Boost covariant gluon distributions in large nuclei
NASA Astrophysics Data System (ADS)
McLerran, Larry; Venugopalan, Raju
1998-04-01
It has been shown recently that there exist analytical solutions of the Yang-Mills equations for non-Abelian Weizsäcker-Williams fields which describe the distribution of gluons in large nuclei at small x. These solutions however depend on the color charge distribution at large rapidities. We here construct a model of the color charge distribution of partons in the fragmentation region and use it to compute the boost covariant momentum distributions of wee gluons. The phenomenological applications of our results are discussed.
The gluon Sivers distribution: Status and future prospects
Boer, Daniël; Lorcé, Cédric; Pisano, Cristian; Zhou, Jian
2015-06-28
In this study, we review what is currently known about the gluon Sivers distribution and what are the opportunities to learn more about it. Because single transverse spin asymmetries in p↑p → πX provide only indirect information about the gluon Sivers function through the relation with the quark-gluon and tri-gluon Qiu-Sterman functions, current data from hadronic collisions at RHIC have not yet been translated into a solid constraint on the gluon Sivers function.
Universality of Unintegrated Gluon Distributions at small x
Dominguez, Fabio; Marquet, Cyrille; Xiao, Bowen; Yuan, Feng
2011-01-04
We systematically study dijet production in various processes in the small-x limit and establish an effective kt-factorization for hard processes in a system with dilute probes scattering on a dense target. In the large-Nc limit, the unintegrated gluon distributions involved in different processes are shown to be related to two widely proposed ones: the Weizsacker-Williams gluon distribution and the dipole gluon distribution.
NASA Astrophysics Data System (ADS)
Devee, Mayuri; Sarma, J. K.
2014-03-01
In this paper we have determined the behavior of gluon distribution function by solving the Gribov-Levin-Reskin-Mueller-Qiu (GLR-MQ) evolution equation,which is nonlinear in gluon density. The moderate Q2 behavior of G(x, t), where t = ln(Q2/Λ2), is obtained by employing the Regge like behaviour of gluon distribution function at small-x. Here Q2 behavior of nonlinear gluon distribution function is investigated for small values x = 10-2, 10-3, 10-4 and 10-5 rexpectively. Our predictions are compared with different parametrisations and are found in good agreement. It is observed from our results that with the nonlinear corrections incorporated, the strong growth of G(x,t) that corresponds to the linear QCD evolution equation is slowed down. Moreover essential taming of gluon distribution function is observed for R = 2 GeV-1 as expected.
The η (η‧) gamma transition form factor and the gluon-gluon distribution amplitude
NASA Astrophysics Data System (ADS)
Kroll, P.; Passek-Kumerički, K.
2013-07-01
The ηγ and η‧γ transition form factors are analyzed to leading-twist accuracy and next-to-leading order of perturbative QCD. Using an η-η‧ mixing scheme and all currently available experimental data the lowest Gegenbauer coefficients of the distribution amplitudes for the valence octet and singlet q\\bar{q} and the gluon-gluon Fock components are extracted. Predictions for the g*g*η‧ vertex function are presented. We also comment on the new BELLE results for the πγ transition form factor.
Accessing the Distribution of Linearly Polarized Gluons in Unpolarized Hadrons
Boer, Daniel; Brodsky, Stanley J.; Mulders, Piet J.; Pisano, Cristian; /Cagliari U. /INFN, Cagliari
2011-08-19
Gluons inside unpolarized hadrons can be linearly polarized provided they have a nonzero transverse momentum. The simplest and theoretically safest way to probe this distribution of linearly polarized gluons is through cos2{phi} asymmetries in heavy quark pair or dijet production in electron-hadron collisions. Future Electron-Ion Collider (EIC) or Large Hadron electron Collider (LHeC) experiments are ideally suited for this purpose. Here we estimate the maximum asymmetries for EIC kinematics.
QCD constraints on the shape of polarized quark and gluon distributions
NASA Astrophysics Data System (ADS)
Brodsky, Stanley J.; Burkardt, Matthias; Schmidt, Ivan
1995-02-01
We develop simple analytic representations of the polarized quark and gluon distributions in the nucleon at low Q2 which incorporate general constraints obtained from the requirements of color coherence of gluon couplings at x ˜ 0 and the helicity retention properties of perturbative QCD couplings at x ˜ 1. The unpolarized predictions are similar to the Do' distributions given by Martin, Roberts, and Stirling. The predictions for the quark helicity distributions are compared with polarized structure functions measured by the E142 experiment at SLAC and the SMC experiment at CERN.
Polarized Parton Distributions and the Polarized Gluon Asymmetry
NASA Astrophysics Data System (ADS)
Ramsey, Gordon P.
The flavor-dependent valence, sea quark and antiquark spin distributions can be determined separately from theoretical assumptions and experimental data. We have determined the valence distributions using the Bjorken sum rule and have extracted polarized sea distributions, assuming that the quarks and anti-quarks for each flavor are symmetric. Other experiments have been proposed which will allow us to completely break the SU(3) symmetry of the sea flavors. To create a physical model for the polarized gluons, we investigate the gluon spin asymmetry in a proton, AG(x, Q2) = (Δ G(x, Q2))/(G(x, Q2)). By assuming that htis is is approximately Q2 invariant, we can completely determine the x-dependence of this asymmetry, which satisfies constituent counting rules and reproduces the basic results of the Bremsstrahlung model originated by Close and Sivers. This asymmetry can be combined with the measured unpolarized gluon density, G(x,Q2) to provide a prediction for Δ G(x,Q2). Existing and proposed experiments can test both the prediction of scale-invariance for AG(x,Q2) and the nature of Δ G itself. These models will be discussed along with suggestions for specific experiments which can be performed at energies typical of HERA, RHIC and LHC to determine the nature of these polarized distributions.
How large is the gluon polarization in the statistical parton distributions approach?
Soffer, Jacques; Bourrely, Claude; Buccella, Franco
2015-04-10
We review the theoretical foundations of the quantum statistical approach to parton distributions and we show that by using some recent experimental results from Deep Inelastic Scattering, we are able to improve the description of the data by means of a new determination of the parton distributions. We will see that a large gluon polarization emerges, giving a significant contribution to the proton spin.
Lipatov, A. V.
2006-09-15
The inclusive production of heavy quarks and quarkonia in photon-photon collisions at the LEP2 collider is considered within the semihard (k{sub T}-factorization) QCD approach. The dependence of the total and differential cross sections for the production of heavy (c and b) quarks and D* and J/{psi} mesons on the choice of unintegrated gluon distribution is studied. The transition of a cc-bar charmed pair to observed J/{psi} mesons is described on the basis of the color-singlet model. The results of the calculations are compared with currently available experimental data obtained by the L3, OPAL, ALEPH, and DELPHI Collaborations. It is shown that the polarization properties of J/{psi} mesons at the LEP2 collider are sensitive to the behavior of unintegrated gluon distributions. This means that experimental investigations of the polarization properties of quarkonia in photon-photon collisions may provide a direct test of the dynamics of gluon distributions in the photon.
Gluons and the Quark Sea at High Energies: Distributions, Polarization, Tomography
Boer, Daniel; Diehl, Markus; Milner, Richard; Venugopalan, Raju; Vogelsang, Werner; Kaplan, David; Montgomery, Hugh; Vigdor, Steven; Accardi, A.; Aschenauer, E.C.; Burkardt, M.; Ent, R.; Guzey, V.; Hasch, D.; Kumar, K.; Lamont, M.A.C.; Li, Ying-chuan; Marciano, W.; Marquet, C.; Sabatie, F.; Stratmann, M.; /more authors..
2012-06-07
This report on the science case for an Electron-Ion Collider (EIC) is the result of a ten-week program at the Institute for Nuclear Theory (INT) in Seattle (from September 13-November 19, 2010), motivated by the need to develop a strong case for the continued study of the QCD description of hadron structure in the coming decades. Hadron structure in the valence quark region will be studied extensively with the Jefferson Lab 12 GeV science program, the subject of an INT program the previous year. The focus of the INT program was on understanding the role of gluons and sea quarks, the important dynamical degrees of freedom describing hadron structure at high energies. Experimentally, the most direct and precise way to access the dynamical structure of hadrons and nuclei at high energies is with a high luminosity lepton probe in collider mode. An EIC with optimized detectors offers enormous potential as the next generation accelerator to address many of the most important, open questions about the fundamental structure of matter. The goal of the INT program, as captured in the writeups in this report, was to articulate these questions and to identify golden experiments that have the greatest potential to provide definitive answers to these questions. At resolution scales where quarks and gluons become manifest as degrees of freedom, the structure of the nucleon and of nuclei is intimately connected with unique features of QCD dynamics, such as confinement and the self-coupling of gluons. Information on hadron sub-structure in DIS is obtained in the form of 'snapshots' by the 'lepton microscope' of the dynamical many-body hadron system, over different momentum resolutions and energy scales. These femtoscopic snapshots, at the simplest level, provide distribution functions which are extracted over the largest accessible kinematic range to assemble fundamental dynamical insight into hadron and nuclear sub-structure. For the proton, the EIC would be the brightest
High energy resummation of transverse momentum distributions: Higgs in gluon fusion
NASA Astrophysics Data System (ADS)
Forte, Stefano; Muselli, Claudio
2016-03-01
We derive a general resummation formula for transverse-momentum distributions of hard processes at the leading logarithmic level in the high-energy limit, to all orders in the strong coupling. Our result is based on a suitable generalization of high-energy factorization theorems, whereby all-order resummation is reduced to the determination of the Born-level process but with incoming off-shell gluons. We validate our formula by applying it to Higgs production in gluon fusion in the infinite top mass limit. We check our result up to next-to-leading order by comparison to the high energy limit of the exact expression and to next-to-next-to leading order by comparison to NNLL transverse momentum (Sudakov) resummation, and we predict the high-energy behaviour at next3-to-leading order. We also show that the structure of the result in the small transverse momentum limit agrees to all orders with general constraints from Sudakov resummation.
Classical gluon production amplitude in heavy-ion collisions
NASA Astrophysics Data System (ADS)
Chirilli, Giovanni Antonio
2016-03-01
The distribution of quarks and gluons produced in the initial stages of nuclear collisions, known as the initial condition of the Quark-Gluon Plasma formation, is the fundamental building block of heavy-ion theory. I will present the scattering amplitude, beyond the leading order, of the classical gluon produced in heavy-ion collisions. The result is obtained in the framework of saturation physics and Wilson lines formalism.
NASA Astrophysics Data System (ADS)
Boer, Daniël
2016-03-01
A high-energy Electron-Ion Collider (EIC) would offer a most promising tool to study in detail the transverse momentum distributions of gluons inside hadrons. This applies to unpolarized as well as linearly polarized gluons inside unpolarized protons, and to left-right asymmetric distributions of gluons inside transversely polarized protons, the so-called gluon Sivers effect. The inherent process dependence of these distributions can be studied by comparing to similar, but often complementary observables at LHC.
Rapidity distribution of photons from an anisotropic quark-gluon plasma
Bhattacharya, Lusaka; Roy, Pradip
2010-05-15
We calculate rapidity distribution of photons due to Compton and annihilation processes from quark gluon plasma with pre-equilibrium momentum-space anisotropy. We also include contributions from hadronic matter with late-stage transverse expansion. A phenomenological model has been used for the time evolution of hard momentum scale, p{sub hard}(tau), and anisotropy parameter, xi(tau). As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of photons rapidity distribution. For example, with the fixed initial condition (FIC) free-streaming (delta=2) interpolating model we observe significant enhancement of photon rapidity distribution at fixed p{sub T}, where as for FIC collisionally broadened (delta=2/3) interpolating model the yield increases till yapprox1. Beyond that suppression is observed. With fixed final multiplicity (FFM) free-streaming interpolating model we predict enhancement of photon yield which is less than the case of FIC. Suppression is always observed for FFM collisionally broadened interpolating model.
NASA Astrophysics Data System (ADS)
Grinyuk, A. A.; Lipatov, A. V.; Lykasov, G. I.; Zotov, N. P.
2016-01-01
We study the role of the nonperturbative input to the transverse momentum dependent (TMD) gluon density in hard processes at the LHC. We derive the input TMD gluon distribution at a low scale μ02˜1 GeV2 from a fit of inclusive hadron spectra measured at low transverse momenta in p p collisions at the LHC and demonstrate that the best description of these spectra for larger hadron transverse momenta can be achieved by matching the derived TMD gluon distribution with the exact solution of the Balitsky-Fadin-Kuraev-Lipatov equation obtained at low x and small gluon transverse momenta outside the saturation region. Then, we extend the input TMD gluon density to higher μ2 numerically using the Catani-Ciafoloni-Fiorani-Marchesini gluon evolution equation. Special attention is paid to phenomenological applications of the obtained TMD gluon density to some LHC processes, which are sensitive to the gluon content of a proton.
Soft-Gluon Resummation and the Valence Parton Distribution Function of the Pion
Aicher, Matthias; Schaefer, Andreas; Vogelsang, Werner
2010-12-17
We determine the valence parton distribution function of the pion by performing a new analysis of data for the Drell-Yan process {pi}{sup -}N{yields}{mu}{sup +}{mu}{sup -}X. Compared to previous analyses, we include next-to-leading-logarithmic threshold resummation effects in the calculation of the Drell-Yan cross section. As a result of these, we find a considerably softer valence distribution at high momentum fractions x than obtained in previous next-to-leading-order analyses, in line with expectations based on perturbative-QCD counting rules or Dyson-Schwinger equations.
Gluons and the quark sea at high energies: distributions, polarization, tomography
Boer, D.; Venugopalan, R.; Diehl, M.; Milner, R.; Vogelsang, W.; et al.
2011-09-30
This report is based on a ten-week program on Gluons and the quark sea at high-energies, which took place at the Institute for Nuclear Theory (INT) in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics (QCD). This report is organized around the following four major themes: (i) the spin and flavor structure of the proton, (ii) three dimensional structure of nucleons and nuclei in momentum and configuration space, (iii) QCD matter in nuclei, and (iv) Electroweak physics and the search for physics beyond the Standard Model. Beginning with an executive summary, the report contains tables of key measurements, chapter overviews for each of the major scientific themes, and detailed individual contributions on various aspects of the scientific opportunities presented by an EIC.
NASA Astrophysics Data System (ADS)
Adams, M. R.; Aïd, S.; Anthony, P. L.; Baker, M. D.; Bartlett, J.; Bhatti, A. A.; Braun, H. M.; Busza, W.; Carroll, T. J.; Conrad, J. M.; Coutrakon, G.; Davisson, R.; Derado, I.; Dhawan, S. K.; Dougherty, W.; Dreyer, T.; Dziunikowska, K.; Eckardt, V.; Ecker, U.; Erdmann, M.; Eskreys, A.; Figiel, J.; Gebauer, H. J.; Geesaman, D. F.; Gilman, R.; Green, M. C.; Haas, J.; Halliwell, C.; Hanlon, J.; Hantke, D.; Hughes, V. W.; Jackson, H. E.; Jancso, G.; Jansen, D. M.; Kaufman, S.; Kennedy, R. D.; Kirk, T.; Kobrak, H. G. E.; Krzywdzinski, S.; Kunori, S.; Lord, J. J.; Lubatti, H. J.; McLeod, D.; Magill, S.; Malecki, P.; Manz, A.; Melanson, H.; Michael, D. G.; Mohr, W.; Montgomery, H. E.; Morfin, J. G.; Nickerson, R. B.; O'Day, S.; Olkiewicz, K.; Osborne, L.; Papavassiliou, V.; Pawlik, B.; Pipkin, F. M.; Ramberg, E. J.; Röser, A.; Ryan, J. J.; Salgado, C. W.; Salvarani, A.; Schellman, H.; Schmitt, M.; Schmitz, N.; Schüler, K. P.; Seyerlein, H. J.; Skuja, A.; Snow, G. A.; Söldner-Rembold, S.; Steinberg, P. H.; Stier, H. E.; Stopa, P.; Swanson, R. A.; Talaga, R.; Tentindo-Repond, S.; Trost, H. J.; Venkataramania, H.; Wilhelm, M.; Wilkes, J.; Wilson, Richard; Wittek, W.; Wolbers, S. A.; Zhao, T.
1996-03-01
We have used the energy-energy angular pattern of hadrons in inelastic muon-deuteron scattering to study perturbative QCD effects and to extract the gluon distribution function ηG( η) of the nucleon, where η is the fractional momentum carried by the gluon. The data were taken with the E665 spectrometer using the Fermilab Tevatron muon beam with a mean beam energy of 490 GeV. We present ηG( η) for 0.005< η<0.05 and at an average Q 2 of 8 GeV2 using this new technique. We find that ηG( η) in this region can be described by ηG( η) α ηλ with λ=-0.87±0.09( stat.)±{0.37/0.32}( sys.). We compare our results to expectations from various parametrizations of the parton distribution function and also to results from HERA.
NASA Astrophysics Data System (ADS)
Boroun, G. R.; Rezaie, B.
2008-06-01
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, λ g , and structure function, λ S , from the Regge-like behavior at low x. The exponents are found to be independent of x and to increase linearly with ln Q 2 and are compared with the most data from the H1 Collaboration. We also calculated the structure function F 2( x,Q 2) and the gluon distribution G( x,Q 2) at low x assuming the Regge-like behavior of the gluon distribution function at this limit and compared them with 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. Glük, E. Reya, and A. Vogt) fit results.
Demartin, Federico; Mariani, Elisa; Forte, Stefano; Vicini, Alessandro; Rojo, Juan
2010-07-01
We present a systematic study of uncertainties due to parton distributions (PDFs) and the strong coupling on the gluon-fusion production cross section of the standard model Higgs at the Tevatron and LHC colliders. We compare procedures and results when three recent sets of PDFs are used, CTEQ6.6, MSTW08, and NNPDF1.2, and we discuss specifically the way PDF and strong coupling uncertainties are combined. We find that results obtained from different PDF sets are in reasonable agreement if a common value of the strong coupling is adopted. We show that the addition in quadrature of PDF and {alpha}{sub s} uncertainties provides an adequate approximation to the full result with exact error propagation. We discuss a simple recipe to determine a conservative PDF+{alpha}{sub s} uncertainty from available global parton sets, and we use it to estimate this uncertainty on the given process to be about 10% at the Tevatron and 5% at the LHC for a light Higgs.
Quark-Gluon Plasma Model and Origin of Magic Numbers
Ghahramany, N.; Ghanaatian, M.; Hooshmand, M.
2008-04-21
Using Boltzman distribution in a quark-gluon plasma sample it is possible to obtain all existing magic numbers and their extensions without applying the spin and spin-orbit couplings. In this model it is assumed that in a quark-gluon thermodynamic plasma, quarks have no interactions and they are trying to form nucleons. Considering a lattice for a central quark and the surrounding quarks, using a statistical approach to find the maximum number of microstates, the origin of magic numbers is explained and a new magic number is obtained.
Asymptocic Freedom of Gluons in Hamiltonian Dynamics
NASA Astrophysics Data System (ADS)
Gómez-Rocha, María; Głazek, Stanisław D.
2016-07-01
We derive asymptotic freedom of gluons in terms of the renormalized SU(3) Yang-Mills Hamiltonian in the Fock space. Namely, we use the renormalization group procedure for effective particles to calculate the three-gluon interaction term in the front-form Yang-Mills Hamiltonian using a perturbative expansion in powers of g up to third order. The resulting three-gluon vertex is a function of the scale parameter s that has an interpretation of the size of effective gluons. The corresponding Hamiltonian running coupling constant exhibits asymptotic freedom, and the corresponding Hamiltonian {β} -function coincides with the one obtained in an earlier calculation using a different generator.
Shining a gluon beam through quark-gluon plasma
NASA Astrophysics Data System (ADS)
Chesler, Paul M.; Ho, Ying-Yu; Rajagopal, Krishna
2012-06-01
We compute the energy density radiated by a quark undergoing circular motion in strongly coupled N=4 supersymmetric Yang-Mills plasma. If it were in vacuum, this quark would radiate a beam of strongly coupled radiation whose angular distribution has been characterized and is very similar to that of synchrotron radiation produced by an electron in circular motion in electrodynamics. Here, we watch this beam of gluons getting quenched by the strongly coupled plasma. We find that a beam of gluons of momenta ˜q≫πT is attenuated rapidly, over a distance ˜q1/3(πT)-4/3 in a plasma with temperature T. As the beam propagates through the plasma at the speed of light, it sheds trailing sound waves with momenta ≲πT. Presumably these sound waves would thermalize in the plasma if they were not hit soon after their production by the next pulse of gluons from the lighthouselike rotating quark. At larger and larger q, the trailing sound wave becomes less and less prominent. The outward-going beam of gluon radiation itself shows no tendency to spread in angle or to shift toward larger wavelengths, even as it is completely attenuated. In this regard, the behavior of the beam of gluons which we analyze is reminiscent of the behavior of jets produced in heavy ion collisions at the LHC which lose a significant fraction of their energy without appreciable change in their angular distribution or their momentum distribution as they plow through the strongly coupled quark-gluon plasma produced in these collisions.
