asymmetry in semi-inclusive deep inelastic scattering: The role of the three-gluon correlator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Ling -Yun; Kang, Zhong -Bo; Prokudin, Alexei

2015-12-22

Here, we study the Sivers asymmetry in semi-inclusive hadron production in deep inelastic scattering. We concentrate on the contribution from the photon-gluon fusion channel at O(α em 2α s), where three-gluon correlation functions play a major role within the twist-3 collinear factorization formalism. We establish the correspondence between such a formalism with three-gluon correlation functions and the usual transverse momentum-dependent (TMD) factorization formalism at moderate hadron transverse momenta. We derive the coefficient functions used in the usual TMD evolution formalism related to the quark Sivers function expansion in terms of the three-gluon correlation functions. We further perform the next-to-leading ordermore » calculation for the transverse momentum-weighted spin-dependent differential cross section and identify the off-diagonal contribution from the three-gluon correlation functions to the QCD collinear evolution of the twist-3 Qiu-Sterman function.« less

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Branch Processes of Vortex Filaments and Hopf Invariant Constraint on Scroll Wave

NASA Astrophysics Data System (ADS)

Zhu, Tao; Ren, Ji-Rong; Mo, Shu-Fan

2009-12-01

In this paper, by making use of Duan's topological current theory, the evolution of the vortex filaments in excitable media is discussed in detail. The vortex filaments are found generating or annihilating at the limit points and encountering, splitting, or merging at the bifurcation points of a complex function Z(vec x, t). It is also shown that the Hopf invariant of knotted scroll wave filaments is preserved in the branch processes (splitting, merging, or encountering) during the evolution of these knotted scroll wave filaments. Furthermore, it also revealed that the “exclusion principle" in some chemical media is just the special case of the Hopf invariant constraint, and during the branch processes the “exclusion principle" is also protected by topology.

Production of identified charged hadrons in Pb-Pb collisions at √{sNN} = 5.02 TeV

NASA Astrophysics Data System (ADS)

Jacazio, Nicolò

2017-11-01

In late 2015, the ALICE collaboration recorded data from Pb-Pb collisions at the unprecedented energy of √{sNN} = 5.02 TeV. The transverse-momentum (pT) spectra of pions, kaons and protons are presented. The evolution of the particle ratios as a function of collision energy and centrality is discussed. The ratio between pT-integrated particle yields are measured and compared to different collision energies as well as smaller collision systems. For the study of energy loss mechanisms in the QCD medium at high transverse momenta, the nuclear modification factors (RAA) are computed and compared with results obtained at lower energy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

MAEZAWA,Y.; AOKI, S.; EJIRI, S.

The authors report the current status of the systematic studies of the QCD thermodynamics by lattice QCD simulations with two flavors of improved Wilson quarks. They evaluate the critical temperature of two flavor QCD in the chiral limit at zero chemical potential and show the preliminary result. Also they discuss fluctuations at none-zero temperature and density by calculating the quark number and isospin susceptibilities and their derivatives with respect to chemical potential.

Heavy-quark production in gluon fusion at two loops in QCD

NASA Astrophysics Data System (ADS)

Czakon, M.; Mitov, A.; Moch, S.

2008-07-01

We present the two-loop virtual QCD corrections to the production of heavy quarks in gluon fusion. The results are exact in the limit when all kinematical invariants are large compared to the mass of the heavy quark up to terms suppressed by powers of the heavy-quark mass. Our derivation uses a simple relation between massless and massive QCD scattering amplitudes as well as a direct calculation of the massive amplitude at two loops. The results presented here together with those obtained previously for quark-quark scattering form important parts of the next-to-next-to-leading order QCD corrections to heavy-quark production in hadron-hadron collisions.

Higgs boson couplings to bottom quarks: two-loop supersymmetry-QCD corrections.

PubMed

Noth, David; Spira, Michael

2008-10-31

We present two-loop supersymmetry (SUSY) QCD corrections to the effective bottom Yukawa couplings within the minimal supersymmetric extension of the standard model (MSSM). The effective Yukawa couplings include the resummation of the nondecoupling corrections Deltam_{b} for large values of tanbeta. We have derived the two-loop SUSY-QCD corrections to the leading SUSY-QCD and top-quark-induced SUSY-electroweak contributions to Deltam_{b}. The scale dependence of the resummed Yukawa couplings is reduced from O(10%) to the percent level. These results reduce the theoretical uncertainties of the MSSM Higgs branching ratios to the accuracy which can be achieved at a future linear e;{+}e;{-} collider.

Determination of $${{\\rm{\\Lambda }}}_{\\overline{{\\rm{MS}}}}$$ at five loops from holographic QCD

DOE PAGES

Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

2017-08-25

Here, the recent determination of themore » $$\\beta$$--function of the QCD running coupling $$\\alpha_{\\overline{MS}}(Q^2)$$ to five-loops, provides a verification of the convergence of a novel method for determining the fundamental QCD parameter $$\\Lambda_s$$ based on the Light-Front Holographic approach to nonperturbative QCD. The new 5-loop analysis, together with improvements in determining the holographic QCD nonperturbative scale parameter $$\\kappa$$ from hadronic spectroscopy, leads to an improved precision of the value of $$\\Lambda_s$$ in the $${\\overline{MS}}$$ scheme close to a factor of two; we find $$\\Lambda^{(3)}_{\\overline{MS}}=0.339\\pm0.019$$ GeV for $$n_{f}=3$$, in excellent agreement with the world average, $$\\Lambda_{\\overline{MS}}^{(3)}=0.332\\pm0.017$$ GeV. Lastly, we also discuss the constraints imposed on the scale dependence of the strong coupling in the nonperturbative domain by superconformal quantum mechanics and its holographic embedding in anti-de Sitter space.« less

Dissociation of heavy quarkonium in hot QCD medium in a quasiparticle model

NASA Astrophysics Data System (ADS)

Agotiya, Vineet Kumar; Chandra, Vinod; Jamal, M. Yousuf; Nilima, Indrani

2016-11-01

Following a recent work on the effective description of the equations of state for hot QCD obtained from a hard thermal loop expression for the gluon self-energy, in terms of the quasigluons and quasiquarks and antiquarks with respective effective fugacities, the dissociation process of heavy quarkonium in hot QCD medium has been investigated. This has been done by investigating the medium modification to a heavy quark potential. The medium-modified potential has a quite different form (a long-range Coulomb tail in addition to the usual Yukawa term) in contrast to the usual picture of Debye screening. The flavor dependence binding energies of the heavy quarkonia states and the dissociation temperature have been obtained by employing the Debye mass for pure gluonic and full QCD case computed employing the quasiparticle picture. Thus, estimated dissociation patterns of the charmonium and bottomonium states, considering Debye mass from different approaches in the pure gluonic case and full QCD, have shown good agreement with the other potential model studies.

Going Beyond QCD in Lattice Gauge Theory

NASA Astrophysics Data System (ADS)

Fleming, G. T.

2011-01-01

Strongly coupled gauge theories (SCGT's) have been studied theoretically for many decades using numerous techniques. The obvious motivation for these efforts stemmed from a desire to understand the source of the strong nuclear force: Quantum Chromo-dynamics (QCD). Guided by experimental results, theorists generally consider QCD to be a well-understood SCGT. Unfortunately, it is not clear how to extend the lessons learned from QCD to other SCGT's. Particularly urgent motivators for new studies of other SCGT's are the ongoing searches for physics beyond the standard model (BSM) at the Large Hadron Collider (LHC) and the Tevatron. Lattice gauge theory (LGT) is a technique for systematically-improvable calculations in many SCGT's. It has become the standard for non-perturbative calculations in QCD and it is widely believed that it may be useful for study of other SCGT's in the realm of BSM physics. We will discuss the prospects and potential pitfalls for these LGT studies, focusing primarily on the flavor dependence of SU(3) gauge theory.

A study of jet production rates and a test of QCD on the Z 0 resonance

NASA Astrophysics Data System (ADS)

Akrawy, M. Z.; Alexander, G.; Allison, J.; Allport, P. P.; Anderson, K. J.; Armitage, J. C.; Arnison, G. T. J.; Ashton, P.; Azuelos, G.; Baines, J. T. M.; Ball, A. H.; Banks, J.; Barker, G. J.; Barlow, R. J.; Batley, J. R.; Bavaria, G.; Beard, C.; Beck, F.; Bell, K. W.; Bella, G.; Bethke, S.; Biebel, O.; Bloodworth, I. J.; Bock, P.; Boerner, H.; Breuker, H.; Brown, R. M.; Brun, R.; Buijs, A.; Burckhart, H. J.; Capiluppi, P.; Carnegie, R. K.; Carter, A. A.; Carter, J. R.; Chang, C. Y.; Charlton, D. G.; Chrin, J. T. M.; Cohen, I.; Conboy, J. E.; Couch, M.; Coupland, M.; Cuffiani, M.; Dado, S.; Dallavalle, G. M.; Davies, O. W.; Deninno, M. M.; Dieckmann, A.; Dittmar, M.; Dixit, M. S.; Duchesneau, D.; Duchovni, E.; Duerdoth, I. P.; Dumas, D.; El Mamouni, H.; Elcombe, P. A.; Estabrooks, P. G.; Fabbri, F.; Farthouat, P.; Fischer, H. M.; Fong, D. G.; French, M. T.; Fukunaga, C.; Gandois, B.; Ganel, O.; Gary, J. W.; Geddes, N. I.; Gee, C. N. P.; Geich-Gimbel, C.; Gensler, S. W.; Gentit, F. X.; Giacomelli, G.; Gibson, W. R.; Gillies, J. D.; Goldberg, J.; Goodrick, M. J.; Gorn, W.; Granite, D.; Gross, E.; Grosse-Wiesmann, P.; Grunhaus, J.; Hagedorn, H.; Hagemann, J.; Hansroul, M.; Hargrove, C. K.; Hart, J.; Hattersley, P. M.; Hatzifotiadou, D.; Hauschild, M.; Hawkes, C. M.; Heflin, E.; Heintze, J.; Hemingway, R. J.; Heuer, R. D.; Hill, J. C.; Hillier, S. J.; Hinde, P. S.; Ho, C.; Hobbs, J. D.; Hobson, P. R.; Hochman, D.; Holl, B.; Homer, R. J.; Hou, S. R.; Howarth, C. P.; Hughes-Jones, R. E.; Igo-Kemenes, P.; Imori, M.; Imrie, D. C.; Jawahery, A.; Jeffreys, P. W.; Jeremie, H.; Jimack, M.; Jin, E.; Jobes, M.; Jones, R. W. L.; Jovanovic, P.; Karlen, D.; Kawagoe, K.; Kawamoto, T.; Kellogg, R. G.; Kennedy, B. W.; Kleinwort, C.; Klem, D. E.; Knop, G.; Kobayashi, T.; Köpke, L.; Kokott, T. P.; Koshiba, M.; Kowalewski, R.; Kreutzmann, H.; Von Krogh, J.; Kroll, J.; Kyberd, P.; Lafferty, G. D.; Lamarche, F.; Larson, W. J.; Lasota, M. M. B.; Layter, J. G.; Le Du, P.; Leblanc, P.; Lellouch, D.; Lennert, P.; Lessard, L.; Levinson, L.; Lloyd, S. L.; Loebinger, F. K.; Lorah, J. M.; Lorazo, B.; Losty, M. J.; Ludwig, J.; Lupu, N.; Ma, J.; Macbeth, A. A.; Mannelli, M.; Marcellini, S.; Maringer, G.; Martin, J. P.; Mashimo, T.; Mättig, P.; Maur, U.; McMahon, T. J.; McPherson, A. C.; Meijers, F.; Menszner, D.; Merritt, F. S.; Mes, H.; Michelini, A.; Middleton, R. P.; Mikenberg, G.; Miller, D. J.; Milstene, C.; Minowa, M.; Mohr, W.; Montanari, A.; Mori, T.; Moss, M. W.; Muller, A.; Murphy, P. G.; Murray, W. J.; Nellen, B.; Nguyen, H. H.; Nozaki, M.; O'Dowd, A. J. P.; O'Neale, S. W.; O'Neill, B.; Oakham, F. G.; Odorici, F.; Ogg, M.; Oh, H.; Oreglia, M. J.; Orito, S.; Patrick, G. N.; Pawley, S. J.; Perez, A.; Pilcher, J. E.; Pinfold, J. L.; Plane, D. E.; Poli, B.; Possoz, A.; Pouladdej, A.; Pritchard, T. W.; Quast, G.; Raab, J.; Redmond, M. W.; Rees, D. L.; Regimbald, M.; Riles, K.; Roach, C. M.; Roehner, F.; Rollnik, A.; Roney, J. M.; Rossi, A. M.; Routenburg, P.; Runge, K.; Runolfsson, O.; Sanghera, S.; Sansum, R. A.; Sasaki, M.; Saunders, B. J.; Schaile, A. D.; Schaile, O.; Schappert, W.; Scharff-Hansen, P.; von der Schmitt, H.; Schreiber, S.; Schwarz, J.; Shapira, A.; Shen, B. C.; Sherwood, P.; Simon, A.; Siroli, G. P.; Skuja, A.; Smith, A. M.; Smith, T. J.; Snow, G. A.; Spreadbury, E. J.; Springer, R. W.; Sproston, M.; Stephens, K.; Stier, H. E.; Ströhmer, R.; Strom, D.; Takeda, H.; Takeshita, T.; Tsukamoto, T.; Turner, M. F.; Tysarczyk, G.; van den Plas, D.; Vandalen, G. J.; Virtue, C. J.; Wagner, A.; Wahl, C.; Wang, H.; Ward, C. P.; Ward, D. R.; Waterhouse, J.; Watkins, P. M.; Watson, A. T.; Watson, N. K.; Weber, M.; Weisz, S.; Wermes, N.; Weymann, M.; Wilson, G. W.; Wilson, J. A.; Wingerter, I.; Winterer, V.-H.; Wood, N. C.; Wotton, S.; Wuensch, B.; Wyatt, T. R.; Yaari, R.; Yamashita, H.; Yang, Y.; Yekutieli, G.; Zeuner, W.; Zorn, G. T.; Zylberajch, S.; OPAL Collaboration

1990-02-01

Relative production rates of multijet hadronic final states of Z 0 boson decays, observed in e +e - annihilation around 91 GeV centre of mass energy, are presented. The data can be well described by analytic O( αs2) QCD calculations and by QCD shower model calaculations with parameters as determined at lower energies. A first judgement of Λ overlineMS and of the renormalization scale μ2 in O( αs2) QCD results in values similar to those obtained in the continuum of e +e - annihilations. Significant scaling violations are observed when the 3-jet fractions are compared to the corresponding results from smaller centre of mass energies. They can be interpreted as being entirely due tot the energy dependence of αs, as proposed by the nonabelian nature of QCD, The possibility of an energy independent coupling constant can be excluded with a significance of 5.7 standard deviations.

QCD corrections to ZZ production in gluon fusion at the LHC

DOE PAGES

Caola, Fabrizio; Melnikov, Kirill; Rontsch, Raoul; ...

2015-11-23

We compute the next-to-leading-order QCD corrections to the production of two Z-bosons in the annihilation of two gluons at the LHC. Being enhanced by a large gluon flux, these corrections provide a distinct and, potentially, the dominant part of the N 3LO QCD contributions to Z-pair production in proton collisions. The gg → ZZ annihilation is a loop-induced process that receives the dominant contribution from loops of five light quarks, that are included in our computation in the massless approximation. We find that QCD corrections increase the gg → ZZ production cross section by O(50%–100%) depending on the values ofmore » the renormalization and factorization scales used in the leading-order computation and the collider energy. Furthermore, the large corrections to the gg → ZZ channel increase the pp → ZZ cross section by about 6% to 8%, exceeding the estimated theoretical uncertainty of the recent next-to-next-to-leading-order QCD calculation.« less

The Top Quark, QCD, And New Physics.

DOE R&D Accomplishments Database

Dawson, S.

2002-06-01

The role of the top quark in completing the Standard Model quark sector is reviewed, along with a discussion of production, decay, and theoretical restrictions on the top quark properties. Particular attention is paid to the top quark as a laboratory for perturbative QCD. As examples of the relevance of QCD corrections in the top quark sector, the calculation of e{sup+}e{sup -}+ t{bar t} at next-to-leading-order QCD using the phase space slicing algorithm and the implications of a precision measurement of the top quark mass are discussed in detail. The associated production of a t{bar t} pair and a Higgs boson in either e{sup+}e{sup -} or hadronic collisions is presented at next-to-leading-order QCD and its importance for a measurement of the top quark Yulrawa coupling emphasized. Implications of the heavy top quark mass for model builders are briefly examined, with the minimal supersymmetric Standard Model and topcolor discussed as specific examples.

Progress towards quantum simulating the classical O(2) Model

DTIC Science & Technology

2014-12-01

approach by building up on simple models sharing some of the basic features of lattice QCD . In the context of condensed matter, a proof of principle that...independently. Explicit Hilbert space repre- sentations of the physical states and of their matrix elements are mostly absent from today’s lattice QCD ...to lattice QCD , seems possible and interesting. ACKNOWLEDGMENTS We thank Masanori Hanada, Peter Orland, Lode Pollet, Boris Svistunov, the participants

The International Conference on Vector and Parallel Computing (2nd)

DTIC Science & Technology

1989-01-17

Computation of the SVD of Bidiagonal Matrices" ...................................... 11 " Lattice QCD -As a Large Scale Scientific Computation...vectorizcd for the IBM 3090 Vector Facility. In addition, elapsed times " Lattice QCD -As a Large Scale Scientific have been reduced by using 3090...benchmarked Lattice QCD on a large number ofcompu- come from the wavefront solver routine. This was exten- ters: CrayX-MP and Cray 2 (vector

Computational Science: Ensuring America’s Competitiveness

DTIC Science & Technology

2005-06-01

Supercharging U. S. Innovation & Competitiveness, Washington, D.C. , July 2004. Davies, C. T. H. , et al. , “High-Precision Lattice QCD Confronts Experiment...together to form a class of particles call hadrons (that include protons and neutrons) . For 30 years, researchers in lattice QCD have been trying to use...the basic QCD equations to calculate the properties of hadrons, especially their masses, using numerical lattice gauge theory calculations in order to

QCDOC: A 10-teraflops scale computer for lattice QCD

NASA Astrophysics Data System (ADS)

Chen, D.; Christ, N. H.; Cristian, C.; Dong, Z.; Gara, A.; Garg, K.; Joo, B.; Kim, C.; Levkova, L.; Liao, X.; Mawhinney, R. D.; Ohta, S.; Wettig, T.

2001-03-01

The architecture of a new class of computers, optimized for lattice QCD calculations, is described. An individual node is based on a single integrated circuit containing a PowerPC 32-bit integer processor with a 1 Gflops 64-bit IEEE floating point unit, 4 Mbyte of memory, 8 Gbit/sec nearest-neighbor communications and additional control and diagnostic circuitry. The machine's name, QCDOC, derives from "QCD On a Chip".

Three-point Green functions in the odd sector of QCD

NASA Astrophysics Data System (ADS)

Kadavý, T.; Kampf, K.; Novotný, J.

2016-11-01

A review of familiar results of the three-point Green functions of currents in the odd-intrinsic parity sector of QCD is presented. Such Green functions include very well-known examples of VVP, VAS or AAP correlators. We also shortly present some of the new results for VVA and AAA Green functions with a discussion of their high-energy behaviour and its relation to the QCD condensates.

Renormalization scheme dependence of high-order perturbative QCD predictions

NASA Astrophysics Data System (ADS)

Ma, Yang; Wu, Xing-Gang

2018-02-01

Conventionally, one adopts typical momentum flow of a physical observable as the renormalization scale for its perturbative QCD (pQCD) approximant. This simple treatment leads to renormalization scheme-and-scale ambiguities due to the renormalization scheme and scale dependence of the strong coupling and the perturbative coefficients do not exactly cancel at any fixed order. It is believed that those ambiguities will be softened by including more higher-order terms. In the paper, to show how the renormalization scheme dependence changes when more loop terms have been included, we discuss the sensitivity of pQCD prediction on the scheme parameters by using the scheme-dependent {βm ≥2}-terms. We adopt two four-loop examples, e+e-→hadrons and τ decays into hadrons, for detailed analysis. Our results show that under the conventional scale setting, by including more-and-more loop terms, the scheme dependence of the pQCD prediction cannot be reduced as efficiently as that of the scale dependence. Thus a proper scale-setting approach should be important to reduce the scheme dependence. We observe that the principle of minimum sensitivity could be such a scale-setting approach, which provides a practical way to achieve optimal scheme and scale by requiring the pQCD approximate be independent to the "unphysical" theoretical conventions.

Spontaneous CP breaking in QCD and the axion potential: an effective Lagrangian approach

NASA Astrophysics Data System (ADS)

Di Vecchia, Paolo; Rossi, Giancarlo; Veneziano, Gabriele; Yankielowicz, Shimon

2017-12-01

Using the well-known low-energy effective Lagrangian of QCD — valid for small (non-vanishing) quark masses and a large number of colors — we study in detail the regions of parameter space where CP is spontaneously broken/unbroken for a vacuum angle θ = π. In the CP broken region there are first order phase transitions as one crosses θ = π, while on the (hyper)surface separating the two regions, there are second order phase transitions signalled by the vanishing of the mass of a pseudo Nambu-Goldstone boson and by a divergent QCD topological susceptibility. The second order point sits at the end of a first order line associated with the CP spontaneous breaking, in the appropriate complex parameter plane. When the effective Lagrangian is extended by the inclusion of an axion these features of QCD imply that standard calculations of the axion potential have to be revised if the QCD parameters fall in the above mentioned CP broken region, in spite of the fact that the axion solves the strong- CP problem. These last results could be of interest for axionic dark matter calculations if the topological susceptibility of pure Yang-Mills theory falls off sufficiently fast when temperature is increased towards the QCD deconfining transition.

Kenneth Wilson and Lattice QCD

NASA Astrophysics Data System (ADS)

Ukawa, Akira

2015-09-01

We discuss the physics and computation of lattice QCD, a space-time lattice formulation of quantum chromodynamics, and Kenneth Wilson's seminal role in its development. We start with the fundamental issue of confinement of quarks in the theory of the strong interactions, and discuss how lattice QCD provides a framework for understanding this phenomenon. A conceptual issue with lattice QCD is a conflict of space-time lattice with chiral symmetry of quarks. We discuss how this problem is resolved. Since lattice QCD is a non-linear quantum dynamical system with infinite degrees of freedom, quantities which are analytically calculable are limited. On the other hand, it provides an ideal case of massively parallel numerical computations. We review the long and distinguished history of parallel-architecture supercomputers designed and built for lattice QCD. We discuss algorithmic developments, in particular the difficulties posed by the fermionic nature of quarks, and their resolution. The triad of efforts toward better understanding of physics, better algorithms, and more powerful supercomputers have produced major breakthroughs in our understanding of the strong interactions. We review the salient results of this effort in understanding the hadron spectrum, the Cabibbo-Kobayashi-Maskawa matrix elements and CP violation, and quark-gluon plasma at high temperatures. We conclude with a brief summary and a future perspective.