Silicon distribution on the lunar surface obtained by Kaguya GRS
NASA Astrophysics Data System (ADS)
Kim, Kyeong Ja; Kobayashi, Masanori; Elphic, Richard; Karouji, Yuzuru; Hamara, Dave; Kobayashi, Shingo; Nagaoka, Hiroshi; Rodriguez, Alexis; Yamashita, Naoyuki; Reedy, Robert; Hasebe, Nobuyuki
Gamma ray spectrometry (GRS) provides a powerful tool to map and characterize the elemental composition of the upper tens centimeters of solid planetary surfaces. Elemental maps generated by the Kaguya GRS (KGRS) include natural radioactive as well as major elements maps (e.g., Fe, Ca, and Ti). Analysis of the Si gamma ray has been investigated using the 4934 keV Si peak produced by the thermal neutron interaction (28) Si(n,gammag) (29) Si, generated during the interaction of galactic cosmic rays and surface material containing Si. The emission rate of gamma rays is directly proportional to the abundance of Si from the lunar surface; however, it is also affected by the thermal neutron density in the lunar surface. Thus, we corrected the Si GRS data by a low energy neutron data (< 0.1 eV) obtained by Lunar Prospector because the Kaguya orbiter did not carry a neutron detector. We used the relative change in thermal neutron flux as a function of topography measured by Lunar Prospector. Normalization of Si elemental abundance using the Kaguya data was accomplished using Apollo 11, 12, 16, and 17 archive data. The normalized Si elemental abundance of the Kaguya GRS data ranged from about 15 to 27% Si. The lowest and highest SiO _{2} abundance correspond to mineral groups like pyroxene group (PKT region) and feldspar group (Northern highlands), respectively. The Si abundance permits the quantification of the relative abundance and distribution of mafic or non-mafic lunar surfaces materials. Our KGRS data analysis shows that highland terrains are Si-enriched relative to lower basins and plains regions, which appear to consist of primarily of mafic rocks. Our elemental map of Si using Kaguya GRS data shows that the highland areas of both near side and far side of the Moon have higher abundance of Si, and the mare regions of the near side of the Moon have the lowest Si abundance on the Moon. Our study clearly shows that there are a number of Si enriched areas compared to
Enhanced Usage of Keys Obtained by Physical, Unconditionally Secure Distributions
NASA Astrophysics Data System (ADS)
Kish, Laszlo B.; Granqvist, Claes-Göran
2015-04-01
Unconditionally secure physical key distribution schemes are very slow, and it is practically impossible to use a one-time-pad based cipher to guarantee unconditional security for the encryption of data because using the key bits more than once gives out statistical information, for example via the known-plain-text-attack or by utilizing known components of the protocol and language statistics. Here, we outline a protocol that reduces this speed problem and allows almost-one-time-pad based communication with an unconditionally secure physical key of finite length. The physical, unconditionally secure key is not used for data encryption but is employed in order to generate and share a new software-based key without any known-plain-text component. The software-only-based key distribution is then changed from computationally secure to unconditionally secure, because the communicated key-exchange data (algorithm parameters, one-way functions of random numbers, etc.) are encrypted in an unconditionally secure way with a one-time-pad. For practical applications, this combined physical/software key distribution based communication looks favorable compared to the software-only and physical-only key distribution based communication whenever the speed of the physical key distribution is much lower than that of the software-based key distribution. A mathematical security proof of this new scheme remains an open problem.
Using liquid dielectrics to obtain spatial thermal distributions.
Kopecky, W J
1980-01-01
A liquid dielectric has been used to determine thermal distributions for several clinically useful waveguide applicators as used in microwave hyperthermia. The system uses a saline/ethanol filled compartment placed within a temperature controlled water bath set to 37.5 degrees C. Thermal distributions are taken with a thermistor probe placed perpendicular to the electric field. In this way longitudinal and transverse cross sections of the heat deposition due to microwave interaction with the liquid dielectric can be elicited. A similar arrangement was carried out using phantom material and an infrared camera as described by Guy. Comparison of the central axis data and cross-sectional thermal distribution of these two systems shows good agreement.
Fully gauge-invariant maximally path-dependent gluon TMD: Coordinate representation
NASA Astrophysics Data System (ADS)
Cherednikov, Igor O.
2016-02-01
We propose an approach to obtain gauge-invariant maximally path-dependent operator definition of the gluon transverse-momentum dependent distribution function (gTMD). We demonstrate that the evolution equations for the gTMD can be derived from the shape- variation integral-differential equations formulated in the coordinate space.
Gluon saturation in a saturated environment
Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan
2011-07-15
A bootstrap equation for self-quenched gluon shadowing leads to a reduced magnitude of broadening for partons propagating through a nucleus. Saturation of small-x gluons in a nucleus, which has the form of transverse momentum broadening of projectile gluons in pA collisions in the nuclear rest frame, leads to a modification of the parton distribution functions in the beam compared with pp collisions. In nucleus-nucleus collisions all participating nucleons acquire enhanced gluon density at small x, which boosts further the saturation scale. Solution of the reciprocity equations for central collisions of two heavy nuclei demonstrate a significant, up to several times, enhancement of Q{sub sA}{sup 2}, in AA compared with pA collisions.
Gluon TMDs in Quarkonium Production
NASA Astrophysics Data System (ADS)
Signori, Andrea
2016-08-01
I report on our investigations into the impact of (un)polarized transverse momentum dependent parton distribution functions (TMD PDFs or TMDs) for gluons at hadron colliders, especially at A Fixed Target Experiment at the LHC (AFTER@LHC). In the context of high energy proton-proton collisions, we look at final states with low mass (e.g. η _b) in order to investigate the nonperturbative part of TMD PDFs. We study the factorization theorem for the q_T spectrum of η _b produced in proton-proton collisions relying on the effective field theory approach, defining the tools to perform phenomenological investigations at next-to-next-to-leading log and next-to-leading order accuracy in the perturbation theory. We provide predictions for the unpolarized cross section and comment on the possibility of extracting nonperturbative information about the gluon content of the proton once data at low transverse momentum are available.
Quarks and gluons at hadron colliders
Bodek, A.; CDF Collaboration
1996-08-01
Data from proton-antiproton collisions at high energy provide important information on constraining the quark and gluon distributions in the nucleon and place limits on quark substructure. The S asymmetry data constrains the slope of the d/u quark distributions and significantly reduces the systematic error on the extracted value of the W mass. Drell-Yan data at high invariant mass provides strong limits on quark substructure. Information on {alpha}{sub s} and the gluon distributions can be extracted from high P{sub T} jet data and direct photons.
Nonperturbative gluon and ghost propagators in d = 3
Papavassiliou, Joannis
2011-05-23
We study the nonperturbative gluon and ghost propagators in d = 3 Yang-Mills, using the Schwinger-Dyson equations of the pinch technique. The use of the Schwinger mechanism leads to the dynamical generation of a gluon mass, which, in turn, gives rise to an infrared finite gluon propagator and ghost dressing function. The propagators obtained are in very good agreement with the results of SU(2) lattice simulations.
Gluons in glueballs: Spin or helicity?
Mathieu, Vincent; Buisseret, Fabien; Semay, Claude
2008-06-01
In the past decade, lattice QCD has been able to compute the low-lying glueball spectrum with accuracy. Like other effective approaches of QCD, potential models still have difficulties to cope with gluonic hadrons. Assuming that glueballs are bound states of valence gluons with zero current mass, it is readily understood that the use of a potential model, intrinsically noncovariant, could be problematic in this case. The main challenge for this kind of model is actually to find a way to introduce properly the more relevant degree of freedom of the gluon: spin or helicity. In this work, we use the so-called helicity formalism of Jacob and Wick to describe two-gluon glueballs. We show, in particular, that this helicity formalism exactly reproduces the J{sup PC} numbers which are observed in lattice QCD when the constituent gluons have a helicity-1, without introducing extra states as is the case in most of the potential models. These extra states appear when gluons are seen as spin-1 particles. Using a simple spinless Salpeter model with Cornell potential within the helicity formalism, we obtain a glueball mass spectrum which is in good agreement with lattice QCD predictions for helicity-1 gluons provided instanton-induced interactions are taken into account.
EXPLORING THE POLARIZATION OF GLUONS IN THE NUCLEON.
STRATMANN,M.; VOGELSANG,W.
2007-10-22
We give an overview of the current status of investigations of the polarization of gluons in the nucleon. We describe some of the physics of the spin-dependent gluon parton distribution and its phenomenology in high-energy polarized hadronic scattering. We also review the recent experimental results.
Thermalization of gluons with Bose-Einstein condensation.
Xu, Zhe; Zhou, Kai; Zhuang, Pengfei; Greiner, Carsten
2015-05-01
We study the thermalization of gluons far from thermal equilibrium in relativistic kinetic theory. The initial distribution of gluons is assumed to resemble that in the early stage of ultrarelativistic heavy ion collisions. Only elastic scatterings in static, nonexpanding gluonic matter are considered. At first we show that the occurrence of condensation in the limit of vanishing particle mass requires a general constraint for the scattering matrix element. Then the thermalization of gluons with Bose-Einstein condensation is demonstrated in a transport calculation. We see a continuously increasing overpopulation of low energy gluons, followed by a decrease to the equilibrium distribution, when the condensation occurs. The times of the completion of the gluon condensation and of the entropy production are calculated. These times scale inversely with the energy density.
NASA Astrophysics Data System (ADS)
Ellis, John
2015-03-01
Soon after the postulation of quarks, it was suggested that they interact via gluons, but direct experimental evidence was lacking for over a decade. In 1976, Mary Gaillard, Graham Ross and the author suggested searching for the gluon via 3-jet events due to gluon bremsstrahlung in e+e- collisions. Following our suggestion, the gluon was discovered at DESY in 1979 by TASSO and the other experiments at the PETRA collider.
NASA Astrophysics Data System (ADS)
Ellis, John
2014-12-01
Soon after the postulation of quarks, it was suggested that they interact via gluons, but direct experimental evidence was lacking for over a decade. In 1976, Mary Gaillard, Graham Ross and the author suggested searching for the gluon via 3-jet events due to gluon bremsstrahlung in e+ e- collisions. Following our suggestion, the gluon was discovered at DESY in 1979 by TASSO and the other experiments at the PETRA collider.
Anisotropic hydrodynamics for a mixture of quark and gluon fluids
NASA Astrophysics Data System (ADS)
Florkowski, Wojciech; Maksymiuk, Ewa; Ryblewski, Radoslaw; Tinti, Leonardo
2015-11-01
A system of equations for anisotropic hydrodynamics is derived that describes a mixture of anisotropic quark and gluon fluids. The consistent treatment of the zeroth, first, and second moments of the kinetic equations allows us to construct a new framework with more general forms of the anisotropic phase-space distribution functions than used before. In this way, the main deficiencies of the previous formulations of anisotropic hydrodynamics for mixtures are overcome and a good agreement with the exact kinetic-theory results is obtained.
NASA Technical Reports Server (NTRS)
Moore, H. J.; Wu, S. C.
1973-01-01
The effect of reading error on two hypothetical slope frequency distributions and two slope frequency distributions from actual lunar data in order to ensure that these errors do not cause excessive overestimates of algebraic standard deviations for the slope frequency distributions. The errors introduced are insignificant when the reading error is small and the slope length is large. A method for correcting the errors in slope frequency distributions is presented and applied to 11 distributions obtained from Apollo 15, 16, and 17 panoramic camera photographs and Apollo 16 metric camera photographs.
THE RESUMMED HIGGS BOSON TRANSVERSE MOMENTUM DISTRIBUTION AT THE LHC.
KULESZA,A.STERMAN,G.VOGELSANG,W.
2003-12-08
We apply QCD resummation techniques to study the transverse momentum distribution of Higgs bosons produced via gluon-gluon fusion at the LHC. In particular we focus on the joint resummation formalism which resume both threshold and transverse momentum corrections simultaneously. A comparison of results obtained in the joint and the standard recoil resummation frameworks is presented.
Technology Transfer Automated Retrieval System (TEKTRAN)
By testing a tapered fiber beard, certain fiber length parameters can be obtained rapidly. This study is aimed at exploring the possibility to obtain the entire length distribution of a sample from the beard test method. In Part 1, the mathematical function describing cotton fiber length was searc...
Dark matter searches employing asymmetric velocity distributions obtained via the Eddington approach
NASA Astrophysics Data System (ADS)
Vergados, J. D.; Moustakidis, Ch. C.; Owen, D.
2016-08-01
Starting from WIMP density profiles, in the framework of the Eddington approach, we obtain the energy distribution f(E) of dark matter in our vicinity. Assuming a factorizable phase space function, f(E , L) = F(E) FL(L) , we obtain the velocity dispersions and the anisotropy parameter β in terms of the parameters describing the angular momentum dependence. By employing the derived expression f(E) we construct axially symmetric WIMP velocity distributions. The obtained distributions automatically have a velocity upper bound, as a consequence of the fact that they are associated with a gravitationally bound system, and are characterized by an anisotropy parameter β. We then show how such velocity distributions can be used in determining the event rates, including modulation, both in the standard as well directional WIMP searches.
Rapidity evolution of gluon TMD from low to moderate x
Balitsky, Ian; Tarasov, A.
2015-10-05
In this article, we study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small $x \\ll 1$ to linear evolution at moderate $x \\sim 1$.
Rapidity evolution of gluon TMD from low to moderate x
Balitsky, Ian; Tarasov, A.
2015-10-05
In this article, we study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at smallmore » $$x \\ll 1$$ to linear evolution at moderate $$x \\sim 1$$.« less
Gluon TMD in particle production from low to moderate x
Balitsky, I.; Tarasov, A.
2016-06-28
Here, we study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.
Gluon TMD in particle production from low to moderate x
NASA Astrophysics Data System (ADS)
Balitsky, I.; Tarasov, A.
2016-06-01
We study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.
Direct Probes of Linearly Polarized Gluons inside Unpolarized Hadrons
Boer, Daniel; Brodsky, Stanley J.; Mulders, Piet J.; Pisano, Cristian; /Cagliari U. /INFN, Cagliari
2011-02-07
We show that the unmeasured distribution of linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production both in electron-hadron and hadron-hadron collisions. We present expressions for the simplest cos 2{phi} asymmetries and estimate their maximal value in the particular case of electron-hadron collisions. Measurements of the linearly polarized gluon distribution in the proton should be feasible in future EIC or LHeC experiments.
Technology Transfer Automated Retrieval System (TEKTRAN)
The beard testing method for measuring cotton fiber length is based on the fibrogram theory. However, in the instrumental implementations, the engineering complexity alters the original fiber length distribution observed by the instrument. This causes challenges in obtaining the entire original le...
Recent COMPASS results on the gluon polarization
Quintans, Catarina
2009-03-23
The spin structure of the nucleon is studied in the COMPASS experiment at CERN/SPS, from the collisions of 160 GeV polarized muon beam with a {sup 6}LiD target. The data collected from 2002 to 2006 provide an accurate measurement of longitudinal double spin cross-section asymmetries. The latest results on the gluon polarization, accessed from two independent analyses of photon-gluon fusion selected events, are presented. The study of the open-charm production allows to extract the gluon polarization (in LO QCD) from the measurement of the asymmetry, the value obtained being {delta}g/g -0.49{+-}0.27(stat){+-}0.11(syst), at an average x{sub g} 0.11{sub -0.05}{sup +0.11} and a scale <{mu}{sup 2}> = 13(GeV/c){sup 2}. An alternative and independent way to study the gluon polarization, by studying the high transverse momentum hadron pairs produced, leads to a value {delta}g/g 0.08{+-}0.10(stat){+-}0.05(syst), at x{sub g}{sup a{nu}} 0.082{sub -0.027}{sup +0.041} and <{mu}{sup 2}> = 3(GeV/c){sup 2}.
Lincoln, Don
2016-07-12
Matter is malleable and can change its properties with temperature. This is most familiar when comparing ice, liquid water and steam, which are all different forms of the same thing. However beyond the usual states of matter, physicists can explore other states, both much colder and hotter. In this video, Fermilabâs Dr. Don Lincoln explains the hottest known state of matter â a state that is so hot that protons and neutrons from the center of atoms can literally melt. This form of matter is called a quark gluon plasma and it is an important research topic being pursued at the LHC.
Lincoln, Don
2015-05-07
Matter is malleable and can change its properties with temperature. This is most familiar when comparing ice, liquid water and steam, which are all different forms of the same thing. However beyond the usual states of matter, physicists can explore other states, both much colder and hotter. In this video, Fermilab’s Dr. Don Lincoln explains the hottest known state of matter – a state that is so hot that protons and neutrons from the center of atoms can literally melt. This form of matter is called a quark gluon plasma and it is an important research topic being pursued at the LHC.
Quark and Gluon Relaxation in Quark-Gluon Plasmas
NASA Technical Reports Server (NTRS)
Heiselberg, H.; Pethick, C. J.
1993-01-01
The quasiparticle decay rates for quarks and gluons in quark-gluon plasmas are calculated by solving the kinetic equation. Introducing an infrared cutoff to allow for nonperturbative effects, we evaluate the quasiparticle lifetime at momenta greater than the inverse Debye screening length to leading order in the coupling constant.
NASA Astrophysics Data System (ADS)
Ma, Chao; An, Wei; Deng, Xinpu
2015-10-01
The Ground Control Points (GCPs) is an important source of fundamental data in geometric correction for remote sensing imagery. The quantity, accuracy and distribution of GCPs are three factors which may affect the accuracy of geometric correction. It is generally required that the distribution of GCP should be uniform, so they can fully control the accuracy of mapping regions. In this paper, we establish an objective standard of evaluating the uniformity of the GCPs' distribution based on regional statistical information (RSI), and get an optimal distribution of GCPs. This sampling method is called RSIS for short in this work. The Amounts of GCPs in different regions by equally partitioning the image in regions in different manners are counted which forms a vector called RSI vector in this work. The uniformity of GCPs' distribution can be evaluated by a mathematical quantity of the RSI vector. An optimal distribution of GCPs is obtained by searching the RSI vector with the minimum mathematical quantity. In this paper, the simulation annealing is employed to search the optimal distribution of GCPs that have the minimum mathematical quantity of the RSI vector. Experiments are carried out to test the method proposed in this paper, and sampling designs compared are simple random sampling and universal kriging model-based sampling. The experiments indicate that this method is highly recommended as new GCPs sampling design method for geometric correction of remotely sensed imagery.
Using Spitzer Data To Obtain Dust Distribution Arounfd The Active Galactic Nucleus NGC 4051
NASA Astrophysics Data System (ADS)
Pereira, Vincent; Burrell, A.; Chavez, O.; Fawcett, E.; Elias, R.; Lugo, T.; Morillo, E.; Purpura, M.; Sorokin, S.; Gorjian, V.; Adkins, J.; Borders, K.; Kelly, S.; Martin, C.; Mendez, B.; Paradis, J.; Pittman, P.; Sepulveda, B.
2010-01-01
We have used the Rees'model of Seyfert I galaxies to make detailed calculations of dust distribution as a function of the slope of the spectral intensity versus frequency curve in the infra-red. From these results and our observations of the active galactic nucleus NGC 4051 with the Spitzer Space Telescope Infrared Array Camera (IRAC) we obtain the dust distribution function for this nucleus. We feel that this research project with its underlying physical concepts serves as a good introduction to the physics of Seyfert galaxies for high school students.
Abeykoon M.; Billinge S.; Malliakas, C.D.; Juhas, P.; Bozin, E.S.; Kanatzidis, M.G.
2012-05-01
Quantitatively reliable atomic pair distribution functions (PDFs) have been obtained from nanomaterials in a straightforward way from a standard laboratory transmission electron microscope (TEM). The approach looks very promising for making electron derived PDFs (ePDFs) a routine step in the characterization of nanomaterials because of the ubiquity of such TEMs in chemistry and materials laboratories. No special attachments such as energy filters were required on the microscope. The methodology for obtaining the ePDFs is described as well as some opportunities and limitations of the method.
NASA Astrophysics Data System (ADS)
Kang, Hyun-Ju; Choi, Hyeok; Kim, Jae-Hyun; Lee, Se-Hun; Yoo, Tae-Ho; Chung, Chin-Wook
2016-06-01
A modified central difference method (MCDM) is proposed to obtain the electron energy distribution functions (EEDFs) in single Langmuir probes. Numerical calculation of the EEDF with MCDM is simple and has less noise. This method provides the second derivatives at a given point as the weighted average of second order central difference derivatives calculated at different voltage intervals, weighting each by the square of the interval. In this paper, the EEDFs obtained from MCDM are compared to those calculated via the averaged central difference method. It is found that MCDM effectively suppresses the noises in the EEDF, while the same number of points are used to calculate of the second derivative.
Dmitriev, A; Kuznetsov, S; Shavrin, P; Lyagushin, V; Nechaev, O; Panasyuk, M; Tolstaya, E; Nikiforova, M
1998-01-01
A set of instruments for measuring energetic particle fluxes, containing two neutron detectors under different plexiglas shielding thicknesses, a scintillation detector, measuring energy release >0.1 MeV and 0.5 MeV and a Geiger counter were launched onboard OS 'MIR'. The latitude dependencies of the cosmic ray measurements were obtained and studied. The distributions of primary particle fluxes (protons and elections) as well as secondary particle fluxes (bremsstrahlung gamma-rays and neutrons) produced in interactions of radiation belt particles with the station materials were obtained. The electron belt, generated during the storm of March 24 1991, is studied.
Neutron angular distribution in a plasma focus obtained using nuclear track detectors.
Castillo-Mejía, F; Herrera, J J E; Rangel, J; Golzarri, J I; Espinosa, G
2002-01-01
The dense plasma focus (DPF) is a coaxial plasma gun in which a high-density, high-temperature plasma is obtained in a focused column for a few nanoseconds. When the filling gas is deuterium, neutrons can be obtained from fusion reactions. These are partially due to a beam of deuterons which are accelerated against the background hot plasma by large electric fields originating from plasma instabilities. Due to a beam-target effect, the angular distribution of the neutron emission is anisotropic, peaked in the forward direction along the axis of the gun. The purpose of this work is to illustrate the use of CR-39 nuclear track detectors as a diagnostic tool in the determination of the time-integrated neutron angular distribution. For the case studied in this work, neutron emission is found to have a 70% contribution from isotropic radiation and a 30% contribution from anisotropic radiation.
Gluon fragmentation functions in the Nambu-Jona-Lasinio model
NASA Astrophysics Data System (ADS)
Yang, Dong-Jing; Li, Hsiang-nan
2016-09-01
We derive gluon fragmentation functions in the Nambu-Jona-Lasinio (NJL) model by treating a gluon as a pair of color lines formed by a fictitious quark and antiquark (q q ¯). Gluon elementary fragmentation functions are obtained from the quark and antiquark elementary fragmentation functions for emitting specific mesons in the NJL model under the requirement that the q q ¯ pair maintains in the flavor-singlet state after meson emissions. An integral equation, which iterates the gluon elementary fragmentation functions to all orders, is then solved to yield the gluon fragmentation functions at a model scale. It is observed that these solutions are stable with respect to variation of relevant model parameters, especially after QCD evolution to a higher scale is implemented. We show that the inclusion of the gluon fragmentation functions into the theoretical predictions from only the quark fragmentation functions greatly improves the agreement with the SLD data for the pion and kaon productions in e+e- annihilation. Our proposal provides a plausible construct for the gluon fragmentation functions, which are supposed to be null in the NJL model.
Schwinger-Dyson Equations and Dynamical gluon mass generation
Aguilar, A.C.; Natale, A.A.
2004-12-02
We obtain a solution for the gluon propagador in Landau gauge within two distinct approximations for the Schwinger-Dyson equations (SDE). The first, named Mandelstam's approximation, consist in neglecting all contributions that come from fermions and ghosts fields while in the second, the ghosts fields are taken into account leading to a coupled system of integral equations. In both cases we show that a dynamical mass for the gluon propagator can arise as a solution.
NASA Technical Reports Server (NTRS)
Cintala, Mark J.; Mcbride, Kathleen M.
1995-01-01
Among the hazards that must be negotiated by lunar-landing spacecraft are blocks on the surface of the Moon. Unfortunately, few data exist that can be used to evaluate the threat posed by such blocks to landing spacecraft. Perhaps the best information is that obtained from Surveyor photographs, but those data do not extend to the dimensions of the large blocks that would pose the greatest hazards. Block distributions in the vicinities of the Surveyor 1, 3, 6, and 7 sites have been determined from Lunar Orbiter photography and are presented here. Only large (i.e., greater than or equal to 2.5 m) blocks are measurable in these pictures, resulting in a size gap between the Surveyor and Lunar Orbiter distributions. Nevertheless, the orbital data are self-consistent, a claim supported by the similarity in behavior between the subsets of data from the Surveyor 1, 3, and 6 sites and by the good agreement in position (if not slopes) between the data obtained from the Surveyor 3 photography and those derived from the Lunar Orbiter photographs. Confidence in the results is also justified by the well-behaved distribution of large blocks at the surveyor site. Comparisons between the Surveyor distributions and those derived from the orbital photography permit these observations: (1) in all cases but that for Surveyor 3, the density of large blocks is overestimated by extrapolation of the Surveyor-derived trends; (2) the slopes of the Surveyor-derived distributions are consistently lower than those determined for the large blocks; and (3) these apparent disagreements could be mitigated if the overall shapes of the cumulative lunar block populations were nonlinear, allowing for different slopes over different size intervals. The relatively large gaps between the Surveyor-derived and Orbiter-derived data sets, however, do not permit a determination of those shapes.
Quark and Gluon Tagging at the LHC
NASA Astrophysics Data System (ADS)
Gallicchio, Jason; Schwartz, Matthew D.
2011-10-01
Being able to distinguish light-quark jets from gluon jets on an event-by-event basis could significantly enhance the reach for many new physics searches at the Large Hadron Collider. Through an exhaustive search of existing and novel jet substructure observables, we find that a multivariate approach can filter out over 95% of the gluon jets while keeping more than half of the light-quark jets. Moreover, a combination of two simple variables, the charge track multiplicity and the pT-weighted linear radial moment (girth), can achieve similar results. Our study is only Monte Carlo based, so other observables constructed using different jet sizes and parameters are used to highlight areas that deserve further theoretical and experimental scrutiny. Additional information, including distributions of around 10 000 variables, can be found at http://jets.physics.harvard.edu/qvg/.
NASA Technical Reports Server (NTRS)
Takeda, K.; Ochiai, H.; Takeuchi, S.
1985-01-01
Maximum snow water equivalence and snowcover distribution are estimated using several LANDSAT data taken in snowmelting season over a four year period. The test site is Okutadami-gawa Basin located in the central position of Tohoku-Kanto-Chubu District. The year to year normalization for snowmelt volume computation on the snow line is conducted by year to year correction of degree days using the snowcover percentage within the test basin obtained from LANDSAT data. The maximum snow water equivalent map in the test basin is generated based on the normalized snowmelt volume on the snow line extracted from four LANDSAT data taken in a different year. The snowcover distribution on an arbitrary day in snowmelting of 1982 is estimated from the maximum snow water equivalent map. The estimated snowcover is compared with the snowcover area extracted from NOAA-AVHRR data taken on the same day. The applicability of the snow estimation using LANDSAT data is discussed.
NASA Technical Reports Server (NTRS)
Schneider, Harold
1959-01-01
This method is investigated for semi-infinite multiple-slab configurations of arbitrary width, composition, and source distribution. Isotropic scattering in the laboratory system is assumed. Isotropic scattering implies that the fraction of neutrons scattered in the i(sup th) volume element or subregion that will make their next collision in the j(sup th) volume element or subregion is the same for all collisions. These so-called "transfer probabilities" between subregions are calculated and used to obtain successive-collision densities from which the flux and transmission probabilities directly follow. For a thick slab with little or no absorption, a successive-collisions technique proves impractical because an unreasonably large number of collisions must be followed in order to obtain the flux. Here the appropriate integral equation is converted into a set of linear simultaneous algebraic equations that are solved for the average total flux in each subregion. When ordinary diffusion theory applies with satisfactory precision in a portion of the multiple-slab configuration, the problem is solved by ordinary diffusion theory, but the flux is plotted only in the region of validity. The angular distribution of neutrons entering the remaining portion is determined from the known diffusion flux and the remaining region is solved by higher order theory. Several procedures for applying the numerical method are presented and discussed. To illustrate the calculational procedure, a symmetrical slab ia vacuum is worked by the numerical, Monte Carlo, and P(sub 3) spherical harmonics methods. In addition, an unsymmetrical double-slab problem is solved by the numerical and Monte Carlo methods. The numerical approach proved faster and more accurate in these examples. Adaptation of the method to anisotropic scattering in slabs is indicated, although no example is included in this paper.
An effective encoding scheme of obtaining radial topology structures in distribution networks.
Wen, Juan; Tan, Yanghong; Zhang, Jianmin
2016-01-01
The structure of a distribution network has great effects on economy, power supply reliability and investment of a power system. To obtain an optimal topology from possible topologies, we need to solve an optimisation problem which aims to find a radial structure satisfying operating constraints. As a basis of solving this optimisation problem, the encoding scheme, is to represent the candidate configurations by a series of codes. Numerical candidate topologies and unfeasible codes would lead low efficiency or premature convergence. This paper presents an effective scheme which can rapidly produce all radial configurations of a distribution network. In order to reduce the computational requirement of solution space, initial network is simplified as a topological graph which reserves loop branches and T-nodes. And a loop-branch chain incidence matrix is derived from analyzing the relationship between any two loops. Then the principles of selecting switches of each variable are designed to determine the ranges of the variables. All radial candidate solutions are available rapidly through applying the theory of combination. The scheme presented minimizes the number of solutions and avoids tedious radial checking procedure in view of avoiding any infeasible solutions. The validity of the proposed scheme is verified by illustrative examples. PMID:27652038
NASA Technical Reports Server (NTRS)
Cintala, Mark J.; Mcbride, Kathleen M.
1994-01-01
Enlargements of Lunar-Orbiter photography were used in conjunction with a digitizing tablet to collect the locations and dimensions of blocks surrounding the Surveyor 1, 3, 6, and 7 landing sites. Data were reduced to the location and the major axis of the visible portion of each block. Shadows sometimes made it difficult to assess whether the visible major axis corresponded with the actual principal dimension. These data were then correlated with the locations of major craters in the study areas, thus subdividing the data set into blocks obviously associated with craters and those in intercrater areas. A block was arbitrarily defined to be associated with a crater when its location was within 1.1 crater radii of the crater's center. Since this study was commissioned for the ultimate purpose of determining hazards to landing spacecraft, such a definition was deemed appropriate in defining block-related hazards associated with craters. Size distributions of smaller fragments as determined from Surveyor photography were obtained as measurements from graphical data. Basic comparisons were performed through use of cumulative frequency distributions identical to those applied to studies of crater-count data.
Gluon propagators and center vortices in gluon plasma
Chernodub, M. N.; Nakagawa, Y.; Nakamura, A.; Saito, T.; Zakharov, V. I.
2011-06-01
We study electric and magnetic components of the gluon propagators in quark-gluon plasma in terms of center vortices by using a quenched simulation of SU(2) lattice theory. In the Landau gauge, the magnetic components of the propagators are strongly affected in the infrared region by removal of the center vortices, while the electric components are almost unchanged by this procedure. In the Coulomb gauge, the time-time correlators, including an instantaneous interaction, also have an essential contribution from the center vortices. As a result, one finds that magnetic degrees of freedom in the infrared region couple strongly to the center vortices in the deconfinement phase.
Jonsson, Jacob C.; Branden, Henrik
2006-10-19
This paper demonstrates a method to determine thebidirectional transfer distribution function (BTDF) using an integratingsphere. Information about the sample's angle dependent scattering isobtained by making transmittance measurements with the sample atdifferent distances from the integrating sphere. Knowledge about theilluminated area of the sample and the geometry of the sphere port incombination with the measured data combines to an system of equationsthat includes the angle dependent transmittance. The resulting system ofequations is an ill-posed problem which rarely gives a physical solution.A solvable system is obtained by using Tikhonov regularization on theill-posed problem. The solution to this system can then be used to obtainthe BTDF. Four bulk-scattering samples were characterised using both twogoniophotometers and the described method to verify the validity of thenew method. The agreement shown is great for the more diffuse samples.The solution to the low-scattering samples contains unphysicaloscillations, butstill gives the correct shape of the solution. Theorigin of the oscillations and why they are more prominent inlow-scattering samples are discussed.
NASA Astrophysics Data System (ADS)
Benedetto, A.; Magazù, S.; Migliardo, F.; Mondelli, C.; Gonzalez, M. A.
2012-02-01
In the present contribution, a procedure for molecular motion characterization based on the evaluation of the Mean Square Displacement (MSD), through the Self-Distribution Function (SDF), is presented. It is shown how MSD, which represents an important observable for the characterization of dynamical properties, can be decomposed into different partial contributions associated to system dynamical processes within a specific spatial scale. It is also shown how the SDF procedure allows us to evaluate both total MSD and partial MSDs through total and partial SDFs. As a result, total MSD is the weighed sum of partial MSDs in which the weights are obtained by the fitting procedure of measured Elastic Incoherent Neutron Scattering (EINS) intensity. We apply SDF procedure to data collected,by IN13, IN10 and IN4 spectrometers (Institute Laue Langevin), on aqueous mixtures of two homologous disaccharides (sucrose and trehalose) and on dry and hydrated (H2O and D2O) lysozyme with and without disaccharides. It emerges that the hydrogen bond imposed network of the water-trehalose mixture appears to be stronger with respect to that of the water-sucrose mixture. This result can justify the higher bioprotectant effectiveness of trehalose. Furthermore, it emerges that partial MSDs of sucrose and trehalose are equivalent in the low Q domain (0÷1.7) Å-1 whereas they are different in the high Q domain (1.7÷4) Å-1. This suggests that the higher structure sensitivity of sucrose should be related to the small spatial observation windows. Moreover, the role of the instrumental resolution in EINS is considered. The nature of the dynamical transition is highlighted and it is shown that it occurs when the system relaxation time becomes shorter than the instrumental energy time. Finally, the bioprotectants effect on protein dynamics and the amplitude of vibrations in lysozyme are presented.
A simple approximate method for obtaining spanwise lift distributions over swept wings
NASA Technical Reports Server (NTRS)
Diederich, Franklin W
1948-01-01
It is shown how Schrenk's empirical method of estimating the lift distribution over straight wings can be adapted to swept wings by replacing the elliptical distribution by a new "ideal" distribution which varies with sweep.The application of the method is discussed in detail and several comparisons are made to show the agreement of the proposed method with more rigorous ones. It is shown how first-order compressibility corrections applicable to subcritical speeds may be included in this method.
Direct probes of linearly polarized gluons inside unpolarized hadrons.
Boer, Daniël; Brodsky, Stanley J; Mulders, Piet J; Pisano, Cristian
2011-04-01
We show that linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production in electron-hadron collisions. We discuss the simplest cos2ϕ asymmetries and estimate their maximal value, concluding that measurements of the unknown linearly polarized gluon distribution in the proton should be feasible in future Electron-Ion Collider or Large Hadron electron Collider experiments. Analogous asymmetries in hadron-hadron collisions suffer from factorization breaking contributions and would allow us to quantify the importance of initial- and final-state interactions.
The evolution of the small x gluon TMD
NASA Astrophysics Data System (ADS)
Zhou, Jian
2016-06-01
We study the evolution of the small x gluon transverse momentum dependent (TMD) distribution in the dilute limit. The calculation has been carried out in the Ji-Ma-Yuan scheme using a simple quark target model. As expected, we find that the resulting small x gluon TMD simultaneously satisfies both the Collins-Soper (CS) evolution equation and the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution equation. We thus confirmed the earlier finding that the high energy factorization (HEF) and the TMD factorization should be jointly employed to resum the different type large logarithms in a process where three relevant scales are well separated.
Antiangular Ordering of Gluon Radiation in QCD Media
Mehtar-Tani, Yacine; Salgado, Carlos A.; Tywoniuk, Konrad
2011-03-25
We investigate angular and energy distributions of medium-induced gluon emission off a quark-antiquark antenna in the framework of perturbative QCD as an attempt toward understanding, from first principles, jet evolution inside the quark-gluon plasma. In-medium color coherence between emitters, neglected in all previous calculations, leads to a novel mechanism of soft-gluon radiation. The structure of the corresponding spectrum, in contrast with known medium-induced radiation, i.e., off a single emitter, retains some properties of the vacuum case; in particular, it exhibits a soft divergence. However, as opposed to the vacuum, the collinear singularity is regulated by the pair opening angle, leading to a strict angular separation between vacuum and medium-induced radiation, denoted as antiangular ordering. We comment on the possible consequences of this new contribution for jet observables in heavy-ion collisions.
Quark and Gluon Orbital Angular Momentum: Where Are We?
NASA Astrophysics Data System (ADS)
Lorcé, Cédric; Liu, Keh-Fei
2016-06-01
The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.
NASA Astrophysics Data System (ADS)
Leader, Elliot
1991-01-01
Models which attribute the high energy growth of total cross-sections to the increasing dominance of the gluon structure function at small x are shown to contradict either the Tevatron σ overlinepp measurement of the CERN S overlineppS data on the ratio of real to imaginary parts of the overlinepp forward amplitude. The origin of the difficulty is explained.
Gluon polarization in the proton
Bass, Steven D.; Casey, Andrew; Thomas, Anthony W.
2011-03-15
We combine heavy-quark renormalization group arguments with our understanding of the nucleon's wave function to deduce a bound on the gluon polarization {Delta}g in the proton. The bound is consistent with the values extracted from spin experiments at COMPASS and RHIC.
NASA Astrophysics Data System (ADS)
McKinney, Cameron Palmer
In the 1980s, polarized deep inelastic lepton-nucleon scattering experiments revealed that only about a third of the proton's spin of ½ h is carried by the quarks and antiquarks, leaving physicists with the puzzle of how to account for the remaining spin. As gluons carry roughly 50% of the proton's momentum, it seemed most logical to look to the gluon spin as another significant contributor. However, lepton-nucleon scattering experiments only access the gluon helicity distribution, Delta g, through effects on the quark distributions via scaling violations. Constraining Deltag through scaling violations requires experiments that together cover a large range of Q 2. Such experiments had been carried out with unpolarized beams, leaving g(x) (the unpolarized gluon distribution) relatively well-known, but the polarized experiments have only thus far provided weak constraints on Deltag in a limited momentum fraction range. With the commissioning in 2000 of the Relativistic Heavy Ion Collider, the first polarized proton-proton (pp) collider, and the first polarized pp running in 2002, the gluon distributions could be accessed directly by studying quark-gluon and gluon-gluon interactions. In 2009, data from measurements of double longitudinal spin asymmetries, ALL, at the STAR and PHENIX experiments through 2006 were included in a QCD global analysis performed by Daniel de Florian, Rodolfo Sassot, Marco Stratmann, and Werner Vogelsang (DSSV), yielding the first direct constraints on the gluon helicity. The DSSV group found that the contribution of the gluon spin to the proton spin was consistent with zero, but the data provided by PHENIX and STAR was all at mid-rapidity, meaning Delta g was constrained by data only a range in x from 0.05 to 0.2, leaving out helicity contributions from the huge number of low- x gluons. A more recent analysis by DSSV from 2014 including RHIC data through 2009 for the first time points to significant gluon polarization at intermediate
Fermionic collective modes of an anisotropic quark-gluon plasma
Schenke, Bjoern; Strickland, Michael
2006-09-15
We determine the fermionic collective modes of a quark-gluon plasma which is anisotropic in momentum space. We calculate the fermion self-energy in both the imaginary- and real-time formalisms and find that numerically and analytically (for two special cases) there are no unstable fermionic modes. In addition we demonstrate that in the hard-loop limit the Kubo-Martin-Schwinger condition, which relates the off-diagonal components of the real-time fermion self-energy, holds even for the anisotropic, and therefore nonequilibrium, quark-gluon plasma considered here. The results obtained here set the stage for the calculation of the nonequilibrium photon production rate from an anisotropic quark-gluon plasma.
On effects of multiple gluons in J/ψ hadroproduction
Motyka, Leszek; Sadzikowski, Mariusz
2015-04-10
The three-gluon contribution to J/ψ hadroproduction is calculated within perturbative QCD in the k{sub T}-factorization framework. This mechanism involves double gluon density and enters at a non-leading twist, but it is enhanced at large energies due to large double gluon density at small x. We obtain results for differential p{sub T}-dependent cross-sections for all J/ψ polarisations. The rescattering contribution is found to provide a significant correction to the standard leading twist cross-section at the energies of the Tevatron or the LHC at moderate p{sub T}. We also discuss a possible contribution of the rescattering correction to the anti-shadowing effect for J/ψ production in proton - nucleus collisions.
NASA Technical Reports Server (NTRS)
Christoffersen, P. A.; Simon, Justin I.; Ross, D. K.; Friedrich, J. M.; Cuzzi, J. N.
2012-01-01
Size distributions of nebular solids in chondrites suggest an efficient sorting of these early forming objects within the protoplanetary disk. The effect of this sorting has been documented by investigations of modal abundances of CAIs (e.g., [1-4]) and chondrules (e.g., [5-8]). Evidence for aerodynamic sorting in the disk is largely qualitative, and needs to be carefully assessed. It may be a way of concentrating these materials into planetesimal-mass clumps, perhaps 100 fs of ka after they formed. A key parameter is size/density distributions of particles (i.e., chondrules, CAIs, and metal grains), and in particular, whether the radius-density product (rxp) is a better metric for defining the distribution than r alone [9]. There is no consensus between r versus rxp based models. Here we report our initial tests and preliminary results, which when expanded will be used to test the accuracy of current dynamical disk models.
LPM Interference and Cherenkov-like Gluon Bremsstrahlung in DenseMatter
Majumder, Abhijit; Wang, Xin-Nian
2005-07-26
Gluon bremsstrahlung induced by multiple parton scattering in a finite dense medium has a unique angular distribution with respect to the initial parton direction. A dead-cone structure with an opening angle; theta2{sub 0}; approx 2(1-z)/(zLE) for gluons with fractional energy z arises from the Landau-Pomeran chuck-Migdal (LPM) interference. In a medium where the gluon's dielectric constant is; epsilon>1, the LPM interference pattern is shown to become Cherenkov-like with an increased opening angle determined by the dielectric constant$/cos2/theta{sub c}=z+(1-z)//epsilon$. For a large dielectric constant/epsilon; gg 1+2/z2LE, the corresponding total radiative parton energy loss is about twice that from normal gluon bremsstrahlung. Implications of this Cherenkov-like gluon bremsstrahlung to the jet correlation pattern in high-energy heavy-ion collisions is discussed.
Technology Transfer Automated Retrieval System (TEKTRAN)
The fiber testing instruments such as HVI can rapidly measure fiber length by testing a tapered fiber beard of the sample. But these instruments that use the beard testing method only report a limited number of fiber length parameters instead of the complete length distribution that is important fo...
Kang, Namjun; Gaboriau, Freddy; Ricard, Andre; Oh, Soo-ghee
2010-01-15
A new method based on time resolved optical absorption spectroscopy is proposed to determine the velocity distribution function of sputtered Cu atoms in a magnetron plasma discharge. The method consists of applying a short pulse of 1.5 {mu}s and of recording time variations in copper atom density in off pulse at different positions (1, 2, and 3 cm) from target surface under 3-30 mTorr. The time evolution of the density is then converted into velocity distribution. We estimate that only sputtered atoms with radial velocity component lower than 0.5 km/s are detected. The average velocity of Cu atoms is evaluated as the first order moment of the velocity distribution functions. The velocity distribution functions become the more dispersive the farther from target surface. The average velocities vary in the range of 2.5-3 km/s at the vicinity of target surface whereas at 3 cm a decrease from 2.5 to 1.2 km/s is observed at 30 mTorr.
The quark-gluon vertex in Landau gauge bound-state studies
NASA Astrophysics Data System (ADS)
Williams, Richard
2015-05-01
We present a practical method for the solution of the quark-gluon vertex for use in Bethe-Salpeter and Dyson-Schwinger calculations. The efficient decomposition into the necessary covariants is detailed, with the numerical algorithm outlined for both real and complex Euclidean momenta. A truncation of the quark-gluon vertex, that neglects explicit back-coupling to enable the application to bound-state calculations, is given together with results for the quark propagator and quark-gluon vertex for different quark flavours. The relative impact of the various components of the quark-gluon vertex is highlighted with the flavour dependence of the effective quark-gluon interaction obtained, thus providing insight for the construction of phenomenological models within the rainbow ladder. Finally, we solve the corresponding Green's functions for complex Euclidean momenta as required in future bound-state calculations.
Mass distribution of meteoroids obtained by a meteor forward-scatter (MFS) radar method.
NASA Astrophysics Data System (ADS)
Cevolani, G.; Gabucci, M. F.
1996-04-01
The cumulative distributions of the number vs. duration of echoes belonging to main meteor showers (Lyrids, η-Aquarids, δ-Aquarids, Perseids, Orionids, Leonids, Geminids) and sporadic background were investigated using a forward-scatter (FS) continuous-wave meteor radar link operational during 1992 - 95 over the long baseline Bologna-Lecce in Italy. The trend of the mass distribution of particles in the quoted meteoroid streams was derived, and the values of the mass index s were compared for each meteor population with the steady-state condition. It was found that the mass index s generally increases towards long-duration echoes, but many of the observed meteor streams appear to have unstable populations. The values of the mass index of the sporadic complex are generally higher than the corresponding ones of meteor showers in the range of echo durations 0.1 ≤ T ≤ 10 s. This is a possible consequence of longer-lasting FS signals, indicating a shift of the mass distribution function vs. higher echo durations. Moreover, non-gravitational forces in connection with solar radiation pressure, Poynting-Robertson effect, solar-wind particle streaming, mutual collisions, etc., appear to be responsible for the observed widespread radiants and for unstable populations in the meteoroid streams.
The Radial Distribution Function (RDF) of Amorphous Selenium Obtained through the Vacuum Evaporator
Guda, Bardhyl; Dede, Marie
2010-01-21
After the amorphous selenium obtained through the vacuum evaporator, the relevant diffraction intensity is taken and its processing is made. Further on the interferential function is calculated and the radial density function is defined. For determining these functions are used two methods, which were compared with each other and finally are received results for amorphous selenium RDF.
NASA Astrophysics Data System (ADS)
Kahana, D. E.; Milana, J.