A study of energy-energy correlations and measurement of {alpha}{sub s} at the Z{sup 0} resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-12-31

We present the energy-energy correlation (EEC) distribution and its asymmetry (AEEC) in hadronic decays of {Zeta}{sup 0} bosons measured by the SLD at SLAC. The data are found to be in good agreement with the predictions of perturbative QCD and fragmentation Monte Carlo models of hadron production. After correction for hadronization effects the data are compared with {Omicron}({alpha}{sub s}{sup 2}) perturbative QCD calculations from various authors. Fits to the central region of the EEC yield substantially different values of the QCD scale {lambda}{sub {ovr MS}} for each of the QCD calculations. There is also a sizeable dependence of the fittedmore » {lambda}{sub {ovr MS}} value on the QCD renormalization scale factor, f. Our preliminary results are {alpha}{sub s}(M {sub Z}) = 0.121 {plus_minus} 0.002(stat.) {plus_minus} 0.004(exp.sys.) {sub {minus}0.009}{sup +0.016} (theor.) for EEC and {alpha}{sub s}(M{sub Z}) = 0.108 {plus_minus} 0.003(stat.) {plus_minus} 0.005(exp.sys.){sub {minus}0.003}{sup +0.008}(theor.) for AEEC. The largest contribution to the error arises from the theoretical uncertainty in choosing the QCD renormalization scale.« less

New Methods in Non-Perturbative QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unsal, Mithat

2017-01-31

In this work, we investigate the properties of quantum chromodynamics (QCD), by using newly developing mathematics and physics formalisms. Almost all of the mass in the visible universe emerges from a quantum chromodynamics (QCD), which has a completely negligible microscopic mass content. An intimately related issue in QCD is the quark confinement problem. Answers to non-perturbative questions in QCD remained largely elusive despite much effort over the years. It is also believed that the usual perturbation theory is inadequate to address these kinds of problems. Perturbation theory gives a divergent asymptotic series (even when the theory is properly renormalized), andmore » there are non-perturbative phenomena which never appear at any order in perturbation theory. Recently, a fascinating bridge between perturbation theory and non-perturbative effects has been found: a formalism called resurgence theory in mathematics tells us that perturbative data and non-perturbative data are intimately related. Translating this to the language of quantum field theory, it turns out that non-perturbative information is present in a coded form in perturbation theory and it can be decoded. We take advantage of this feature, which is particularly useful to understand some unresolved mysteries of QCD from first principles. In particular, we use: a) Circle compactifications which provide a semi-classical window to study confinement and mass gap problems, and calculable prototypes of the deconfinement phase transition; b) Resurgence theory and transseries which provide a unified framework for perturbative and non-perturbative expansion; c) Analytic continuation of path integrals and Lefschetz thimbles which may be useful to address sign problem in QCD at finite density.« less

The infrared behaviour of QCD Green's functions. Confinement, dynamical symmetry breaking, and hadrons as relativistic bound states

NASA Astrophysics Data System (ADS)

Alkofer, Reinhard; von Smekal, Lorenz

2001-11-01

Recent studies of QCD Green's functions and their applications in hadronic physics are reviewed. We discuss the definition of the generating functional in gauge theories, in particular, the rôle of redundant degrees of freedom, possibilities of a complete gauge fixing versus gauge fixing in presence of Gribov copies, BRS invariance and positivity. The apparent contradiction between positivity and colour antiscreening in combination with BRS invariance in QCD is considered. Evidence for the violation of positivity by quarks and transverse gluons in the covariant gauge is collected, and it is argued that this is one manifestation of confinement. We summarise the derivation of the Dyson-Schwinger equations (DSEs) of QED and QCD. For the latter, the implications of BRS invariance on the Green's functions are explored. The possible influence of instantons on DSEs is discussed in a two-dimensional model. In QED in (2+1) and (3+1) dimensions, the solutions for Green's functions provide tests of truncation schemes which can under certain circumstances be extended to the DSEs of QCD. We discuss some limitations of such extensions and assess the validity of assumptions for QCD as motivated from studies in QED. Truncation schemes for DSEs are discussed in axial and related gauges, as well as in the Landau gauge. Furthermore, we review the available results from a systematic non-perturbative expansion scheme established for Landau gauge QCD. Comparisons to related lattice results, where available, are presented. The applications of QCD Green's functions to hadron physics are summarised. Properties of ground state mesons are discussed on the basis of the ladder Bethe-Salpeter equation for quarks and antiquarks. The Goldstone nature of pseudoscalar mesons and a mechanism for diquark confinement beyond the ladder approximation are reviewed. We discuss some properties of ground state baryons based on their description as Bethe-Salpeter/Faddeev bound states of quark-diquark correlations in the quantum field theory of confined quarks and gluons.

Analysis of the economic and ideological factors involved in the development of rights to water in the West, focusing on Colorado

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penn, D.A.

1984-01-01

This study represents a limited step towards addressing the problems of the continuous development of property rights in natural resources. First a model of the evolution of water rights in the West is developed. In the model, the specification of property rights in water is treated as a continuous variable, ranging from completely nonexclusive to completely exclusive. The particular position on the continuum depends on the benefits of increasing the level of exclusivity relative to the costs. As the net benefits of increasing water right exclusivity increase, the model predicts greater property rights defining and enforcing activity. The second portionmore » of the study provides a historical context of the development of property rights in the West, focusing on the experience in Colorado. The evolution of property rights is analyzed, given the actual economic and ideological constraints and motivations existing at the time. The last portion of the study offers an empirical test of the hypotheses generated by the model. Ordinary least-squares equations are estimated, using the number of water-rights cases as an indicator of defining and enforcing activity. The quantitative and historical evidence suggests that water rights exhibit a tendency to develop efficiently, but that this tendency is constrained by the costs of defining exclusive rights to water and by ideology.« less

From RHIC to LHC: Lessons on the QGP

NASA Astrophysics Data System (ADS)

Heinz, Ulrich

2011-10-01

Recent data from heavy-ion collisions at RHIC and LHC, together with significant advances in theory, have allowed us to make significant first steps in proceeding from a qualitative understanding of high energy collision dynamics to a quantitative characterization of the transport properties of the hot and dense QCD matter created in these collisions. The almost perfectly liquid nature of the Quark-Gluon Plasma (QGP) created at RHIC has recently also been confirmed at the much higher LHC energies, and we can now constrain the specific QGP shear viscosity (η / s) QGP to within a factor of 2.5 of its conjectured lower quantum bound. Viscous hydrodynamics, coupled to a microscopic hadron cascade at late times, has proven to be an extremely successful and highly predictive model for the QGP evolution at RHIC and LHC. The experimental discovery of higher order harmonic flow coefficients and their theoretically predicted differential sensitivity to shear viscosity promises additional gains in precision by about a factor 5 in (η / s) QGP for the very near future. The observed modification of jets and suppression of high-pT hadrons confirms the picture of the QGP as a strongly coupled colored liquid, and recent LHC data yield strong constraints on parton energy loss models, putting significant strain on some theoretical approaches, tuned to RHIC data, that are based on leading-order perturbative QCD. Thermal photon radiation provides important cross-checks on the early stages of dynamical evolution models and constrains the initial QGP temperature, but the recently measured strong photon elliptic flow challenges our present understanding of photon emission rates in the hadronic phase. Recent progress in developing a complete theoretical model for all stages of the QGP fireball expansion, from strong fluctuating gluon fields at its beginning to final hadronic freeze-out, and remaining challenges will be discussed. Work supported by DOE (grants DE-SC0004286 and DE-SC0004104 (JET Collaboration)).

Closeout Report for CTEQ Summer School 2015

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Tao

The CTEQ Collaboration is an informal group of 37 experimental and theoretical high energy physicists from 20 universities and 5 national labs, engaged in a program to advance research in and understanding of QCD. This program includes the well-known collaborative project on global QCD analysis of parton distributions, the organization of a variety of workshops, periodic collaboration meetings, and the subject of this proposal: the CTEQ Summer Schools on QCD Analysis and Phenomenology.

Complex Langevin dynamics and zeroes of the fermion determinant

NASA Astrophysics Data System (ADS)

Aarts, Gert; Seiler, Erhard; Sexty, Dénes; Stamatescu, Ion-Olimpiu

2017-05-01

QCD at nonzero baryon chemical potential suffers from the sign problem, due to the complex quark determinant. Complex Langevin dynamics can provide a solution, provided certain conditions are met. One of these conditions, holomorphicity of the Langevin drift, is absent in QCD since zeroes of the determinant result in a meromorphic drift. We first derive how poles in the drift affect the formal justification of the approach and then explore the various possibilities in simple models. The lessons from these are subsequently applied to both heavy dense QCD and full QCD, and we find that the results obtained show a consistent picture. We conclude that with careful monitoring, the method can be justified a posteriori, even in the presence of meromorphicity.

Quark-hadron phase structure of QCD matter from SU(4) Polyakov linear sigma model

NASA Astrophysics Data System (ADS)

Diab, Abdel Magied Abdel Aal; Tawfik, Abdel Nasser

2018-04-01

The SU(4) Polyakov linear sigma model (PLSM) is extended towards characterizing the chiral condensates, σl, σs and σc of light, strange and charm quarks, respectively and the deconfinement order-parameters φ and φ at finite temperatures and densities (chemical potentials). The PLSM is considered to study the QCD equation of state in the presence of the chiral condensate of charm for different finite chemical potentials. The PLSM results are in a good agreement with the recent lattice QCD simulations. We conclude that, the charm condensate is likely not affected by the QCD phase-transition, where the corresponding critical temperature is greater than that of the light and strange quark condensates.

Moving Forward to Constrain the Shear Viscosity of QCD Matter

DOE PAGES

Denicol, Gabriel; Monnai, Akihiko; Schenke, Björn

2016-05-26

In this work, we demonstrate that measurements of rapidity differential anisotropic flow in heavy-ion collisions can constrain the temperature dependence of the shear viscosity to entropy density ratio η/s of QCD matter. Comparing results from hydrodynamic calculations with experimental data from the RHIC, we find evidence for a small η/s ≈ 0.04 in the QCD crossover region and a strong temperature dependence in the hadronic phase. A temperature independent η/s is disfavored by the data. We further show that measurements of the event-by-event flow as a function of rapidity can be used to independently constrain the initial state fluctuations inmore » three dimensions and the temperature dependent transport properties of QCD matter.« less

Lepton-rich cold QCD matter in protoneutron stars

NASA Astrophysics Data System (ADS)

Jiménez, J. C.; Fraga, E. S.

2018-05-01

We investigate protoneutron star matter using the state-of-the-art perturbative equation of state for cold and dense QCD in the presence of a fixed lepton fraction in which both electrons and neutrinos are included. Besides computing the modifications in the equation of state due to the presence of trapped neutrinos, we show that stable strange quark matter has a more restricted parameter space. We also study the possibility of nucleation of unpaired quark matter in the core of protoneutron stars by matching the lepton-rich QCD pressure onto a hadronic equation of state, namely TM1 with trapped neutrinos. Using the inherent dependence of perturbative QCD on the renormalization scale parameter, we provide a measure of the uncertainty in the observables we compute.

Curvature of the freeze-out line in heavy ion collisions

DOE PAGES

Bazavov, A.; Ding, H. -T.; Hegde, P.; ...

2016-01-28

Here, we calculate the mean and variance of net-baryon number and net-electric charge distributions from quantum chromodynamics (QCD) using a next-to-leading order Taylor expansion in terms of temperature and chemical potentials. Moreover, these expansions with experimental data from STAR and PHENIX are compared, we determine the freeze-out temperature in the limit of vanishing baryon chemical potential, and, for the first time, constrain the curvature of the freeze-out line through a direct comparison between experimental data on net-charge fluctuations and a QCD calculation. We obtain a bound on the curvature coefficient, κmore » $^f$$_2$$<0.011, that is compatible with lattice QCD results on the curvature of the QCD transition line.« less

Windows on the axion. [quantum chromodynamics (QCD)

NASA Technical Reports Server (NTRS)

Turner, Michael S.

1989-01-01

Peccei-Quinn symmetry with attendant axion is a most compelling, and perhaps the most minimal, extension of the standard model, as it provides a very elegant solution to the nagging strong CP-problem associated with the theta vacuum structure of QCD. However, particle physics gives little guidance as to the axion mass; a priori, the plausible values span the range: 10(-12)eV is approx. less than m(a) which is approx. less than 10(6)eV, some 18 orders-of-magnitude. Laboratory experiments have excluded masses greater than 10(4)eV, leaving unprobed some 16 orders-of-magnitude. Axions have a host of interesting astrophysical and cosmological effects, including, modifying the evolution of stars of all types (our sun, red giants, white dwarfs, and neutron stars), contributing significantly to the mass density of the Universe today, and producting detectable line radiation through the decays of relic axions. Consideration of these effects has probed 14 orders-of-magnitude in axion mass, and has left open only two windows for further exploration: 10(-6)eV is approx. less than m(a) is approx. less than 10(-3)eV and 1eV is approx. less than m(a) is approx. less than 5eV (hadronic axions only). Both these windows are accessible to experiment, and a variety of very interesting experiments, all of which involve heavenly axions, are being planned or are underway.

Probing superfast quarks in nuclei through dijet production at the LHC

DOE PAGES

Freese, Adam J.; Sargsian, Misak M.; Strikman, Mark I.

2015-11-12

We investigate dijet production from proton-nucleus collisions at the Large Hadron Collider (LHC) as a means for observing superfast quarks in nuclei with Bjorken x>1 . Kinematically, superfast quarks can be identified through directly measurable jet kinematics. Dynamically, their description requires understanding several elusive properties of nuclear QCD, such as nuclear forces at very short distances, as well as medium modification of parton distributions in nuclei. In the present work, we develop a model for nuclear parton distributions at large x in which the nuclear dynamics at short distance scales are described by two- and three-nucleon short range correlations (SRCs).more » Nuclear modifications are accounted for using the color screening model, and an improved description of the EMC effect is reached by using a structure function parametrization that includes higher-twist contributions. We apply QCD evolution at the leading order to obtain nuclear parton distributions in the kinematic regime of the LHC, and based on the obtained distributions calculate the cross section for dijet production. We find that the rates of the dijet production in pA collisions at kinematics accessible by ATLAS and CMS are sufficient not only to observe superfast quarks but also to get information about the practically unexplored three-nucleon SRCs in nuclei. Additionally, the LHC can extend our knowledge of the EMC effect to large Q 2 where higher-twist effects are negligible.« less

Q2-EVOLUTION of ΔNγ Form Factors up to 4 (GEV/C)2 from Jlab Data

NASA Astrophysics Data System (ADS)

Aznauryan, I. G.

2002-12-01

We present the results on the ratios E(3/2)1+/M(3/2)1+ and S(3/2)1+/M(3/2)1+ for the γ*N → Δ(1232) transition at Q2 ≤ 4 (GeV/c)2 extracted from the p(e,e'p)π0 cross section using two approaches: dispersion relations and modified version of unitary isobar model. The obtained results are in good agreement with the results of other analyses obtained using truncated multipole expansion at Q2 = 0.4, 0.525, 0.65, 0.75, 0.9, 1.15, 1.45, 1.8 (GeV/c)2 and within dynamical and unitary isobar models at Q2 = 2.8, 4 (GeV/c)2. According to obtained results the ratio E(3/2)1+/M(3/2)1+ remains small in all investigated region of Q2 with very unclear tendency to cross zero above 2 (GeV/c)2. The absolute value of the ratio S(3/2)1+/M(3/2)1+ is clearly increasing with increasing Q2, while it should be a constant value in the pQCD asymptotics. So, at Q2 ≤ 4 (GeV/c)2 there is no evidence of approaching pQCD regime for these ratios. None of the soft approaches gives satisfactory description of the obtained results.

Probing superfast quarks in nuclei through dijet production at the LHC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freese, Adam J.; Sargsian, Misak M.; Strikman, Mark I.

2015-11-01

We investigate dijet production from proton-nucleus collisions at the Large Hadron Collider (LHC) as a means for observing superfast quarks in nuclei with Bjorken x>1 . Kinematically, superfast quarks can be identified through directly measurable jet kinematics. Dynamically, their description requires understanding several elusive properties of nuclear QCD, such as nuclear forces at very short distances, as well as medium modification of parton distributions in nuclei. In the present work, we develop a model for nuclear parton distributions at large x in which the nuclear dynamics at short distance scales are described by two- and three-nucleon short range correlations (SRCs).more » Nuclear modifications are accounted for using the color screening model, and an improved description of the EMC effect is reached by using a structure function parametrization that includes higher-twist contributions. We apply QCD evolution at the leading order to obtain nuclear parton distributions in the kinematic regime of the LHC, and based on the obtained distributions calculate the cross section for dijet production. We find that the rates of the dijet production in pA collisions at kinematics accessible by ATLAS and CMS are sufficient not only to observe superfast quarks but also to get information about the practically unexplored three-nucleon SRCs in nuclei. Additionally, the LHC can extend our knowledge of the EMC effect to large Q2 where higher-twist effects are negligible.« less

Cooperation induced by random sequential exclusion

NASA Astrophysics Data System (ADS)

Li, Kun; Cong, Rui; Wang, Long

2016-06-01

Social exclusion is a common and powerful tool to penalize deviators in human societies, and thus to effectively elevate collaborative efforts. Current models on the evolution of exclusion behaviors mostly assume that each peer excluder independently makes the decision to expel the defectors, but has no idea what others in the group would do or how the actual punishment effect will be. Thus, a more realistic model, random sequential exclusion, is proposed. In this mechanism, each excluder has to pay an extra scheduling cost and then all the excluders are arranged in a random order to implement the exclusion actions. If one free rider has already been excluded by an excluder, the remaining excluders will not participate in expelling this defector. We find that this mechanism can help stabilize cooperation under more unfavorable conditions than the normal peer exclusion can do, either in well-mixed population or on social networks. However, too large a scheduling cost may undermine the advantage of this mechanism. Our work validates the fact that collaborative practice among punishers plays an important role in further boosting cooperation.

Concerns Expressed by Parents of Children with Pervasive Developmental Disorders for Different Time Periods of the Day: A Case–Control Study

PubMed Central

Sasaki, Yoshinori; Usami, Masahide; Sasayama, Daimei; Okada, Takashi; Iwadare, Yoshitaka; Watanabe, Kyota; Ushijima, Hirokage; Tanaka, Tetsuya; Harada, Maiko; Tanaka, Hiromi; Kodaira, Masaki; Sugiyama, Nobuhiro; Sawa, Tetsuji; Saito, Kazuhiko

2015-01-01

Background/Aim The Questionnaire: Children with Difficulties (QCD) is a parent-assessed questionnaire designed to evaluate child’s difficulties in functioning during specific periods of the day. This study aimed to evaluate difficulties in daily functioning of children and adolescents with pervasive developmental disorder (PDD) using the QCD. Results were compared with those for a community sample. Methods A case–control design was used. The cases comprised elementary school students (182 males, 51 females) and junior high school students (100 males, 39 females) with PDD, whereas a community sample of elementary school students (568 males, 579 females) and junior high school students (180 males, 183 females) was enrolled as controls. Their behavior was assessed using the QCD, the Tokyo Autistic Behavior Scale (TABS), the ADHD-rating scale (ADHD-RS), and the Oppositional Defiant Behavior Inventory (ODBI) for elementary and junior high school students, respectively. Effects of gender and diagnosis on the QCD scores were analyzed. Correlation coefficients between QCD and TABS, ADHD-RS, and ODBI scores were analyzed. Results The QCD scores for the children with PDD were significantly lower compared with those from the community sample (P < 0.001). Significantly strong correlations were observed in more areas of the ADHD-RS and ODBI scores compared with the TABS scores. Conclusions Children with PDD experienced greater difficulties in completing basic daily activities; moreover, their QCD scores revealed stronger associations with their ADHD-RS and ODBI scores in comparison with their TABS scores. The difficulties of PDD, ADHD and OBDI symptoms combined in children makes it necessary to assess all diagnoses before any therapy for PDD is initiated in order to be able to evaluate its results properly. PMID:25898260

QCD and Light-Front Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.

2011-01-10

AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equalmore » light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.« less

Three-particle N π π state contribution to the nucleon two-point function in lattice QCD

NASA Astrophysics Data System (ADS)

Bär, Oliver

2018-05-01

The three-particle N π π state contribution to the QCD two-point function of standard nucleon interpolating fields is computed to leading order in chiral perturbation theory. Using the experimental values for two low-energy coefficients, the impact of this contribution on lattice QCD calculations of the nucleon mass is estimated. The impact is found to be at the per mille level at most and negligible in practice.

Better than $l/Mflops sustained: a scalable PC-based parallel computer for lattice QCD

NASA Astrophysics Data System (ADS)

Fodor, Zoltán; Katz, Sándor D.; Papp, Gábor

2003-05-01

We study the feasibility of a PC-based parallel computer for medium to large scale lattice QCD simulations. The Eötvös Univ., Inst. Theor. Phys. cluster consists of 137 Intel P4-1.7GHz nodes with 512 MB RDRAM. The 32-bit, single precision sustained performance for dynamical QCD without communication is 1510 Mflops/node with Wilson and 970 Mflops/node with staggered fermions. This gives a total performance of 208 Gflops for Wilson and 133 Gflops for staggered QCD, respectively (for 64-bit applications the performance is approximately halved). The novel feature of our system is its communication architecture. In order to have a scalable, cost-effective machine we use Gigabit Ethernet cards for nearest-neighbor communications in a two-dimensional mesh. This type of communication is cost effective (only 30% of the hardware costs is spent on the communication). According to our benchmark measurements this type of communication results in around 40% communication time fraction for lattices upto 48 3·96 in full QCD simulations. The price/sustained-performance ratio for full QCD is better than l/Mflops for Wilson (and around 1.5/Mflops for staggered) quarks for practically any lattice size, which can fit in our parallel computer. The communication software is freely available upon request for non-profit organizations.

Bose-Fermi degeneracies in large N adjoint QCD

DOE PAGES

Basar, Gokce; Cherman, Aleksey; McGady, David

2015-07-06

Here, we analyze the large N limit of adjoint QCD, an SU( N) gauge theory with N f flavors of massless adjoint Majorana fermions, compactified on S 3 × S 1. We focus on the weakly-coupled confining small- S 3 regime. If the fermions are given periodic boundary conditions on S 1, we show that there are large cancellations between bosonic and fermionic contributions to the twisted partition function. These cancellations follow a pattern previously seen in the context of misaligned supersymmetry, and lead to the absence of Hagedorn instabilities for any S 1 size L, even though the bosonicmore » and fermionic densities of states both have Hagedorn growth. Adjoint QCD stays in the confining phase for any L ~ N 0, explaining how it is able to enjoy large N volume independence for any L. The large N boson-fermion cancellations take place in a setting where adjoint QCD is manifestly non-supersymmetric at any finite N, and are consistent with the recent conjecture that adjoint QCD has emergent fermionic symmetries in the large N limit.« less

Three-loop hard-thermal-loop perturbation theory thermodynamics at finite temperature and finite baryonic and isospin chemical potential

NASA Astrophysics Data System (ADS)

Andersen, Jens O.; Haque, Najmul; Mustafa, Munshi G.; Strickland, Michael

2016-03-01

In a previous paper [N. Haque et al., J. High Energy Phys. 05 (2014) 27], we calculated the three-loop thermodynamic potential of QCD at finite temperature T and quark chemical potentials μq using the hard-thermal-loop perturbation theory (HTLpt) reorganization of finite temperature and density QCD. The result allows us to study the thermodynamics of QCD at finite temperature and finite baryon, strangeness, and isospin chemical potentials μB, μS, and μI. We calculate the pressure at nonzero μB and μI with μS=0 , and the energy density, the entropy density, the trace anomaly, and the speed of sound at nonzero μI with μB=μS=0 . The second- and fourth-order isospin susceptibilities are calculated at μB=μS=μI=0 . Our results can be directly compared to lattice QCD without Taylor expansions around μq=0 since QCD has no sign problem at μB=μS=0 and finite isospin chemical potential μI.

Lattice QCD results on soft and hard probes of strongly interacting matter

NASA Astrophysics Data System (ADS)

Kaczmarek, Olaf

2017-11-01

We present recent results from lattice QCD relevant for the study of strongly interacting matter as it is produced in heavy ion collision experiments. The equation of state at non-vanishing density from a Taylor expansion up to 6th order will be discussed for a strangeness neutral system and using the expansion coefficients of the series limits on the critical point are estimated. Chemical freeze-out temperatures from the STAR and ALICE Collaborations will be compared to lines of constant physics calculated from the Taylor expansion of QCD bulk thermodynamic quantities. We show that qualitative features of the √{sNN} dependence of skewness and kurtosis ratios of net proton-number fluctuations measured by the STAR Collaboration can be understood from QCD results for cumulants of conserved baryon-number fluctuations. As an example for recent progress towards the determination of spectral and transport properties of the QGP from lattice QCD, we will present constraints on the thermal photon rate determined from a spectral reconstruction of continuum extrapolated lattice correlation functions in combination with input from most recent perturbative calculations.

Inclusive jet cross section and strong coupling constant measurements at CMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cerci, Salim, E-mail: Salim.Cerci@cern.ch

2016-03-25

The probes which are abundantly produced in high energetic proton-proton (pp) collisions at the LHC are called jets. Events with jets can be described by Quantum Chromodynamics (QCD) in terms of parton-parton scattering. The inclusive jet cross section in pp collision is the fundamental quantity which can be measured and predicted within the framework of perturbative QCD (pQCD). The strong coupling constant α{sub S} which can be determined empirically in the limit of massless quarks, is the single parameter in QCD. The jet measurements can also be used to determine strong coupling constant α{sub S} and parton density functions (PDFs).more » The recent jet measurements which are performed with the data collected by the CMS detector at different center-of-mass energies and down to very low transverse momentum p{sub T} are presented. The measurements are compared to Monte Carlo predictions and perturbative calculations up to next-to-next-to leading order. Finally, the precision jet measurements give further insight into the QCD dynamics.« less

Conjecture about the 2-Flavour QCD Phase Diagram

NASA Astrophysics Data System (ADS)

Nava Blanco, M. A.; Bietenholz, W.; Fernández Téllez, A.

2017-10-01

The QCD phase diagram, in particular its sector of high baryon density, is one of the most prominent outstanding mysteries within the Standard Model of particle physics. We sketch a project how to arrive at a conjecture for the case of two massless quark flavours. The pattern of spontaneous chiral symmetry breaking is isomorphic to the spontaneous magnetisation in an O(4) non-linear σ-model, which can be employed as a low-energy effective theory to study the critical behaviour. We focus on the 3d O(4) model, where the configurations are divided into topological sectors, as in QCD. A topological winding with minimal Euclidean action is denoted as a skyrmion, and the topological charge corresponds to the QCD baryon number. This effective model can be simulated on a lattice with a powerful cluster algorithm, which should allow us to identify the features of the critical temperature, as we proceed from low to high baryon density. In this sense, this projected numerical study has the potential to provide us with a conjecture about the phase diagram of QCD with two massless quark flavours.