1987-07-01
A perturbative QCD calculation of gluon exchange corrections to the cranking moment of inertia of the chiral bag model is done using the full time-dependent cavity propagators. Cranking is used to construct the nucleon and delta states and a value of the effective strong coupling constant is extracted by fitting the empirical Δ N mass splitting. The MIT bag limit (large bag radius) of the chiral bag model is also examined.
Semi-inclusive polarised lepton-nucleon scattering and the anomalous gluon contribution
NASA Astrophysics Data System (ADS)
Güllenstern, St.; Veltri, M.; Górnicki, P.; Mankiewicz, L.; Schäfer, A.
1993-08-01
We discuss a new observable for semi-inclusive pion production in polarised lepton-nucleon collisions. This observable is sensitive to the polarised and unpolarised strange quark distribution and the anomalous gluon contribution, provided that their fragmentation functions into pions differ substantially from that of light quarks. From Monte Carlo data generated with our PEPSI code we conclude that HERMES might be able to decide whether the polarized strange quark and gluon distributions are large.
The gluon mass generation mechanism: A concise primer
NASA Astrophysics Data System (ADS)
Aguilar, A. C.; Binosi, D.; Papavassiliou, J.
2016-04-01
We present a pedagogical overview of the nonperturbative mechanism that endows gluons with a dynamical mass. This analysis is performed based on pure Yang-Mills theories in the Landau gauge, within the theoretical framework that emerges from the combination of the pinch technique with the background field method. In particular, we concentrate on the Schwinger-Dyson equation satisfied by the gluon propagator and examine the necessary conditions for obtaining finite solutions within the infrared region. The role of seagull diagrams receives particular attention, as do the identities that enforce the cancellation of all potential quadratic divergences.We stress the necessity of introducing nonperturbative massless poles in the fully dressed vertices of the theory in order to trigger the Schwinger mechanism, and explain in detail the instrumental role of these poles in maintaining the Becchi-Rouet-Stora-Tyutin symmetry at every step of the mass-generating procedure. The dynamical equation governing the evolution of the gluon mass is derived, and its solutions are determined numerically following implementation of a set of simplifying assumptions. The obtained mass function is positive definite, and exhibits a power law running that is consistent with general arguments based on the operator product expansion in the ultraviolet region. A possible connection between confinement and the presence of an inflection point in the gluon propagator is briefly discussed.
D-meson enhancement in pp collisions at the LHC due to nonlinear gluon evolution
Dainese, A.; Vogt, R.; Bondila, M.; Eskola, K.J.; Kolhinen, V.J.
2004-08-22
When nonlinear effects on the gluon evolution are included with constraints from HERA, the gluon distribution in the free proton is enhanced at low momentum fractions, x {approx}< 0.01, and low scales, Q{sup 2} {approx}< 10 GeV{sup 2}, relative to standard, DGLAP-evolved, gluon distributions. Consequently, such gluon distributions can enhance charm production in pp collisions at center of mass energy 14 TeV by up to a factor of five at midrapidity, y {approx} 0, and transverse momentum p{sub T} {yields} 0 in the most optimistic case. We show that most of this enhancement survives hadronization into D mesons. Assuming the same enhancement at leading and next-to-leading order, we show that the D enhancement may be measured by D{sup 0} reconstruction in the K{sup -}{pi}{sup +} decay channel with the ALICE detector.
Jarmusik, Keith E; Eppell, Steven J; Lacks, Daniel J; Zypman, Fredy R
2011-03-01
We develop the self-consistent sum of dipoles (SCSD) theory for the purpose of recovering charge densities present on nanostructures using scanning force microscope (SFM) force-separation experiments. The dielectric probe is discretized into volume elements characterized by their atomic polarizabilities. Magnitudes of the induced dipole in each element are calculated based on discrete charges placed on the surfaces, dipole-dipole interactions, and dielectric and ionic properties of the surrounding medium. We perform two model-model comparisons, one with a macroscopic dielectric sphere and one with a nanocluster of silicon atoms. In both cases, using a single adjustable parameter, our SCSD theory agrees with the accepted theories to better than 99%. Force-separation curves between a silicon nitride probe and the basal plane of highly oriented pyrolytic graphite in nine ionic concentration and pH combinations were fit with a root-mean-square error of 3.6 pN, an improvement over the 12 pN error obtained using the Derjaguin approximation. These results suggest that the SCSD will be useful in modeling SFM force-separation data to obtain spatially varying charge densities on surfaces with complex geometries.
Weipeng, Wang; Jianli, Liu; Bingzi, Zhao; Jiabao, Zhang; Xiaopeng, Li; Yifan, Yan
2015-01-01
Mathematical descriptions of classical particle size distribution (PSD) data are often used to estimate soil hydraulic properties. Laser diffraction methods (LDM) now provide more detailed PSD measurements, but deriving a function to characterize the entire range of particle sizes is a major challenge. The aim of this study was to compare the performance of eighteen PSD functions for fitting LDM data sets from a wide range of soil textures. These models include five lognormal models, five logistic models, four van Genuchten models, two Fredlund models, a logarithmic model, and an Andersson model. The fits were evaluated using Akaike’s information criterion (AIC), adjusted R2, and root-mean-square error (RMSE). The results indicated that the Fredlund models (FRED3 and FRED4) had the best performance for most of the soils studied, followed by one logistic growth function extension model (MLOG3) and three lognormal models (ONLG3, ORLG3, and SHCA3). The performance of most PSD models was better for soils with higher silt content and poorer for soils with higher clay and sand content. The FRED4 model best described the PSD of clay, silty clay, clay loam, silty clay loam, silty loam, loam, and sandy loam, whereas FRED3, MLOG3, ONLG3, ORLG3, and SHCA3 showed better performance for most soils studied. PMID:25927441
Methods for obtaining true particle size distributions from cross section measurements
Lord, Kristina Alyse
2013-01-01
Sectioning methods are frequently used to measure grain sizes in materials. These methods do not provide accurate grain sizes for two reasons. First, the sizes of features observed on random sections are always smaller than the true sizes of solid spherical shaped objects, as noted by Wicksell [1]. This is the case because the section very rarely passes through the center of solid spherical shaped objects randomly dispersed throughout a material. The sizes of features observed on random sections are inversely related to the distance of the center of the solid object from the section [1]. Second, on a plane section through the solid material, larger sized features are more frequently observed than smaller ones due to the larger probability for a section to come into contact with the larger sized portion of the spheres than the smaller sized portion. As a result, it is necessary to find a method that takes into account these reasons for inaccurate particle size measurements, while providing a correction factor for accurately determining true particle size measurements. I present a method for deducing true grain size distributions from those determined from specimen cross sections, either by measurement of equivalent grain diameters or linear intercepts.
Jet energy loss in the quark-gluon plasma by stream instabilities
Mannarelli, Massimo; Manuel, Cristina; Gonzalez-Solis, Sergi; Strickland, Michael
2010-04-01
We study the evolution of the plasma instabilities induced by two jets of particles propagating in opposite directions and crossing a thermally equilibrated non-Abelian plasma. In order to simplify the analysis we assume that the two jets of partons can be described with uniform distribution functions in coordinate space and by Gaussian distribution functions in momentum space. We find that while crossing the quark-gluon plasma, the jets of particles excite unstable chromomagnetic and chromoelectric modes. These fields interact with the particles (or hard modes) of the plasma inducing the production of currents; thus, the energy lost by the jets is absorbed by both the gauge fields and the hard modes of the plasma. We compare the outcome of the numerical simulations with the analytical calculation performed assuming that the jets of particles can be described by a tsunamilike distribution function. We find qualitative and semiquantitative agreement between the results obtained with the two methods.
NASA Technical Reports Server (NTRS)
Peters, B. C., Jr.; Walker, H. F.
1975-01-01
New results and insights concerning a previously published iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions were discussed. It was shown that the procedure converges locally to the consistent maximum likelihood estimate as long as a specified parameter is bounded between two limits. Bound values were given to yield optimal local convergence.
Controversy concerning the definition of quark and gluon angular momentum
NASA Astrophysics Data System (ADS)
Leader, Elliot
2011-05-01
A major controversy has arisen in QCD as to how to split the total angular momentum into separate quark and gluon contributions, and as to whether the gluon angular momentum can itself be split, in a gauge-invariant way, into a spin and orbital part. Several authors have proposed various answers to these questions and offered a variety of different expressions for the relevant operators. I argue that none of these is acceptable and suggest that the canonical expression for the momentum and angular momentum operators is the correct and physically meaningful one. It is then an inescapable fact that the gluon angular momentum operator cannot, in general, be split in a gauge-invariant way into a spin and orbital part. However, the projection of the gluon spin onto its direction of motion, i.e. its helicity is gauge invariant and is measured in deep inelastic scattering on nucleons. The Ji sum rule, relating the quark angular momentum to generalized parton distributions, though not based on the canonical operators, is shown to be correct, if interpreted with due care. I also draw attention to several interesting aspects of QED and QCD, which, to the best of my knowledge, are not commented upon in the standard textbooks on field theory.
Quark ACM with topologically generated gluon mass
NASA Astrophysics Data System (ADS)
Choudhury, Ishita Dutta; Lahiri, Amitabha
2016-03-01
We investigate the effect of a small, gauge-invariant mass of the gluon on the anomalous chromomagnetic moment (ACM) of quarks by perturbative calculations at one-loop level. The mass of the gluon is taken to have been generated via a topological mass generation mechanism, in which the gluon acquires a mass through its interaction with an antisymmetric tensor field Bμν. For a small gluon mass ( < 10 MeV), we calculate the ACM at momentum transfer q2 = -M Z2. We compare those with the ACM calculated for the gluon mass arising from a Proca mass term. We find that the ACM of up, down, strange and charm quarks vary significantly with the gluon mass, while the ACM of top and bottom quarks show negligible gluon mass dependence. The mechanism of gluon mass generation is most important for the strange quarks ACM, but not so much for the other quarks. We also show the results at q2 = -m t2. We find that the dependence on gluon mass at q2 = -m t2 is much less than at q2 = -M Z2 for all quarks.
Production of b and overlineb quarks by photon-gluon fusion in heavy-ion collisions
NASA Astrophysics Data System (ADS)
Hofmann, Ch.; Soff, G.; Schäfer, A.; Greiner, W.
1991-06-01
Electromagnetic Higgs production in ultrarelativistic heavy-ion collisions has been proposed as an alternative for detecting Higgs particles in the mass range mZ< mH<2 mW. We consider the fussion of a photon and a gluon into b and overlineb quarks as background to the b overlineb decay of the Higgs boson. This completely hides the Higgs signal. We also discuss the possibility of utilizing photon-gluon fusion into b overlineb and c overlinec as a sensitive tool to determine the gluon distribution of the nucleon inside the nucleus, e.g., at RHIC.
NASA Technical Reports Server (NTRS)
Hacker, Paul T.
1956-01-01
An airborne cloud aeroscope by which droplet size, size distribution, and liquid-water content of clouds can be determined has been developed and tested in flight and in wind tunnels with water sprays. In this aeroscope the cloud droplets are continuously captured in a stream of oil, which Is then photographed by a photomicrographic camera. The droplet size and size distribution can be determined directly from the photographs. With the droplet size distribution known, the liquid-water content of the cloud can be computed from the geometry of the aeroscope, the airspeed, and the oil-flow rate. The aeroscope has the following features: Data are obtained semi-automatically, and permanent data are taken in the form of photographs. A single picture usually contains a sufficient number of droplets to establish the droplet size distribution. Cloud droplets are continuously captured in the stream of oil, but pictures are taken at Intervals. The aeroscope can be operated in icing and non-icing conditions. Because of mixing of oil in the instrument, the droplet-distribution patterns and liquid-water content values from a single picture are exponentially weighted average values over a path length of about 3/4 mile at 150 miles per hour. The liquid-water contents, volume-median diameters, and distribution patterns obtained on test flights and in the Lewis icing tunnel are similar to previously published data.
Visvalingam, Jeyachchandran; Wang, Hui; Youssef, Mohamed K; Devos, Julia; Gill, Colin O; Yang, Xianqin
2016-08-01
The objective of this study was to determine the immediate source of Escherichia coli on beef trimmings produced at a large packing plant by analyzing the E. coli on trimmings at various locations of a combo bin filled on the same day and of bins filled on different days. Ten 2,000-lb (907-kg) combo bins (B1 through B10) of trimmings were obtained from a large plant on 6 days over a period of 5 weeks. Thin slices of beef with a total area of approximately 100 cm(2) were excised from five locations (four corners and the center) at each of four levels of the bins: the top surface and 30, 60, and 90 cm below the top. The samples were enriched for E. coli in modified tryptone soya broth supplemented with 20 mg/liter novobiocin. The positive enrichment cultures, as determined by PCR, were plated on E. coli/coliform count plates for recovery of E. coli. Selected E. coli isolates were genotyped using multiple-locus variable-number tandem repeat analysis (MLVA). Of the 200 enrichment cultures, 43 were positive by PCR for E. coli, and 32 of these cultures yielded E. coli isolates. Two bins did not yield any positive enrichment cultures, and three PCR-positive bins did not yield any E. coli isolates. MLVA of 165 E. coli isolates (30, 62, 56, 5, and 12 from B6 through B10, respectively) revealed nine distinct genotypes. MLVA types 263 and 89 were most prevalent overall and on individual days, accounting for 49.1 and 37.6% of the total isolates, respectively. These two genotypes were also found at multiple locations within a bin. All nine genotypes belonged to the phylogenetic group A0 of E. coli, suggesting an animal origin. The finding that the trimmings carried very few E. coli indicates an overall effective control over contamination of beef with E. coli at this processing plant. The lack of strain diversity of the E. coli on trimmings suggests that most E. coli isolates may have come from common sources, most likely equipment used in the fabrication process.
Ordering Multiple Soft Gluon Emissions.
Ángeles Martínez, René; Forshaw, Jeffrey R; Seymour, Michael H
2016-05-27
We present an expression for the QCD amplitude for a general hard scattering process with any number of soft gluon emissions, to one-loop accuracy. The amplitude is written in two different but equivalent ways: as a product of operators ordered in dipole transverse momentum and as a product of loop-expanded currents. We hope that these results will help in the development of an all-orders algorithm for multiple emissions that includes the full color structure and both the real and imaginary contributions to the amplitude. PMID:27284651
Nonperturbative gluon and ghost propagators for d=3 Yang-Mills theory
Aguilar, A. C.; Binosi, D.; Papavassiliou, J.
2010-06-15
We study a manifestly gauge-invariant set of Schwinger-Dyson equations to determine the nonperturbative dynamics of the gluon and ghost propagators in d=3 Yang-Mills theory. The use of the well-known Schwinger mechanism, in the Landau gauge leads to the dynamical generation of a mass for the gauge boson (gluon in d=3), which, in turn, gives rise to an infrared finite gluon propagator and ghost dressing function. The propagators obtained from the numerical solution of these nonperturbative equations are in very good agreement with the results of SU(2) lattice simulations.
NASA Astrophysics Data System (ADS)
Chen, Jiunn-Wei; Deng, Jian; Dong, Hui; Wang, Qun
2013-02-01
The leading-order contribution to the shear and bulk viscosities, η and ζ, of a gluon plasma in perturbative QCD includes the gg↔gg (22) process, gg↔ggg (23) process, and multiple scattering processes known as the Landau-Pomeranchuk-Migdal (LPM) effect. Complete leading-order computations for η and ζ were obtained by Arnold, Moore, and Yaffe (AMY) and Arnold, Dogan, and Moore (ADM), respectively, with the inelastic processes computed by an effective g↔gg gluon splitting. We study how complementary calculations with 22 and 23 processes and a simple treatment to model the LPM effect compare with the results of AMY and ADM. We find that our results agree with theirs within errors. By studying the contribution of the 23 process to η, we find that the minimum angle θ among the final-state gluons in the fluid local rest frame has a distribution that is peaked at θ˜αs, analogous to the near-collinear splitting asserted by AMY and ADM. However, the average of θ is much bigger than its peak value, as its distribution is skewed with a long tail. The same θ behavior is also seen if the 23 matrix element is taken to the soft-gluon bremsstrahlung limit in the center-of-mass (CM) frame. This suggests that the soft-gluon bremsstrahlung in the CM frame still has some near-collinear behavior in the fluid local rest frame. We also generalize our result to a general SU(Nc) pure gauge theory and summarize the current viscosity computations in QCD.
Consequences Of Fully Dressing Quark-Gluon Vertex Function With Two-Point Gluon Lines
Hrayr Matevosyan; Anthony Thomas; Peter Tandy
2007-06-18
We extend recent studies of the effects of quark-gluon vertex dressing upon the solutions of the Dyson-Schwinger equation for the quark propagator. A momentum delta function is used to represent the dominant infrared strength of the effective gluon propagator so that the resulting integral equations become algebraic. The guark-gluon vertex is constructed from the complete set of diagrams involving only 2-point gluon lines. The additional diagrams, including those with crossed gluon lines, are shown to make an important contribution to the DSE solutions for the quark propagator, because of their large color factors and the rapid growth in their number.
Probing the Linear Polarization of Gluons in Unpolarized Hadrons at EIC
Boer, Daniel; Brodsky, Stanley J.; Mulders, Piet J.; Pisano, Cristian; /Cagliari U. /INFN, Cagliari
2011-08-17
Gluons inside unpolarized hadrons can be linearly polarized provided they have a nonzero transverse momentum. The simplest and theoretically safest way to probe this TMD distribution of linearly polarized gluons is through cos 2{phi} asymmetries in heavy quark pair or dijet production in electron-hadron collisions. Future EIC or LHeC experiments are ideally suited for this purpose. Here we estimate the maximum asymmetries for EIC kinematics.
NASA Technical Reports Server (NTRS)
Peterson, Harold; Koshak, William J.
2009-01-01
An algorithm has been developed to estimate the altitude distribution of one-meter lightning channel segments. The algorithm is required as part of a broader objective that involves improving the lightning NOx emission inventories of both regional air quality and global chemistry/climate models. The algorithm was tested and applied to VHF signals detected by the North Alabama Lightning Mapping Array (NALMA). The accuracy of the algorithm was characterized by comparing algorithm output to the plots of individual discharges whose lengths were computed by hand; VHF source amplitude thresholding and smoothing were applied to optimize results. Several thousands of lightning flashes within 120 km of the NALMA network centroid were gathered from all four seasons, and were analyzed by the algorithm. The mean, standard deviation, and median statistics were obtained for all the flashes, the ground flashes, and the cloud flashes. One-meter channel segment altitude distributions were also obtained for the different seasons.
NASA Astrophysics Data System (ADS)
Canon-Tapia, E.; Hamilton, C.; Lopes, R. M. C.
2015-12-01
Clues concerning dynamic aspects of planetary interiors can be obtained through the characterization of volcano distribution at a global scale. On past years, results obtained from global distribution of volcanism on Earth and Venus have been presented, and compared with each other. In this work, the global distribution of volcanism on Io (the innermost of Jupiter's Galilean satellites and the most volcanically active body in the Solar System) is explored using the same tools. Volcanic centers on Io can be divided in two groups: The first including positive thermal anomalies, or hotspots, and the second formed by volcano-tectonic depressions called paterae. Approximately 20% of the documented patera coincide with hotspots, but not all of Io's current volcanic activity is directly associated to paterae. It is uncertain whether hotspots located outside paterae represent volcanic systems still lacking a caldera-like structure, or they represent an entirely different type of volcanism. To account for this source of uncertainty, the analysis reported here was completed on different databases (hotspots, paterae, patera floor units and a combination of hotspots and paterae referred to as volcanic systems). In addition, the distribution of Io's mountains also was studied. As a result, we show that the main clusters of volcanism on Io support the existence of mantle convection patterns that include a combined heating between the astenosphere and the deep mantle (with the former source being more important, but not necessarily on a 2:1 proportion), takes place at moderate to high Reynolds numbers, and includes some degree of impermeability between the astenosphere and the mantle. We also show that although the long-wavelength volcano distribution is controlled by the patterns of mantle convection, the astenosphere serves as a buffer zone where magma is distributed laterally giving place to volcanic activity away from the zones of influence of the hot mantle isotherms. The
HUNTING THE QUARK GLUON PLASMA.
LUDLAM, T.; ARONSON, S.
2005-04-11
The U.S. Department of Energy's Relativistic Heavy Ion Collider (RHIC) construction project was completed at BNL in 1999, with the first data-taking runs in the summer of 2000. Since then the early measurements at RHIC have yielded a wealth of data, from four independent detectors, each with its international collaboration of scientists: BRAHMS, PHENIX, PHOBOS, and STAR [1]. For the first time, collisions of heavy nuclei have been carried out at colliding-beam energies that have previously been accessible only for high-energy physics experiments with collisions of ''elementary'' particles such as protons and electrons. It is at these high energies that the predictions of quantum chromodynamics (QCD), the fundamental theory that describes the role of quarks and gluons in nuclear matter, come into play, and new phenomena are sought that may illuminate our view of the basic structure of matter on the sub-atomic scale, with important implications for the origins of matter on the cosmic scale. The RHIC experiments have recorded data from collisions of gold nuclei at the highest energies ever achieved in man-made particle accelerators. These collisions, of which hundreds of millions have now been examined, result in final states of unprecedented complexity, with thousands of produced particles radiating from the nuclear collision. All four of the RHIC experiments have moved quickly to analyze these data, and have begun to understand the phenomena that unfold from the moment of collision as these particles are produced. In order to provide benchmarks of simpler interactions against which to compare the gold-gold collisions, the experiments have gathered comparable samples of data from collisions of a very light nucleus (deuterium) with gold nuclei, as well as proton-proton collisions, all with identical beam energies and experimental apparatus. The early measurements have revealed compelling evidence for the existence of a new form of nuclear matter at extremely high
Collision Rate and Symmetry Factor in Gluon Plasma
NASA Astrophysics Data System (ADS)
Deng, Jian; Wang, Qun
2013-03-01
The elastic and inelastic collision rates in a gluon gas are calculated. The symmetry factor and the phase space integral are discussed in detail. With a symmetry factor and well constrained phase space, the same result can be obtained as that of the full phase space without the factor. Such an equivalence is illustrated by analytic and numerical calculations for gg → gg and gg → ggg processes.