In-medium jet evolution: interplay between broadening and decoherence effects. The XXVth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

NASA Astrophysics Data System (ADS)

Apolinário, Liliana; Armesto, Néstor; Milhano, Guilherme; Salgado, Carlos A.

2016-12-01

The description of the modifications of the coherence pattern in a parton shower, in the presence of a QGP, has been actively addressed in recent studies. Among the several achievements, finite energy corrections, transverse momentum broadening due to medium interactions and interference effects between successive emissions have been extensively improved as they seem to be essential features for a correct description of the results obtained in heavy-ion collisions. In this work, based on the insights of our previous work [L. Apolinário, N. Armesto, J. G. Milhano, C. A. Salgado, Medium-induced gluon radiation and colour decoherence beyond the soft approximation, JHEP 1502 (2015) 119. arxiv:arXiv:1407.0599], we explore the physical interplay between broadening and decoherence, by generalising previous studies of medium-modifications of the antenna spectrum [Y. Mehtar-Tani, C. A. Salgado, K. Tywoniuk, Antiangular Ordering of Gluon Radiation in QCD Media, Phys. Rev. Lett. 106 (2011) 122002. arxiv:arXiv:1009.2965, J. Casalderrey-Solana, E. Iancu, Interference effects in medium-induced gluon radiation, JHEP 08 (2011) 015. arxiv:arXiv:1105.1760, Y. Mehtar-Tani, C. A. Salgado, K. Tywoniuk, The Radiation pattern of a QCD antenna in a dense medium, JHEP 10 (2012) 197. arxiv:arXiv:1205.5739] - so far restricted to the case where transverse motion is neglected. The result allow us to identify two quantities controlling the decoherence of a medium modified shower that can be used as building blocks for a successful future generation of jet quenching Monte Carlo simulators: a generalisation of the Δmed parameter of the works of [Y. Mehtar-Tani, C. A. Salgado, K. Tywoniuk, Antiangular Ordering of Gluon Radiation in QCD Media, Phys. Rev. Lett. 106 (2011) 122002. arxiv:arXiv:1009.2965, Y. Mehtar-Tani, C. A. Salgado, K. Tywoniuk, The Radiation pattern of a QCD antenna in a dense medium, JHEP 10 (2012) 197. arxiv:arXiv:1205.5739] - that controls the interplay between the transverse scale of the hard probe and the transverse resolution of the medium - and of the Δcoh in [L. Apolinário, N. Armesto, J. G. Milhano, C. A. Salgado, Medium-induced gluon radiation and colour decoherence beyond the soft approximation, JHEP 1502 (2015) 119. arxiv:arXiv:1407.0599] - that dictates the interferences between two emitters as a function of the transverse momentum broadening acquired by multiple scatterings with the medium.

mr: A C++ library for the matching and running of the Standard Model parameters

NASA Astrophysics Data System (ADS)

Kniehl, Bernd A.; Pikelner, Andrey F.; Veretin, Oleg L.

2016-09-01

We present the C++ program library mr that allows us to reliably calculate the values of the running parameters in the Standard Model at high energy scales. The initial conditions are obtained by relating the running parameters in the MS bar renormalization scheme to observables at lower energies with full two-loop precision. The evolution is then performed in accordance with the renormalization group equations with full three-loop precision. Pure QCD corrections to the matching and running are included through four loops. We also provide a Mathematica interface for this program library. Catalogue identifier: AFAI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AFAI_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 517613 No. of bytes in distributed program, including test data, etc.: 2358729 Distribution format: tar.gz Programming language: C++. Computer: IBM PC. Operating system: Linux, Mac OS X. RAM: 1 GB Classification: 11.1. External routines: TSIL [1], OdeInt [2], boost [3] Nature of problem: The running parameters of the Standard Model renormalized in the MS bar scheme at some high renormalization scale, which is chosen by the user, are evaluated in perturbation theory as precisely as possible in two steps. First, the initial conditions at the electroweak energy scale are evaluated from the Fermi constant GF and the pole masses of the W, Z, and Higgs bosons and the bottom and top quarks including the full two-loop threshold corrections. Second, the evolution to the high energy scale is performed by numerically solving the renormalization group evolution equations through three loops. Pure QCD corrections to the matching and running are included through four loops. Solution method: Numerical integration of analytic expressions Additional comments: Available for download from URL: http://apik.github.io/mr/. The MathLink interface is tested to work with Mathematica 7-9 and, with an additional flag, also with Mathematica 10 under Linux and with Mathematica 10 under Mac OS X. Running time: less than 1 second References: [1] S. P. Martin and D. G. Robertson, Comput. Phys. Commun. 174 (2006) 133-151 [hep-ph/0501132]. [2] K. Ahnert and M. Mulansky, AIP Conf. Proc. 1389 (2011) 1586-1589 [arxiv:1110.3397 [cs.MS

Electroweak Higgs production with HiggsPO at NLO QCD

NASA Astrophysics Data System (ADS)

Greljo, Admir; Isidori, Gino; Lindert, Jonas M.; Marzocca, David; Zhang, Hantian

2017-12-01

We present the HiggsPO UFO model for Monte Carlo event generation of electroweak VH and VBF Higgs production processes at NLO in QCD in the formalism of Higgs pseudo-observables (PO). We illustrate the use of this tool by studying the QCD corrections, matched to a parton shower, for several benchmark points in the Higgs PO parameter space. We find that, while being sizable and thus important to be considered in realistic experimental analyses, the QCD higher-order corrections largely factorize. As an additional finding, based on the NLO results, we advocate to consider 2D distributions of the two-jet azimuthal-angle difference and the leading jet p_T for new physics searches in VBF Higgs production. The HiggsPO UFO model is publicly available.

Search for the pentaquark resonance signature in lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

B. G. Lasscock; J. Hedditch; Derek Leinweber

2005-02-01

Claims concerning the possible discovery of the {Theta}{sup +} pentaquark, with minimal quark content uudd{bar s}, have motivated our comprehensive study into possible pentaquark states using lattice QCD. We review various pentaquark interpolating fields in the literature and create a new candidate ideal for lattice QCD simulations. Using these interpolating fields we attempt to isolate a signal for a five-quark resonance. Calculations are performed using improved actions on a large 20{sup 3} x 40 lattice in the quenched approximation. The standard lattice resonance signal of increasing attraction between baryon constituents for increasing quark mass is not observed for spin-1/2 pentaquarkmore » states. We conclude that evidence supporting the existence of a spin-1/2 pentaquark resonance does not exist in quenched QCD.« less

The decay of Λ _b→ p~K^- in QCD factorization approach

NASA Astrophysics Data System (ADS)

Zhu, Jie; Ke, Hong-Wei; Wei, Zheng-Tao

2016-05-01

With only the tree-level operator, the decay of Λ _b→ pK is predicted to be one order smaller than the experimental data. The QCD penguin effects should be taken into account. In this paper, we explore the one-loop QCD corrections to the decay of Λ _b→ pK within the framework of QCD factorization approach. For the baryon system, the diquark approximation is adopted. The transition hadronic matrix elements between Λ _b and p are calculated in the light-front quark model. The branching ratio of Λ _b→ pK is predicted to be about 4.85× 10^{-6}, which is consistent with experimental data (4.9± 0.9)× 10^{-6}. The CP violation is about 5 % in theory.

RPA treatment of a motivated QCD Hamiltonian in the SO(4) (2 + 1)-flavor limit: Light and strange mesons

NASA Astrophysics Data System (ADS)

Yepez-Martinez, Tochtli; Civitarese, Osvaldo; Hess, Peter O.

The SO(4) symmetry of a sector of the quantum chromodynamics (QCD) Hamiltonian was analyzed in a previous work. The numerical calculations were then restricted to a particle-hole (ph) space and the comparison with experimental data was reasonable in spite of the complexity of the QCD spectrum at low energy. Here on, we continue along this line of research and show our new results of the treatment of the QCD Hamiltonian in the SO(4) representation, including ground state correlations by means of the Random Phase Approximation (RPA). We are able to identify, within this model, states which may be associated to physical pseudo-scalar and vector mesons, like η,η‧,K,ρ,ω,ϕ, as well as the pion (π).

Hadron interactions and exotic hadrons from lattice QCD

NASA Astrophysics Data System (ADS)

Ikeda, Yoichi

2014-09-01

One of the interesting subjects in hadron physics is to look for the multiquark configurations. One of candidates is the H-dibaryon (udsuds), and the possibility of the bound H-dibaryon has been recently studied from lattice QCD. We also extend the HAL QCD method to define potentials on the lattice between baryons to meson-meson systems including charm quarks to search for the bound tetraquark Tcc (ud c c) and Tcs (ud c s). In the presentation, after reviewing the HAL QCD method, we report the results on the H-dibaryon, the tetraquark Tcc (ud c c) and Tcs (ud c s), where we have employed the relativistic heavy quark action to treat the charm quark dynamics with pion masses, mπ = 410, 570, 700 MeV.

Kaon-Nucleon potential from lattice QCD

NASA Astrophysics Data System (ADS)

Ikeda, Y.; Aoki, S.; Doi, T.; Hatsuda, T.; Inoue, T.; Ishii, N.; Murano, K.; Nemura, H.; Sasaki, K.

2010-04-01

We study the K N interactions in the I(Jπ) = 0(1/2-) and 1(1/2-) channels and associated exotic state Θ+ from 2+1 flavor full lattice QCD simulation for relatively heavy quark mass corresponding to mπ = 871 MeV. The s-wave K N potentials are obtained from the Bethe-Salpeter wave function by using the method recently developed by HAL QCD (Hadrons to Atomic nuclei from Lattice QCD) Collaboration. Potentials in both channels reveal short range repulsions: Strength of the repulsion is stronger in the I = 1 potential, which is consistent with the prediction of the Tomozawa-Weinberg term. The I = 0 potential is found to have attractive well at mid range. From these potentials, the K N scattering phase shifts are calculated and compared with the experimental data.

Exposing the QCD Splitting Function with CMS Open Data.

PubMed

Larkoski, Andrew; Marzani, Simone; Thaler, Jesse; Tripathee, Aashish; Xue, Wei

2017-09-29

The splitting function is a universal property of quantum chromodynamics (QCD) which describes how energy is shared between partons. Despite its ubiquitous appearance in many QCD calculations, the splitting function cannot be measured directly, since it always appears multiplied by a collinear singularity factor. Recently, however, a new jet substructure observable was introduced which asymptotes to the splitting function for sufficiently high jet energies. This provides a way to expose the splitting function through jet substructure measurements at the Large Hadron Collider. In this Letter, we use public data released by the CMS experiment to study the two-prong substructure of jets and test the 1→2 splitting function of QCD. To our knowledge, this is the first ever physics analysis based on the CMS Open Data.

Time Evolution of Meson Density During Formation of Expanding Quark-Antiquark System

NASA Astrophysics Data System (ADS)

Ghaffary, Tooraj

2018-04-01

Recently some researchers (Sepehri and Shoorvazi Astrophys. Spaces Sci. 344(2), 521-527, 2013) have considered the Universe as an acceleration cylindrical system. Motivated by their work and using their method in QCD, this paper has been cleared that because the acceleration of expansion in quark-antiquark system is relatively very large, one horizon is appeared outside the system. To obtain the total cross section of meson near this horizon, we need to multiply the production cross section for appeared horizon by the density of meson produced outside the system. As it can be seen by an observer who is outside the meson formation process, this cross section depends on time so the event horizon is now a time depended process.

J/ψ production in polarized and unpolarized ep collision and Sivers and cos 2φ asymmetries

NASA Astrophysics Data System (ADS)

Mukherjee, Asmita; Rajesh, Sangem

2017-12-01

We calculate the Sivers and cos 2φ azimuthal asymmetries in J/ψ production in the polarized and unpolarized semi-inclusive ep collision, respectively, using the formalism based on the transverse momentum-dependent parton distributions (TMDs). The non-relativistic QCD-based color octet model is employed in calculating the J/ψ production rate. The Sivers asymmetry in this process directly probes the gluon Sivers function. The estimated Sivers asymmetry at z=1 is negative, which is in good agreement with the COMPASS data. The effect of TMD evolution on the Sivers asymmetry is also investigated. The cos 2φ asymmetry is sizable and probes the linearly polarized gluon distribution in an unpolarized proton.

Inclusive reconstruction of hadron resonances in elementary and heavy-ion collisions with HADES

NASA Astrophysics Data System (ADS)

Kornakov, Georgy

2016-11-01

The unambiguous identification of hadron modifications in hot and dense QCD matter is one of the important goals in nuclear physics. In the regime of 1 - 2 GeV kinetic energy per nucleon, HADES has measured rare and penetrating probes in elementary and heavy-ion collisions. The main creation mechanism of mesons is the excitation and decay of baryonic resonances throughout the fireball evolution. The reconstruction of shortlived (≈ 1 fm/c) resonance states through their decay products is notoriously difficult. We have developed a new iterative algorithm, which builds the best hypothesis of signal and background by distortion of individual particle properties. This allows to extract signals with signal-to-background ratios of <1%.

Two loop renormalization of the magnetic coupling in hot QCD

NASA Astrophysics Data System (ADS)

Giovannangeli, P.

2004-04-01

Well above the critical temperature hot QCD is described by 3d electrostatic QCD with gauge coupling gE and Debye mass mE. We integrate out the Debye scales to two loop accuracy and find for the gauge coupling in the resulting magnetostatic action gM2=gE21-{1}/{48}{gE2N}/{πmE}-{17}/{4608}{gE2N}/{πmE}2+O{gE2N}/{πmE}3.

QCD unitarity constraints on Reggeon Field Theory

NASA Astrophysics Data System (ADS)

Kovner, Alex; Levin, Eugene; Lublinsky, Michael

2016-08-01

We point out that the s-channel unitarity of QCD imposes meaningful constraints on a possible form of the QCD Reggeon Field Theory. We show that neither the BFKL nor JIMWLK nor Braun's Hamiltonian satisfy the said constraints. In a toy, zero transverse dimensional case we construct a model that satisfies the analogous constraint and show that at infinite energy it indeed tends to a "black disk limit" as opposed to the model with triple Pomeron vertex only, routinely used as a toy model in the literature.

Spectral functions at small energies and the electrical conductivity in hot quenched lattice QCD.

PubMed

Aarts, Gert; Allton, Chris; Foley, Justin; Hands, Simon; Kim, Seyong

2007-07-13

In lattice QCD, the maximum entropy method can be used to reconstruct spectral functions from Euclidean correlators obtained in numerical simulations. We show that at finite temperature the most commonly used algorithm, employing Bryan's method, is inherently unstable at small energies and gives a modification that avoids this. We demonstrate this approach using the vector current-current correlator obtained in quenched QCD at finite temperature. Our first results indicate a small electrical conductivity above the deconfinement transition.

Nuclear physics from lattice QCD at strong coupling.

PubMed

de Forcrand, Ph; Fromm, M

2010-03-19

We study numerically the strong coupling limit of lattice QCD with one flavor of massless staggered quarks. We determine the complete phase diagram as a function of temperature and chemical potential, including a tricritical point. We clarify the nature of the low temperature dense phase, which is strongly bound "nuclear" matter. This strong binding is explained by the nuclear potential, which we measure. Finally, we determine, from this first-principles limiting case of QCD, the masses of "atomic nuclei" up to A=12 "carbon".

OPE of Green functions in the odd sector of QCD

NASA Astrophysics Data System (ADS)

Kadavý, T.; Kampf, K.; Novotný, J.

2017-03-01

A review of familiar results of the three-point Green functions of currents in the odd-intrinsic parity sector of QCD is presented. Such Green functions include very well-known examples of VVP, VAS or AAP correlators. We also present new results for VVA and AAA Green functions that have not yet been studied extensively in the literature before, more importantly with a phenomenological study and a discussion of the highenergy behaviour and its relation to the QCD condensates.

QCD Sum Rules and Models for Generalized Parton Distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anatoly Radyushkin

2004-10-01

I use QCD sum rule ideas to construct models for generalized parton distributions. To this end, the perturbative parts of QCD sum rules for the pion and nucleon electromagnetic form factors are interpreted in terms of GPDs and two models are discussed. One of them takes the double Borel transform at adjusted value of the Borel parameter as a model for nonforward parton densities, and another is based on the local duality relation. Possible ways of improving these Ansaetze are briefly discussed.

New QCD sum rules based on canonical commutation relations

NASA Astrophysics Data System (ADS)

Hayata, Tomoya

2012-04-01

New derivation of QCD sum rules by canonical commutators is developed. It is the simple and straightforward generalization of Thomas-Reiche-Kuhn sum rule on the basis of Kugo-Ojima operator formalism of a non-abelian gauge theory and a suitable subtraction of UV divergences. By applying the method to the vector and axial vector current in QCD, the exact Weinberg’s sum rules are examined. Vector current sum rules and new fractional power sum rules are also discussed.

REMARKS ON THE MAXIMUM ENTROPY METHOD APPLIED TO FINITE TEMPERATURE LATTICE QCD.

DOE Office of Scientific and Technical Information (OSTI.GOV)

UMEDA, T.; MATSUFURU, H.

2005-07-25

We make remarks on the Maximum Entropy Method (MEM) for studies of the spectral function of hadronic correlators in finite temperature lattice QCD. We discuss the virtues and subtlety of MEM in the cases that one does not have enough number of data points such as at finite temperature. Taking these points into account, we suggest several tests which one should examine to keep the reliability for the results, and also apply them using mock and lattice QCD data.

Anomaly inflow on QCD axial domain-walls and vortices

NASA Astrophysics Data System (ADS)

Fukushima, Kenji; Imaki, Shota

2018-06-01

We study the chiral effective theory in the presence of quantum chromodynamics (QCD) vortices. Gauge invariance requires novel terms from vortex singularities in the gauged Wess-Zumino-Witten action, which incorporate anomaly-induced currents along the vortices. We examine these terms for systems with QCD axial domain-walls bounded by vortices (vortons) under magnetic fields. We discuss how the baryon and electric charge conservations are satisfied in these systems through interplay between domain-walls and vortices, manifesting Callan-Harvey's mechanism of anomaly inflow.

Cellular automaton model for molecular traffic jams

NASA Astrophysics Data System (ADS)

Belitsky, V.; Schütz, G. M.

2011-07-01

We consider the time evolution of an exactly solvable cellular automaton with random initial conditions both in the large-scale hydrodynamic limit and on the microscopic level. This model is a version of the totally asymmetric simple exclusion process with sublattice parallel update and thus may serve as a model for studying traffic jams in systems of self-driven particles. We study the emergence of shocks from the microscopic dynamics of the model. In particular, we introduce shock measures whose time evolution we can compute explicitly, both in the thermodynamic limit and for open boundaries where a boundary-induced phase transition driven by the motion of a shock occurs. The motion of the shock, which results from the collective dynamics of the exclusion particles, is a random walk with an internal degree of freedom that determines the jump direction. This type of hopping dynamics is reminiscent of some transport phenomena in biological systems.

Pollen-specific, but not sperm-specific, genes show stronger purifying selection and higher rates of positive selection than sporophytic genes in Capsella grandiflora.

PubMed

Arunkumar, Ramesh; Josephs, Emily B; Williamson, Robert J; Wright, Stephen I

2013-11-01

Selection on the gametophyte can be a major force shaping plant genomes as 7-11% of genes are expressed only in that phase and 60% of genes are expressed in both the gametophytic and sporophytic phases. The efficacy of selection on gametophytic tissues is likely to be influenced by sexual selection acting on male and female functions of hermaphroditic plants. Moreover, the haploid nature of the gametophytic phase allows selection to be efficient in removing recessive deleterious mutations and fixing recessive beneficial mutations. To assess the importance of gametophytic selection, we compared the strength of purifying selection and extent of positive selection on gametophyte- and sporophyte-specific genes in the highly outcrossing plant Capsella grandiflora. We found that pollen-exclusive genes had a larger fraction of sites under strong purifying selection, a greater proportion of adaptive substitutions, and faster protein evolution compared with seedling-exclusive genes. In contrast, sperm cell-exclusive genes had a smaller fraction of sites under strong purifying selection, a lower proportion of adaptive substitutions, and slower protein evolution compared with seedling-exclusive genes. Observations of strong selection acting on pollen-expressed genes are likely explained by sexual selection resulting from pollen competition aided by the haploid nature of that tissue. The relaxation of selection in sperm might be due to the reduced influence of intrasexual competition, but reduced gene expression may also be playing an important role.

Generalized parton distributions and transversity from full lattice QCD

NASA Astrophysics Data System (ADS)

Göckeler, M.; Hägler, Ph.; Horsley, R.; Pleiter, D.; Rakow, P. E. L.; Schäfer, A.; Schierholz, G.; Zanotti, J. M.; Qcdsf Collaboration

2005-06-01

We present here the latest results from the QCDSF collaboration for moments of gener- alized parton distributions and transversity in two-flavour QCD, including a preliminary analysis of the pion mass dependence.

QCD for Postgraduates (4/5)

ScienceCinema

Zanderighi, Giulia

2018-05-23

Modern QCD - Lecture 4. We will consider some processes of interest at the LHC and will discuss the main elements of their cross-section calculations. We will also summarize the current status of higher order calculations.

Second-order QCD effects in Higgs boson production through vector boson fusion

NASA Astrophysics Data System (ADS)

Cruz-Martinez, J.; Gehrmann, T.; Glover, E. W. N.; Huss, A.

2018-06-01

We compute the factorising second-order QCD corrections to the electroweak production of a Higgs boson through vector boson fusion. Our calculation is fully differential in the kinematics of the Higgs boson and of the final state jets, and uses the antenna subtraction method to handle infrared singular configurations in the different parton-level contributions. Our results allow us to reassess the impact of the next-to-leading order (NLO) QCD corrections to electroweak Higgs-plus-three-jet production and of the next-to-next-to-leading order (NNLO) QCD corrections to electroweak Higgs-plus-two-jet production. The NNLO corrections are found to be limited in magnitude to around ± 5% and are uniform in several of the kinematical variables, displaying a kinematical dependence only in the transverse momenta and rapidity separation of the two tagging jets.

Poincare recurrence theorem and the strong CP problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalloniatis, Alex C.; Nedelko, Sergei N.; Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna

2006-02-01

The existence in the physical QCD vacuum of nonzero gluon condensates, such as , requires dominance of gluon fields with finite mean action density. This naturally allows any real number value for the unit 'topological charge' q characterizing the fields approximating the gluon configurations which should dominate the QCD partition function. If q is an irrational number then the critical values of the {theta} parameter for which CP is spontaneously broken are dense in R, which provides for a mechanism of resolving the strong CP problem simultaneously with a correct implementation of U{sub A}(1) symmetry. We present anmore » explicit realization of this mechanism within a QCD motivated domain model. Some model independent arguments are given that suggest the relevance of this mechanism also to genuine QCD.« less

Determination of the chiral condensate from (2+1)-flavor lattice QCD.

PubMed

Fukaya, H; Aoki, S; Hashimoto, S; Kaneko, T; Noaki, J; Onogi, T; Yamada, N

2010-03-26

We perform a precise calculation of the chiral condensate in QCD using lattice QCD with 2+1 flavors of dynamical overlap quarks. Up and down quark masses cover a range between 3 and 100 MeV on a 16{3}x48 lattice at a lattice spacing approximately 0.11 fm. At the lightest sea quark mass, the finite volume system on the lattice is in the regime. By matching the low-lying eigenvalue spectrum of the Dirac operator with the prediction of chiral perturbation theory at the next-to-leading order, we determine the chiral condensate in (2+1)-flavor QCD with strange quark mass fixed at its physical value as Sigma;{MS[over ]}(2 GeV)=[242(04)(+19/-18) MeV]{3} where the errors are statistical and systematic, respectively.

Testing the QCD string at large Nc from the thermodynamics of the hadronic phase

NASA Astrophysics Data System (ADS)

Cohen, Thomas D.

2007-02-01

It is generally believed that in the limit of a large number of colors (Nc) the description of confinement via flux tubes becomes valid and QCD can be modeled accurately via a hadronic string theory—at least for highly excited states. QCD at large Nc also has a well-defined deconfinement transition at a temperature Tc. In this talk it is shown how the thermodyanmics of the metastable hadronic phase of QCD (above Tc) at large NC can be related directly to properties of the effective QCD string. The key points in the derivation is the weakly interacting nature of hadrons at large Nc and the existence of a Hagedorn temperature TH for the effective string theory. From this it can be seen at large Nc and near TH, the energy density and pressure of the hadronic phase scale as E ˜ (TH - T)-(D⊥-6)/2 (for D⊥ < 6) and P ˜ (TH - T)-(D⊥-4)/2 (for D⊥ < 4) where D⊥ is the effective number of transverse dimensions of the string theory. This behavior for D⊥ < 6 is qualitatively different from typical models in statistical mechanics and if observed on the lattice would provide a direct test of the stringy nature of large Nc QCD. However since it can be seen that TH > Tc this behavior is of relevance only to the metastable phase. The prospect of using this result to extract D⊥ via lattice simulations of the metastable hadronic phase at moderately large Nc is discussed.

Sexual selection and genital evolution: an overview.

PubMed

Shamloul, Rany; el-Sakka, Ahmed; Bella, Anthony J

2010-05-01

Genital morphology (especially male) among the animal kingdom is characterized by extensive differences that even members of closely related species with similar general morphology may have remarkably diverse genitalia. To present the sexual medicine specialist with a basic understanding of the current hypotheses on genital evolution with an emphasis on the sexual selection theories. A review of current literature on the theories of genital evolution. Analysis of the supporting evidence for the sexual selection theories of genital evolution. Several theories have been proposed to explain genital evolution. Currently, the sexual selection theories are being considered to present valid and solid evidence explaining genital evolution. However, other theories, including sexual conflict, are still being investigated. All theories of genital evolution have their own weaknesses and strengths. Given that many complex biological mechanisms, mostly unknown yet, are involved in the process of genital evolution, it is thus reasonable to conclude that not one theory can independently explain genital evolution. It is likely that these mechanisms may prove to have synergistic rather than exclusive effects.

Application of the principle of maximum conformality to the hadroproduction of the Higgs boson at the LHC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Sheng-Quan; Wu, Xing-Gang; Brodsky, Stanley J.

We present improved perturbative QCD (pQCD) predictions for Higgs boson hadroproduction at the LHC by applying the principle of maximum conformality (PMC), a procedure which resums the pQCD series using the renormalization group (RG), thereby eliminating the dependence of the predictions on the choice of the renormalization scheme while minimizing sensitivity to the initial choice of the renormalization scale. In previous pQCD predictions for Higgs boson hadroproduction, it has been conventional to assume that the renormalization scale μ r of the QCD coupling α s ( μ r ) is the Higgs mass and then to vary this choice overmore » the range 1 / 2 m H < μ r < 2 m H in order to estimate the theory uncertainty. However, this error estimate is only sensitive to the nonconformal β terms in the pQCD series, and thus it fails to correctly estimate the theory uncertainty in cases where a pQCD series has large higher-order contributions, as is the case for Higgs boson hadroproduction. Furthermore, this ad hoc choice of scale and range gives pQCD predictions which depend on the renormalization scheme being used, in contradiction to basic RG principles. In contrast, after applying the PMC, we obtain next-to-next-to-leading-order RG resummed pQCD predictions for Higgs boson hadroproduction which are renormalization-scheme independent and have minimal sensitivity to the choice of the initial renormalization scale. Taking m H = 125 GeV , the PMC predictions for the p p → H X Higgs inclusive hadroproduction cross sections for various LHC center-of-mass energies are σ Incl | 7 TeV = 21.2 1 + 1.36 - 1.32 pb , σ Incl | 8 TeV = 27.3 7 + 1.65 - 1.59 pb , and σ Incl | 13 TeV = 65.7 2 + 3.46 - 3.0 pb . We also predict the fiducial cross section σ fid ( p p → H → γ γ ) : σ fid | 7 TeV = 30.1 + 2.3 - 2.2 fb , σ fid | 8 TeV = 38.3 + 2.9 - 2.8 fb , and σ fid | 13 TeV = 85.8 + 5.7 - 5.3 fb . The error limits in these predictions include the small residual high-order renormalization-scale dependence plus the uncertainty from the factorization scale. The PMC predictions show better agreement with the ATLAS measurements than the LHC Higgs Cross Section Working Group predictions which are based on conventional renormalization-scale setting.« less

The lepton+jets Selection and Determination of the Lepton Fake Rate with the Full RunIIb Data Set

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meister, Daniel

2013-01-01

This thesis presents the combined single top andmore » $$ t\\overline{ }\\ t $$ lepton+jets selection for the full RunIIb dataset of the DØ detector. The selection uses the newest soft- ware versions including all standard central object identifications and corrections and has various additions and improvements compared to the previous 7 . 3 fb - 1 $$ t\\overline{ }\\ t $$ selection and the previous single top selection in order to accommodate even more different analyses. The lepton fake rate $$\\epsilon_{\\rm QCD}$$ and the real lepton efficiency $$\\epsilon_{\\rm sig}$$ are estimated using the matrix method and different variations are considered in order to determine the systematic errors. The calculation has to be done for each run period and every set of analysis cuts separately. In addition the values for the exclusive jet bins and for the new single top analysis cuts have been derived and the thesis shows numerous control plots to demonstrate the excellent agreement between data and Monte Carlo.« less

Electroproduction of η Mesons in the S 11(1535) Resonance Region at High Momentum Transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalton, Mark Macrae

2008-08-01

The differential cross-section for the exclusive process p(e, e0p) has been measured at Q 2 5.7 and 7.0 (GeV/c) 2, which represents the highest momentum transfer measurement of this to date, significantly higher than the previous highest at Q 2 3.6 (GeV/c) 2. Data was taken for centre-of-mass energies from threshold to 1.8 GeV, encompassing the S11(1535) resonance, which dominates the pη channel. The total cross section is obtained, from which is extracted the helicity-conserving transition amplitude A 1/2, for the production of the S11(1535) resonance. This quantity appears to begin scaling as Q -3, a predicted signal of themore » dominance of perturbative QCD, within the Q 2 range of this measurement. No currently available theoretical predictions can account for the behaviour of this quantity over the full measured range of Q 2.« less

Revisiting the pseudoscalar meson and glueball mixing and key issues in the search for a pseudoscalar glueball state

NASA Astrophysics Data System (ADS)

Qin, Wen; Zhao, Qiang; Zhong, Xian-Hui

2018-05-01

We revisit the mixing mechanism for pseudoscalar mesons and glueball which is introduced by the axial vector anomaly. We demonstrate that the physical mass of the pseudoscalar glueball does not favor to be lower than 1.8 GeV if all the parameters are reasonably constrained. This conclusion, on the one hand, can accommodate the pseudoscalar glueball mass calculated by lattice QCD, and on the other hand, is consistent with the high-statistics analyses at BESIII that all the available measurements do not support the presence of two closely overlapping pseudoscalar states in any exclusive channel. Such a result is in agreement with the recent claim that the slightly shifted peak positions for two possible states η (1405 ) and η (1475 ) observed in different channels are actually originated from one single state with the triangle singularity interferences. By resolving this long-standing paradox, one should pay more attention to higher mass region for the purpose of searching for the pseudoscalar glueball candidate.

Double Collins effect in e+e-→Λ Λ ¯ X and e+e-→Λ π X processes in a diquark spectator model

NASA Astrophysics Data System (ADS)

Wang, Xiaoyu; Yang, Yongliang; Lu, Zhun

2018-06-01

We study the Collins function H1⊥ of the Λ hyperon, which describes the fragmentation of a transversely polarized quark into an unpolarized Λ hyperon. We calculate H1⊥ for light quarks of the Λ hyperon, in the diquark spectator model with a Gaussian form factor for the hyperon-quark-diquark vertex. The model calculation includes contributions from both the scalar diquark and vector diquark spectators. Using the model result, we estimate the azimuthal asymmetry A12, which appears in the ratio of unlike-sign events to like-sign events contributed by double Collins effects, in the processes e+e-→Λ Λ ¯X and e+e-→Λ π X . The QCD evolution effects for the half kT moment of the Collins function and the unpolarized fragmentation function D1(z ) are also included. The results show that the asymmetries are sizable and measurable at the kinematical configurations of Belle and BABAR experiments. We also find that the evolution effects play an important role in the phenomenological analysis.

Fluctuations in the quark-meson model for QCD with isospin chemical potential

NASA Astrophysics Data System (ADS)

Kamikado, Kazuhiko; Strodthoff, Nils; von Smekal, Lorenz; Wambach, Jochen

2013-01-01

We study the two-flavor quark-meson (QM) model with the functional renormalization group (FRG) to describe the effects of collective mesonic fluctuations on the phase diagram of QCD at finite baryon and isospin chemical potentials, μB and μI. With only isospin chemical potential there is a precise equivalence between the competing dynamics of chiral versus pion condensation and that of collective mesonic and baryonic fluctuations in the quark-meson-diquark model for two-color QCD at finite baryon chemical potential. Here, finite μB = 3 μ introduces an additional dimension to the phase diagram as compared to two-color QCD, however. At zero temperature, the (μI, μ) plane of this phase diagram is strongly constrained by the "Silver Blaze problem." In particular, the onset of pion condensation must occur at μI =mπ / 2, independent of μ as long as μ +μI stays below the constituent quark mass of the QM model or the liquid-gas transition line of nuclear matter in QCD. In order to maintain this relation beyond mean field it is crucial to compute the pion mass from its timelike correlator with the FRG in a consistent way.

Higher-order QCD predictions for dark matter production at the LHC in simplified models with s-channel mediators.

PubMed

Backović, Mihailo; Krämer, Michael; Maltoni, Fabio; Martini, Antony; Mawatari, Kentarou; Pellen, Mathieu

Weakly interacting dark matter particles can be pair-produced at colliders and detected through signatures featuring missing energy in association with either QCD/EW radiation or heavy quarks. In order to constrain the mass and the couplings to standard model particles, accurate and precise predictions for production cross sections and distributions are of prime importance. In this work, we consider various simplified models with s -channel mediators. We implement such models in the FeynRules/MadGraph5_aMC@NLO framework, which allows to include higher-order QCD corrections in realistic simulations and to study their effect systematically. As a first phenomenological application, we present predictions for dark matter production in association with jets and with a top-quark pair at the LHC, at next-to-leading order accuracy in QCD, including matching/merging to parton showers. Our study shows that higher-order QCD corrections to dark matter production via s -channel mediators have a significant impact not only on total production rates, but also on shapes of distributions. We also show that the inclusion of next-to-leading order effects results in a sizeable reduction of the theoretical uncertainties.

QCD triple Pomeron coupling from string amplitudes

NASA Astrophysics Data System (ADS)

Bialas, A.; Navelet, H.; Peschanski, R.

1998-06-01

Using the recent solution of the triple Pomeron coupling in the QCD dipole picture as a closed string amplitude with six legs, its analytical form in terms of hypergeometric functions and numerical value are derived.

Hadronic Correlations and Fluctuations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koch, Volker

2008-10-09

We will provide a review of some of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. We will discuss Lattice QCD results on fluctuations and correlations and will put them into context with observables which have been measured in heavy-ion collisions. Special attention will be given to the QCD critical point and the first order co-existence region, and we will discuss how the measurement of fluctuations and correlations can help in an experimental search for non-trivial structures in the QCD phase diagram.

Merging weak and QCD showers with matrix elements

DOE PAGES

Christiansen, Jesper Roy; Prestel, Stefan

2016-01-22

In this study, we present a consistent way of combining associated weak boson radiation in hard dijet events with hard QCD radiation in Drell–Yan-like scatterings. This integrates multiple tree-level calculations with vastly different cross sections, QCD- and electroweak parton-shower resummation into a single framework. The new merging strategy is implemented in the P ythia event generator and predictions are confronted with LHC data. Improvements over the previous strategy are observed. Results of the new electroweak-improved merging at a future 100 TeV proton collider are also investigated.

Lattice QCD Application Development within the US DOE Exascale Computing Project

NASA Astrophysics Data System (ADS)

Brower, Richard; Christ, Norman; DeTar, Carleton; Edwards, Robert; Mackenzie, Paul

2018-03-01

In October, 2016, the US Department of Energy launched the Exascale Computing Project, which aims to deploy exascale computing resources for science and engineering in the early 2020's. The project brings together application teams, software developers, and hardware vendors in order to realize this goal. Lattice QCD is one of the applications. Members of the US lattice gauge theory community with significant collaborators abroad are developing algorithms and software for exascale lattice QCD calculations. We give a short description of the project, our activities, and our plans.

Massive QCD Amplitudes at Higher Orders

NASA Astrophysics Data System (ADS)

Moch, S.; Mitov, A.

2007-11-01

We consider the factorisation properties of on-shell QCD amplitudes with massive partons in the limit when all kinematical invariants are large compared to the parton mass and discuss the structure of their infrared singularities. The dimensionally regulated soft poles and the large collinear logarithms of the parton masses exponentiate to all orders. Based on this factorisation a simple relation between massless and massive scattering amplitudes in gauge theories can be established. We present recent applications of this relation for the calculation of the two-loop virtual QCD corrections to the hadro-production of heavy quarks.

Inclusive heavy flavor hadroproduction in NLO QCD: The exact analytic result

NASA Astrophysics Data System (ADS)

Czakon, M.; Mitov, A.

2010-01-01

We present the first exact analytic result for all partonic channels contributing to the total cross section for the production of a pair of heavy flavors in hadronic collisions in NLO QCD. Our calculation is a step in the derivation of the top quark pair production cross section at NNLO in QCD, which is a cornerstone of the precision LHC program. Our results uncover the analytical structures behind observables with heavy flavors at higher orders. They also reveal surprising and non-trivial implications for kinematics close to partonic threshold.

A comparison of NNLO QCD predictions with 7 TeV ATLAS and CMS data for V+jet processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boughezal, Radja; Liu, Xiaohui; Petriello, Frank

2016-06-17

Here, we perform a detailed comparison of next-to-next-to-leading order (NNLO) QCD predictions for the W+jet and Z+jet processes with 7 TeV experimental data from ATLAS and CMS. We observe excellent agreement between theory and data for most studied observables, which span several orders of magnitude in both cross section and energy. For some observables, such as the HT distribution, the NNLO QCD corrections are essential for resolving existing discrepancies between theory and data.

Critical opalescence in baryonic QCD matter.

PubMed

Antoniou, N G; Diakonos, F K; Kapoyannis, A S; Kousouris, K S

2006-07-21

We show that critical opalescence, a clear signature of second-order phase transition in conventional matter, manifests itself as critical intermittency in QCD matter produced in experiments with nuclei. This behavior is revealed in transverse momentum spectra as a pattern of power laws in factorial moments, to all orders, associated with baryon production. This phenomenon together with a similar effect in the isoscalar sector of pions (sigma mode) provide us with a set of observables associated with the search for the QCD critical point in experiments with nuclei at high energies.

Constraining axion dark matter with Big Bang Nucleosynthesis

DOE PAGES

Blum, Kfir; D'Agnolo, Raffaele Tito; Lisanti, Mariangela; ...

2014-08-04

We show that Big Bang Nucleosynthesis (BBN) significantly constrains axion-like dark matter. The axion acts like an oscillating QCD θ angle that redshifts in the early Universe, increasing the neutron–proton mass difference at neutron freeze-out. An axion-like particle that couples too strongly to QCD results in the underproduction of during BBN and is thus excluded. The BBN bound overlaps with much of the parameter space that would be covered by proposed searches for a time-varying neutron EDM. The QCD axion does not couple strongly enough to affect BBN

Chiral magnetic effect in lattice QCD with a chiral chemical potential.

PubMed

Yamamoto, Arata

2011-07-15

We perform a first lattice QCD simulation including a two-flavor dynamical fermion with a chiral chemical potential. Because the chiral chemical potential gives rise to no sign problem, we can exactly analyze a chirally imbalanced QCD matter by Monte Carlo simulation. By applying an external magnetic field to this system, we obtain a finite induced current along the magnetic field, which corresponds to the chiral magnetic effect. The obtained induced current is proportional to the magnetic field and to the chiral chemical potential, which is consistent with an analytical prediction.

Evidence from lattice data for a new particle on the worldsheet of the QCD flux tube.

PubMed

Dubovsky, Sergei; Flauger, Raphael; Gorbenko, Victor

2013-08-09

We propose a new approach for the calculation of the spectrum of excitations of QCD flux tubes. It relies on the fact that the worldsheet theory is integrable at low energies. With this approach, energy levels can be calculated for much shorter flux tubes than was previously possible, allowing for a quantitative comparison with existing lattice data. The improved theoretical control makes it manifest that existing lattice data provides strong evidence for a new pseudoscalar particle localized on the QCD flux tube--the worldsheet axion.

QCD inequalities for hadron interactions.

PubMed

Detmold, William

2015-06-05

We derive generalizations of the Weingarten-Witten QCD mass inequalities for particular multihadron systems. For systems of any number of identical pseudoscalar mesons of maximal isospin, these inequalities prove that near threshold interactions between the constituent mesons must be repulsive and that no bound states can form in these channels. Similar constraints in less symmetric systems are also extracted. These results are compatible with experimental results (where known) and recent lattice QCD calculations, and also lead to a more stringent bound on the nucleon mass than previously derived, m_{N}≥3/2m_{π}.

The magnetic moment of the Z_c(3900) as an axialvector tetraquark state with QCD sum rules

NASA Astrophysics Data System (ADS)

Wang, Zhi-Gang

2018-04-01

In this article, we assign the Z_c^± (3900) to be the diquark-antidiquark type axialvector tetraquark state, study its magnetic moment with the QCD sum rules in the external weak electromagnetic field by carrying out the operator product expansion up to the vacuum condensates of dimension 8. We pay special attention to matching the hadron side with the QCD side of the correlation function to obtain solid duality, the routine can be applied to study other electromagnetic properties of the exotic particles.

Has the QCD critical point been signaled by observations at the BNL relativistic heavy ion collider?

PubMed

Lacey, Roy A; Ajitanand, N N; Alexander, J M; Chung, P; Holzmann, W G; Issah, M; Taranenko, A; Danielewicz, P; Stöcker, Horst

2007-03-02

The shear viscosity to entropy ratio (eta/s) is estimated for the hot and dense QCD matter created in Au+Au collisions at BNL Relativistic Heavy Ion Collider (square root[s_{NN}]=200 GeV). A very low value is found; eta/s approximately 0.1, which is close to the conjectured lower bound (1/4pi). It is argued that such a low value is indicative of thermodynamic trajectories for the decaying matter which lie close to the QCD critical end point.

Constraining axion dark matter with Big Bang Nucleosynthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blum, Kfir; D'Agnolo, Raffaele Tito; Lisanti, Mariangela

We show that Big Bang Nucleosynthesis (BBN) significantly constrains axion-like dark matter. The axion acts like an oscillating QCD θ angle that redshifts in the early Universe, increasing the neutron–proton mass difference at neutron freeze-out. An axion-like particle that couples too strongly to QCD results in the underproduction of during BBN and is thus excluded. The BBN bound overlaps with much of the parameter space that would be covered by proposed searches for a time-varying neutron EDM. The QCD axion does not couple strongly enough to affect BBN

Hadron scattering, resonances, and QCD

NASA Astrophysics Data System (ADS)

Briceño, R. A.

2016-11-01

The non-perturbative nature of quantum chromodynamics (QCD) has historically left a gap in our understanding of the connection between the fundamental theory of the strong interactions and the rich structure of experimentally observed phenomena. For the simplest properties of stable hadrons, this is now circumvented with the use of lattice QCD (LQCD). In this talk I discuss a path towards a rigorous determination of few-hadron observables from LQCD. I illustrate the power of the methodology by presenting recently determined scattering amplitudes in the light-meson sector and their resonance content.

Lattice QCD Application Development within the US DOE Exascale Computing Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brower, Richard; Christ, Norman; DeTar, Carleton

In October, 2016, the US Department of Energy launched the Exascale Computing Project, which aims to deploy exascale computing resources for science and engineering in the early 2020's. The project brings together application teams, software developers, and hardware vendors in order to realize this goal. Lattice QCD is one of the applications. Members of the US lattice gauge theory community with significant collaborators abroad are developing algorithms and software for exascale lattice QCD calculations. We give a short description of the project, our activities, and our plans.

Merging weak and QCD showers with matrix elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christiansen, Jesper Roy; Prestel, Stefan

In this study, we present a consistent way of combining associated weak boson radiation in hard dijet events with hard QCD radiation in Drell–Yan-like scatterings. This integrates multiple tree-level calculations with vastly different cross sections, QCD- and electroweak parton-shower resummation into a single framework. The new merging strategy is implemented in the P ythia event generator and predictions are confronted with LHC data. Improvements over the previous strategy are observed. Results of the new electroweak-improved merging at a future 100 TeV proton collider are also investigated.

The QCD corrections of the process h → ηbZ

NASA Astrophysics Data System (ADS)

Zhu, Rong-Fei; Feng, Tai-Fu; Zhang, Hai-Bin

2018-05-01

We investigate the 125 GeV Higgs boson decay to a pseudoscalar quarkonium ηb and Z boson. We calculate the quantum chromodynamics (QCD) one-loop corrections to the branching ratio of the process, Br(h → ηbZ), both in the Standard Model (SM) and in the two Higgs double models (THDM). Adding the QCD one-loop corrections, the branching ratio of h → ηbZ in the SM is Br(h → ηbZ) = (4.739‑0.244+0.276) × 10‑5. The relative correction of that QCD one-loop level relative to the tree level of Br(h → ηbZ) is around 76% in the SM. Similarly, the relative correction in the THDM also can be around 75%. The key parameter, tan β, can affect the relative correction in the THDM.

Present constraints on the H-dibaryon at the physical point from Lattice QCD

DOE PAGES

Beane, S. R.; Chang, E.; Detmold, W.; ...

2011-11-10

The current constraints from Lattice QCD on the existence of the H-dibaryon are discussed. With only two significant Lattice QCD calculations of the H-dibaryon binding energy at approximately the same lattice spacing, the form of the chiral and continuum extrapolations to the physical point are not determined. In this brief report, an extrapolation that is quadratic in the pion mass, motivated by low-energy effective field theory, is considered. An extrapolation that is linear in the pion mass is also considered, a form that has no basis in the effective field theory, but is found to describe the light-quark mass dependencemore » observed in Lattice QCD calculations of the octet baryon masses. In both cases, the extrapolation to the physical pion mass allows for a bound H-dibaryon or a near-threshold scattering state.« less

Current matrix element in HAL QCD's wavefunction-equivalent potential method

NASA Astrophysics Data System (ADS)

Watanabe, Kai; Ishii, Noriyoshi

2018-04-01

We give a formula to calculate a matrix element of a conserved current in the effective quantum mechanics defined by the wavefunction-equivalent potentials proposed by the HAL QCD collaboration. As a first step, a non-relativistic field theory with two-channel coupling is considered as the original theory, with which a wavefunction-equivalent HAL QCD potential is obtained in a closed analytic form. The external field method is used to derive the formula by demanding that the result should agree with the original theory. With this formula, the matrix element is obtained by sandwiching the effective current operator between the left and right eigenfunctions of the effective Hamiltonian associated with the HAL QCD potential. In addition to the naive one-body current, the effective current operator contains an additional two-body term emerging from the degrees of freedom which has been integrated out.

Most Strange Dibaryon from Lattice QCD

NASA Astrophysics Data System (ADS)

Gongyo, Shinya; Sasaki, Kenji; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Iritani, Takumi; Ishii, Noriyoshi; Miyamoto, Takaya; Nemura, Hidekatsu; HAL QCD Collaboration

2018-05-01

The Ω Ω system in the 1S0 channel (the most strange dibaryon) is studied on the basis of the (2 +1 )-flavor lattice QCD simulations with a large volume (8.1 fm )3 and nearly physical pion mass mπ≃146 MeV at a lattice spacing of a ≃0.0846 fm . We show that lattice QCD data analysis by the HAL QCD method leads to the scattering length a0=4.6 (6 )(-0.5+1.2) fm , the effective range reff=1.27 (3 )(-0.03+0.06) fm , and the binding energy BΩ Ω=1.6 (6 )(-0.6+0.7) MeV . These results indicate that the Ω Ω system has an overall attraction and is located near the unitary regime. Such a system can be best searched experimentally by the pair-momentum correlation in relativistic heavy-ion collisions.

Bs and Ds decay constants in three-flavor lattice QCD.

PubMed

Wingate, Matthew; Davies, Christine T H; Gray, Alan; Lepage, G Peter; Shigemitsu, Junko

2004-04-23

Capitalizing on recent advances in lattice QCD, we present a calculation of the leptonic decay constants f(B(s)) and f(D(s)) that includes effects of one strange sea quark and two light sea quarks via an improved staggered action. By shedding the quenched approximation and the associated lattice scale uncertainty, lattice QCD greatly increases its predictive power. Nonrelativistic QCD is used to simulate heavy quarks with masses between 1.5m(c) and m(b). We arrive at the following results: f(B(s))=260+/-7+/-26+/-8+/-5 and f(D(s))=290+/-20+/-29+/-29+/-6 MeV. The first quoted error is the statistical uncertainty, and the rest estimate the sizes of higher order terms neglected in this calculation. All of these uncertainties are systematically improvable by including another order in the weak coupling expansion, the nonrelativistic expansion, or the Symanzik improvement program.

Most Strange Dibaryon from Lattice QCD.