Abelian non-global logarithms from soft gluon clustering
NASA Astrophysics Data System (ADS)
Kelley, Randall; Walsh, Jonathan R.; Zuberi, Saba
2012-09-01
Most recombination-style jet algorithms cluster soft gluons in a complex way. This leads to previously identified correlations in the soft gluon phase space and introduces logarithmic corrections to jet cross sections, which are known as clustering logarithms. The leading Abelian clustering logarithms occur at least at next-to leading logarithm (NLL) in the exponent of the distribution. Using the framework of Soft Collinear Effective Theory (SCET), we show that new clustering effects contributing at NLL arise at each order. While numerical resummation of clustering logs is possible, it is unlikely that they can be analytically resummed to NLL. Clustering logarithms make the anti-kT algorithm theoretically preferred, for which they are power suppressed. They can arise in Abelian and non-Abelian terms, and we calculate the Abelian clustering logarithms at O ( {α_s^2} ) for the jet mass distribution using the Cambridge/Aachen and kT algorithms, including jet radius dependence, which extends previous results. We find that clustering logarithms can be naturally thought of as a class of non-global logarithms, which have traditionally been tied to non-Abelian correlations in soft gluon emission.
Glauber gluons in pion-induced Drell-Yan processes
NASA Astrophysics Data System (ADS)
Chang, Chun-peng; Li, Hsiang-nan
2013-10-01
We point out that the existence of Glauber gluons in the kT factorization theorem can account for the violation of the Lam-Tung relation, namely, the anomalous lepton angular distribution observed in pion-induced Drell-Yan processes. The emission of a final-state parton, that balances the lepton-pair transverse momentum, causes the responsible spin-transverse-momentum correlation in the Glauber-gluon background. It is argued that the Glauber effect is significant in the pion due to its unique role of being a Nambu-Goldstone boson and a qqbar bound state simultaneously. This mechanism is compared to other resolutions in the literature by means of vacuum effects and Boer-Mulders functions. We propose to discriminate the above resolutions by measuring the ppbar Drell-Yan process at GSI and J-PARC.
NASA Astrophysics Data System (ADS)
Gunár, S.; Mackay, D. H.
2016-07-01
Aims: We analyze distributions of the magnetic field strength and prominence plasma (temperature, pressure, plasma β, and mass) using the 3D whole-prominence fine structure model. Methods: The model combines a 3D magnetic field configuration of an entire prominence, obtained from non-linear force-free field simulations, with a detailed semi-empirically derived description of the prominence plasma. The plasma is located in magnetic dips in hydrostatic equilibrium and is distributed along multiple fine structures within the 3D magnetic model. Results: We show that in the modeled prominence, the variations of the magnetic field strength and its orientation are insignificant on scales comparable to the smallest dimensions of the observed prominence fine structures. We also show the ability of the 3D whole-prominence fine structure model to reveal the distribution of the prominence plasma with respect to its temperature within the prominence volume. This provides new insights into the composition of the prominence-corona transition region. We further demonstrate that the values of the plasma β are small throughout the majority of the modeled prominences when realistic photospheric magnetic flux distributions and prominence plasma parameters are assumed. While this is generally true, we also find that in the region with the deepest magnetic dips, the plasma β may increase towards unity. Finally, we show that the mass of the modeled prominence plasma is in good agreement with the mass of observed non-eruptive prominences.
NASA Technical Reports Server (NTRS)
Gerstell, M. F.
1993-01-01
A review of the convolution theorem for obtaining the cumulative k-distribution of a gas mixture proven in Goody et al. (1989) and a discussion of its application to natural spectra are presented. Computational optimizations for use in analyzing high-altitude gas mixtures are introduced. Comparisons of the results of the optimizations, and criteria for deciding what altitudes are 'high' in this context are given. A few relevant features of the testing support software are examined. Some spectrally integrated results, and the circumstances the might permit substituting the method of principal absorbers are examined.
Hydrodynamics of anisotropic quark and gluon fluids
NASA Astrophysics Data System (ADS)
Florkowski, Wojciech; Maj, Radoslaw; Ryblewski, Radoslaw; Strickland, Michael
2013-03-01
The recently developed framework of anisotropic hydrodynamics is generalized to describe the dynamics of coupled quark and gluon fluids. The quark and gluon components of the fluids are characterized by different dynamical anisotropy parameters. The dynamical equations describing such mixtures are derived from kinetic theory, with the collisional kernel treated in the relaxation-time approximation, allowing for different relaxation times for quarks and gluons. Baryon number conservation is enforced in the quark and antiquark components of the fluid, but overall parton number nonconservation is allowed in the system. The resulting equations are solved numerically in the (0+1)-dimensional boost-invariant case at zero and finite baryon density.
Gluons and the NJL coupling constant
Braghin, Fábio L.; Barros Jr, Ednaldo; Paulo Jr, Ademar
2014-11-11
The QCD origin of the NJL model is re-analysed by considering the gluon condensate of order two . The key point is the treatment of the gluon interactions. To linearize the action the auxiliary variable method is employed to introduce a scalar variable φ(x) that yield such condensate by means of its value in the vacuum, and then another auxiliary variable that corresponds to an antisymmetric gluon configuration φ(x). For that, besides that, two different possible limits of the fourth order non local quark interaction that may contribute to the NJL coupling are compared.
On the zero crossing of the three-gluon vertex
NASA Astrophysics Data System (ADS)
Athenodorou, A.; Binosi, D.; Boucaud, Ph.; De Soto, F.; Papavassiliou, J.; Rodríguez-Quintero, J.; Zafeiropoulos, S.
2016-10-01
We report on new results on the infrared behavior of the three-gluon vertex in quenched Quantum Chromodynamics, obtained from large-volume lattice simulations. The main focus of our study is the appearance of the characteristic infrared feature known as 'zero crossing', the origin of which is intimately connected with the nonperturbative masslessness of the Faddeev-Popov ghost. The appearance of this effect is clearly visible in one of the two kinematic configurations analyzed, and its theoretical origin is discussed in the framework of Schwinger-Dyson equations. The effective coupling in the momentum subtraction scheme that corresponds to the three-gluon vertex is constructed, revealing the vanishing of the effective interaction at the exact location of the zero crossing.
The Gluon Contribution to the Sivers Effect COMPASS results
NASA Astrophysics Data System (ADS)
Kurek, Krzysztof; Szabelski, Adam
2016-02-01
The Sivers effect describes the correlation between the spin of the nucleon and the orbital motion of partons. It can be measured via Semi-Inclusive Deep Inelastic Scattering of lepton on a transversely polarised proton and deuteron targets by determining the azimuthal asymmetry related to the modulation in the Sivers angle ϕSiv. In the paper a method of obtaining the Sivers asymmetry for gluons is presented. It is based on the model of lepton nucleon interactions via three single-photon-exchange processes: photon-gluon fusion (PGF), QCD Compton (QCDC) and leading process (LP). A method of simultaneous extraction of the Sivers asymmetries of the three processes with the use of Monte Carlo (MC) and neural networks (NN) approach is presented. The method has been applied to COMPASS data taken with 160GeV/c muon beam scattered off transversely polarised deuteron and transversely polarised proton target. For each target a data sample of events containing at least two hadrons with large transverse momentum has been selected. Finally the results for gluon Sivers asymmetry were obtained to be: Adg = -0.14 ± 0.15(stat.) ± 0.06(syst.) at
Transport properties of quark and gluon plasmas
Heiselberg, H.
1993-12-01
The kinetic properties of relativistic quark-gluon and electron-photon plasmas are described in the weak coupling limit. The troublesome Rutherford divergence at small scattering angles is screened by Debye screening for the longitudinal or electric part of the interactions. The transverse or magnetic part of the interactions is effectively screened by Landau damping of the virtual photons and gluons transferred in the QED and QCD interactions respectively. Including screening a number of transport coefficients for QCD and QED plasmas can be calculated to leading order in the interaction strength, including rates of momentum and thermal relaxation, electrical conductivity, viscosities, flavor and spin diffusion of both high temperature and degenerate plasmas. Damping of quarks and gluons as well as color diffusion in quark-gluon plasmas is, however, shown not to be sufficiently screened and the rates depends on an infrared cut-off of order the ``magnetic mass,`` m{sub mag} {approximately} g{sup 2}T.
Effective multi-Higgs couplings to gluons
NASA Astrophysics Data System (ADS)
Spira, Michael
2016-10-01
Standard-Model Higgs bosons are dominantly produced via the gluon-fusion mechanism gg → H at the LHC, i.e. in a loop-mediated process with top loops providing the dominant contribution. For the measured Higgs boson mass of ˜ 125 GeV the limit of heavy top quarks provides a reliable approximation as long as the relative QCD corrections are scaled with the full mass-dependent LO cross section. In this limit the Higgs coupling to gluons can be described by an effective Lagrangian. The same approach can also be applied to the coupling of more than one Higgs boson to gluons. We will derive the effective Lagrangian for multi-Higgs couplings to gluons up to N4LO thus extending previous results for more than one Higgs boson. Moreover we discuss gluonic Higgs couplings up to NNLO, if several heavy quarks contribute.
Two-gluon rapidity correlations of strong colour field in pp, pA and AA collisions
NASA Astrophysics Data System (ADS)
Zhao, Ye-Yin; Xu, Ming-Mei; Zhang, Heng-Ying; Wu, Yuan-Fang
2016-11-01
Using the CGC formalism, we calculate the two-gluon rapidity correlations of strong colour fields in pp, pA and AA collisions, respectively. If one trigger gluon is fixed at central rapidity, a ridge-like correlation pattern is obtained in symmetry pp and AA collisions, and a huge bump-like correlation pattern is presented in asymmetry pA collisions. It is demonstrated that long-range ridge-like rapidity correlations are caused by the stronger correlation with the gluon of colour source. These features are independent of the azimuthal angular of two selected gluon. They are qualitatively consistent with current observed data at LHC. The transverse momentum and incident energy dependence of the ridge and bump-like correlations are also systematically studied. The ridge is more likely observed at higher incident energy and lower transverse momentum of trigger gluon.
Pennington, M. R.; Wilson, D. J.
2011-11-01
The gluon and ghost propagators in Landau gauge QCD are investigated using the Schwinger-Dyson equation approach. Working in Euclidean spacetime, we solve for these propagators using a selection of vertex inputs, initially for the ghost equation alone and then for both propagators simultaneously. The results are shown to be highly sensitive to the choices of vertices. We favor the infrared finite ghost solution from studying the ghost equation alone where we argue for a specific unique solution. In order to solve this simultaneously with the gluon using a dressed-one-loop truncation, we find that a nontrivial full ghost-gluon vertex is required in the vanishing gluon momentum limit. The self-consistent solutions we obtain correspond to having a masslike term in the gluon propagator dressing, in agreement with similar studies supporting the long-held proposal of Cornwall.
Measuring gluon shadowing with prompt photons at RHIC and LHC
NASA Astrophysics Data System (ADS)
Arleo, François; Gousset, Thierry
2008-02-01
The possibility to observe the nuclear modification of the gluon distribution at small-x (gluon shadowing) using high-p⊥ prompt photon production at RHIC and at LHC is discussed. The per-nucleon ratio, σ (p + A → γ + X) / (A × σ (p + p → γ + X)), is computed for both inclusive and isolated prompt photons in perturbative QCD at NLO using different parameterizations of nuclear parton densities, in order to assess the visibility of the shadowing signal. The production of isolated photons turns out to be a promising channel which allows for a reliable extraction of the gluon density, RGA, and the structure function, RF2A, in a nucleus over that in a proton. Moreover, the production ratio of prompt photons at forward-over-backward rapidity in p-A collisions provides an estimate of RGA (at small x) over RF2A (at large x), without the need of p- p reference data at the same energy.
Bulk Properties and Collective Flow of Quark Gluon Plasma
NASA Astrophysics Data System (ADS)
Kapusta, Joseph
2007-10-01
Quantum Chromodynamics predicts a transition from a hadronic phase at temperatures less than 150-200 MeV to a quark gluon plasma phase at higher temperatures. Lattice calculations show a big increase in the entropy density in this vicinity. Whether the transition is first or second order or a smooth rapid crossover depends upon the values of the up, down and strange quark masses. The goal of the heavy ion experimental program at RHIC is to observe this transition and to study the nature of the quark gluon plasma quantitatively. Two big surprises arose from these experiments: Substantial collective flow has been observed, as evidenced by single-particle transverse momentum distributions and by azimuthal correlations among the produced particles, and the degree to which high energy jets are attenuated in the produced matter. A variety of theoretical models of these collisions require initial energy densities more than a factor of 10 greater than in neutron star cores and more than a factor of 100 greater than within atomic nuclei. Taken together this body of work implies a strongly interacting phase of quarks and gluons beyond the capabilities of perturbation theory. This has motivated approaches based on gauge theories with gravity duals where physical observables may be calculated in a strong coupling limit. This in turn has stimulated interest from members of the string theory community who are currently bringing their expertise to bear on the problem.
Frederico, T.; Pace, E.; Pasquini, B.; Salme, G.
2010-08-05
Longitudinal and transverse parton distributions for pion and nucleon are calculated from hadron vertexes obtained by a study of form factors within relativistic quark models. The relevance of the one-gluon-exchange dominance at short range for the behavior of the form factors at large momentum transfer and of the parton distributions at the end points is stressed.
NASA Technical Reports Server (NTRS)
Smiley, Robert F.; Haines, Gilbert A.
1949-01-01
Bureau of Aeronautics Design Specifications SS-IC-2 for water loads in sheltered water are compared with experimental water loads obtained during a full--scale landing investigation. This investigation was conducted with a JRS-1 flying boat which has a 20 degrees dead-rise V-bottom with a partial chine flare. The range of landing conditions included airspeeds between 88 and 126 feet per second, sinking speeds between 1.6 and 9.1 feet per second, flight angles less than 6 degrees, and trims between 2 degrees and 12 degrees. Landings were moderate and were made in calm water. Measurements were obtained of maximum over-all loads, maximum pitching moments, and pressure distributions. Maximum experimental loads include over-all load factors of 2g, moments of 128,000 pound-feet, and maximum local pressures greater than 40 pounds per square inch. Experimental over-all loads are approximately one-half the design values, while local pressures are of the same order as or larger than pressures calculated from specifications for plating, stringer, floor, and frame design. The value of this comparison is limited, to some extent, by the moderate conditions of the test and by the necessary simplifying assumptions used in comparing the specifications with the experimental loads.
Testing the running coupling kT-factorization formula for the inclusive gluon production
NASA Astrophysics Data System (ADS)
Durães, F. O.; Giannini, A. V.; Gonçalves, V. P.; Navarra, F. S.
2016-09-01
The inclusive gluon production at midrapidities is described in the color glass condensate formalism using the kT-factorization formula, which was derived at fixed coupling constant considering the scattering of a dilute system of partons with a dense one. Recent analysis demonstrated that this approach provides a satisfactory description of the experimental data for the inclusive hadron production in p p /p A /A A collisions. However, these studies are based on the fixed coupling kT-factorization formula. This formula does not take into account the running coupling corrections, which are important to set the scales present in the cross section. In this paper we consider the running coupling corrected kT-factorization formula conjectured some years ago and investigate the impact of the running coupling corrections on the observables. In particular, the pseudorapidity distributions and charged hadrons' multiplicity are calculated considering p p , d A u /p P b , and A u A u /P b P b collisions at RHIC and LHC energies. We compare the corrected running coupling predictions with those obtained using the original kT-factorization assuming a fixed coupling or a prescription for the inclusion of the running of the coupling. Considering the Kharzeev-Levin-Nardi unintegrated gluon distribution and a simplified model for the nuclear geometry, we demonstrate that the distinct predictions are similar for the pseudorapidity distributions in p p /p A /A A collisions and for the charged hadrons' multiplicity in p p /p A collisions. On the other hand, the running coupling corrected kT-factorization formula predicts a smoother energy dependence for d N /d η in A A collisions.
Bugaev, K. A.; Petrov, V. K.; Zinovjev, G. M.
2009-05-15
The influence of the medium-dependent finite width of quark gluon plasma (QGP) bags on their equation of state is analyzed within an exactly solvable model. It is argued that the large width of the QGP bags not only explains the observed deficit in the number of hadronic resonances but also clarifies the reason why the heavy QGP bags cannot be directly observed as metastable states in a hadronic phase. The model allows us to estimate the minimal value of the width of QGP bags being heavier than 2 GeV from a variety of the lattice QCD data and get that the minimal resonance width at zero temperature is about 600 MeV, whereas the minimal resonance width at the Hagedorn temperature is about 2000 MeV. As shown, these estimates are almost insensitive to the number of the elementary degrees of freedom. The recent lattice QCD data are analyzed and it is found that in addition to the {sigma}T{sup 4} term the lattice QCD pressure contains T-linear and T{sup 4}lnT terms in the range of temperatures between 240 and 420 MeV. The presence of the last term in the pressure bears almost no effect on the width estimates. Our analysis shows that at high temperatures the average mass and width of the QGP bags behave in accordance with the upper bound of the Regge trajectory asymptotics (the linear asymptotics), whereas at low temperatures they obey the lower bound of the Regge trajectory asymptotics (the square root one). Since the model explicitly contains the Hagedorn mass spectrum, it allows us to remove an existing contradiction between the finite number of hadronic Regge families and the Hagedorn idea of the exponentially growing mass spectrum of hadronic bags.
Dynamical equation of the effective gluon mass
Aguilar, A. C.; Binosi, D.; Papavassiliou, J.
2011-10-15
In this article, we derive the integral equation that controls the momentum dependence of the effective gluon mass in the Landau gauge. This is accomplished by means of a well-defined separation of the corresponding ''one-loop dressed'' Schwinger-Dyson equation into two distinct contributions, one associated with the mass and one with the standard kinetic part of the gluon. The entire construction relies on the existence of a longitudinally coupled vertex of nonperturbative origin, which enforces gauge invariance in the presence of a dynamical mass. The specific structure of the resulting mass equation, supplemented by the additional requirement of a positive-definite gluon mass, imposes a rather stringent constraint on the derivative of the gluonic dressing function, which is comfortably satisfied by the large-volume lattice data for the gluon propagator, both for SU(2) and SU(3). The numerical treatment of the mass equation, under some simplifying assumptions, is presented for the aforementioned gauge groups, giving rise to a gluon mass that is a nonmonotonic function of the momentum. Various theoretical improvements and possible future directions are briefly discussed.
Quasilinear transport approach to equilibration of quark-gluon plasmas
Mrowczynski, Stanislaw; Mueller, Berndt
2010-03-15
We derive the transport equations of quark-gluon plasma in the quasilinear approximation. The equations are either of the Balescu-Lenard or Fokker-Planck form. The plasma's dynamics is assumed to be governed by longitudinal chromoelectric fields. The isotropic plasma, which is stable, and the two-stream system, which is unstable, are considered in detail. A process of equilibration is briefly discussed in both cases. The peaks of the two-stream distribution are shown to rapidly dissolve in time.
NASA Astrophysics Data System (ADS)
Kyoden, Tomoaki; Yasue, Youichi; Ishida, Hiroki; Akiguchi, Shunsuke; Andoh, Tsugunobu; Takada, Yogo; Teranishi, Tsunenobu; Hachiga, Tadashi
2015-01-01
A laser Doppler velocimeter (LDV) has been developed that is capable of performing two-dimensional (2D) cross-sectional measurements. It employs two horizontal laser light sheets that intersect at an angle of 13.3°. Since the intersection region is thin, it can be used to approximately determine the 2D flow field. An 8 × 8 array of optical fibers is used to simultaneously measure Doppler frequencies at 64 points. Experiments were conducted to assess the performance of the LDV, and it was found to be capable of obtaining spatial and temporal velocity information at multiple points in a flow field. The technique is fast, noninvasive, and accurate over long sampling periods. Furthermore, its applicability to an actual flow field was confirmed by measuring the temporal velocity distribution of a pulsatile flow in a rectangular flow channel with an obstruction. The proposed device is thus a useful, compact optical instrument for conducting simultaneous 2D cross-sectional multipoint measurements.
Ion-induced quark-gluon implosion.
Frankfurt, L; Strikman, M
2003-07-11
We investigate nuclear fragmentation in the central proton-nucleus and nucleus-nucleus collisions at the energies of CERN LHC. Within the semiclassical approximation we argue that because of the fast increase with energy of the cross sections of soft and hard interactions each nucleon is stripped in the average process off "soft" partons and fragments into a collection of leading quarks and gluons with large p(t). Valence quarks and gluons are streaming in the opposite directions when viewed in the c.m. of the produced system. The resulting pattern of the fragmentation of the colliding nuclei leads to an implosion of the quark and gluon constituents of the nuclei. The nonequilibrium state produced at the initial stage in the nucleus fragmentation region is estimated to have densities >/=50 GeV/fm(3) at the LHC energies and probably >/=10 GeV/fm(3) at BNL RHIC. PMID:12906475
Asymptotic freedom in the front-form Hamiltonian for quantum chromodynamics of gluons
NASA Astrophysics Data System (ADS)
Gómez-Rocha, María; Głazek, Stanisław D.
2015-09-01
Asymptotic freedom of gluons in pure-gauge QCD is obtained in the leading terms of their renormalized Hamiltonian in the Fock space, instead of considering virtual Green's functions or scattering amplitudes. Namely, we calculate the three-gluon interaction term in the effective front-form Hamiltonian for gluons in the Minkowski space-time using the renormalization group procedure for effective particles (RGPEP), with a new generator. The resulting three-gluon vertex is a function of the scale parameter, s , that has an interpretation of the size of effective gluons. The corresponding Hamiltonian running coupling constant, gλ, depending on the associated momentum scale λ =1 /s , is calculated in the series expansion in powers of g0=gλ 0 up to the terms of third order, assuming some small value for g0 at some large λ0. The result exhibits the same finite sensitivity to small-x regularization as the one obtained in an earlier RGPEP calculation, but the new calculation is simpler than the earlier one because of a simpler generator. This result establishes a degree of universality for pure-gauge QCD in the RGPEP.
Quark-gluon plasma in an external magnetic field.
Levkova, L; DeTar, C
2014-01-10
Using numerical simulations of lattice QCD we calculate the effect of an external magnetic field on the equation of state of the quark-gluon plasma. The results are obtained using a Taylor expansion of the pressure with respect to the magnetic field for the first time. The coefficients of the expansion are computed to second order in the magnetic field. Our setup for the external magnetic field avoids complications arising from toroidal boundary conditions, making a Taylor series expansion straightforward. This study is exploratory and is meant to serve as a proof of principle.
Shear Viscosity in a Gluon Gas
Xu Zhe; Greiner, Carsten
2008-05-02
The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio {eta}/s for a gluon gas, which involves elastic gg{yields}gg perturbative QCD (PQCD) scatterings as well as inelastic gg{r_reversible}ggg PQCD bremsstrahlung. For {alpha}{sub s}=0.3 we find {eta}/s=0.13 and for {alpha}{sub s}=0.6, {eta}/s=0.076. The small {eta}/s values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.
Shear viscosity in a gluon gas.
Xu, Zhe; Greiner, Carsten
2008-05-01
The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio eta/s for a gluon gas, which involves elastic gg-->gg perturbative QCD (PQCD) scatterings as well as inelastic gg<-->ggg PQCD bremsstrahlung. For alpha_{s}=0.3 we find eta/s=0.13 and for alpha_{s}=0.6, eta/s=0.076. The small eta/s values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.
NASA Astrophysics Data System (ADS)
Zeng, X.; Lancelle, C.; Thurber, C. H.; Fratta, D.; Wang, H. F.; Chalari, A.; Clarke, A.
2015-12-01
The field test of Distributed Acoustic Sensing (DAS) conducted at Garner Valley, California on September 11-12, 2013 provided a continuous overnight record of ambient noise. The DAS array recorded ground motions every one meter of optical cable that was arranged approximately in the shape of a rectangle with dimensions of 160 m by 80 m. The long dimension of the array was adjacent to a state highway. Three hours of record were used to compute noise cross-correlation functions (NCFs) in one-minute windows. The trace from each sensor channel was pre-processed by downsampling to 200 Hz, followed by normalization in the time-domain and bandpass filtering between 2 and 20 Hz (Bensen et al., 2007). The one-minute NCFs were then stacked using the time-frequency domain phase-weighted stacking method (Schimmel & Gallart, 2007). The NCFs between channels were asymmetrical reflecting the direction of traffic noise. The group velocities were found using the frequency-time analysis method. The energy was concentrated between 5 and 15 Hz, which falls into the typical traffic noise frequency band. The resulting velocities were between 100 and 300 m/s for frequencies between 10 and 20 Hz, which are in the same range as described in the results for surface-wave dispersion obtained using an active source for the same site (Lancelle et al., 2015). The group velocity starts to decrease for frequencies greater than ~10 Hz, which was expected on the basis of a previous shear-wave velocity model (Steidl et al., 1996). Then, the phase velocity was calculated using the multichannel analysis of surface wave technique (MASW - Park et al., 1999) with 114 NCFs spaced one meter apart. The resulting dispersion curve between 5 and 15 Hz gave phase velocities that ranged from approximately 170 m/s at 15 Hz to 250 m/s at 5 Hz. These results are consistent with other results of active-source DAS and seismometer records obtained at the Garner Valley site (e.g., Stokoe et al. 2004). This analysis is
Gluon jets from heavy paraquarkonium
Kamal, A.N.; Kodaira, J.; Muta, T.
1982-02-01
The GGG and qq-barG jets in the decay of very heavy paraquarkonia are analyzed in perturbative quantum chromodynamics. The thrust distributions are calculated and the result is compared with the thrust distributions in the orthoquarkonium decay and in e/sup +/e/sup -/..-->..qq-barG jets.
Gluon and Wilson loop TMDs for hadrons of spin ≤ 1
NASA Astrophysics Data System (ADS)
Boer, Daniël; Cotogno, Sabrina; van Daal, Tom; Mulders, Piet J.; Signori, Andrea; Zhou, Ya-Jin
2016-10-01
In this paper we consider the parametrizations of gluon transverse momentum dependent (TMD) correlators in terms of TMD parton distribution functions (PDFs). These functions, referred to as TMDs, are defined as the Fourier transforms of hadronic matrix elements of nonlocal combinations of gluon fields. The nonlocality is bridged by gauge links, which have characteristic paths (future or past pointing), giving rise to a process dependence that breaks universality. For gluons, the specific correlator with one future and one past pointing gauge link is, in the limit of small x, related to a correlator of a single Wilson loop. We present the parametrization of Wilson loop correlators in terms of Wilson loop TMDs and discuss the relation between these functions and the small- x `dipole' gluon TMDs. This analysis shows which gluon TMDs are leading or suppressed in the small- x limit. We discuss hadronic targets that are unpolarized, vector polarized (relevant for spin-1 /2 and spin-1 hadrons), and tensor polarized (relevant for spin-1 hadrons). The latter are of interest for studies with a future Electron-Ion Collider with polarized deuterons.
Strongly and weakly unstable anisotropic quark-gluon plasma
Manuel, Cristina; Mrowczynski, Stanislaw
2005-08-01
Using explicit solutions of the QCD transport equations, we derive an effective potential for an anisotropic quark-gluon plasma which under plausible assumptions holds beyond the Hard Loop approximation. The configurations, which are unstable in the linear response approach, are characterized by a negative quadratic term of the effective potential. The signs of higher-order terms can be either negative or positive, depending on the parton momentum distribution. In the case of a Gaussian momentum distribution, the potential is negative and unbound from below. Therefore, the modes, which are unstable for gauge fields of small amplitude, remain unstable for arbitrary large amplitudes. We also present an example of a momentum distribution which gives a negative quadratic term of the effective potential but the whole potential has a minimum and it grows for sufficiently large gauge fields. Then, the system is weakly unstable. The character of the instability is important for the dynamical evolution of the plasma system.
Productions of heavy charged leptons via gluon fusion at the LHC: A revisit
Liu Chun; Yang Shuo
2010-05-01
Heavy charged lepton productions via gluon fusion at the LHC are revisited. Full loop calculations are adopted with an updated parton distribution function and electroweak data. Including contribution from new generation quarks in the loop, pair production of the sequential heavy lepton via gluon fusion at the LHC dominates over that via the Drell-Yan mechanism in some heavy lepton mass range. Exotic lepton single production of vectorlike lepton extended models is also calculated. In the later case, the gluon fusion mechanism via the Higgs exchange is emphasized. Our numerical results for both pair and single production of heavy leptons are smaller than previous studies especially for a large heavy lepton mass as a result of full loop calculation and due to the mixing angles.
SU(3) Landau gauge gluon and ghost propagators using the logarithmic lattice gluon field definition
Ilgenfritz, Ernst-Michael; Menz, Christoph; Mueller-Preussker, Michael; Schiller, Arwed; Sternbeck, Andre
2011-03-01
We study the Landau gauge gluon and ghost propagators of SU(3) gauge theory, employing the logarithmic definition for the lattice gluon fields and implementing the corresponding form of the Faddeev-Popov matrix. This is necessary in order to consistently compare lattice data for the bare propagators with that of higher-loop numerical stochastic perturbation theory. In this paper we provide such a comparison, and introduce what is needed for an efficient lattice study. When comparing our data for the logarithmic definition to that of the standard lattice Landau gauge we clearly see the propagators to be multiplicatively related. The data of the associated ghost-gluon coupling matches up almost completely. For the explored lattice spacings and sizes discretization artifacts, finite size, and Gribov-copy effects are small. At weak coupling and large momentum, the bare propagators and the ghost-gluon coupling are seen to be approached by those of higher-order numerical stochastic perturbation theory.
Exploring Quarks, Gluons and the Higgs Boson
ERIC Educational Resources Information Center
Johansson, K. Erik
2013-01-01
With real particle collision data available on the web, the amazing dynamics of the fundamental particles of the standard model can be explored in classrooms. Complementing the events from the ATLAS experiment with animations of the fundamental processes on the quark and gluon level makes it possible to better understand the invisible world of…
Squeezed colour states in gluon jet
NASA Technical Reports Server (NTRS)
Kilin, S. YA.; Kuvshinov, V. I.; Firago, S. A.
1993-01-01
The possibility of the formation of squeezed states of gluon fields in quantum chromodynamics due to nonlinear nonperturbative self interaction during jet evolution in the process of e(+)e(-) annihilation into hadrons, which are analogous to the quantum photon squeezed states in quantum electrodynamics, is demonstrated. Additionally, the squeezing parameters are calculated.
Sambamurti Memorial Lecture: Spotlight on the Gluon
Michael Begelas
2016-07-12
Begel uses results from the Fermilab D0 and E706 experiments to explain how the production rate and energy spectrum of photons produced during proton collisions helped to clarify how the energy inside the proton is shared between quarks and gluons.
Renormalization of dimension 6 gluon operators
NASA Astrophysics Data System (ADS)
Kim, HyungJoo; Lee, Su Houng
2015-09-01
We identify the independent dimension 6 twist 4 gluon operators and calculate their renormalization in the pure gauge theory. By constructing the renormalization group invariant combinations, we find the scale invariant condensates that can be estimated in nonperturbative calculations and used in QCD sum rules for heavy quark systems in medium.
We compare measurements of aerosol mass concentrations obtained gravimetrically using Teflon coated glass fiber filters and by integrating mass distributions measured with the differential mobility analyzer–aerosol particle mass analyzer (DMA–APM) technique (Aero...
Hybrid neutron stars with the Dyson-Schwinger quark model and various quark-gluon vertices
NASA Astrophysics Data System (ADS)
Chen, H.; Wei, J.-B.; Baldo, M.; Burgio, G. F.; Schulze, H.-J.
2015-05-01
We study cold dense quark matter and hybrid neutron stars with a Dyson-Schwinger quark model and various choices of the quark-gluon vertex. We obtain the equation of state of quark matter in beta equilibrium and investigate the hadron-quark phase transition in combination with a hadronic equation of state derived within the Brueckner-Hartree-Fock many-body theory. Comparing with the results for quark matter within the rainbow approximation, the Ball-Chiu (BC) Ansatz and the 1BC Ansatz for the quark-gluon vertex lead to a reduction of the effective interaction at finite chemical potential, qualitatively similar to the effect of our gluon propagator. We find that the phase transition and the equation of state of the quark or mixed phase and consequently the resulting hybrid star mass and radius depend mainly on a global reduction of the effective interaction due to effects of both the quark-gluon vertex and gluon propagator, but are not sensitive to details of the vertex Ansatz.
Koyama, Kento; Hokunan, Hidekazu; Hasegawa, Mayumi; Kawamura, Shuso; Koseki, Shigenobu
2016-12-01
We investigated a bacterial sample preparation procedure for single-cell studies. In the present study, we examined whether single bacterial cells obtained via 10-fold dilution followed a theoretical Poisson distribution. Four serotypes of Salmonella enterica, three serotypes of enterohaemorrhagic Escherichia coli and one serotype of Listeria monocytogenes were used as sample bacteria. An inoculum of each serotype was prepared via a 10-fold dilution series to obtain bacterial cell counts with mean values of one or two. To determine whether the experimentally obtained bacterial cell counts follow a theoretical Poisson distribution, a likelihood ratio test between the experimentally obtained cell counts and Poisson distribution which parameter estimated by maximum likelihood estimation (MLE) was conducted. The bacterial cell counts of each serotype sufficiently followed a Poisson distribution. Furthermore, to examine the validity of the parameters of Poisson distribution from experimentally obtained bacterial cell counts, we compared these with the parameters of a Poisson distribution that were estimated using random number generation via computer simulation. The Poisson distribution parameters experimentally obtained from bacterial cell counts were within the range of the parameters estimated using a computer simulation. These results demonstrate that the bacterial cell counts of each serotype obtained via 10-fold dilution followed a Poisson distribution. The fact that the frequency of bacterial cell counts follows a Poisson distribution at low number would be applied to some single-cell studies with a few bacterial cells. In particular, the procedure presented in this study enables us to develop an inactivation model at the single-cell level that can estimate the variability of survival bacterial numbers during the bacterial death process.
Koyama, Kento; Hokunan, Hidekazu; Hasegawa, Mayumi; Kawamura, Shuso; Koseki, Shigenobu
2016-12-01
We investigated a bacterial sample preparation procedure for single-cell studies. In the present study, we examined whether single bacterial cells obtained via 10-fold dilution followed a theoretical Poisson distribution. Four serotypes of Salmonella enterica, three serotypes of enterohaemorrhagic Escherichia coli and one serotype of Listeria monocytogenes were used as sample bacteria. An inoculum of each serotype was prepared via a 10-fold dilution series to obtain bacterial cell counts with mean values of one or two. To determine whether the experimentally obtained bacterial cell counts follow a theoretical Poisson distribution, a likelihood ratio test between the experimentally obtained cell counts and Poisson distribution which parameter estimated by maximum likelihood estimation (MLE) was conducted. The bacterial cell counts of each serotype sufficiently followed a Poisson distribution. Furthermore, to examine the validity of the parameters of Poisson distribution from experimentally obtained bacterial cell counts, we compared these with the parameters of a Poisson distribution that were estimated using random number generation via computer simulation. The Poisson distribution parameters experimentally obtained from bacterial cell counts were within the range of the parameters estimated using a computer simulation. These results demonstrate that the bacterial cell counts of each serotype obtained via 10-fold dilution followed a Poisson distribution. The fact that the frequency of bacterial cell counts follows a Poisson distribution at low number would be applied to some single-cell studies with a few bacterial cells. In particular, the procedure presented in this study enables us to develop an inactivation model at the single-cell level that can estimate the variability of survival bacterial numbers during the bacterial death process. PMID:27554145
A T-matrix calculation for in-medium heavy-quark gluon scattering
NASA Astrophysics Data System (ADS)
Huggins, K.; Rapp, R.
2012-12-01
The interactions of charm and bottom quarks in a quark-gluon plasma (QGP) are evaluated using a thermodynamic 2-body T-matrix. We specifically focus on heavy-quark (HQ) interactions with thermal gluons with an input potential motivated by lattice-QCD computations of the HQ free energy. The latter is implemented into a field-theoretic ansatz for color-Coulomb and (remnants of) confining interactions. This, in particular, enables to discuss corrections to the potential approach, specifically hard-thermal-loop corrections to the vertices, relativistic corrections deduced from pertinent Feynman diagrams, and a suitable projection on transverse thermal gluons. The resulting potentials are applied to compute scattering amplitudes in different color channels and utilized for a calculation of the corresponding HQ drag coefficient in the QGP. A factor of ˜2-3 enhancement over perturbative results is obtained, mainly driven by the resummation in the attractive color-channels.
NASA Astrophysics Data System (ADS)
Greif, Moritz; Bouras, Ioannis; Greiner, Carsten; Xu, Zhe
2014-11-01
Electric conductivity is sensitive to effective cross sections among the particles of the partonic medium. We investigate the electric conductivity of a hot plasma of quarks and gluons, solving the relativistic Boltzmann equation. In order to extract this transport coefficient, we employ the Green-Kubo formalism and, independently, a method motivated by the classical definition of electric conductivity. To this end we evaluate the static electric diffusion current upon the influence of an electric field. Both methods give identical results. For the first time, we obtain numerically the Drude electric conductivity formula for an ultrarelativistic gas of quarks and gluons employing constant isotropic binary cross sections. Furthermore, we extract the electric conductivity for a system of massless quarks and gluons including screened binary and inelastic, radiative 2 ↔3 perturbative QCD scattering. Comparing with recent lattice results, we find an agreement in the temperature dependence of the conductivity.
NASA Technical Reports Server (NTRS)
Peters, B. C., Jr.; Walker, H. F.
1975-01-01
A general iterative procedure is given for determining the consistent maximum likelihood estimates of normal distributions. In addition, a local maximum of the log-likelihood function, Newtons's method, a method of scoring, and modifications of these procedures are discussed.
We report the draft genome sequences of six Mycobacterium immunogenum isolated from a chloraminated drinking water distribution system simulator subjected to changes in operational parameters. M. immunogenum, a rapidly growing mycobacteria previously reported as the cause of hyp...
Gluon saturation and Feynman scaling in leading neutron production
NASA Astrophysics Data System (ADS)
Carvalho, F.; Gonçalves, V. P.; Spiering, D.; Navarra, F. S.
2016-01-01
In this paper we extend the color dipole formalism for the study of leading neutron production in e + p → e + n + X collisions at high energies and estimate the related observables which were measured at HERA and could be analyzed in future electron-proton (ep) colliders. In particular, we calculate the Feynman xF distribution of leading neutrons, which is expressed in terms of the pion flux and the photon-pion total cross section. In the color dipole formalism, the photon-pion cross section is described in terms of the dipole-pion scattering amplitude, which contains information about the QCD dynamics at high energies and gluon saturation effects. We consider different models for the scattering amplitude, which have been used to describe the inclusive and diffractive ep HERA data. Moreover, the model dependence of our predictions with the description of the pion flux is analyzed in detail. We demonstrate the recently released H1 leading neutron spectra can be described using the color dipole formalism and that these spectra could help us to observe more clearly gluon saturation effects in future ep colliders.
Revetta, Randy P.
2016-01-01
We report here the draft genome sequences of six Mycobacterium immunogenum strains isolated from a chloraminated drinking water distribution system simulator subjected to changes in operational parameters. M. immunogenum, a rapidly growing mycobacterium previously reported to be the cause of hypersensitivity pneumonitis from contaminated metalworking fluid aerosols, is becoming a public health concern. PMID:26744376
Gomez-Alvarez, Vicente; Revetta, Randy P
2016-01-01
We report here the draft genome sequences of six Mycobacterium immunogenum strains isolated from a chloraminated drinking water distribution system simulator subjected to changes in operational parameters. M. immunogenum, a rapidly growing mycobacterium previously reported to be the cause of hypersensitivity pneumonitis from contaminated metalworking fluid aerosols, is becoming a public health concern. PMID:26744376
Gluon-glueball duality and glueball searches
Nussinov, Shmuel; Shrock, Robert
2009-09-01
We discuss a notion of gluon-glueball duality analogous to quark-hadron duality. We apply this idea to the radiative decay of heavy orthoquarkonium, QQ{yields}{gamma}gg, which has been used to search for glueballs. The duality is first introduced in two simplified contexts: (i) a hypothetical version of QCD without any light quarks and (ii) QCD in the large-N{sub c} limit. We then discuss how an approximate form of this duality could hold in real QCD, based on a hierarchy of time scales in the temporal evolution of the gg subsystem in radiative orthoquarkonium decay. We apply this notion of gluon-glueball duality to suggest a method that could be useful in experimental searches for glueballs.
Searching for $Z'$ bosons decaying to gluons
Alwall, Johan; Khader, Mazin; Rajaraman, Arvind; Whiteson, Daniel; Yen, Michael; /UC, Irvine
2012-02-01
The production and decay of a new heavy vector boson, a chromophilic Z{prime} vector boson, is described. The chromophilic Z{prime} couples only to two gluons, but its two-body decays are absent, leading to a dominant decay mode of Z{prime} {yields} q{bar q}g. The unusual nature of the interaction predicts a cross-section which grows with m{sub Z{prime}} for a fixed coupling and an accompanying gluon with a coupling that rises with its energy. We study the t{bar t}g decay mode, proposing distinct reconstruction techniques for the observation of an excess and for the measurement of m{sub Z{prime}}. We estimate the sensitivity of current experimental datasets.
Colliding solitary waves in quark gluon plasmas
NASA Astrophysics Data System (ADS)
Rafiei, Azam; Javidan, Kurosh
2016-09-01
We study the head-on collision of propagating waves due to perturbations in quark gluon plasmas. We use the Massachusetts Institute of Technology bag model, hydrodynamics equation, and suitable equation of state for describing the time evolution of such localized waves. A nonlinear differential equation is derived for the propagation of small amplitude localized waves using the reductive perturbation method. We show that these waves are unstable and amplitude of the left-moving (right-moving) wave increases (decreases) after the collision, and so they reach the borders of a quark gluon plasma fireball with different amplitudes. Indeed we show that such arrangements are created because of the geometrical symmetries of the medium.
Equilibrium distribution of heavy quarks in fokker-planck dynamics
Walton; Rafelski
2000-01-01
We obtain an explicit generalization, within Fokker-Planck dynamics, of Einstein's relation between drag, diffusion, and the equilibrium distribution for a spatially homogeneous system, considering both the transverse and longitudinal diffusion for dimension n>1. We provide a complete characterization of the equilibrium distribution in terms of the drag and diffusion transport coefficients. We apply this analysis to charm quark dynamics in a thermal quark-gluon plasma for the case of collisional equilibration.
Nonperturbative study of the four gluon vertex
NASA Astrophysics Data System (ADS)
Binosi, D.; Ibañez, D.; Papavassiliou, J.
2014-09-01
In this paper we study the nonperturbative structure of the SU(3) four-gluon vertex in the Landau gauge, concentrating on contributions quadratic in the metric. We employ an approximation scheme where "one-loop" diagrams are computed using fully dressed gluon and ghost propagators, and tree-level vertices. When a suitable kinematical configuration depending on a single momentum scale p is chosen, only two structures emerge: the tree-level four-gluon vertex, and a tensor orthogonal to it. A detailed numerical analysis reveals that the form factor associated with this latter tensor displays a change of sign (zero-crossing) in the deep infrared, and finally diverges logarithmically. The origin of this characteristic behavior is proven to be entirely due to the masslessness of the ghost propagators forming the corresponding ghost-loop diagram, in close analogy to a similar effect established for the three-gluon vertex. However, in the case at hand, and under the approximations employed, this particular divergence does not affect the form factor proportional to the tree-level tensor, which remains finite in the entire range of momenta, and deviates moderately from its naive tree-level value. It turns out that the kinematic configuration chosen is ideal for carrying out lattice simulations, because it eliminates from the connected Green's function all one-particle reducible contributions, projecting out the genuine one-particle irreducible vertex. Motivated by this possibility, we discuss in detail how a hypothetical lattice measurement of this quantity would compare to the results presented here, and the potential interference from an additional tensorial structure, allowed by Bose symmetry, but not encountered within our scheme.
The structure of gluon radiation in QCD
Parke, S.; Mangano, M.
1989-08-01
For massless QCD the hard scattering amplitudes are naturally written in terms of the dual color expansion. here I present this expansion for purely gluonic processes and processes involving quark-antiquark pairs and gluons. The properties of the sub-amplitudes as well as explicit algebraic expressions are given for a number of these processes. Also, I demonstrate how to recover massless QED amplitudes from the dual expansion of massless QCD. 16 refs., 3 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Stumpf, H.
1987-03-01
The model is defined by a selfregularizing nonlinear preon field equation and all observable (elementary and non-elementary) particles are assumed to be bound (quantum) states of the fermionic preon fields. In particular electroweak gauge bosons are two-particle composites, leptons and quarks are three-particle composites, and gluons are six-particle composites. Electroweak gauge bosons, leptons and quarks and their effective interactions etc. were studied in preceding papers. In this paper gluons and their effective dynamics are discussed. Due to the complications of a six-particle bound state dynamics the formation of gluons is performed in two steps: First the effective dynamics of three-particle composites (quarks) is derived, and secondly gluons are fusioned from two quarks respectively. The resulting effective gluon dynamics is a non-abelian SU(3) dynamics, i.e. this local gauge dynamics is produced by the properties of the composites and need not be introduced in the original preon field equation. Mathematically these results are achieved by the application of functional quantum theory to the model under consideration and subsequent evaluation of weak mapping procedures, both introduced in preceding papers. PACS 11.10 Field theory. PACS 12.10 Unified field theories and models. PACS 12.35 Composite models of particles.