PubMed

Gongyo, Shinya; Sasaki, Kenji; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Iritani, Takumi; Ishii, Noriyoshi; Miyamoto, Takaya; Nemura, Hidekatsu

2018-05-25

The ΩΩ system in the ^{1}S_{0} channel (the most strange dibaryon) is studied on the basis of the (2+1)-flavor lattice QCD simulations with a large volume (8.1  fm)^{3} and nearly physical pion mass m_{π}≃146  MeV at a lattice spacing of a≃0.0846  fm. We show that lattice QCD data analysis by the HAL QCD method leads to the scattering length a_{0}=4.6(6)(_{-0.5}^{+1.2})  fm, the effective range r_{eff}=1.27(3)(_{-0.03}^{+0.06})  fm, and the binding energy B_{ΩΩ}=1.6(6)(_{-0.6}^{+0.7})  MeV. These results indicate that the ΩΩ system has an overall attraction and is located near the unitary regime. Such a system can be best searched experimentally by the pair-momentum correlation in relativistic heavy-ion collisions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

Here, the recent determination of themore » $$\\beta$$--function of the QCD running coupling $$\\alpha_{\\overline{MS}}(Q^2)$$ to five-loops, provides a verification of the convergence of a novel method for determining the fundamental QCD parameter $$\\Lambda_s$$ based on the Light-Front Holographic approach to nonperturbative QCD. The new 5-loop analysis, together with improvements in determining the holographic QCD nonperturbative scale parameter $$\\kappa$$ from hadronic spectroscopy, leads to an improved precision of the value of $$\\Lambda_s$$ in the $${\\overline{MS}}$$ scheme close to a factor of two; we find $$\\Lambda^{(3)}_{\\overline{MS}}=0.339\\pm0.019$$ GeV for $$n_{f}=3$$, in excellent agreement with the world average, $$\\Lambda_{\\overline{MS}}^{(3)}=0.332\\pm0.017$$ GeV. Lastly, we also discuss the constraints imposed on the scale dependence of the strong coupling in the nonperturbative domain by superconformal quantum mechanics and its holographic embedding in anti-de Sitter space.« less

Constructing a neutron star from the lattice in G2-QCD

NASA Astrophysics Data System (ADS)

Hajizadeh, Ouraman; Maas, Axel

2017-10-01

The inner structure of neutron stars is still an open question. One obstacle is the infamous sign problem of lattice QCD, which bars access to the high-density equation of state. A possibility to make progress and understand the qualitative impact of gauge interactions on the neutron star structure is to study a modified version of QCD without the sign problem. In the modification studied here the gauge group of QCD is replaced by the exceptional Lie group G_2 , which keeps neutrons in the spectrum. Using an equation of state from lattice calculations only we determine the mass-radius-relation for a neutron star using the Tolman-Oppenheimer-Volkoff equation. This allows us to understand the challenges and approximations currently necessary to use lattice data for this purpose. We discuss in detail the particular uncertainties and systematic problems of this approach.

Relaxion window

NASA Astrophysics Data System (ADS)

Kobayashi, Tatsuo; Seto, Osamu; Shimomura, Takashi; Urakawa, Yuko

2017-09-01

We investigate cosmological constraints on the original relaxion scenario proposed by Graham, Kaplan and Rajendran. We first discuss the appropriate sign choice of the terms in the scalar potential, when the QCD axion is the relaxion with a relaxion-inflaton coupling proposed in the original paper. We next derive the cosmologically consistent ranges of the mass and a coupling of the relaxion for both the QCD relaxion and non-QCD relaxion. The mass range is obtained by 10-5eV ≪ m ϕ ≲ 104eV. We also find that a strong correlation between the Hubble parameter at the relaxion stabilization and the scale Λ of non-QCD strong dynamics, which generates the non-perturbative relaxion cosine potential. For a higher relaxion mass, a large scale Λ becomes available. However, for its lower mass, Λ should be small and constructing such a particle physics model is challenging.

ATLAS measurement of Electroweak Vector Boson production

NASA Astrophysics Data System (ADS)

Vittori, C.; Atlas Collaboration

2017-01-01

The measurements of the Drell-Yan production of W and Z /γ* bosons at the LHC provide a benchmark of our understanding of the perturbative QCD and probe the proton structure in a unique way. The ATLAS collaboration has performed new high precision measurements of the double differential cross-sections as a function of the dilepton mass and rapidity. The measurements are compared to state of calculations at NNLO in QCD and constrain the photon content of the proton. The angular distributions of the Drell-Yan lepton pairs around the Z-boson mass peak probe the underlying QCD dynamics of the Z-boson production mechanisms. The complete set of angular coefficients describing these distributions is presented and compared to theoretical predictions highlighting different approaches of the QCD and EW modelling. First precise inclusive measurements of W and Z production at 13 TeV are presented. W / Z and W+ /W- ratios profit from a cancellation of experimental uncertainties.

Connecting the hadron mass scale to the fundamental mass scale of quantum chromodynamics

DOE PAGES

Deur, Alexandre; Brodsky, Stanley J.; de Teramond, Guy F.

2015-10-01

We establish an explicit connection between the long distance physics of confinement and the dynamical interactions of quarks and gluons at short distances and it has been a long-sought goal of quantum chromodynamics. Using holographic QCD, we derive a direct analytic relation between the scale κ which determines the masses of hadrons and the scale Λ s which controls the predictions of perturbative QCD at very short distances. The resulting prediction Λ s=0.341±0.032 GeV in the MS -scheme agrees well with the experimental average 0.339±0.016 GeV. We also derive a relation between Λs and the QCD string tension σ. Furthermore,more » this connection between the fundamental hadronic scale underlying the physics of quark confinement and the perturbative QCD scale controlling hard collisions can be carried out in any renormalization scheme.« less

Inverse magnetic catalysis from improved holographic QCD in the Veneziano limit

NASA Astrophysics Data System (ADS)

Gürsoy, Umut; Iatrakis, Ioannis; Järvinen, Matti; Nijs, Govert

2017-03-01

We study the dependence of the chiral condensate on external magnetic field in the context of holographic QCD at large number of flavors. We consider a holographic QCD model where the flavor degrees of freedom fully backreact on the color dynamics. Perturbative QCD calculations have shown that B acts constructively on the chiral condensate, a phenomenon called "magnetic catalysis". In contrast, recent lattice calculations show that, depending on the number of flavors and temperature, the magnetic field may also act destructively, which is called "inverse magnetic catalysis". Here we show that the holographic theory is capable of both behaviors depending on the choice of parameters. For reasonable choice of the potentials entering the model we find qualitative agreement with the lattice expectations. Our results provide insight for the physical reasons behind the inverse magnetic catalysis. In particular, we argue that the backreaction of the flavors to the background geometry decatalyzes the condensate.

Physics of the 1 Teraflop RIKEN-BNL-Columbia QCD project. Proceedings of RIKEN BNL Research Center workshop: Volume 13

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1998-10-16

A workshop was held at the RIKEN-BNL Research Center on October 16, 1998, as part of the first anniversary celebration for the center. This meeting brought together the physicists from RIKEN-BNL, BNL and Columbia who are using the QCDSP (Quantum Chromodynamics on Digital Signal Processors) computer at the RIKEN-BNL Research Center for studies of QCD. Many of the talks in the workshop were devoted to domain wall fermions, a discretization of the continuum description of fermions which preserves the global symmetries of the continuum, even at finite lattice spacing. This formulation has been the subject of analytic investigation for somemore » time and has reached the stage where large-scale simulations in QCD seem very promising. With the computational power available from the QCDSP computers, scientists are looking forward to an exciting time for numerical simulations of QCD.« less

From e+e- to Heavy Ion Collisions - Proceedings of the XXX International Symposium on Multiparticle Dynamics

NASA Astrophysics Data System (ADS)

Csörgő, Tamás Hegyi, Sándor Kittel, Wolfram

The Table of Contents for the book is as follows: * Preface * QCD IN MULTIPARTICLE PRODUCTION * QCD and multiparticle production - The status of the perturbative cascade * Test of QCD predictions for multiparticle production at LEP * Multijet final states in e+e- annihilation * Tests of QCD in two photon physics at LEP * Interplay between perturbative and non-perturbative QCD in three-jet events * QCD and hadronic final states at the LHC * Transverse energy and minijets in high energy collisions * Multiparticle production at RHIC and LHC: A classical point of view * High energy interaction with the nucleus in the perturbative QCD with Nc → ∞ * DIFFRACTIVE PRODUCTION AND SMALL-x * Introduction to low-x physics and diffraction * Low-x physics at HERA * Diffractive structure functions at the Tevatron * What is the experimental evidence for the BFKL Pomeron? * Self-organized criticality in gluon systems and its consequences * Scale anomaly and dipole scattering in QCD * Pomeron and AdS/CFT correspondence for QCD * INTERPLAY BETWEEN SOFT AND HARD PHENOMENA * Inclusive jet cross sections and BFKL dynamics searches in dijet cross sections * Soft and hard interactions in p bar{p} Collisions at √ s = 1800 and 630 GeV * Recent results on particle production from OPAL * New results on αs and optimized scales * Preliminary results of the standard model Higgs boson search at LEP 2 in 2000 * Ways to go between hard and soft QCD * Alternative scenarios for fragmentation of a gluonic Lund String * A simultaneous measurement of the QCD colour charges and the strong coupling from LEP multijet data * Branching processes and Koenigs function * Soft and hard QCD dynamics in J/ψ hadroproduction * HADRONIC FINAL STATES IN 1+1, 1+h AND h+h REACTIONS * Universality in hadron production in electron-positron, lepton-hadron and hadron-hadron reactions * Search for gluonic mesons in gluon jets * Vector-to-pseudoscalar and meson-to-baryon ratios in hadronic Z decays at LEP * Polarization and spin alignment in multihadronic Z0 decays * Jet physics at HERA * Final state studies at HERA * A gauge-invariant subtraction technique for non-inclusive observables in QCD * Baryon transport in dual models and the possibility of a backward peak in diffraction * ASTROPARTICLE PHYSICS * Cosmic rays in the energy range of the knee - Recent results from KASCADE * Imaging atmospheric Čerenkov telescopes: Techniques and results * Extensive air shower simulations with CORSIKA and the influence of high-energy hadronic interaction models * Future directions in astroparticle physics and the AUGER experiment * p+A COLLISIONS * pp and pA collisions at CERN SPS * Charmonium attenuation and the quark-gluon plasma * Gluon depletion and J/ψ suppression in pA collisions * CORRELATIONS AND FLUCTUATIONS - EXPERIMENT * Experimental correlation analysis: Foundations and practice * Intermittency and correlations at LEP and at HERA * Moments of the charged-particle multiplicity distribution in Z decays at LEP * On the scale of visible jets in high energy electron-positron collisions * HBT in relativistic heavy ion collisions * Comparison of the pion emission function in hadron-hadron and heavy ion collisions * Multiparticle correlations at LEP1 * Inter-W Bose-Einstein correlations ellipse ... or not? * Colour reconnection at LEP2 * CORRELATIONS AND FLUCTUATIONS - THEORY * Correlations and fluctuations - introduction * Coherence and incoherence in Bose-Einstein correlations * Bose-Einstein correlations in cascade processes and non-extensive statistics * A systematic approach to anomalous phenomena at high energies * Reconstruction of hadronization stage in Pb+Pb collisions at 158A GeV/c * Status of ring-like correlations and wavelets * Fluctuation probes of quark deconfinement * PQCD structure and hadronization in jets and heavy-ion collisions * Net-baryon fluctuations at the QCD critical point * Fractional Fokker-Planck equation in time variable and oscillation of cumulant moments * QCD and multiplicity scaling * RELATIVISTIC HEAVY ION COLLISIONS - EXPERIMENT * Introduction to multiparticle dynamics at RHIC * First results from the STAR experiment at RHIC * Preliminary results from the PHENIX experiment at RHIC * Forward energy and multiplicity in Au-Au reactions at √ {s_{nn} } = 130{text{GeV}} * Results from the PHOBOS experiment on Au+Au collisions at RHIC * Strangeness production in Pb-Pb collisions at the CERN SPS: Results from the WA97 experiment * Direct photon production in 158A GeV 208Pb+208Pb collisions * Search for critical phenomena in Pb+Pb collisions * Recent NA49 results on Pb+Pb collisions at CERN SPS * J/ψ suppression in Pb+Pb collisions at CERN SPS * RELATIVISTIC HEAVY ION COLLISIONS - THEORY * Hyperon ratios at RHIC and the coalescence predictions at mid-rapidity * Dynamics of nuclear collisions and the dependence of the onset of anomalous J/ψ suppression on nucleon numbers of colliding nuclei * Multi-boson effects in Bose-Einstein interferometry * The source of the "third flow component" * Collective flow and multiparticle azimuthal correlations * Microscopic strangeness enhancement mechanisms at the SPS * Jet quenching at finite opacity and its application at RHIC energy * Particle rapidity density and collective phenomena in heavy ion collisions * Elliptic flow from an on-shell parton cascade * Dilepton production in ultrarelativistic heavy ion collisions * Coulomb and core/halo corrections to Bose-Einstein n-particle correlations * CP VIOLATION IN MULTIPARTICLE DYNAMICS * New results from NA48 experiment on neutral kaon rare decays * Measurement of direct CP violation by the NA48 experiment at CERN * Aspects of parity, CP, and time reversal violation in hot QCD * Decay of parity odd bubbles * Parity and time reversal studies at RHIC * Constraining CP-violating TGCS and measuring W-polarization at OPAL * Buckyballs of QCD: Gluon junction networks * List of participants

Elastic and Diffractive Scattering - Proceedings of the International Conference on Vth Blois Workshop

NASA Astrophysics Data System (ADS)

Kang, K.; Fried, H. M.; Tan, C.-I.

1994-02-01

The Table of Contents for the book is as follows: * Preface * `Overview' on Elastic Scattering and Total Cross-Sections * A Precise Measurement of the Real Part of the Elastic Scattering Amplitude at the {S bar{p}pS} * Luminosity Dependent Measurement of the p bar{p} Total Cross Section at √{s} = 541 GeV * Status of Fermilab E-710 * Luminosity-Independent Measurement of bar{p}p Elastic Scattering, Single Diffraction, Dissociation and Total Cross Section at √{s} = 546 and 1800 GeV * Phase Relations Revisited: A Challenge for SSC and LHC * Status of Near-Forward Elastic Scattering * bar{p}p Collisions at √{s} = 1.8 TeV: p, σt and B * p bar{p} Forward Scattering Parameters Results from Fermilab E760 * Photoproduction Results from H1 at HERA * Total and Jet Photoproduction Cross Sections at HERA and Fermilab * Minijet Model for High Energy γp Cross Sections * The Pomeron as Massive Gluons * Large N Theories with Glueball-like Spectra * Unitarity Relations for Gluonic Pomeron * The Donnachie-Landshoff Pomeron vs. QCD * The Odderon Intercept in Perturbative QCD * Theoret. and Phenomenol. Aspects of the Odderon * First Theorist's Gaze at HERA Data at Low xB * H1 Results for Structure Functions at Small x * Partial Photoproduction Cross Sections at √{s} ≈prox 180 GeV and First Results on F2 of the Proton from the ZEUS Experiment * Observation of a New Class of Events in Deep Inelastic Scattering * Jet Production in Muon-Proton and Muon-Nuclei Scattering at Fermilab-E665 * D0 Studies of Perturbative QCD * Large Rapidity Gaps and Single Diffraction Dissociation in High Energy pp and bar{p}p Collisions * Hadron and Reggeon Structure in High Energy Collisions * Monte Carlo Studies of Diffractive Processes in Deep Inelastic Scattering * Elastic Parton-Parton Amplitudes in Geometrical Models * Non-Perturbative QCD Calculations of High-Energy Observables * Effective Field Theory for Diffractive QCD Processes * High Energy Behavior of σtot, ρ, and B - Asymptotic Amplitude Analysis and a QCD-Inspired Analysis * Rapidity Gaps and Multiplicity Fluctuations * Branching Processes and Multi-Particle Production * High Energy Elastic Scattering and Nucleon as a Topological Soliton * The Behavior of Cross Sections at Very High Energies * The Pomeron and QCD with Many Light Quarks * Heterotic Pomeron: High Energy Hadronic Collisions in QCD * CDF Results on Electroweak Physics * DØ Results on Electroweak Physics * Search for the Top Quark and Other New Particles at DØ * Rapidity Gaps and Forward Physics at DØ * High Energy Asymptotics of Perturbative Multi-Color QCD * Rapidity Gaps in e+e- Collisions * Large Rapidity Gap, Jet Events at HERA: a PQCD Approach * High Energy Parton-Parton Elastic Scattering in QCD * Parton-Parton Elastic Scattering and Rapidity Gaps at Tevatron Energies * Hard Elastic Scattering * Hard Diffractive Processes * Three Successful Tests of Color Transparency and Nuclear Filtering * New KNO in QCD * A Chiral Condensate Search at the Tevatron * Cosmic Ray Evidences for Aligned High Energy Jets at Supertevatron Energy and Hard DDD * "New Hadronic State" Observed in Extremely High Energy Cosmic-Ray Interactions * Meson and Nucleon Form Factors in PQCD * Elastic Charge Form Factors for Pseudoscalar Mesons * The Ultimate Experiment * Search for Coherent Charm Production in 800 GeV/c Proton-Silicon Interactions * Chiral Quark Model and Hadron Scattering * Elastic Spin Experiments at UNK, Fermilab and SSC * Spin-Flip in Elastic and Diffractive Scattering * FNAL Polarized Beams and Spin Dependence at RHIC * Particle Tracking in the Close-to-Forward Region (η > 5.5) * Blois V: Experimental Summary * Blois V: Summary Talk * List of Participants

Calculation of neutral weak nucleon form factors with the AdS/QCD correspondence

NASA Astrophysics Data System (ADS)

Lohmann, Mark

The AdS/QCD (Anti-de Sitter/Quantum Chromodynamics) is a mathematical formalism applied to a theory based on the original AdS/CFT (Anti-de Sitter/ Conformal Field Theory) correspondence. The aim is to describe properties of the strong force in an essentially non-perturbative way. AdS/QCD theories break the conformal symmetry of the AdS metric (a sacrifice) to arrive at a boundary theory which is QCD-like (a payoff). This correspondence has been used to calculate well-known quantities in nucleon spectra and structure like Regge trajectories, form factors, and many others within an error of less than 20% from experiment. This is impressive considering that ordinary perturbation theory in QCD applied to the strongly interacting domain usually obtains an error of about 30%. In this thesis, the AdS/QCD correspondence method of light-front holography established by Brodsky and de Teramond is used in an attempt to calculate the Dirac and Pauli neutral weak form factors, FZ1 (Q2) and FZ2 (Q 2) respectively, for both the proton and the neutron. With this approach, we were able to determine the neutral weak Dirac form factor for both nucleons and the Pauli form factor for the proton, while the method did not succeed at determining the neutral weak Pauli form factor for the neutron. With these we were also able to extract the proton's strange electric and magnetic form factor, which addresses important questions in nucleon sub-structure that are currently being investigated through experiments at the Thomas Jefferson National Accelerator Facility.

Statistics of baryon correlation functions in lattice QCD

NASA Astrophysics Data System (ADS)

Wagman, Michael L.; Savage, Martin J.; Nplqcd Collaboration

2017-12-01

A systematic analysis of the structure of single-baryon correlation functions calculated with lattice QCD is performed, with a particular focus on characterizing the structure of the noise associated with quantum fluctuations. The signal-to-noise problem in these correlation functions is shown, as long suspected, to result from a sign problem. The log-magnitude and complex phase are found to be approximately described by normal and wrapped normal distributions respectively. Properties of circular statistics are used to understand the emergence of a large time noise region where standard energy measurements are unreliable. Power-law tails in the distribution of baryon correlation functions, associated with stable distributions and "Lévy flights," are found to play a central role in their time evolution. A new method of analyzing correlation functions is considered for which the signal-to-noise ratio of energy measurements is constant, rather than exponentially degrading, with increasing source-sink separation time. This new method includes an additional systematic uncertainty that can be removed by performing an extrapolation, and the signal-to-noise problem reemerges in the statistics of this extrapolation. It is demonstrated that this new method allows accurate results for the nucleon mass to be extracted from the large-time noise region inaccessible to standard methods. The observations presented here are expected to apply to quantum Monte Carlo calculations more generally. Similar methods to those introduced here may lead to practical improvements in analysis of noisier systems.

The Secret Life of Quarks, Final Report for the University of North Carolina at Chapel Hill

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fowler, Robert J.

This final report summarizes activities and results at the University of North Carolina as part of the the SciDAC-2 Project The Secret Life of Quarks: National Computational Infrastructure for Lattice Quantum Chromodynamics. The overall objective of the project is to construct the software needed to study quantum chromo- dynamics (QCD), the theory of the strong interactions of subatomic physics, and similar strongly coupled gauge theories anticipated to be of importance in the LHC era. It built upon the successful efforts of the SciDAC-1 project National Computational Infrastructure for Lattice Gauge Theory, in which a QCD Applications Programming Interface (QCD API)more » was developed that enables lat- tice gauge theorists to make effective use of a wide variety of massively parallel computers. In the SciDAC-2 project, optimized versions of the QCD API were being created for the IBM Blue- Gene/L (BG/L) and BlueGene/P (BG/P), the Cray XT3/XT4 and its successors, and clusters based on multi-core processors and Infiniband communications networks. The QCD API is being used to enhance the performance of the major QCD community codes and to create new applications. Software libraries of physics tools have been expanded to contain sharable building blocks for inclusion in application codes, performance analysis and visualization tools, and software for au- tomation of physics work flow. New software tools were designed for managing the large data sets generated in lattice QCD simulations, and for sharing them through the International Lattice Data Grid consortium. As part of the overall project, researchers at UNC were funded through ASCR to work in three general areas. The main thrust has been performance instrumentation and analysis in support of the SciDAC QCD code base as it evolved and as it moved to new computation platforms. In support of the performance activities, performance data was to be collected in a database for the purpose of broader analysis. Third, the UNC work was done at RENCI (Renaissance Computing Institute), which has extensive expertise and facilities for scientific data visualization, so we acted in an ongoing consulting and support role in that area.« less

Analytic derivation of the next-to-leading order proton structure function F2p(x ,Q2) based on the Laplace transformation

NASA Astrophysics Data System (ADS)

Khanpour, Hamzeh; Mirjalili, Abolfazl; Tehrani, S. Atashbar

2017-03-01

An analytical solution based on the Laplace transformation technique for the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations is presented at next-to-leading order accuracy in perturbative QCD. This technique is also applied to extract the analytical solution for the proton structure function, F2p(x ,Q2) , in the Laplace s space. We present the results for the separate parton distributions of all parton species, including valence quark densities, the antiquark and strange sea parton distribution functions (PDFs), and the gluon distribution. We successfully compare the obtained parton distribution functions and the proton structure function with the results from GJR08 [Gluck, Jimenez-Delgado, and Reya, Eur. Phys. J. C 53, 355 (2008)], 10.1140/epjc/s10052-007-0462-9 and KKT12 [Khanpour, Khorramian, and Tehrani, J. Phys. G 40, 045002 (2013)], 10.1088/0954-3899/40/4/045002 parametrization models as well as the x -space results using QCDnum code. Our calculations show a very good agreement with the available theoretical models as well as the deep inelastic scattering (DIS) experimental data throughout the small and large values of x . The use of our analytical solution to extract the parton densities and the proton structure function is discussed in detail to justify the analysis method, considering the accuracy and speed of calculations. Overall, the accuracy we obtain from the analytical solution using the inverse Laplace transform technique is found to be better than 1 part in 104 to 105. We also present a detailed QCD analysis of nonsinglet structure functions using all available DIS data to perform global QCD fits. In this regard we employ the Jacobi polynomial approach to convert the results from Laplace s space to Bjorken x space. The extracted valence quark densities are also presented and compared to the JR14, MMHT14, NNPDF, and CJ15 PDFs sets. We evaluate the numerical effects of target mass corrections (TMCs) and higher twist (HT) terms on various structure functions, and compare fits to data with and without these corrections.