NASA Astrophysics Data System (ADS)
Sarrico, C. O. R.
2015-10-01
The system of conservation laws {u_t} + {( {{{u^2} + {v^2}}/2} )_x} = 0, v t + ( uv - v)x = 0 with the initial conditions u( x, 0) = l 0 + b 0 H( x), v( x, 0) = k 0 + c 0 H( x), where H is the Heaviside function is studied. This strictly hyperbolic system was introduced by M. Brio in 1988 and provides a simplified model for the magnetohydrodynamics equations. Under certain compatibility conditions for the constants l 0, b 0, k 0, c 0, an explicit solution containing a Dirac mass is given and we prove the uniqueness of this solution within a convenient class of distributions which includes Dirac-delta measures. Our concept of solution is defined within the framework of a distributional product, and it is a consistent extension of the concept of a classical solution. This direct method seems considerably simpler than the weak asymptotic method usually used in the study of delta-shocks emergence in nonlinear conservation laws.
NASA Astrophysics Data System (ADS)
Ahmadov, Azad I.; Kuraev, Eduard A.
2014-08-01
We considered the three jet production processes in the region of the incident lepton, photon, quark or gluon fragmentation. The fourth jet is created by the recoil proton. The kinematics of jet production is discussed in jets production in the fragmentation region. The non-trivial relation between the momenta of the recoil proton and the polar angle of its emission was derived. Based on this formalism the differential cross sections of QCD processes gp→(ggg)p; qp→(qQbarQ)p; gp→(gQQbar)p were obtained, including the distribution on transverse momentum component of jets fragments. It was shown that the role of the contribution of “non-Abelian” nature may become dominant in a particular kinematics of the final particles. The kinematics, in which the initial particle changes the direction of movement to the opposite one, was considered in the case of heavy quark-antiquark pair production. Different distributions, including spectral, azimuthal and polar angle distribution on the fragments of jets can be arranged using our results. We present besides the behavior of the ratio of non-Abelian contribution to the cross section to the total contribution. We show that it dominates for large values of the transverse momenta of jets component (gluons or quarks). Some historical introduction to the cross-sections of peripheral processes, including 2γ creation mechanism production, including the result Brodsky-Kinoshita-Terazawa, is given.
Hatta, Yoshitaka; Xiao, Bo-Wen; Yuan, Feng
2016-05-20
We investigate the close connection between the quantum phase space Wigner distribution of small-x gluons and the color dipole scattering amplitude, and we propose studying it experimentally in the hard diffractive dijet production at the planned electron-ion collider. The angular correlation between the nucleon recoiled momentum and the dijet transverse momentum probes the nontrivial correlation in the phase space Wigner distribution. This experimental study not only provides us with three-dimensional tomographic pictures of gluons inside high energy protons-it gives a unique and interesting signal for the small-x dynamics with QCD evolution effects. PMID:27258865
NASA Astrophysics Data System (ADS)
Hatta, Yoshitaka; Xiao, Bo-Wen; Yuan, Feng
2016-05-01
We investigate the close connection between the quantum phase space Wigner distribution of small-x gluons and the color dipole scattering amplitude, and we propose studying it experimentally in the hard diffractive dijet production at the planned electron-ion collider. The angular correlation between the nucleon recoiled momentum and the dijet transverse momentum probes the nontrivial correlation in the phase space Wigner distribution. This experimental study not only provides us with three-dimensional tomographic pictures of gluons inside high energy protons—it gives a unique and interesting signal for the small-x dynamics with QCD evolution effects.
Semirelativistic potential model for three-gluon glueballs
Mathieu, Vincent; Semay, Claude; Silvestre-Brac, Bernard
2008-05-01
The three-gluon glueball states are studied with the generalization of a semirelativistic potential model giving good results for two-gluon glueballs. The Hamiltonian depends only on 3 parameters fixed on two-gluon glueball spectra: the strong coupling constant, the string tension, and a gluon size which removes singularities in the potential. The Casimir scaling determines the structure of the confinement. Our results are in good agreement with other approaches and lattice calculation for the odderon trajectory but differ strongly from lattice in the J{sup +-} sector. We propose a possible explanation for this problem.
NASA Astrophysics Data System (ADS)
Canon-Tapia, E.
2014-12-01
The distribution of volcanic features is ultimately controlled by processes taking place beneath the surface of a planet. For this reason, characterization of volcano distribution at a global scale can be used to obtain insights concerning dynamic aspects of planetary interiors. In this work, description of the distribution of volcanic features observed on Earth and Venus is completed using density contours obtained with the Fisher kernel. Attention is focused on similar features observed in both planets. In particular two features are examined with more detail: First, a pattern of groups of clusters defining the boundaries of elliptical regions that tentatively can be associated to large mantle plumes. Second, the existence of a uniform distribution of background volcanism. The former pattern is considered to constitute the first order convective pattern of the mantle in Venus, and although it is present on Earth, it is not as prominent. In contrast, the persistent occurrence of volcanic clusters at a lower significance level, suggests the occurrence of a different scale of mantle convection that controls a more uniformly distributed volcanism. Both, the first order related to large mantle-plumes and the background volcanism are superimposed on Earth to the volcanism controlled by plate tectonics. Consequently, the global distribution of volcanism in both planets reveals that at least three types of mantle convection can take place in the terrestrial planets, and that such types of mantle convection can coexist simultaneously in one given planet, although in each case, a dominant mode is different.
Equation of state of gluon plasma from local action
Zwanziger, Daniel
2007-12-15
We review recent analytic and numerical results concerning the confinement scenario in Coulomb gauge. We then consider a local, renormalizable, BRST(Becchi-Rouet-Stora-Tyutin)-invariant action for QCD in Coulomb gauge that contains auxiliary bose and fermi ghost fields and sources. When the auxiliary fields are integrated out, one obtains the standard Coulomb gauge action with a cutoff at the Gribov horizon. We use the local formulation to calculate the leading correction to the Stefan-Boltzmann equation of state at high temperature due to the cutoff at the Gribov horizon. It is of order g{sup 6}, which is precisely the order at which the infrared divergence found by Linde divergence first occurs. No such divergence arises in the present calculation because the propagator of would-be physical gluons is suppressed in the infrared due to the proximity of the Gribov horizon in infrared directions.
NASA Astrophysics Data System (ADS)
Gonçalves, V. P.; Martins, L. A. S.; Sauter, W. K.
2016-02-01
The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken- x variable and low values of the hard scale Q^2. An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon-hadron and hadron-hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrisations for the gluon distribution and estimate the exclusive vector meson photoproduction cross section at HERA and LHC using the leading logarithmic formalism. We perform a fit of the normalisation of the γ h cross section and the value of the hard scale for the process and demonstrate that the current LHCb experimental data are better described by models that assume a slow increasing of the gluon distribution at small x and low Q^2.
Chromodynamic fluctuations in quark-gluon plasma
Mrowczynski, Stanislaw
2008-05-15
Fluctuations of chromodynamic fields in the collisionless quark-gluon plasma are found as a solution of the initial value linearized problem. The plasma initial state is on average colorless, stationary, and homogeneous. When the state is stable, the initial fluctuations decay exponentially and in the long-time limit a stationary spectrum of fluctuations is established. For the equilibrium plasma it reproduces the spectrum which is provided by the fluctuation-dissipation relation. Fluctuations in the unstable plasma, where the memory of initial fluctuations is not lost, are also discussed.
Aaltonen, T.; Maki, T.; Mehtala, P.; Orava, R.; Osterberg, K.; Saarikko, H.; Remortel, N. van; Adelman, J.; Brubaker, E.; Fedorko, W. T.; Grosso-Pilcher, C.; Kim, Y. K.; Krop, D.; Kwang, S.; Paramonov, A. A.; Schmidt, M. A.; Shiraishi, S.; Shochet, M.; Wolfe, C.; Yang, U. K.
2009-02-01
We present a measurement of the ratio of the tt production cross section via gluon-gluon fusion to the total tt production cross section in pp collisions at {radical}(s)=1.96 TeV at the Tevatron. Using a data sample with an integrated luminosity of 955 pb{sup -1} recorded by the CDF II detector at Fermilab, we select events based on the tt decay to lepton+jets. Using an artificial neural network technique we discriminate between tt events produced via qq annihilation and gg fusion, and find G{sub f}={sigma}(gg{yields}tt)/{sigma}(pp{yields}tt)<0.33 at the 68% confidence level. This result is combined with a previous measurement to obtain the most stringent measurement of this quantity by CDF to date, G{sub f}=0.07{sub -0.07}{sup +0.15}.
NASA Astrophysics Data System (ADS)
Cañon-Tapia, Edgardo
2014-06-01
The distribution of volcanic features is ultimately controlled by processes taking place beneath the surface of a planet. For this reason, characterization of volcano distribution at a global scale can be used to obtain insights concerning dynamic aspects of planetary interiors. Until present, studies of this type commonly have focused on volcanic features of a specific type (e.g., large volcanoes in Venus or hot-spot volcanism on Earth), or have concentrated on relatively small regions (i.e., vent distribution within individual volcanic fields), but no comparison of extensive databases has been made by using the same tools in both planets. In this work, the description of the distribution of volcanic features observed over the entire surface of Venus is made using the same tool used for Earth, and is applied to an extensive database. The analysis is based on density contours obtained with the Fisher kernel. As a result, several groupings of volcanoes are identified refining the already documented concentration of volcanoes on the BAT zone. In particular some doughnut-like patterns are observed that might be related to the action of mantle plumes. The occurrence of such features on Earth, as well as the existence of a uniform distribution of background volcanism on both planets, suggests similarities on their geodynamic behavior that had not been identified previously.
Verbaro, Daniel; Ghosh, Indrajit; Nau, Werner M; Schweitzer-Stenner, Reinhard
2010-12-30
Structural preferences in the unfolded state of peptides determined by molecular dynamics still contradict experimental data. A remedy in this regard has been suggested by MD simulations with an optimized Amber force field ff03* ( Best, R. Hummer, G. J. Phys. Chem. B 2009 , 113 , 9004 - 9015 ). The simulations yielded a statistical coil distribution for alanine which is at variance with recent experimental results. To check the validity of this distribution, we investigated the peptide H-A(5)W-OH, which with the exception of the additional terminal tryptophan is analogous to the peptide used to optimize the force fields ff03*. Electronic circular dichroism, vibrational circular dichroism, and infrared spectroscopy as well as J-coupling constants obtained from NMR experiments were used to derive the peptide's conformational ensemble. Additionally, Förster resonance energy transfer between the terminal chromophores of the fluorescently labeled peptide analogue H-Dbo-A(5)W-OH was used to determine its average length, from which the end-to-end distance of the unlabeled peptide was estimated. Qualitatively, the experimental (3)J(H(N),C(α)), VCD, and ECD indicated a preference of alanine for polyproline II-like conformations. The experimental (3)J(H(N),C(α)) for A(5)W closely resembles the constants obtained for A(5). In order to quantitatively relate the conformational distribution of A(5) obtained with the optimized AMBER ff03* force field to experimental data, the former was used to derive a distribution function which expressed the conformational ensemble as a mixture of polyproline II, β-strand, helical, and turn conformations. This model was found to satisfactorily reproduce all experimental J-coupling constants. We employed the model to calculate the amide I' profiles of the IR and vibrational circular dichroism spectrum of A(5)W, as well as the distance between the two terminal peptide carbonyls. This led to an underestimated negative VCD couplet and an
An approach to fast fits of the unintegrated gluon density
Knutsson, Albert; Bacchetta, Alessandro; Kutak, Krzyzstof; Jung, Hannes
2009-01-01
An approach to fast fits of the unintegrated gluon density has been developed and used to determine the unintegrated gluon density by fits to deep inelastic scatting di-jet data from HERA. The fitting method is based on the determination of the parameter dependence by help of interpolating between grid points in the parameter-observable space before the actual fit is performed.
Gluon Polarisation in the Nucleon from High Transverse Momentum Hadron Pairs at COMPASS
Kurek, Krzysztof
2009-08-04
The main goal of the COMPASS spin physics programme is the measurement of the helicity contribution of the gluons, {delta}G/G, to the nucleon spin. It is determined from the longitudinal spin asymmetry in the scattering of 160 GeV polarised muons off a polarised LiD target. The new analysis and new COMPASS {delta}G/G result obtained from high transverse momentum hadron pairs for Q{sup 2}>1(GeV/c){sup 2} is presented. The weighted method based on a Neural Network approach is discussed. The result of {delta}G/G 0.08{+-}0.10(stat){+-}0.05(syst)disfavors a large positive contribution to the nucleon spin for a gluon momentum fraction around 0.08 and agrees with the previously obtained result from the analysis for the small Q{sup 2} kinematical region (Q{sup 2}<1(GeV/c){sup 2})
Probing Quark-Gluon Structure of Matter with e-p and e-A Reactions
Jian-Ping Chen
2011-11-01
Understanding the strong interaction (QCD) in the truly strong ('non-perturbative') region remains a major challenge in modern physics. Nucleon and nuclei provide natural laboratories to study the strong interaction. The quark-gluon structure of the nucleon and nuclei are important by themselves since they are the main (>99%) part of the visible world. With electroweak interaction well-understood, e-p and e-A are clean means to probe the nucleon and nuclear structure and to study the strong interaction (QCD). Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinally-polarized parton (quark and gluon) distributions (PDFs). It has becoming clear that transverse spin and transverse structure (both transverse spatial structure via generalized parton distributions (GPDs) and transverse momentum structure via transverse- momentum-dependent distributions (TMDs)) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction(QCD). The transverse spin, GPDs and TMDs have been the subjects of increasingly intense theoretical and experimental study recently. With 12 GeV energy upgrade, Jefferson Lab (JLab) will provide the most precise multi-dimensional map of the TMDs and GPDs in the valence quark region through Semi-Inclusive DIS (SIDIS) and Deep-Exclusive experiments, providing a 3-d partonic picture of the nucleon in momentum and spatial spaces. The precision information on TMDs and GPDs will provide access to the quark orbital angular momentum and its correlation with the quark and the nucleon spins. The planned future Electron-Ion Collider (EIC) will enable a precision study of the TMDs and GPDs of the sea quarks and gluons, in addition to completing the study in the valence region. The EIC will also open a new window to study the role of gluons in nuclei.
The gluon contribution to nucleon spin
Antje Bruell
2006-04-06
EIC is the ideal machine to finally determine the contribution of the gluons to the nucleon spin. Measurements of G{sub 1} will allow: (1) a determination of {Delta}G/G from its scaling violation and (2) a statistically very precise determination of the Bjorken Sum (systematics due to uncertainty in proton beam polarization). Measurements of charm cross section asymmetries will provide a precise determination of {Delta}G/G for 0.003 < x < 0.5 at a fixed value of Q{sup 2} of {approx} GeV{sup 2} provided they can measure the scattered electron at extremely small angles; separate the primary and secondary vertex with sufficient precision; and control the contribution of resolved photons. More work is needed to define the necessary detector requirements.
Gluon Green functions free of quantum fluctuations
NASA Astrophysics Data System (ADS)
Athenodorou, A.; Boucaud, Ph.; De Soto, F.; Rodríguez-Quintero, J.; Zafeiropoulos, S.
2016-09-01
This letter reports on how the Wilson flow technique can efficaciously kill the short-distance quantum fluctuations of 2- and 3-gluon Green functions, remove the ΛQCD scale and destroy the transition from the confining non-perturbative to the asymptotically-free perturbative sector. After the Wilson flow, the behavior of the Green functions with momenta can be described in terms of the quasi-classical instanton background. The same behavior also occurs, before the Wilson flow, at low-momenta. This last result permits applications as, for instance, the detection of instanton phenomenological properties or a determination of the lattice spacing only from the gauge sector of the theory.
Check of the gluon-reggeization condition in the next-to-leading order: Gluon part
Kozlov, M. G. Reznichenko, A. V. Fadin, V. S.
2012-04-15
The last bootstrap condition whose validity has not been verified to date is considered. This condition is an indispensable element in the unitarity-relation-based proof of themulti-Regge form of highenergy gluon-exchange QCD amplitudes in the next-to-leading-logarithm approximation. The approach used here relies on the s-channel unitarity and makes it possible to reproduce successively, in all orders of perturbation theory, themulti-Regge form of the amplitude, provided that specific nonlinear relations, called bootstrap conditions, hold. All of them were derived, and all, with the exception of one, were tested. An explicit verification of fulfillment of the last condition (the bootstrap condition for the inelastic amplitude of the production of one gluon inmulti-Regge kinematics) is performed. In our preceding study, we performed such a verification for purely fermion contributions, while, in the present study, we complete it for one-loop gluon corrections to the components of the condition being considered.
Inclusive b-jet and bb¯-dijet production at the LHC via Reggeized gluons
NASA Astrophysics Data System (ADS)
Saleev, V. A.; Shipilova, A. V.
2012-08-01
We study inclusive b-jet and bb¯-dijet production at the CERN LHC invoking the hypothesis of gluon Reggeization in t-channel exchanges at high energy. The b-jet cross section includes contributions from open b-quark production and from b-quark production via gluon-to-bottom-pair fragmentation. The transverse-momentum distributions of inclusive b-jet production measured with the ATLAS detector at the CERN LHC in different rapidity ranges are calculated both within multi-Regge kinematics and quasi-multi-Regge kinematics. The bb¯-dijet cross section is calculated within quasi-multi-Regge kinematics as a function of the dijet invariant mass Mjj, the azimuthal angle between the two jets Δϕ, and the angular variable χ. At the numerical calculation, we adopt the Kimber-Martin-Ryskin and Blümlein prescriptions to derive unintegrated gluon distribution function of the proton from its collinear counterpart for which we use the Martin-Roberts-Stirling-Thorne set. We find good agreement with measurements by the ATLAS and CMS Collaborations at the LHC at the hadronic c.m. energy of S=7TeV.
Exclusive J/ψ and ϒ photoproduction and the low x gluon
NASA Astrophysics Data System (ADS)
Jones, S. P.; Martin, A. D.; Ryskin, M. G.; Teubner, T.
2016-04-01
We study exclusive vector meson photoproduction, γ p\\to V+p with V=J/\\psi or ϒ, at next-to-leading order (NLO) in collinear factorisation, in order to examine what may be learnt about the gluon distribution at very low x. We examine the factorisation scale dependence of the predictions. We argue that, using knowledge of the NLO corrections, terms enhanced by a large {ln}(1/ξ ) can be reabsorbed in the LO part by a choice of the factorisation scale. (In these exclusive processes ξ takes the role of Bjorken-x.) Then, the scale dependence coming from the remaining NLO contributions has no {ln}(1/ξ ) enhancements. As a result, we find that predictions for the amplitude of ϒ production are stable to within about ±15%. This will allow data for the exclusive process {pp}\\to p{{\\Upsilon }}p at the Large Hadron Collider (LHC), particularly from LHCb, to be included in global parton analyses to constrain the gluon parton distribution function (PDF) down to x∼ {10}-5. Moreover, the study of exclusive J/\\psi photoproduction indicates that the gluon density found in the recent global PDF analyses is too small at low x and low scales.
Continuum study of the QCD phase diagram through an OPE-modified gluon propagator
NASA Astrophysics Data System (ADS)
Shi, Chao; Du, Yi-Lun; Xu, Shu-Sheng; Liu, Xiao-Jun; Zong, Hong-Shi
2016-02-01
Within the Dyson-Schwinger equation framework, a gluon propagator model incorporating a quark's feedback through operator product expansion is introduced to investigate the QCD phase diagram in the temperature-chemical-potential (T -μ ) plane. Partial restoration of chiral symmetry at zero temperature and finite temperature are both studied, suggesting a first order phase transition point on the μ axis and a critical end point at (TE,μE)/Tc=(0.85 ,1.11 ), where Tc is the pseudocritical temperature. In addition, we find the pseudocritical line can be well parametrized with the curvature parameter κ and a consistent decrease in κ , with more of the gluon propagator distributed to the quark's feedback.
NASA Astrophysics Data System (ADS)
Tsankov, Tsanko V.; Czarnetzki, Uwe
2016-08-01
A paper by El Saghir and Shannon (2012 Plasma Sources Sci. Technol. 21 025003) raises the question about the validity of the widely-used Druyvesteyn formula for obtaining the electron energy distribution function by cylindrical probes. They conclude that there are deviations between the Druyvesteyn formula for cylindrical and for spherical probes. In this comment this conclusion is questioned and the correct expressions are derived. It is shown that no such difference exists when all three velocity components are correctly accounted for. Furthermore, the disturbance to the plasma introduced by the probe is estimated.
Properties of Non-Conformal Quark Gluon Plasma of Holographic QCD Models from Compactified D4 Branes
NASA Astrophysics Data System (ADS)
Naji, J.
2016-08-01
In this article, we obtain some thermodynamics quantities of non-conformal gluonic matter. We extract specific heat, enthalpy and equation of state in terms of the temperature. Using transport properties we find important quantities of corresponding quark gluon plasma like drag force and jet-quenching.
NASA Technical Reports Server (NTRS)
VonGlahn, Uwe H.; Gelder, Thomas F.; Smyers, William H., Jr.
1955-01-01
A dye-tracer technique has been developed whereby the quantity of dyed water collected on a blotter-wrapped body exposed to an air stream containing a dyed-water spray cloud can be colorimetrically determined in order to obtain local collection efficiencies, total collection efficiency, and rearward extent of impingement on the body. In addition, a method has been developed whereby the impingement characteristics obtained experimentally for a body can be related to theoretical impingement data for the same body in order to determine the droplet size distribution of the impinging cloud. Several cylinders, a ribbon, and an aspirating device to measure cloud liquid-water content were used in the studies presented herein for the purpose of evaluating the dye-tracer technique. Although the experimental techniques used in the dye-tracer technique require careful control, the methods presented herein should be applicable for any wind tunnel provided the humidity of the air stream can be maintained near saturation.
Chromohydrodynamic approach to the unstable quark-gluon plasma
Manuel, Cristina; Mrowczynski, Stanislaw
2006-11-15
We derive hydrodynamic-like equations that are applicable to short-time-scale color phenomena in the quark-gluon plasma. The equations are solved in the linear response approximation, and the gluon polarization tensor is derived. As an application, we study the collective modes in a two-stream system and find plasma instabilities when the fluid velocity is larger than the speed of sound in the plasma. The chromohydrodynamic approach, discussed here in detail, should be considered as simpler over other approaches and well-designed for numerical studies of the dynamics of an unstable quark-gluon plasma.