Extraction of the gluon density of the proton at x

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Repond, J.; Schlereth, J.; Stanek, R.; Talaga, R. L.; Thron, J.; Arzarello, F.; Ayad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Cara Romeo, G.; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Ciralli, F.; Contin, A.; D'Auria, S.; Frasconi, F.; Gialas, I.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Zamora Garcia, Y.; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Eckert, M.; Feld, L.; Frey, A.; Geerts, M.; Geitz, G.; Grothe, M.; Hartmann, H.; Haun, D.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mari, S. M.; Mass, A.; Mengel, S.; Mollen, J.; Paul, E.; Rembser, Ch.; Schattevoy, R.; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Llewellyn, T. J.; Morgado, C. J. S.; Norman, D. J. P.; O'Mara, J. A.; Tapper, R. J.; Wilson, S. S.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Eskreys, K.; Jelén, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Kȩdzierski, T.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Bienlein, J. K.; Böttcher, S.; Coldewey, C.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Göttlicher, P.; Gutjahr, B.; Haas, T.; Hain, W.; Hasell, D.; Heβling, H.; Hultschig, H.; Iga, Y.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Kröger, W.; Krüger, J.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mańczak, O.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schulz, W.; Selonke, F.; Stiliaris, E.; Voβ, T.; Westphal, D.; Wolf, G.; Youngman, C.; Grabosch, H. J.; Leich, A.; Meyer, A.; Rethfeldt, C.; Schlenstedt, S.; Barbagli, G.; Pelfer, P.; Anzivino, G.; Maccarrone, G.; De Pasquale, S.; Qian, S.; Votano, L.; Bamberger, A.; Freidhof, A.; Poser, T.; Söldner-Rembold, S.; Schroeder, J.; Theisen, G.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Fleck, I.; Jamieson, V. A.; Saxon, D. H.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Kammerlocher, H.; Krebs, B.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Fürtjes, A.; Hagge, L.; Lohrmann, E.; Mainusch, J.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Terron, J.; Zetsche, F.; Bacon, T. C.; Beuselinck, R.; Butterworth, I.; Gallo, E.; Harris, V. L.; Hung, B. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Zhang, Y.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Nam, S. W.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; del Peso, J.; Puga, J.; de Trocóniz, J. F.; Ikraiam, F.; Mayer, J. K.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; St. Laurent, M.; Ullmann, R.; Zacek, G.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Y. A.; Kobrin, V. D.; Kuzmin, V. A.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Bentvelsen, S.; Botje, M.; Chlebana, F.; Dake, A.; Engelen, J.; de Jong, P.; de Kamps, M.; Kooijman, P.; Kruse, A.; O'Dell, V.; Tenner, A.; Tiecke, H.; Verkerke, W.; Vreeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Bailey, D. S.; Blair, G. A.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Daniels, D.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Luffman, P. E.; Lindemann, L.; McFall, J.; Nath, C.; Quadt, A.; Uijterwaal, H.; Walczak, R.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; De Giorgi, M.; Dosselli, U.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Feild, R. G.; Oh, B. Y.; Whitmore, J. J.; D'Agostini, G.; Iori, M.; Marini, G.; Mattioli, M.; Nigro, A.; Tassi, E.; Hart, J. C.; McCubbin, N. A.; Prytz, K.; Shah, T. P.; Short, T. L.; Barberis, E.; Cartiglia, N.; Dubbs, T.; Heusch, C.; Van Hook, M.; Hubbard, B.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Biltzinger, J.; Seifert, R. J.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nagira, T.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nagayama, S.; Nakamitsu, Y.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Crombie, M. B.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Blankenship, K.; Kochocki, J.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchuł; a, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Zarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Glasman, C.; Karshon, U.; Revel, D.; Shapira, A.; Ali, I.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Tsurugai, T.; Bhadra, S.; Frisken, W. R.; Furutani, K. M.; Zeus Collaboration

1995-02-01

The gluon momentum density xg( x, Q2) of the proton was extracted at Q2 = 20 GeV 2 for small values of x between 4 × 10 -4 and 10 -2 from the scaling violations of the proton structure function F2 measured recently by ZEUS in deep inelastic neutral current ep scattering at HERA. The extraction was performed in two ways. Firstly, using a global NLO fit to the ZEUS data on F2 at low x constrained by measurementsfrom NMC at larger x; and secondly using published approximate methods for the solution of the GLAP QCD evolution equations. Consistent results are obtained. A substantial increase of the gluon density is found at small x in comparison with the NMC result obtained at larger values of x.

Fluctuations of conserved charges in relativistic heavy ion collisions: An introduction

NASA Astrophysics Data System (ADS)

Asakawa, Masayuki; Kitazawa, Masakiyo

2016-09-01

Bulk fluctuations of conserved charges measured by event-by-event analysis in relativistic heavy ion collisions are observables which are believed to carry significant amount of information on the hot medium created by the collisions. Active studies have been done recently experimentally, theoretically, and on the lattice. In particular, non-Gaussianity of the fluctuations has acquired much attention recently. In this review, we give a pedagogical introduction to these issues, and survey recent developments in this field of research. Starting from the definition of cumulants, basic concepts in fluctuation physics, such as thermal fluctuations in statistical mechanics and time evolution of fluctuations in diffusive systems, are described. Phenomena which are expected to occur in finite temperature and/or density QCD matter and their measurement by event-by-event analyses are also elucidated.

Supersymmetric flaxion

NASA Astrophysics Data System (ADS)

Ema, Yohei; Hagihara, Daisuke; Hamaguchi, Koichi; Moroi, Takeo; Nakayama, Kazunori

2018-04-01

Recently, a new minimal extension of the Standard Model has been proposed, where a spontaneously broken, flavor-dependent global U(1) symmetry is introduced. It not only explains the hierarchical flavor structure in the quark and lepton sector, but also solves the strong CP problem by identifying the Nambu-Goldstone boson as the QCD axion, which we call flaxion. In this work, we consider supersymmetric extensions of the flaxion scenario. We study the CP and flavor violations due to supersymmetric particles, the effects of R-parity violations, the cosmological gravitino and axino problems, and the cosmological evolution of the scalar partner of the flaxion, sflaxion. We also propose an attractor-like inflationary model where the flaxion multiplet contains the inflaton field, and show that a consistent cosmological scenario can be obtained, including inflation, leptogenesis, and dark matter.

Observables of QCD diffraction

NASA Astrophysics Data System (ADS)

Mieskolainen, Mikael; Orava, Risto

2017-03-01

A new combinatorial vector space measurement model is introduced for soft QCD diffraction. The model independent mathematical construction resolves experimental complications; the theoretical framework of the approach includes the Good-Walker view of diffraction, Regge phenomenology together with AGK cutting rules and random fluctuations.

Reliable semiclassical computations in QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dine, Michael; Department of Physics, Stanford University Stanford, California 94305-4060; Festuccia, Guido

We revisit the question of whether or not one can perform reliable semiclassical QCD computations at zero temperature. We study correlation functions with no perturbative contributions, and organize the problem by means of the operator product expansion, establishing a precise criterion for the validity of a semiclassical calculation. For N{sub f}>N, a systematic computation is possible; for N{sub f}

Study of QCD-dynamics in η and η' production and decays

NASA Astrophysics Data System (ADS)

Beck, Reinhard; Wiedner, Ulrich

2017-01-01

One aim of this project lies in studying QCD dynamics using photoproduction of η and η' mesons with the CBELSA/TAPS experiment at the accelerator facility ELSA. Hadronic decay modes of η and η' are analyzed that allow the study of symmetry breaking effects in QCD. Furthermore, excited η-states produced with a photon beam are studied within the scope of this project. Of special interest is hereby the nature of the η(1405). The high data samples for η- and η'-photoproduction off the proton allow in addition the determination of polarization observables.

a Holographic Model of Hadrons

NASA Astrophysics Data System (ADS)

Stephanov, M. A.

2007-03-01

This short talk is based on the work with J. Erlich, E. Katz and D. Son, hep-ph/0501128. Inspired by ideas of gauge/string duality, we propose a five-dimensional framework for modeling low energy properties of QCD. The model naturally incorporates properties of QCD dictated by chiral symmetry, which we demonstrate by deriving the Gell-Mann-Oakes-Renner relationship for the pion mass. The couplings and masses of the infinite towers of vector and axial vector mesons described by the model automatically obey QCD sum rules. The phenomenon of vector-meson dominance is a straightforward consequence of the model.

Matching next-to-leading order predictions to parton showers in supersymmetric QCD

DOE PAGES

Degrande, Céline; Fuks, Benjamin; Hirschi, Valentin; ...

2016-02-03

We present a fully automated framework based on the FeynRules and MadGraph5_aMC@NLO programs that allows for accurate simulations of supersymmetric QCD processes at the LHC. Starting directly from a model Lagrangian that features squark and gluino interactions, event generation is achieved at the next-to-leading order in QCD, matching short-distance events to parton showers and including the subsequent decay of the produced supersymmetric particles. As an application, we study the impact of higher-order corrections in gluino pair-production in a simplified benchmark scenario inspired by current gluino LHC searches.

Matching next-to-leading order predictions to parton showers in supersymmetric QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Degrande, Céline; Fuks, Benjamin; Hirschi, Valentin

We present a fully automated framework based on the FeynRules and MadGraph5_aMC@NLO programs that allows for accurate simulations of supersymmetric QCD processes at the LHC. Starting directly from a model Lagrangian that features squark and gluino interactions, event generation is achieved at the next-to-leading order in QCD, matching short-distance events to parton showers and including the subsequent decay of the produced supersymmetric particles. As an application, we study the impact of higher-order corrections in gluino pair-production in a simplified benchmark scenario inspired by current gluino LHC searches.

Searching for the rules that govern hadron construction

DOE PAGES

Shepherd, Matthew R.; Dudek, Jozef J.; Mitchell, Ryan E.

2016-06-22

Just as quantum electrodynamics describes how electrons are bound in atoms by the electromagnetic force, mediated by the exchange of photons, quantum chromodynamics (QCD) describes how quarks are bound inside hadrons by the strong force, mediated by the exchange of gluons. QCD seems to allow hadrons constructed from increasingly many quarks to exist, just as atoms with increasing numbers of electrons exist, yet such complex constructions seemed, until recently, not to be present in nature. In this paper, we describe advances in the spectroscopy of mesons that are refining our understanding of the rules for predicting hadron structure from QCD.

Direct CP asymmetry in D → π-π+ and D → K-K+ in QCD-based approach

NASA Astrophysics Data System (ADS)

Khodjamirian, Alexander; Petrov, Alexey A.

2017-11-01

We present the first QCD-based calculation of hadronic matrix elements with penguin topology determining direct CP-violating asymmetries in D0 →π-π+ and D0 →K-K+ nonleptonic decays. The method is based on the QCD light-cone sum rules and does not rely on any model-inspired amplitude decomposition, instead leaning heavily on quark-hadron duality. We provide a Standard Model estimate of the direct CP-violating asymmetries in both pion and kaon modes and their difference and comment on further improvements of the presented computation.

Gluon and ghost correlation functions of 2-color QCD at finite density

NASA Astrophysics Data System (ADS)

Hajizadeh, Ouraman; Boz, Tamer; Maas, Axel; Skullerud, Jon-Ivar

2018-03-01

2-color QCD, i. e. QCD with the gauge group SU(2), is the simplest non-Abelian gauge theory without sign problem at finite quark density. Therefore its study on the lattice is a benchmark for other non-perturbative approaches at finite density. To provide such benchmarks we determine the minimal-Landau-gauge 2-point and 3-gluon correlation functions of the gauge sector and the running gauge coupling at finite density. We observe no significant effects, except for some low-momentum screening of the gluons at and above the supposed high-density phase transition.

QCD Physics with the CMS Experiment

NASA Astrophysics Data System (ADS)

Cerci, S.

2017-12-01

Jets which are the signatures of quarks and gluons in the detector can be described by Quantum Chromodynamics (QCD) in terms of parton-parton scattering. Jets are abundantly produced at the LHC's high energy scales. Measurements of inclusive jets, dijets and multijets can be used to test perturbative QCD predictions and to constrain parton distribution functions (PDF), as well as to measure the strong coupling constant αS . The measurements use the samples of proton-proton collisions collected with the CMS detector at the LHC at various center-of-mass energies of 7, 8 and 13 TeV.

Hadron mass spectrum from lattice QCD.

PubMed

Majumder, Abhijit; Müller, Berndt

2010-12-17

Finite temperature lattice simulations of quantum chromodynamics (QCD) are sensitive to the hadronic mass spectrum for temperatures below the "critical" temperature T(c) ≈ 160 MeV. We show that a recent precision determination of the QCD trace anomaly shows evidence for the existence of a large number of hadron states beyond those known from experiment. The lattice results are well represented by an exponentially growing mass spectrum up to a temperature T=155 MeV. Using simple parametrizations of the hadron mass spectrum we show how one may estimate the total spectral weight in these yet undermined states.

Individual complex Dirac eigenvalue distributions from random matrix theory and comparison to quenched lattice QCD with a quark chemical potential.

PubMed

Akemann, G; Bloch, J; Shifrin, L; Wettig, T

2008-01-25

We analyze how individual eigenvalues of the QCD Dirac operator at nonzero quark chemical potential are distributed in the complex plane. Exact and approximate analytical results for both quenched and unquenched distributions are derived from non-Hermitian random matrix theory. When comparing these to quenched lattice QCD spectra close to the origin, excellent agreement is found for zero and nonzero topology at several values of the quark chemical potential. Our analytical results are also applicable to other physical systems in the same symmetry class.

Virtual Compton scattering off a spinless target in AdS/QCD

NASA Astrophysics Data System (ADS)

Marquet, Cyrille; Roiesnel, Claude; Wallon, Samuel

2010-04-01

We study the doubly virtual Compton scattering off a spinless target γ* P → γ* P' within the Anti-de Sitter(AdS)/QCD formalism. We find that the general structure allowed by the Lorentz invariance and gauge invariance of the Compton amplitude is not easily reproduced with the standard recipes of the AdS/QCD correspondence. In the soft-photon regime, where the semi-classical approximation is supposed to apply best, we show that the measurements of the electric and magnetic polarizabilities of a target like the charged pion in real Compton scattering, can already serve as stringent tests.

Next-to-leading-order QCD corrections to Higgs boson production plus three jets in gluon fusion.

PubMed

Cullen, G; van Deurzen, H; Greiner, N; Luisoni, G; Mastrolia, P; Mirabella, E; Ossola, G; Peraro, T; Tramontano, F

2013-09-27

We report on the calculation of the cross section for Higgs boson production in association with three jets via gluon fusion, at next-to-leading-order (NLO) accuracy in QCD, in the infinite top-mass approximation. After including the complete NLO QCD corrections, we observe a strong reduction in the scale dependence of the result, and an increased steepness in the transverse momentum distributions of both the Higgs boson and the leading jets. The results are obtained with the combined use of GOSAM, SHERPA, and the MADDIPOLE-MADEVENT framework.

NΩ interaction from two approaches in lattice QCD

NASA Astrophysics Data System (ADS)

Etminan, Faisal; Firoozabadi, Mohammad Mehdi

2014-10-01

We compare the standard finite volume method by Lüscher with the potential method by HAL QCD collaboration, by calculating the ground state energy of N(nucleon)-Ω(Omega) system in 5 S2 channel. We employ 2+1 flavor full QCD configurations on a (1.9 fm)3×3.8 fm lattice at the lattice spacing a≃0.12 fm, whose ud(s) quark mass corresponds to mπ = 875(1) (mK = 916(1)) MeV. We have found that both methods give reasonably consistent results that there is one NΩ bound state at this parameter.

Resolving the SELEX--LHCb Double-Charm Baryon Conflict: The Impact of Intrinsic Heavy-Quark Hadroproduction and Supersymmetric Light-Front Holographic QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley

2017-01-01

In this paper we show that the intrinsic heavy-quark QCD mechanism for the hadroproduction of heavy hadrons at largemore » $$x_F$$ can resolve the apparent conflict between measurements of double-charm baryons by the SELEX fixed-target experiment and the LHCb experiment at the LHC collider. We show that both experiments are compatible, and that both results can be correct. The observed spectroscopy of double-charm hadrons is in agreement with the predictions of supersymmetric light front holographic QCD.« less

A study of energy-energy correlations and measurement of [alpha][sub s] at the Z[sup 0] resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-01-01

We present the energy-energy correlation (EEC) distribution and its asymmetry (AEEC) in hadronic decays of [Zeta][sup 0] bosons measured by the SLD at SLAC. The data are found to be in good agreement with the predictions of perturbative QCD and fragmentation Monte Carlo models of hadron production. After correction for hadronization effects the data are compared with [Omicron]([alpha][sub s][sup 2]) perturbative QCD calculations from various authors. Fits to the central region of the EEC yield substantially different values of the QCD scale [lambda][sub [ovr MS

NNLO QCD corrections to associated W H production and H →b b ¯ decay

NASA Astrophysics Data System (ADS)

Caola, Fabrizio; Luisoni, Gionata; Melnikov, Kirill; Röntsch, Raoul

2018-04-01

We present a computation of the next-to-next-to-leading-order (NNLO) QCD corrections to the production of a Higgs boson in association with a W boson at the LHC and the subsequent decay of the Higgs boson into a b b ¯ pair, treating the b quarks as massless. We consider various kinematic distributions and find significant corrections to observables that resolve the Higgs decay products. We also find that a cut on the transverse momentum of the W boson, important for experimental analyses, may have a significant impact on kinematic distributions and radiative corrections. We show that some of these effects can be adequately described by simulating QCD radiation in Higgs boson decays to b quarks using parton showers. We also describe contributions to Higgs decay to a b b ¯ pair that first appear at NNLO and that were not considered in previous fully differential computations. The calculation of NNLO QCD corrections to production and decay sub-processes is carried out within the nested soft-collinear subtraction scheme presented by some of us earlier this year. We demonstrate that this subtraction scheme performs very well, allowing a computation of the coefficient of the second-order QCD corrections at the level of a few per mill.

Prompt atmospheric neutrino fluxes: perturbative QCD models and nuclear effects

DOE PAGES

Bhattacharya, Atri; Enberg, Rikard; Jeong, Yu Seon; ...

2016-11-28

We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD, k T factorization including low-x resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest datamore » on forward charm meson production from LHCb at 7 TeV and at 13 TeV, finding good agreement with the data. In addition, we investigate the role of nuclear shadowing by including nuclear parton distribution functions (PDF) for the target air nucleus using two different nuclear PDF schemes. Depending on the scheme used, we find the reduction of the flux due to nuclear effects varies from 10% to 50% at the highest energies. Finally, we compare our results with the IceCube limit on the prompt neutrino flux, which is already providing valuable information about some of the QCD models.« less

The evolution of social monogamy in mammals.

PubMed

Lukas, D; Clutton-Brock, T H

2013-08-02

The evolution of social monogamy has intrigued biologists for over a century. Here, we show that the ancestral condition for all mammalian groups is of solitary individuals and that social monogamy is derived almost exclusively from this social system. The evolution of social monogamy does not appear to have been associated with a high risk of male infanticide, and paternal care is a consequence rather than a cause of social monogamy. Social monogamy has evolved in nonhuman mammals where breeding females are intolerant of each other and female density is low, suggesting that it represents a mating strategy that has developed where males are unable to defend access to multiple females.

Model of reversible vesicular transport with exclusion

NASA Astrophysics Data System (ADS)

Bressloff, Paul C.; Karamched, Bhargav R.

2016-08-01

A major question in neurobiology concerns the mechanics behind the motor-driven transport and delivery of vesicles to synaptic targets along the axon of a neuron. Experimental evidence suggests that the distribution of vesicles along the axon is relatively uniform and that vesicular delivery to synapses is reversible. A recent modeling study has made explicit the crucial role that reversibility in vesicular delivery to synapses plays in achieving uniformity in vesicle distribution, so called synaptic democracy (Bressloff et al 2015 Phys. Rev. Lett. 114 168101). In this paper we generalize the previous model by accounting for exclusion effects (hard-core repulsion) that may occur between molecular motor-cargo complexes (particles) moving along the same microtubule track. The resulting model takes the form of an exclusion process with four internal states, which distinguish between motile and stationary particles, and whether or not a particle is carrying vesicles. By applying a mean field approximation and an adiabatic approximation we reduce the system of ODEs describing the evolution of occupation numbers of the sites on a 1D lattice to a system of hydrodynamic equations in the continuum limit. We find that reversibility in vesicular delivery allows for synaptic democracy even in the presence of exclusion effects, although exclusion does exacerbate nonuniform distributions of vesicles in an axon when compared with a model without exclusion. We also uncover the relationship between our model and other models of exclusion processes with internal states.

Miracles in Scattering Amplitudes: from QCD to Gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volovich, Anastasia

2016-10-09

The goal of my research project "Miracles in Scattering Amplitudes: from QCD to Gravity" involves deepening our understanding of gauge and gravity theories by exploring hidden structures in scattering amplitudes and using these rich structures as much as possible to aid practical calculations.

One-loop QCD thermodynamics in a strong homogeneous and static magnetic field

NASA Astrophysics Data System (ADS)

Rath, Shubhalaxmi; Patra, Binoy Krishna

2017-12-01

We have studied how the equation of state of thermal QCD with two light flavors is modified in a strong magnetic field. We calculate the thermodynamic observables of hot QCD matter up to one-loop, where the magnetic field affects mainly the quark contribution and the gluon part is largely unaffected except for the softening of the screening mass. We have first calculated the pressure of a thermal QCD medium in a strong magnetic field, where the pressure at fixed temperature increases with the magnetic field faster than the increase with the temperature at constant magnetic field. This can be understood from the dominant scale of thermal medium in the strong magnetic field, being the magnetic field, in the same way that the temperature dominates in a thermal medium in the absence of magnetic field. Thus although the presence of a strong magnetic field makes the pressure of hot QCD medium larger, the dependence of pressure on the temperature becomes less steep. Consistent with the above observations, the entropy density is found to decrease with the temperature in the presence of a strong magnetic field which is again consistent with the fact that the strong magnetic field restricts the dynamics of quarks to two dimensions, hence the phase space becomes squeezed resulting in the reduction of number of microstates. Moreover the energy density is seen to decrease and the speed of sound of thermal QCD medium increases in the presence of a strong magnetic field. These findings could have phenomenological implications in heavy ion collisions because the expansion dynamics of the medium produced in non-central ultra-relativistic heavy ion collisions is effectively controlled by both the energy density and the speed of sound.

AdS/QCD and Light Front Holography: A New Approximation to QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodsky, Stanley J.; de Teramond, Guy

2010-02-15

The combination of Anti-de Sitter space (AdS) methods with light-front holography leads to a semi-classical first approximation to the spectrum and wavefunctions of meson and baryon light-quark bound states. Starting from the bound-state Hamiltonian equation of motion in QCD, we derive relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. Its eigenvalues give themore » hadronic spectrum, and its eigenmodes represent the probability distribution of the hadronic constituents at a given scale. Applications to the light meson and baryon spectra are presented. The predicted meson spectrum has a string-theory Regge form M{sup 2} = 4{kappa}{sup 2}(n+L+S/2); i.e., the square of the eigenmass is linear in both L and n, where n counts the number of nodes of the wavefunction in the radial variable {zeta}. The space-like pion form factor is also well reproduced. One thus obtains a remarkable connection between the description of hadronic modes in AdS space and the Hamiltonian formulation of QCD in physical space-time quantized on the light-front at fixed light-front time {tau}. The model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms.« less

Evolution of the mean jet shape and dijet asymmetry distribution of an ensemble of holographic jets in strongly coupled plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brewer, Jasmine; Rajagopal, Krishna; Sadofyev, Andrey

Some of the most important experimentally accessible probes of the quark- gluon plasma (QGP) produced in heavy ion collisions come from the analysis of how the shape and energy of sprays of energetic particles produced within a cone with a specified opening angle (jets) in a hard scattering are modified by their passage through the strongly coupled, liquid, QGP. We model an ensemble of back-to-back dijets for the purpose of gaining a qualitative understanding of how the shapes of the individual jets and the asymmetry in the energy of the pairs of jets in the ensemble are modified by theirmore » passage through an expanding cooling droplet of strongly coupled plasma, in the model in a holographic gauge theory that is dual to a 4+1-dimensional black-hole spacetime that is asymptotically anti-de Sitter (AdS). We build our model by constructing an ensemble of strings in the dual gravitational description of the gauge theory. We model QCD jets in vacuum using strings whose endpoints are moving “downward” into the gravitational bulk spacetime with some fixed small angle, an angle that represents the opening angle (ratio of jet mass to jet energy) that the QCD jet would have in vacuum. Such strings must be moving through the gravitational bulk at (close to) the speed of light; they must be (close to) null. This condition does not specify the energy distribution along the string, meaning that it does not specify the shape of the jet being modeled. We study the dynamics of strings that are initially not null and show that strings with a wide range of initial conditions rapidly accelerate and become null and, as they do, develop a similar distribution of their energy density. We use this distribution of the energy density along the string, choose an ensemble of strings whose opening angles and energies are distributed as in perturbative QCD, and show that we can then fix one of the two model parameters such that the mean jet shape for the jets in the ensemble that we have built matches that measured in proton-proton collisions reasonably well. This is a novel way for hybridizing relevant inputs from perturbative QCD and a strongly coupled holographic gauge theory in the service of modeling jets in QGP. We send our ensemble of strings through an expanding cooling droplet of strongly coupled plasma, choosing the second model parameter so as to get a reasonable value for R AA jet , the suppression in the number of jets, and study how the mean jet shape and the dijet asymmetry are modified, comparing both to measurements from heavy ion collisions at the LHC.« less

Evolution of the mean jet shape and dijet asymmetry distribution of an ensemble of holographic jets in strongly coupled plasma

DOE PAGES

Brewer, Jasmine; Rajagopal, Krishna; Sadofyev, Andrey; ...

2018-02-02

Some of the most important experimentally accessible probes of the quark- gluon plasma (QGP) produced in heavy ion collisions come from the analysis of how the shape and energy of sprays of energetic particles produced within a cone with a specified opening angle (jets) in a hard scattering are modified by their passage through the strongly coupled, liquid, QGP. We model an ensemble of back-to-back dijets for the purpose of gaining a qualitative understanding of how the shapes of the individual jets and the asymmetry in the energy of the pairs of jets in the ensemble are modified by theirmore » passage through an expanding cooling droplet of strongly coupled plasma, in the model in a holographic gauge theory that is dual to a 4+1-dimensional black-hole spacetime that is asymptotically anti-de Sitter (AdS). We build our model by constructing an ensemble of strings in the dual gravitational description of the gauge theory. We model QCD jets in vacuum using strings whose endpoints are moving “downward” into the gravitational bulk spacetime with some fixed small angle, an angle that represents the opening angle (ratio of jet mass to jet energy) that the QCD jet would have in vacuum. Such strings must be moving through the gravitational bulk at (close to) the speed of light; they must be (close to) null. This condition does not specify the energy distribution along the string, meaning that it does not specify the shape of the jet being modeled. We study the dynamics of strings that are initially not null and show that strings with a wide range of initial conditions rapidly accelerate and become null and, as they do, develop a similar distribution of their energy density. We use this distribution of the energy density along the string, choose an ensemble of strings whose opening angles and energies are distributed as in perturbative QCD, and show that we can then fix one of the two model parameters such that the mean jet shape for the jets in the ensemble that we have built matches that measured in proton-proton collisions reasonably well. This is a novel way for hybridizing relevant inputs from perturbative QCD and a strongly coupled holographic gauge theory in the service of modeling jets in QGP. We send our ensemble of strings through an expanding cooling droplet of strongly coupled plasma, choosing the second model parameter so as to get a reasonable value for R AA jet , the suppression in the number of jets, and study how the mean jet shape and the dijet asymmetry are modified, comparing both to measurements from heavy ion collisions at the LHC.« less

Evolution of the mean jet shape and dijet asymmetry distribution of an ensemble of holographic jets in strongly coupled plasma

NASA Astrophysics Data System (ADS)

Brewer, Jasmine; Rajagopal, Krishna; Sadofyev, Andrey; van der Schee, Wilke

2018-02-01

Some of the most important experimentally accessible probes of the quark- gluon plasma (QGP) produced in heavy ion collisions come from the analysis of how the shape and energy of sprays of energetic particles produced within a cone with a specified opening angle (jets) in a hard scattering are modified by their passage through the strongly coupled, liquid, QGP. We model an ensemble of back-to-back dijets for the purpose of gaining a qualitative understanding of how the shapes of the individual jets and the asymmetry in the energy of the pairs of jets in the ensemble are modified by their passage through an expanding cooling droplet of strongly coupled plasma, in the model in a holographic gauge theory that is dual to a 4+1-dimensional black-hole spacetime that is asymptotically anti-de Sitter (AdS). We build our model by constructing an ensemble of strings in the dual gravitational description of the gauge theory. We model QCD jets in vacuum using strings whose endpoints are moving "downward" into the gravitational bulk spacetime with some fixed small angle, an angle that represents the opening angle (ratio of jet mass to jet energy) that the QCD jet would have in vacuum. Such strings must be moving through the gravitational bulk at (close to) the speed of light; they must be (close to) null. This condition does not specify the energy distribution along the string, meaning that it does not specify the shape of the jet being modeled. We study the dynamics of strings that are initially not null and show that strings with a wide range of initial conditions rapidly accelerate and become null and, as they do, develop a similar distribution of their energy density. We use this distribution of the energy density along the string, choose an ensemble of strings whose opening angles and energies are distributed as in perturbative QCD, and show that we can then fix one of the two model parameters such that the mean jet shape for the jets in the ensemble that we have built matches that measured in proton-proton collisions reasonably well. This is a novel way for hybridizing relevant inputs from perturbative QCD and a strongly coupled holographic gauge theory in the service of modeling jets in QGP. We send our ensemble of strings through an expanding cooling droplet of strongly coupled plasma, choosing the second model parameter so as to get a reasonable value for R AA jet , the suppression in the number of jets, and study how the mean jet shape and the dijet asymmetry are modified, comparing both to measurements from heavy ion collisions at the LHC.

Hard quark-quark scattering with exclusive reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barton, D.S.; Bunce, G.M.; Carroll, A.S.

1984-07-19

We have begun a program designed to study hard quark-quark scattering with exclusive reactions, focusing on quasi-elastic two-body reactions with all possible quark flavor exchanges. Examples are ..pi../sup -/p ..-->.. ..pi../sup -/p, rho/sup -/p, ..pi../sup +/..delta../sup -/, K/sup +/..sigma../sup -/, or K..lambda... Of the two-body exclusives, only elastic scattering had been measured at such large t previous to our experiment. By comparing the relative importance of different final states, the energy dependence of the production ratios of these states, the prominence of resonances such as rho/sup -/ over background in this region, and measuring polarizations where accessible, we have collectedmore » a large body of data on hard scattering in a completely new domain. Previously, essential all short distance QCD tests have been for inclusive processes. We have taken data with both negative and positive incident beam at 10 GeV/c on a hydrogen target and will present the first results, for ..pi../sup -/p ..-->.. ..pi../sup -/p and rho/sup -/p at THETA/sub cm/ = 90/sup 0/, -t = 9 GeV/sup 2//c/sup 2/. The apparatus consists of a magnetic spectrometer, with Cerenkov particle identification, which selects stable charged particles (protons in this case) at high momentum near 90/sup 0/ in the center-of-mass. A large aperture array of PWCs observes the recoil particle or charged decay products. Cross sections are extremely low, approximately a 1 nb/(GeV/c)/sup 2/ for elastic scattering. We will report on a sample of more than 1000 ..pi../sup -/p elastic events, and on rho/sup -/p, where the rho/sup -/ decay distribution was observed. We find a surprisingly large rho/sup -/p cross section in this large momentum transfer region, with rho/sup -/p about half the elastic cross section, and a striking spin alignment of the rho/sup -/.« less

Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS and CLAS12

DOE Office of Scientific and Technical Information (OSTI.GOV)

Philip L. Cole, Volker D. Burkert, Ralf W. Gothe, Victor I. Mokeev

2012-12-01

The CLAS detector at Jefferson Lab is a unique instrument, which has provided the lion's share of the world's data on meson photo- and electroproduction in the resonance excitation region. The electroexcitation amplitudes for the low-lying resonances P{sub 33} (1232), P{sub 11} (1440), D{sub 13} (1520), and S {sub 11} (1535) were determined over a wide range of Q{sub 2} < 5.0 GeV{sub 2} in a comprehensive analysis of exclusive single-meson ( {pi}{sup +} n, {pi}{sup 0} p) reactions in the electroproduction off protons. Further, we were able to precisely measure {pi}{sup +}{pi}{sup -}p electroproduction differential cross sections provided bymore » the nearly full kinematic coverage of the CLAS detector. And, for the first time, the electrocouplings of the P{sub 11} (1440), D{sub 13} (1520) excited states are determined from the exclusive-{pi}{sup +}{pi}{sup -}p reaction. Consistent results on the electrocouplings from two-independent analyses (single- and double-pion electroproduction) have provided compelling evidence for the reliable extraction of the N* electrocouplings. And preliminary results on the electrocouplings of the S{sub 31} (1620), S{sub 11} (1650), D{sub 33} (1700), and P{sub 13} (1720) states, which decay preferentially to the N{pi} {pi} final states, have recently become available. Theoretical analyses of these results have revealed that there are two major contributions to the resonance structure: a) an internal quark core and b) an external meson-baryon cloud. These CLAS results have had considerable impact on QCD-based studies on N* structure and in the search for manifestations of the dynamical masses of the dressed quarks. Future CLAS12 N* structure studies at high photon virtualities will considerably extend our capabilities in exploring the nature of confinement in baryons.« less

Shear viscosity of the quark-gluon plasma in a weak magnetic field in perturbative QCD: Leading log

NASA Astrophysics Data System (ADS)

Li, Shiyong; Yee, Ho-Ung

2018-03-01

We compute the shear viscosity of two-flavor QCD plasma in an external magnetic field in perturbative QCD at leading log order, assuming that the magnetic field is weak or soft: e B ˜g4log (1 /g )T2. We work in the assumption that the magnetic field is homogeneous and static, and the electrodynamics is nondynamical in a formal limit e →0 while e B is kept fixed. We show that the shear viscosity takes a form η =η ¯(B ¯)T3/(g4log (1 /g )) with a dimensionless function η ¯(B ¯) in terms of a dimensionless variable B ¯=(e B )/(g4log (1 /g )T2). The variable B ¯ corresponds to the relative strength of the effect of cyclotron motions compared to the QCD collisions: B ¯˜lmfp/lcyclo. We provide a full numerical result for the scaled shear viscosity η ¯(B ¯).

Heavy flavor puzzle at LHC: a serendipitous interplay of jet suppression and fragmentation.

PubMed

Djordjevic, Magdalena

2014-01-31

Both charged hadrons and D mesons are considered to be excellent probes of QCD matter created in ultrarelativistic heavy ion collisions. Surprisingly, recent experimental observations at LHC show the same jet suppression for these two probes, which--contrary to pQCD expectations--may suggest similar energy losses for light quarks and gluons in the QCD medium. We here use our recently developed energy loss formalism in a finite-size dynamical QCD medium to analyze this phenomenon that we denote as the "heavy flavor puzzle at LHC." We show that this puzzle is a consequence of an unusual combination of the suppression and fragmentation patterns and, in fact, does not require invoking the same energy loss for light partons. Furthermore, we show that this combination leads to a simple relationship between the suppressions of charged hadrons and D mesons and the corresponding bare quark suppressions. Consequently, a coincidental matching of jet suppression and fragmentation allows considerably simplifying the interpretation of the corresponding experimental data.

Wilson loops and QCD/string scattering amplitudes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makeenko, Yuri; Olesen, Poul; Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen O

2009-07-15

We generalize modern ideas about the duality between Wilson loops and scattering amplitudes in N=4 super Yang-Mills theory to large N QCD by deriving a general relation between QCD meson scattering amplitudes and Wilson loops. We then investigate properties of the open-string disk amplitude integrated over reparametrizations. When the Wilson-loop is approximated by the area behavior, we find that the QCD scattering amplitude is a convolution of the standard Koba-Nielsen integrand and a kernel. As usual poles originate from the first factor, whereas no (momentum-dependent) poles can arise from the kernel. We show that the kernel becomes a constant whenmore » the number of external particles becomes large. The usual Veneziano amplitude then emerges in the kinematical regime, where the Wilson loop can be reliably approximated by the area behavior. In this case, we obtain a direct duality between Wilson loops and scattering amplitudes when spatial variables and momenta are interchanged, in analogy with the N=4 super Yang-Mills theory case.« less

The QCD Equation of state and critical end-point estimates at O (μB6)

NASA Astrophysics Data System (ADS)

Sharma, Sayantan; Bielefeld-BNL-CCNU Collaboration

2017-11-01

We present results for the QCD Equation of State at non-zero chemical potentials corresponding to the conserved charges in QCD using Taylor expansion upto sixth order in the baryon number, electric charge and strangeness chemical potentials. The latter two are constrained by the strangeness neutrality and a fixed electric charge to baryon number ratio. In our calculations, we use the Highly Improved Staggered Quarks (HISQ) discretization scheme at physical quark masses and at different values of the lattice spacings to control lattice cut-off effects. Furthermore we calculate the pressure along lines of constant energy density, which serve as proxies for the freeze-out conditions and discuss their dependence on μB, which is necessary for hydrodynamic modelling near freezeout. We also provide an estimate of the radius of convergence of the Taylor series from the 6th order coefficients which provides a new constraint on the location of the critical end-point in the T-μB plane of the QCD phase diagram.

Regge spectra of excited mesons, harmonic confinement, and QCD vacuum structure

NASA Astrophysics Data System (ADS)

Nedelko, Sergei N.; Voronin, Vladimir E.

2016-05-01

An approach to QCD vacuum as a medium describable in terms of a statistical ensemble of almost everywhere homogeneous Abelian (anti-)self-dual gluon fields is briefly reviewed. These fields play the role of the confining medium for color charged fields as well as underline the mechanism of realization of chiral S UL(Nf)×S UR(Nf) and UA(1 ) symmetries. Hadronization formalism based on this ensemble leads to manifestly defined quantum effective meson action. Strong, electromagnetic, and weak interactions of mesons are represented in the action in terms of nonlocal n -point interaction vertices given by the quark-gluon loops averaged over the background ensemble. New systematic results for the mass spectrum and decay constants of radially excited light, heavy-light mesons, and heavy quarkonia are presented. The interrelation between the present approach, models based on ideas of soft-wall anti-de Sitter/QCD, light-front holographic QCD, and the picture of harmonic confinement is outlined.

Anomalous magnetic moment of the muon: A hybrid approach

NASA Astrophysics Data System (ADS)

Dominguez, C. A.; Horch, H.; Jäger, B.; Nasrallah, N. F.; Schilcher, K.; Spiesberger, H.; Wittig, H.

2017-10-01

A new QCD sum rule determination of the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, aμhvp, is proposed. This approach combines data on e+e- annihilation into hadrons, perturbative QCD and lattice QCD results for the first derivative of the electromagnetic current correlator at zero momentum transfer, ΠEM'(0 ). The idea is based on the observation that, in the relevant kinematic domain, the integration kernel K (s ), entering the formula relating aμhvp to e+e- annihilation data, behaves like 1 /s times a very smooth function of s , the squared energy. We find an expression for aμ in terms of ΠEM'(0 ), which can be calculated in lattice QCD. Using recent lattice results we find a good approximation for aμhvp, but the precision is not yet sufficient to resolve the discrepancy between the R (s ) data-based results and the experimentally measured value.

Implications of the principle of maximum conformality for the QCD strong coupling

DOE PAGES

Deur, Alexandre; Shen, Jian -Ming; Wu, Xing -Gang; ...

2017-08-14

The Principle of Maximum Conformality (PMC) provides scale-fixed perturbative QCD predictions which are independent of the choice of the renormalization scheme, as well as the choice of the initial renormalization scale. In this article, we will test the PMC by comparing its predictions for the strong couplingmore » $$\\alpha^s_{g_1}(Q)$$, defined from the Bjorken sum rule, with predictions using conventional pQCD scale-setting. The two results are found to be compatible with each other and with the available experimental data. However, the PMC provides a significantly more precise determination, although its domain of applicability ($$Q \\gtrsim 1.5$$ GeV) does not extend to as small values of momentum transfer as that of a conventional pQCD analysis ($$Q \\gtrsim 1$$ GeV). In conclusion, we suggest that the PMC range of applicability could be improved by a modified intermediate scheme choice or using a single effective PMC scale.« less

Moriond QCD 2013 Experimental Summary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denisov, Dmitri

2013-06-28

The article presents experimental highlights of Moriond 2013 QCD conference. This was fantastic conference and the first Moriond QCD since the discovery of the Higgs boson. Many new results about its properties have been presented at the conference with Higgs-like particle becoming a Higgs as it properties match expected for the Higgs boson pretty well. There were many new results presented in all experimental areas including QCD, elecroweak, studies of the top, bottom and charm quarks, searches for physics beyond Standard Model as well as studies of the heavy ion collisions. 56 experimental talks have been presented at the conferencemore » and it is impossible to cover each result in the summary, so highlights are limited to what I was able to present in my summary talk presented on March 16 2013. The proceedings of the conference cover in depth all talks presented and I urge you to get familiar with all of them. Theoretical Summary of the conference was given by Michelangelo Mangano, so theory talks are not covered in the article.« less

Freeze-out conditions in heavy ion collisions from QCD thermodynamics.

PubMed

Bazavov, A; Ding, H-T; Hegde, P; Kaczmarek, O; Karsch, F; Laermann, E; Mukherjee, Swagato; Petreczky, P; Schmidt, C; Smith, D; Soeldner, W; Wagner, M

2012-11-09

We present a determination of freeze-out conditions in heavy ion collisions based on ratios of cumulants of net electric charge fluctuations. These ratios can reliably be calculated in lattice QCD for a wide range of chemical potential values by using a next-to-leading order Taylor series expansion around the limit of vanishing baryon, electric charge and strangeness chemical potentials. From a computation of up to fourth order cumulants and charge correlations we first determine the strangeness and electric charge chemical potentials that characterize freeze-out conditions in a heavy ion collision and confirm that in the temperature range 150 MeV ≤ T ≤ 170 MeV the hadron resonance gas model provides good approximations for these parameters that agree with QCD calculations on the 5%-15% level. We then show that a comparison of lattice QCD results for ratios of up to third order cumulants of electric charge fluctuations with experimental results allows us to extract the freeze-out baryon chemical potential and the freeze-out temperature.

Searching for beauty-fully bound tetraquarks using lattice nonrelativistic QCD

NASA Astrophysics Data System (ADS)

Hughes, Ciaran; Eichten, Estia; Davies, Christine T. H.

2018-03-01

Motivated by multiple phenomenological considerations, we perform the first search for the existence of a b ¯b ¯b b tetraquark bound state with a mass below the lowest noninteracting bottomonium-pair threshold using the first-principles lattice nonrelativistic QCD methodology. We use a full S -wave color/spin basis for the b ¯b ¯b b operators in the three 0++, 1+- and 2++ channels. We employ four gluon field ensembles at multiple lattice spacing values ranging from a =0.06 - 0.12 fm , all of which include u , d , s and c quarks in the sea, and one ensemble which has physical light-quark masses. Additionally, we perform novel exploratory work with the objective of highlighting any signal of a near threshold tetraquark, if it existed, by adding an auxiliary potential into the QCD interactions. With our results we find no evidence of a QCD bound tetraquark below the lowest noninteracting thresholds in the channels studied.

Chiral phase transition at finite chemical potential in 2 +1 -flavor soft-wall anti-de Sitter space QCD

NASA Astrophysics Data System (ADS)

Bartz, Sean P.; Jacobson, Theodore

2018-04-01

The phase transition from hadronic matter to chirally symmetric quark-gluon plasma is expected to be a rapid crossover at zero quark chemical potential (μ ), becoming first order at some finite value of μ , indicating the presence of a critical point. Using a three-flavor soft-wall model of anti-de Sitter/QCD, we investigate the effect of varying the light and strange quark masses on the order of the chiral phase transition. At zero quark chemical potential, we reproduce the Columbia Plot, which summarizes the results of lattice QCD and other holographic models. We then extend this holographic model to examine the effects of finite quark chemical potential. We find that the the chemical potential does not affect the critical line that separates first-order from rapid crossover transitions. This excludes the possibility of a critical point in this model, suggesting that a different setup is necessary to reproduce all the features of the QCD phase diagram.

K-->pipi amplitudes from lattice QCD with a light charm quark.

PubMed

Giusti, L; Hernández, P; Laine, M; Pena, C; Wennekers, J; Wittig, H

2007-02-23

We compute the leading-order low-energy constants of the DeltaS=1 effective weak Hamiltonian in the quenched approximation of QCD with up, down, strange, and charm quarks degenerate and light. They are extracted by comparing the predictions of finite-volume chiral perturbation theory with lattice QCD computations of suitable correlation functions carried out with quark masses ranging from a few MeV up to half of the physical strange mass. We observe a DeltaI=1/2 enhancement in this corner of the parameter space of the theory. Although matching with the experimental result is not observed for the DeltaI=1/2 amplitude, our computation suggests large QCD contributions to the physical DeltaI=1/2 rule in the GIM limit, and represents the first step to quantify the role of the charm-quark mass in K-->pipi amplitudes. The use of fermions with an exact chiral symmetry is an essential ingredient in our computation.

End point of a first-order phase transition in many-flavor lattice QCD at finite temperature and density.

PubMed

Ejiri, Shinji; Yamada, Norikazu

2013-04-26

Towards the feasibility study of the electroweak baryogenesis in realistic technicolor scenario, we investigate the phase structure of (2+N(f))-flavor QCD, where the mass of two flavors is fixed to a small value and the others are heavy. For the baryogenesis, an appearance of a first-order phase transition at finite temperature is a necessary condition. Using a set of configurations of two-flavor lattice QCD and applying the reweighting method, the effective potential defined by the probability distribution function of the plaquette is calculated in the presence of additional many heavy flavors. Through the shape of the effective potential, we determine the critical mass of heavy flavors separating the first-order and crossover regions and find it to become larger with N(f). We moreover study the critical line at finite density and the first-order region is found to become wider as increasing the chemical potential. Possible applications to real (2+1)-flavor QCD are discussed.

Dual representation of lattice QCD with worldlines and worldsheets of Abelian color fluxes

NASA Astrophysics Data System (ADS)

Marchis, Carlotta; Gattringer, Christof

2018-02-01

We present a new dual representation for lattice QCD in terms of wordlines and worldsheets. The exact reformulation is carried out using the recently developed Abelian color flux method where the action is decomposed into commuting minimal terms that connect different colors on neighboring sites. Expanding the Boltzmann factors for these commuting terms allows one to reorganize the gauge field contributions according to links such that the gauge fields can be integrated out in closed form. The emerging constraints give the dual variables the structure of worldlines for the fermions and worldsheets for the gauge degrees of freedom. The partition sum has the form of a strong coupling expansion, and with the Abelian color flux approach discussed here all coefficients of the expansion are known in closed form. We present the dual form for three cases: pure SU(3) lattice gauge theory, strong coupling QCD and full QCD, and discuss in detail the constraints for the color fluxes and their physical interpretation.

Searching for beauty-fully bound tetraquarks using lattice nonrelativistic QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, Ciaran; Eichten, Estia; Davies, Christine T. H.

Motivated by multiple phenomenological considerations, we perform the first search for the existence of amore » $$\\bar{bb}bb$$ tetraquark bound state with a mass below the lowest noninteracting bottomonium-pair threshold using the first-principles lattice nonrelativistic QCD methodology. Here, we use a full S-wave color/spin basis for the $$\\bar{bb}bb$$ operators in the three 0 ++, 1 +- and 2 ++ channels. We employ four gluon field ensembles at multiple lattice spacing values ranging from a=0.06–0.12 fm, all of which include u, d, s and c quarks in the sea, and one ensemble which has physical light-quark masses. Additionally, we perform novel exploratory work with the objective of highlighting any signal of a near threshold tetraquark, if it existed, by adding an auxiliary potential into the QCD interactions. With our results we find no evidence of a QCD bound tetraquark below the lowest noninteracting thresholds in the channels studied.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caola, Fabrizio; Melnikov, Kirill; Rontsch, Raoul

We compute the next-to-leading-order QCD corrections to the production of two Z-bosons in the annihilation of two gluons at the LHC. Being enhanced by a large gluon flux, these corrections provide a distinct and, potentially, the dominant part of the N 3LO QCD contributions to Z-pair production in proton collisions. The gg → ZZ annihilation is a loop-induced process that receives the dominant contribution from loops of five light quarks, that are included in our computation in the massless approximation. We find that QCD corrections increase the gg → ZZ production cross section by O(50%–100%) depending on the values ofmore » the renormalization and factorization scales used in the leading-order computation and the collider energy. Furthermore, the large corrections to the gg → ZZ channel increase the pp → ZZ cross section by about 6% to 8%, exceeding the estimated theoretical uncertainty of the recent next-to-next-to-leading-order QCD calculation.« less

Symmetries and mass splittings QCD 2 coupled to adjoint fermions

NASA Astrophysics Data System (ADS)

Boorstein, Joshua; Kutasov, David

1994-06-01

Two-dimensional QCD coupled to fermions in the adjoint representation of the gauge group SU( N), a useful toy model of QCD strings, is supersymmetric for a certain ratio of quark mass and gauge coupling constant. Here we study the theory in the vicinity of the supersymmetric point; in particular we exhibit the algebraic structure of the model and show that the mass splittings as one moves away from the supersymmetric point obey a universal relation of the form Mi2(B)- Mi2(F) = Miδm + O( δm3). We discuss the connection of this relation to string and quark model expectations and verify it numerically for large N. At least for low lying states the O( δm3) corrections are extremely small. We also discuss a natural generalization of QCD 2 with an infinite number of couplings, which preserves SUSY. This leads to a Landau-Ginzburg description of the theory, and may be useful for defining a scaling limit in which smooth worldsheets appear.

Charmed tetraquarks Tcc and Tcs from dynamical lattice QCD simulations

NASA Astrophysics Data System (ADS)

Ikeda, Yoichi; Charron, Bruno; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

2014-02-01

Charmed tetraquarks Tcc=(ccubardbar) and Tcs=(csubardbar) are studied through the S-wave meson-meson interactions, D-D, Kbar-D, D-D* and Kbar-D*, on the basis of the (2+1)-flavor lattice QCD simulations with the pion mass mπ≃410, 570 and 700 MeV. For the charm quark, the relativistic heavy quark action is employed to treat its dynamics on the lattice. Using the HAL QCD method, we extract the S-wave potentials in lattice QCD simulations, from which the meson-meson scattering phase shifts are calculated. The phase shifts in the isospin triplet (I=1) channels indicate repulsive interactions, while those in the I=0 channels suggest attraction, growing as mπ decreases. This is particularly prominent in the Tcc (JP=1+,I=0) channel, though neither bound state nor resonance are found in the range mπ=410-700 MeV. We make a qualitative comparison of our results with the phenomenological diquark picture.

Searching for beauty-fully bound tetraquarks using lattice nonrelativistic QCD

DOE PAGES

Hughes, Ciaran; Eichten, Estia; Davies, Christine T. H.

2018-03-14

Motivated by multiple phenomenological considerations, we perform the first search for the existence of amore » $$\\bar{bb}bb$$ tetraquark bound state with a mass below the lowest noninteracting bottomonium-pair threshold using the first-principles lattice nonrelativistic QCD methodology. Here, we use a full S-wave color/spin basis for the $$\\bar{bb}bb$$ operators in the three 0 ++, 1 +- and 2 ++ channels. We employ four gluon field ensembles at multiple lattice spacing values ranging from a=0.06–0.12 fm, all of which include u, d, s and c quarks in the sea, and one ensemble which has physical light-quark masses. Additionally, we perform novel exploratory work with the objective of highlighting any signal of a near threshold tetraquark, if it existed, by adding an auxiliary potential into the QCD interactions. With our results we find no evidence of a QCD bound tetraquark below the lowest noninteracting thresholds in the channels studied.« less

Dissociation of 1P states in hot QCD Medium Using Quasi-Particle Model

NASA Astrophysics Data System (ADS)

Nilima, Indrani; Agotiya, Vineet Kumar

2018-03-01

We extend the analysis of a very recent work [1] to study the dissociation phenomenon of 1P states of the charmonium and bottomonium spectra (χc and χb) in a hot QCD medium using Quasi-Particle Model. This study employed a medium modified heavy quark potential which has quite different form in the sense that it has a lomg range Coulombic tail in addition to the Yukawa term even above the deconfinement temperature. Then we study the flavor dependence of their binding energies and explore the nature of dissociation temperatures by employing the Quasi-Particle debye mass for pure gluonic and full QCD case. Interestingly, the dissociation temperatures obtained by employing EoS1 and EoS2 with the Γ criterion, is closer to the upper bound of the dissociation temperatures which are obtained by the dissolution of a given quarkonia state by the mean thermal energy of the quasi-partons in the hot QCD/QGP medium.

Test Theory Reconceived.

ERIC Educational Resources Information Center

Mislevy, Robert J.

Educational test theory consists of statistical and methodological tools to support inferences about examinees' knowledge, skills, and accomplishments. The evolution of test theory has been shaped by the nature of users' inferences which, until recently, have been framed almost exclusively in terms of trait and behavioral psychology. Progress in…

Mass-improvement of the vector current in three-flavor QCD

NASA Astrophysics Data System (ADS)

Fritzsch, P.

2018-06-01

We determine two improvement coefficients which are relevant to cancel mass-dependent cutoff effects in correlation functions with operator insertions of the non-singlet local QCD vector current. This determination is based on degenerate three-flavor QCD simulations of non-perturbatively O( a) improved Wilson fermions with tree-level improved gauge action. Employing a very robust strategy that has been pioneered in the quenched approximation leads to an accurate estimate of a counterterm cancelling dynamical quark cutoff effects linear in the trace of the quark mass matrix. To our knowledge this is the first time that such an effect has been determined systematically with large significance.

Analytical Computation of Energy-Energy Correlation at Next-to-Leading Order in QCD [The Energy-Energy Correlation at Next-to-Leading Order in QCD, Analytically

DOE PAGES

Dixon, Lance J.; Luo, Ming-xing; Shtabovenko, Vladyslav; ...

2018-03-09

Here, the energy-energy correlation (EEC) between two detectors in e +e – annihilation was computed analytically at leading order in QCD almost 40 years ago, and numerically at next-to-leading order (NLO) starting in the 1980s. We present the first analytical result for the EEC at NLO, which is remarkably simple, and facilitates analytical study of the perturbative structure of the EEC. We provide the expansion of the EEC in the collinear and back-to-back regions through next-to-leading power, information which should aid resummation in these regions.

Neutron Electric Dipole Moment on the Lattice

NASA Astrophysics Data System (ADS)

Yoon, Boram; Bhattacharya, Tanmoy; Gupta, Rajan

2018-03-01

For the neutron to have an electric dipole moment (EDM), the theory of nature must have T, or equivalently CP, violation. Neutron EDM is a very good probe of novel CP violation in beyond the standard model physics. To leverage the connection between measured neutron EDM and novel mechanism of CP violation, one requires the calculation of matrix elements for CP violating operators, for which lattice QCD provides a first principle method. In this paper, we review the status of recent lattice QCD calculations of the contributions of the QCD Θ-term, the quark EDM term, and the quark chromo-EDM term to the neutron EDM.

Moment analysis of hadronic vacuum polarization. Proposal for a lattice QCD evaluation of gμ - 2

NASA Astrophysics Data System (ADS)

de Rafael, Eduardo

2014-09-01

I suggest a new approach to the determination of the hadronic vacuum polarization (HVP) contribution to the anomalous magnetic moment of the muon aμHVP in lattice QCD. It is based on properties of the Mellin transform of the hadronic spectral function and their relation to the HVP self-energy in the Euclidean. I show how aμHVP is very well approximated by a few moments associated to this Mellin transform and how these moments can be evaluated in lattice QCD, providing thus a series of tests when compared with the corresponding determinations using experimental data.

Constraints on spin-dependent parton distributions at large x from global QCD analysis

DOE PAGES

Jimenez-Delgado, P.; Avakian, H.; Melnitchouk, W.

2014-09-28

This study investigate the behavior of spin-dependent parton distribution functions (PDFs) at large parton momentum fractions x in the context of global QCD analysis. We explore the constraints from existing deep-inelastic scattering data, and from theoretical expectations for the leading x → 1 behavior based on hard gluon exchange in perturbative QCD. Systematic uncertainties from the dependence of the PDFs on the choice of parametrization are studied by considering functional forms motivated by orbital angular momentum arguments. Finally, we quantify the reduction in the PDF uncertainties that may be expected from future high-x data from Jefferson Lab at 12 GeV.

NLO QCD effective field theory analysis of W+W- production at the LHC including fermionic operators

NASA Astrophysics Data System (ADS)

Baglio, Julien; Dawson, Sally; Lewis, Ian M.

2017-10-01

We study the impact of anomalous gauge boson and fermion couplings on the production of W+W- pairs at the LHC. Helicity amplitudes are presented separately to demonstrate the sources of new physics contributions and the impact of QCD and electroweak corrections. The QCD corrections have important effects on the fits to anomalous couplings, in particular when one W boson is longitudinally polarized and the other is transversely polarized. In effective field theory language, we demonstrate that the dimension-6 approximation to constraining new physics effects in W+W- pair production fails at pT˜500 - 1000 GeV .

Universal Off-Equilibrium Scaling of Critical Cumulants in the QCD Phase Diagram

DOE PAGES

Mukherjee, Swagato; Venugopalan, Raju; Yin, Yi

2016-11-23

Exploiting the universality between the QCD critical point and the three-dimensional Ising model, closed form expressions derived for nonequilibrium critical cumulants on the crossover side of the critical point reveal that they can differ in both magnitude and sign from equilibrium expectations. Here, we demonstrate here that key elements of the Kibble-Zurek framework of nonequilibrium phase transitions can be employed to describe the dynamics of these critical cumulants. Lastly, our results suggest that observables sensitive to critical dynamics in heavy-ion collisions should be expressible as universal scaling functions, thereby providing powerful model-independent guidance in searches for the QCD critical point.

Flux tubes in the QCD vacuum

NASA Astrophysics Data System (ADS)

Cea, Paolo; Cosmai, Leonardo; Cuteri, Francesca; Papa, Alessandro

2017-06-01

The hypothesis that the QCD vacuum can be modeled as a dual superconductor is a powerful tool to describe the distribution of the color field generated by a quark-antiquark static pair and, as such, can provide useful clues for the understanding of confinement. In this work we investigate, by lattice Monte Carlo simulations of the S U (3 ) pure gauge theory and of (2 +1 )-flavor QCD with physical mass settings, some properties of the chromoelectric flux tube at zero temperature and their dependence on the physical distance between the static sources. We draw some conclusions about the validity domain of the dual superconductor picture.

Analytical Computation of Energy-Energy Correlation at Next-to-Leading Order in QCD [The Energy-Energy Correlation at Next-to-Leading Order in QCD, Analytically

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixon, Lance J.; Luo, Ming-xing; Shtabovenko, Vladyslav

Here, the energy-energy correlation (EEC) between two detectors in e +e – annihilation was computed analytically at leading order in QCD almost 40 years ago, and numerically at next-to-leading order (NLO) starting in the 1980s. We present the first analytical result for the EEC at NLO, which is remarkably simple, and facilitates analytical study of the perturbative structure of the EEC. We provide the expansion of the EEC in the collinear and back-to-back regions through next-to-leading power, information which should aid resummation in these regions.

Light composite scalar in twelve-flavor QCD on the lattice.

PubMed

Aoki, Yasumichi; Aoyama, Tatsumi; Kurachi, Masafumi; Maskawa, Toshihide; Nagai, Kei-ichi; Ohki, Hiroshi; Rinaldi, Enrico; Shibata, Akihiro; Yamawaki, Koichi; Yamazaki, Takeshi

2013-10-18

On the basis of lattice simulations using highly improved staggered quarks for twelve-flavor QCD with several bare fermion masses, we observe a flavor-singlet scalar state lighter than the pion in the correlators of fermionic interpolating operators. The same state is also investigated using correlators of gluonic interpolating operators. Combined with our previous study that showed twelve-flavor QCD to be consistent with being in the conformal window, we infer that the lightness of the scalar state is due to infrared conformality. This result shed some light on the possibility of a light composite Higgs boson ("technidilaton") in walking technicolor theories.

Bound H dibaryon in flavor SU(3) limit of lattice QCD.

PubMed

Inoue, Takashi; Ishii, Noriyoshi; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Ikeda, Yoichi; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

2011-04-22

The flavor-singlet H dibaryon, which has strangeness -2 and baryon number 2, is studied by the approach recently developed for the baryon-baryon interactions in lattice QCD. The flavor-singlet central potential is derived from the spatial and imaginary-time dependence of the Nambu-Bethe-Salpeter wave function measured in N(f)=3 full QCD simulations with the lattice size of L≃2,3,4  fm. The potential is found to be insensitive to the volume, and it leads to a bound H dibaryon with the binding energy of 30-40 MeV for the pseudoscalar meson mass of 673-1015 MeV.

Strong-Isospin-Breaking Correction to the Muon Anomalous Magnetic Moment from Lattice QCD at the Physical Point

NASA Astrophysics Data System (ADS)

Chakraborty, B.; Davies, C. T. H.; Detar, C.; El-Khadra, A. X.; Gámiz, E.; Gottlieb, Steven; Hatton, D.; Koponen, J.; Kronfeld, A. S.; Laiho, J.; Lepage, G. P.; Liu, Yuzhi; MacKenzie, P. B.; McNeile, C.; Neil, E. T.; Simone, J. N.; Sugar, R.; Toussaint, D.; van de Water, R. S.; Vaquero, A.; Fermilab Lattice, Hpqcd,; Milc Collaborations

2018-04-01

All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction to aμHVP for the first time with physical values of mu and md and dynamical u , d , s , and c quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of δ aμHVP ,mu≠md=+1.5 (7 )% , in agreement with estimates from phenomenology.

η and η' mesons from lattice QCD.

PubMed

Christ, N H; Dawson, C; Izubuchi, T; Jung, C; Liu, Q; Mawhinney, R D; Sachrajda, C T; Soni, A; Zhou, R

2010-12-10

The large mass of the ninth pseudoscalar meson, the η', is believed to arise from the combined effects of the axial anomaly and the gauge field topology present in QCD. We report a realistic, 2+1-flavor, lattice QCD calculation of the η and η' masses and mixing which confirms this picture. The physical eigenstates show small octet-singlet mixing with a mixing angle of θ=-14.1(2.8)°. Extrapolation to the physical light quark mass gives, with statistical errors only, mη=573(6) MeV and mη'=947(142) MeV, consistent with the experimental values of 548 and 958 MeV.

QCD sum rules study of meson-baryon sigma terms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erkol, Gueray; Oka, Makoto; Turan, Guersevil

2008-11-01

The pion-baryon sigma terms and the strange-quark condensates of the octet and the decuplet baryons are calculated by employing the method of QCD sum rules. We evaluate the vacuum-to-vacuum transition matrix elements of two baryon interpolating fields in an external isoscalar-scalar field and use a Monte Carlo-based approach to systematically analyze the sum rules and the uncertainties in the results. We extract the ratios of the sigma terms, which have rather high accuracy and minimal dependence on QCD parameters. We discuss the sources of uncertainties and comment on possible strangeness content of the nucleon and the Delta.

Coupled-channel approach to strangeness S = -2 baryon-bayron interactions in lattice QCD

NASA Astrophysics Data System (ADS)

Sasaki, Kenji; Aoki, Sinya; Doi, Takumi; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Ishii, Noriyoshi; Murano, Keiko

2015-11-01

Baryon-baryon interactions with strangeness S=-2 with flavor SU(3) breaking are calculated for the first time by using the HAL QCD method extended to the coupled-channel system in lattice QCD. The potential matrices are extracted from the Nambu-Bethe-Salpeter wave functions obtained by the 2+1-flavor gauge configurations of the CP-PACS/JLQCD Collaborations with a physical volume of (1.93 fm)^3 and with m_{π }/m_K=0.96, 0.90, 0.86. The spatial structure and the quark mass dependence of the potential matrix in the baryon basis and in the SU(3) basis are investigated.

Renormalization of QCD in the interpolating momentum subtraction scheme at three loops

NASA Astrophysics Data System (ADS)

Gracey, J. A.; Simms, R. M.

2018-04-01

We introduce a more general set of kinematic renormalization schemes than the original momentum subtraction schemes of Celmaster and Gonsalves. These new schemes will depend on a parameter ω , which tags the external momentum of one of the legs of the three-point vertex functions in QCD. In each of the three new schemes, we renormalize QCD in the Landau and maximal Abelian gauges and establish the three-loop renormalization group functions in each gauge. For an application, we evaluate two critical exponents at the Banks-Zaks fixed point and demonstrate that their values appear to be numerically scheme independent in a subrange of the conformal window.

A computational system for lattice QCD with overlap Dirac quarks

NASA Astrophysics Data System (ADS)

Chiu, Ting-Wai; Hsieh, Tung-Han; Huang, Chao-Hsi; Huang, Tsung-Ren

2003-05-01

We outline the essential features of a Linux PC cluster which is now being developed at National Taiwan University, and discuss how to optimize its hardware and software for lattice QCD with overlap Dirac quarks. At present, the cluster constitutes of 30 nodes, with each node consisting of one Pentium 4 processor (1.6/2.0 GHz), one Gbyte of PC800 RDRAM, one 40/80 Gbyte hard disk, and a network card. The speed of this system is estimated to be 30 Gflops, and its price/performance ratio is better than $1.0/Mflops for 64-bit (double precision) computations in quenched lattice QCD with overlap Dirac quarks.

Strong-Isospin-Breaking Correction to the Muon Anomalous Magnetic Moment from Lattice QCD at the Physical Point

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, B.; Davies, C. T. H.; DeTar, C.

All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon’s anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction tomore » $${a}_{{\\mu}}^{\\mathrm{HVP}}$$ for the first time with physical values of $${m}_{u}$$ and $${m}_{d}$$ and dynamical $u$, $d$, $s$, and $c$ quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of $${\\delta}{a}_{{\\mu}}^{\\mathrm{HVP},{m}_{u}{\

Strong-Isospin-Breaking Correction to the Muon Anomalous Magnetic Moment from Lattice QCD at the Physical Point

DOE PAGES

Chakraborty, B.; Davies, C. T. H.; DeTar, C.; ...

2018-04-12

All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon’s anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction tomore » $${a}_{{\\mu}}^{\\mathrm{HVP}}$$ for the first time with physical values of $${m}_{u}$$ and $${m}_{d}$$ and dynamical $u$, $d$, $s$, and $c$ quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of $${\\delta}{a}_{{\\mu}}^{\\mathrm{HVP},{m}_{u}{\

Cyclic Mario worlds — color-decomposition for one-loop QCD

NASA Astrophysics Data System (ADS)

Kälin, Gregor

2018-04-01

We present a new color decomposition for QCD amplitudes at one-loop level as a generalization of the Del Duca-Dixon-Maltoni and Johansson-Ochirov decomposition at tree level. Starting from a minimal basis of planar primitive amplitudes we write down a color decomposition that is free of linear dependencies among appearing primitive amplitudes or color factors. The conjectured decomposition applies to any number of quark flavors and is independent of the choice of gauge group and matter representation. The results also hold for higher-dimensional or supersymmetric extensions of QCD. We provide expressions for any number of external quark-antiquark pairs and gluons. [Figure not available: see fulltext.

Cooperative breeding and monogamy in mammalian societies

PubMed Central

Lukas, Dieter; Clutton-Brock, Tim

2012-01-01

Comparative studies of social insects and birds show that the evolution of cooperative and eusocial breeding systems has been confined to species where females mate completely or almost exclusively with a single male, indicating that high levels of average kinship between group members are necessary for the evolution of reproductive altruism. In this paper, we show that in mammals, the evolution of cooperative breeding has been restricted to socially monogamous species which currently represent 5 per cent of all mammalian species. Since extra-pair paternity is relatively uncommon in socially monogamous and cooperatively breeding mammals, our analyses support the suggestion that high levels of average kinship between group members have played an important role in the evolution of cooperative breeding in non-human mammals, as well as in birds and insects. PMID:22279167

Increasing total cross sections and flavoring of Pomeron in QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Chung-I.

A unified treatment of both the elastic and inelastic hadronic production is presented from the viewpoint of a topological expansion of nonperturbative QCD. The phenomenon of increasing total cross sections is examined and its relation to the flavoring of Pomeron is clarified. 12 refs.

Drell-Yan Lepton pair production at NNLO QCD with parton showers

DOE PAGES

Hoeche, Stefan; Li, Ye; Prestel, Stefan

2015-04-13

We present a simple approach to combine NNLO QCD calculations and parton showers, based on the UNLOPS technique. We apply the method to the computation of Drell-Yan lepton-pair production at the Large Hadron Collider. We comment on possible improvements and intrinsic uncertainties.

Surface energy from order parameter profile: At the QCD phase transition

NASA Technical Reports Server (NTRS)

Frei, Z.; Patkos, A.

1989-01-01

The order parameter profile between coexisting confined and plasma regions at the quantum chromodynamic (QCD) phase transition is constructed. The dimensionless combination of the surface energy (Sigma) and the correlation length (Zeta) is estimated to be Sigma Zeta 3 approximately equals 0.8.

Importance of proper renormalization scale-setting for QCD testing at colliders

DOE PAGES

Wu, Xing -Gang; Wang, Sheng -Quan; Brodsky, Stanley J.

2015-12-22

A primary problem affecting perturbative quantum chromodynamic (pQCD) analyses is the lack of a method for setting the QCD running-coupling renormalization scale such that maximally precise fixed-order predictions for physical observables are obtained. The Principle of Maximum Conformality (PMC) eliminates the ambiguities associated with the conventional renormalization scale-setting procedure, yielding predictions that are independent of the choice of renormalization scheme. The QCD coupling scales and the effective number of quark flavors are set order-by-order in the pQCD series. The PMC has a solid theoretical foundation, satisfying the standard renormalization group invariance condition and all of the self-consistency conditions derived frommore » the renormalization group. The PMC scales at each order are obtained by shifting the arguments of the strong force coupling constant αs to eliminate all non-conformal {βi} terms in the pQCD series. The {βi} terms are determined from renormalization group equations without ambiguity. The correct behavior of the running coupling at each order and at each phase-space point can then be obtained. The PMC reduces in the N C → 0 Abelian limit to the Gell-Mann-Low method. In this brief report, we summarize the results of our recent application of the PMC to a number of collider processes, emphasizing the generality and applicability of this approach. A discussion of hadronic Z decays shows that, by applying the PMC, one can achieve accurate predictions for the total and separate decay widths at each order without scale ambiguities. We also show that, if one employs the PMC to determine the top-quark pair forward-backward asymmetry at the next-to-next-to-leading order level, one obtains a comprehensive, self-consistent pQCD explanation for the Tevatron measurements of the asymmetry. This accounts for the “increasing-decreasing” behavior observed by the D0 collaboration for increasing tt¯ invariant mass. At lower energies, the angular distributions of heavy quarks can be used to obtain a direct determination of the heavy quark potential. A discussion of the angular distributions of massive quarks and leptons is also presented, including the fermionic component of the two-loop corrections to the electromagnetic form factors. Furthermore, these results demonstrate that the application of the PMC systematically eliminates a major theoretical uncertainty for pQCD predictions, thus increasing collider sensitivity to possible new physics beyond the Standard Model.« less

Hadronic decays of B →a1(1260 )b1(1235 ) in the perturbative QCD approach

NASA Astrophysics Data System (ADS)

Jing, Hao-Yang; Liu, Xin; Xiao, Zhen-Jun

2017-12-01

We calculate the branching ratios and polarization fractions of the B →a1b1 decays in the perturbative QCD(pQCD) approach at leading order, where a1(b1) stands for the axial-vector a1(1260 )[b1(1235 )] state. By combining the phenomenological analyses with the perturbative calculations, we find the following results: (a) the large decay rates around 10-5 to 10-6 of the B →a1b1 decays dominated by the longitudinal polarization(except for the B+→b1+a10 mode) are predicted and basically consistent with those in the QCD factorization(QCDF) within errors, which are expected to be tested by the Large Hadron Collider and Belle-II experiments. The large B0→a10b10 branching ratio could provide hints to help explore the mechanism of the color-suppressed decays. (b) the rather different QCD behaviors between the a1 and b1 mesons result in the destructive(constructive) contributions in the nonfactorizable spectator diagrams with a1(b1) emission. Therefore, an interesting pattern of the branching ratios appears for the color-suppressed B0→a10a10,a10b10, and b10b10 modes in the pQCD approach, BR (B0→b10b10)>BR (B0→a10b10)≳BR (B0→a10a10), which is different from BR (B0→b10b10)˜BR (B0→a10b10)≳BR (B0→a10a10) in the QCDF and would be verified at future experiments. (c) the large naive factorization breaking effects are observed in these B →a1b1 decays. Specifically, the large nonfactorizable spectator(weak annihilation) amplitudes contribute to the B0→b1+a1-(B+→a1+b10andB+→b1+a10) mode(s), which demand confirmations via the precise measurements. Furthermore, the different phenomenologies shown among B →a1b1, B →a1a1, and B →b1b1 decays are also expected to be tested stringently, which could shed light on the typical QCD dynamics involved in these modes, even further distinguish those two popular pQCD and QCDF approaches.

How hadron collider experiments contributed to the development of QCD: from hard-scattering to the perfect liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tannenbaum, M. J.

A revolution in elementary particle physics occurred during the period from the ICHEP1968 to the ICHEP1982 with the advent of the parton model from discoveries in Deeply Inelastic electron-proton Scattering at SLAC, neutrino experiments, hard-scattering observed in p+p collisions at the CERN ISR, the development of QCD, the discovery of the J/Ψ at BNL and SLAC and the clear observation of high transverse momentum jets at the CERN SPSmore » $$\\bar{p}$$ + p collider. These and other discoveries in this period led to the acceptance of QCD as the theory of the strong interactions. The desire to understand nuclear physics at high density such as in neutron stars led to the application of QCD to this problem and to the prediction of a Quark-Gluon Plasma (QGP) in nuclei at high energy density and temperatures. This eventually led to the construction of the Relativistic Heavy Ion Collider (RHIC) at BNL to observe superdense nuclear matter in the laboratory. This article discusses how experimental methods and results which confirmed QCD at the first hadron collider, the CERN ISR, played an important role in experiments at the first heavy ion collider, RHIC, leading to the discovery of the QGP as a perfect liquid as well as discoveries at RHIC and the LHC which continue to the present day.« less

How hadron collider experiments contributed to the development of QCD: from hard-scattering to the perfect liquid

DOE PAGES

Tannenbaum, M. J.

2018-01-30

A revolution in elementary particle physics occurred during the period from the ICHEP1968 to the ICHEP1982 with the advent of the parton model from discoveries in Deeply Inelastic electron-proton Scattering at SLAC, neutrino experiments, hard-scattering observed in p+p collisions at the CERN ISR, the development of QCD, the discovery of the J/Ψ at BNL and SLAC and the clear observation of high transverse momentum jets at the CERN SPSmore » $$\\bar{p}$$ + p collider. These and other discoveries in this period led to the acceptance of QCD as the theory of the strong interactions. The desire to understand nuclear physics at high density such as in neutron stars led to the application of QCD to this problem and to the prediction of a Quark-Gluon Plasma (QGP) in nuclei at high energy density and temperatures. This eventually led to the construction of the Relativistic Heavy Ion Collider (RHIC) at BNL to observe superdense nuclear matter in the laboratory. This article discusses how experimental methods and results which confirmed QCD at the first hadron collider, the CERN ISR, played an important role in experiments at the first heavy ion collider, RHIC, leading to the discovery of the QGP as a perfect liquid as well as discoveries at RHIC and the LHC which continue to the present day.« less