Gluon multiplication in high energy heavy ion collisions
Xiong, L.; Shuryak, E.V. )
1994-04-01
Hot gluons are the dominant components of the QCD plasma to be formed in future high energy heavy ion experiments. In this paper we study the elementary processes in the plasma medium for gluon multiplication based on all orders of the tree diagrams in perturbative QCD. When applying to the chemical equilibration in the expanding system, we found that the gluon reaches chemical equilibrium well within its plasma phase. The inclusion of all the next-to-leading-order processes makes the equilibration considerably faster than the simple [ital gg][leftrightarrow][ital ggg] one considered previously.
Numerical Study of the Ghost-Ghost-Gluon Vertex on the Lattice
Mihara, A.; Cucchieri, A.; Mendes, T.
2004-12-02
It is well known that, in Landau gauge, the renormalization function of the ghost-ghost-gluon vertex Z-tilde1 (p2) is finite and constant, at least to all orders of perturbation theory. On the other hand, a direct non-perturbative verification of this result using numerical simulations of lattice QCD is still missing. Here we present a preliminary numerical study of the ghost-ghost-gluon vertex and of its corresponding renormalization function using Monte Carlo simulations in SU(2) lattice Landau gauge. Data were obtained in 4 dimensions for lattice couplings {beta} = 2.2, 2.3, 2.4 and lattice sides N = 4, 8, 16.
CP-even scalar boson production via gluon fusion at the LHC
NASA Astrophysics Data System (ADS)
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Lazopoulos, Achilleas; Mistlberger, Bernhard
2016-09-01
In view of the searches at the LHC for scalar particle resonances in addition to the 125 GeV Higgs boson, we present the cross-section for a CP-even scalar produced via gluon fusion at N3LO in perturbative QCD assuming that it couples directly to gluons in an effective theory approach. We refine our prediction by taking into account the possibility that the scalar couples to the top-quark and computing the corresponding contributions through NLO in perturbative QCD. We assess the theoretical uncertainties of the crosssection due to missing higher-order QCD effects and we provide the necessary information for obtaining the cross-section value and uncertainty from our results in specific scenarios beyond the Standard Model. We also give detailed results for the case of a 750 GeV scalar, which will be the subject of intense experimental studies.
A global reanalysis of nuclear parton distribution functions
NASA Astrophysics Data System (ADS)
Eskola, Kari J.; Kolhinen, Vesa J.; Paukkunen, Hannu; Salgado, Carlos A.
2007-05-01
We determine the nuclear modifications of parton distribution functions of bound protons at scales Q2 >= 1.69 GeV2 and momentum fractions 10-5 <= x <= 1 in a global analysis which utilizes nuclear hard process data, sum rules and leading-order DGLAP scale evolution. The main improvements over our earlier work EKS98 are the automated χ2 minimization, simplified and better controllable fit functions, and most importantly, the possibility for error estimates. The resulting 16-parameter fit to the N = 514 datapoints is good, χ2/d.o.f = 0.82. Within the error estimates obtained, the old EKS98 parametrization is found to be fully consistent with the present analysis, with no essential difference in terms of χ2 either. We also determine separate uncertainty bands for the nuclear gluon and sea quark modifications in the large-x region where they are not stringently constrained by the available data. Comparison with other global analyses is shown and uncertainties demonstrated. Finally, we show that RHIC-BRAHMS data for inclusive hadron production in d+Au collisions lend support for a stronger gluon shadowing at x < 0.01 and also that fairly large changes in the gluon modifications do not rapidly deteriorate the goodness of the overall fits, as long as the initial gluon modifications in the region x ~ 0.02-0.04 remain small.
NASA Astrophysics Data System (ADS)
Romano, F.; Trasatti, E.; Lorito, S.; Ito, Y.; Piatanesi, A.; Lanucara, P.; Hirata, K.; D'Agostino, N.; Cocco, M.
2012-12-01
The rupture process of the Great 2011 Tohoku-oki earthquake has been particularly well studied by using an unprecedented collection of geophysical data. There is a general agreement among the different source models obtained by modeling seismological, geodetic and tsunami data. A slip patch of nearly 40÷50 meters has been imaged and located around and up-dip from the hypocenter by most of published models, while some differences exist in the slip pattern retrieved at shallow depths near the trench, likely due to the different resolving power of distinct data sets and to the adopted fault geometry. It is well known that the modeling of great subduction earthquakes requires the use of 3-D structural models in order to properly account for the effects of topography, bathymetry and the geometrical variations of the plate interface as well as for the effects of elastic contrasts between the subducting plate and the continental lithosphere. In this study we build a 3-D Finite Element (FE) model of the Tohoku-oki area in order to infer the slip distribution of the 2011 earthquake by performing a joint inversion of geodetic (GPS and seafloor observations) and tsunami (ocean bottom pressure sensors, DART and GPS buoys) data. The FE model is used to compute the geodetic and tsunami Green's functions. In order to understand how geometrical and elastic heterogeneities control the inferred slip distribution of the Tohoku-oki earthquake, we compare the slip patterns obtained using both homogeneous and heterogeneous structural models. The goal of this study is to better constrain the slip distribution and the maximum slip amplitudes. In particular, we aim to focus on the rupture process in the shallower part of the fault plane and near the trench, which is crucial to model the tsunami data and to assess the tsunamigenic potential of earthquakes in this region.
Probing the Gluon Self-Interaction in Light Mesons
Fischer, Christian S.; Williams, Richard
2009-09-18
We investigate masses and decay constants of light mesons from a coupled system of Dyson-Schwinger and Bethe-Salpeter equations. We explicitly take into account dominant non-Abelian contributions to the dressed quark-gluon vertex stemming from the gluon self-interaction. We construct the corresponding Bethe-Salpeter kernel that satisfies the axial-vector Ward-Takahashi identity. Our numerical treatment fully includes all momentum dependencies with all equations solved completely in the complex plane. This approach goes well beyond the rainbow-ladder approximation and permits us to investigate the influence of the gluon self-interaction on the properties of mesons. As a first result we find indications of a nonperturbative cancellation of the gluon self-interaction contributions and pion cloud effects in the mass of the rho meson.
Resummation and the gluon damping rate in hot QCD
Pisarski, R.D.
1990-08-01
At high temperature a consistent perturbative expansion requires the resummation of an infinite subset of loop corrections into an effective expansion. This effective exansion is used to compute the gluon damping rate at leading order. 25 refs.
Veneziano ghost, modified gluon propagator, and gauge copies in QCD
NASA Astrophysics Data System (ADS)
Dudal, D.; Guimaraes, M. S.
2016-04-01
In this short note, we come back to the recent proposal put forward by Kharzeev and Levin [Phys. Rev. Lett. 114, 242001 (2015)], in which they phenomenologically couple the nonperturbative Veneziano ghost to the perturbative gluon, leading to a modified gluon propagator (the "glost") of the Gribov type, with complex poles. As such, a possible link was made between the QCD topological θ -vacuum (Veneziano ghost) and color confinement (no physically observable gluons). We discuss some subtleties concerning gauge (Becchi-Rouet-Stora-Tuytin) invariance of this proposal, related to the choice of Feynman gauge. We draw particular attention to the incompatibility in the longitudinal sector with available nonperturbative results for the linear covariant gauge. We furthermore provide an example in the Landau gauge of a similar phenomenological vertex that also describes the necessary Veneziano ghost but does not affect the Landau gauge gluon propagator.
Proper definition and evolution of generalized transverse momentum dependent distributions
NASA Astrophysics Data System (ADS)
Echevarria, Miguel G.; Idilbi, Ahmad; Kanazawa, Koichi; Lorcé, Cédric; Metz, Andreas; Pasquini, Barbara; Schlegel, Marc
2016-08-01
We consider one of the most fundamental sets of hadronic matrix elements, namely the generalized transverse momentum dependent distributions (GTMDs), and argue that their existing definitions lack proper evolution properties. By exploiting the similarity of GTMDs with the much better understood transverse momentum distributions, we argue that the existing definitions of GTMDs have to include an additional dependence on soft gluon radiation in order to render them properly defined. With this, we manage to obtain the evolution kernel of all (un)polarized quark and gluon GTMDs, which turns out to be spin independent. As a byproduct, all large logarithms can be resummed up to next-to-next-to-leading-logarithmic accuracy with the currently known perturbative ingredients.
Physics of the gluon-helicity contribution to proton spin.
Ji, Xiangdong; Zhang, Jian-Hui; Zhao, Yong
2013-09-13
The total gluon helicity in a polarized proton, measurable in high-energy scattering, is shown to be the large momentum limit of a gauge-invariant but nonlocal, frame-dependent gluon spin E × A⊥ in QCD. This opens a door for a nonperturbative calculation of this quantity in lattice QCD and also justifies using free-field expressions in the light-cone gauge as physical observables.
NASA Technical Reports Server (NTRS)
Siemers, P. M., III; Henry, M. W.
1986-01-01
Pressure distribution test data obtained on a 0.10-scale model of the forward fuselage of the Space Shuttle Orbiter are presented without analysis. The tests were completed in the AEDC 16T Propulsion Wind Tunnel. The 0.10-scale model was tested at angles of attack from -2 deg to 18 deg and angles of side slip from -6 to 6 deg at Mach numbers from 0.25 to 1/5 deg. The tests were conducted in support of the development of the Shuttle Entry Air Data System (SEADS). In addition to modeling the 20 SEADS orifices, the wind-tunnel model was also instrumented with orifices to match Development Flight Instrumentation (DFI) port locations that existed on the Space Shuttle Orbiter Columbia (OV-102) during the Orbiter Flight Test program. This DFI simulation has provided a means of comparisons between reentry flight pressure data and wind-tunnel and computational data.
NASA Astrophysics Data System (ADS)
Domènech, Guillem; Mavrouli, Olga; Corominas, Jordi; Abellán, Antonio; Merchel, Silke; Pavetich, Stefan; Rugel, Georg
2015-04-01
Magnitude-cumulative frequency (MCF) relations are commonly used components for assessing the rockfall hazard using databases of recorded events. However, in some cases, data are lacking or incomplete. To overcome this restriction, the volume distribution of the rockfall scars has been used instead. The latter may yield the temporal probability of occurrence if the time span required to generate the scars is known. The Montsec range, located in the Eastern Pyrenees, Spain, was chosen as a pilot study area for investigating MCF distributions. This cliff, which is composed of limestones from Upper Cretaceous age, shows distinct evidences of rockfall activity, including large recent rockfall scars. These areas are identifiable by their orange colour, which contrasts in front of the greyish old stable (reference) surface of the cliff face. We present a procedure to obtain the MCF of the rockfall scars by dating an old reference cliff surface and measuring the total volume released since then. The reference cliff surface was dated using the terrestrial cosmogenic nuclide (TCN) chlorine-36 (Merchel et al., 2013). We used the Rockfall Scar Size Distribution (RSSD) obtained in Domènech et al. (2014) that considers several rockfall pattern scenarios. Scenario 1 allows for, mostly, large rockfall scar volumes, scenario 2 considers smaller occurrences and scenario 3 suggests that rockfall scars can be the result of one or several rockfall events, and thus contemplating a wider range of scar volumes. The main steps of the methodology are: a) Obtaining the RSSD, b) Volume calculation of material lost, c) Calculation of time (T0) elapsed for the cliff to retreat (age of the old reference surface), and d) generation of the MCF curve from the RSSD. A total volume of material lost of 78900 m3 was obtained as well as an elapsed period of time of 15350 years. The MCF curves for different rockfall scenarios are found to be well fitted by a power law with exponents -1.7, -1.1 and -1
Gluon radiation off hard quarks in a nuclear environment: opacity expansion
NASA Astrophysics Data System (ADS)
Wiedemann, Urs Achim
2000-11-01
We study the relation between the Baier-Dokshitzer-Mueller-Peigné-Schiff (BDMPS) and Zakharov formalisms for medium-induced gluon radiation off hard quarks, and the radiation off very few scattering centers. Based on the non-abelian Furry approximation for the motion of hard partons in a spatially extended colour field, we derive a compact diagrammatic and explicitly colour trivial expression for the N th order term of the k⊥ -differential gluon radiation cross section in an expansion in the opacity of the medium. Resumming this quantity to all orders in opacity, we obtain Zakharov's path-integral expression (supplemented with a regularization prescription). This provides a new proof of the equivalence of the BDMPS and Zakharov formalisms which extends previous arguments to the k⊥ -differential cross section. We give explicit analytical results up to third order in opacity for both the gluon radiation cross section of free incoming and of in-medium produced quarks. The N th order term in the opacity expansion of the radiation cross section is found to be a convolution of the radiation associated to N -fold rescattering and a readjustment of the probabilities that rescattering occurs with less than N scattering centers. Both informations can be disentangled by factorizing out of the radiation cross section a term which depends only on the mean free path of the projectile. This allows to infer analytical expressions for the totally coherent and totally incoherent limits of the radiation cross section to arbitrary orders in opacity.
NASA Astrophysics Data System (ADS)
Williamson, Nathan H.; Röding, Magnus; Galvosas, Petrik; Miklavcic, Stanley J.; Nydén, Magnus
2016-08-01
We present the pseudo 2-D relaxation model (P2DRM), a method to estimate multidimensional probability distributions of material parameters from independent 1-D measurements. We illustrate its use on 1-D T1 and T2 relaxation measurements of saturated rock and evaluate it on both simulated and experimental T1-T2 correlation measurement data sets. Results were in excellent agreement with the actual, known 2-D distribution in the case of the simulated data set. In both the simulated and experimental case, the functional relationships between T1 and T2 were in good agreement with the T1-T2 correlation maps from the 2-D inverse Laplace transform of the full 2-D data sets. When a 1-D CPMG experiment is combined with a rapid T1 measurement, the P2DRM provides a double-shot method for obtaining a T1-T2 relationship, with significantly decreased experimental time in comparison to the full T1-T2 correlation measurement.
Phenomenological determination of polarized quark distributions in the nucleon
NASA Astrophysics Data System (ADS)
Bartelski, Jan; Tatur, Stanisław
1996-03-01
We present a fit to spin asymmetries which gives polarized quark distributions. These functions are closely related to the ones given by the Martin, Roberts and Stirling fit for unpolarized structure functions. The integrals of polarized distributions are discussed and compared with the corresponding quantities obtained from neutron and hyperon β-decay data. We use the combination of proton, neutron and deuteron spin asymmetries in order to determine the coefficients of our polarized quark distributions. Our fit shows that phenomenologically there is no need for taking polarized gluons into account.
Dual QCD thermodynamics and quark-gluon plasma
NASA Astrophysics Data System (ADS)
Chandola, H. C.; Punetha, Garima; Dehnen, H.
2016-01-01
Using grand canonical ensemble formulation of a multi-particle statistical system, the thermodynamical description of dual QCD based on magnetic symmetry has been presented and analyzed for the quark-gluon plasma phase of hadronic matter. The dual QCD based bag construction has been shown to lead to the radial pressure on bag surface in terms of the vector glueball masses of magnetically condensed QCD vacuum. Constructing the grand canonical partition function, the energy density and plasma pressure have been derived and used to compute the critical temperatures for QGP-hadron phase transition along with its dynamics. A comparison of the values of critical temperatures for QGP-hadron phase transition with those obtained for the deconfinement-phase transition, has been shown to lead to either the relaxation of the system via a mixed phase of QGP and hot hadron gas or go through a crossover. The associated profiles of the normalized energy density and specific heat have been shown to lead to a large latent heat generation and indicate the onset of a first-order QGP phase transition which turns into a rapid crossover for the case of temperature dependent bag parameter. The squared speed of sound has been shown to act as a physical measure of large thermodynamical fluctuations near transition point. The possible implications of trace anomaly and conformal measure on QGP formation have also been discussed.
Higher-Twist Mechanism and Inclusive Gluon Production in Pion-Proton Collisions
NASA Astrophysics Data System (ADS)
Ahmadov, A. I.; Aydin, C.; Myrzakulov, R.; Uzun, O.
2016-01-01
We calculate the contribution of the higher-twist Feynman diagrams to the large-pT inclusive gluon production cross section in πp collisions incase of the running coupling and frozen coupling approaches within perturbative and holographic QCD. The structure of infrared renormalon singularities of the higher-twist subprocess cross section are obtained and the resummed higher-twist cross sections (Borel sum) with the ones obtained in the framework of the frozen coupling approach and leading-twist cross section are compared and analyzed.
Higher-twist mechanism and inclusive gluon production in pion-proton collisions
NASA Astrophysics Data System (ADS)
Ahmadov, A. I.; Aydin, C.; Myrzakulov, R.; Uzun, O.
2015-12-01
We calculate the contribution of the higher-twist Feynman diagrams to the large-pT inclusive gluon production cross-section in πp collisions in case of the running coupling and frozen coupling approaches within perturbative and holographic QCD. The structure of infrared renormalon singularities of the higher-twist subprocess cross-section is obtained and the resummed higher-twist cross-sections (Borel sum) with the ones obtained in the framework of the frozen coupling approach and leading-twist cross-section are compared and analyzed.
LUCERO, DANIEL A; PERKINS, W GEORGE
1999-08-26
The US DOE, with technical assistance from Sandia National Laboratories, has successfully received EPA certification and opened the Waste Isolation Pilot Plant (WIPP), a nuclear waste disposal facility located approximately 42 km east of Carlsbad, New Mexico. Performance assessment analyses indicate that human intrusions by inadvertent, intermittent drilling for resources provide the only credible mechanisms for releases of radionuclides from the disposal system. In modeling long-term brine releases, subsequent to a drilling event, potential migration pathways through the permeable layers of rock above the Salado formation were analyzed. Major emphasis is placed on the Culebra Member of the Rustler Formation because this is the most transmissive geologic layer overlying the WIPP site. In order to help quantify parameters for the calculated releases, radionuclide transport experiments have been earned out using intact-core columns obtained from the Culebra dolomite member of the Rustler Formation within the WIPP site. This paper deals primarily with results of analyses for {sup 241}Pu and {sup 241}Am distributions developed during transport experiments in one of these cores. Transport experiments were done using a synthetic brine that simulates Culebra brine at the core recovery location (the WIPP air-intake shaft--AIS). Hydraulic characteristics (i.e., apparent porosity and apparent dispersion coefficient) for intact-core columns were obtained via experiments using the conservative tracer {sup 22}Na. Elution experiments carried out over periods of a few days with tracers {sup 232}U and {sup 239}Np indicated that these tracers were weakly retarded as indicated by delayed elution of the species. Elution experiments with tracers {sup 241}Pu and {sup 241}Am were attempted, but no elution of either species has been observed to date, including experiments of many months' duration. In order to quantify retardation of the non-eluted species {sup 241}Pu and {sup 241}Am
Gluon-gluon contributions to W+ W- production and Higgs interference effects
Campbell, John M.; Ellis, R.Keith; Williams, Ciaran
2011-07-01
In this paper we complete our re-assessment of the production of W boson pairs at the LHC, by calculating analytic results for the gg {yields} W{sup +}W{sup -} {yields} {nu}{ell}{sup +}{ell}{sup -}{bar {nu}} process including the effect of massive quarks circulating in the loop. Together with the one-loop amplitudes containing the first two generations of massless quarks propagating in the loop, these diagrams can give a significant contribution with a large flux of gluons. One of the component parts of this calculation is the production of a standard model Higgs boson, gg {yields} H and its subsequent decay, H {yields} W{sup +}({yields} {nu}{ell}{sup +})W{sup -}({yields} {ell}{sup -}{bar {nu}}). We will quantify the importance of the interference between the Higgs boson production process and the gluon-induced continuum production in the context of searches for the Higgs boson at the Tevatron and the LHC. For instance, for m{sub H} < 140 GeV the effect of the interference typically results in around a 10% reduction in the expected number of Higgs signal events. The majority of this interference is due to non-resonant contributions. Therefore cuts on the transverse mass such as those currently used by the ATLAS collaboration reduce the destructive interference to about a 1% effect. We advocate that a cut on the maximum transverse mass be used in future Higgs searches in this channel.
Kertesz, Vilmos; Van Berkel, Gary J; Vavek, Marissa; Koeplinger, Kenneth A.; Schneider, Bradley B; Covey, Thomas R.
2008-01-01
Desorption electrospray ionization tandem mass spectrometry (DESI-MS/MS) and whole-body autoradiography (WBA) were used for chemical imaging of whole-body thin tissue sections of mice intravenously dosed with propranolol (7.5 mg/kg). DESI-MS/MS imaging utilized selected reaction monitoring detection performed on an AB/MDS SCIEX 4000 QTRAP mass spectrometer equipped with a prototype extended length particle discriminator interface. Propranolol images of the tissue sections using DESI-MS/MS were obtained at surface scan rates of 0.1, 0.5, 2 and 7 mm/s. Although signal decreased with increasing scan rate, useful whole-body images for propranolol were obtained from the tissues even at 7 mm/s, which required just 79 min of analysis time. Attempts to detect and image the distribution of the known propranolol metabolites were unsuccessful. Regions of the tissue sections showing the most radioactivity from WBA sections were excised and analyzed by HPLC with radiochemical detection to determine relative levels of propranolol and metabolites present. Comparison of the DESI-MS/MS signal for propranolol and the radioactivity attributed to propranolol from WBA sections indicated nominal agreement between the two techniques for the amount of propranolol in the brain, lung, and liver. Data from the kidney showed an unexplained disparity between the two techniques. The results of this study show the feasibility of using DESI-MS/MS to obtain useful chemical images of a drug in whole-body thin tissue sections following drug administration at a pharmacologically relevant level. Further optimization to improve sensitivity and enable detection of the drug metabolites will be among the requirements necessary to move DESI-MS/MS chemical imaging forward as a practical tool in drug discovery.
NASA Astrophysics Data System (ADS)
Harlander, Robert V.; Liebler, Stefan; Mantler, Hendrik
2013-06-01
This article describes the code SusHi (for "Supersymmetric Higgs") [108] which calculates the cross sections pp/pp ¯ →ϕ+X in gluon fusion and bottom-quark annihilation in the SM and the MSSM, where ϕ is any of the neutral Higgs bosons within these models. Apart from inclusive cross sections up to NNLO QCD, differential cross sections with respect to the Higgs transverse momentum pT and (pseudo-)rapidity y(η) can be calculated through NLO QCD. In the case of gluon fusion, SusHi contains NLO QCD contributions from the third family of quarks and squarks, NNLO corrections due to top-quarks, approximate NNLO corrections due to top-squarks, and electro-weak effects. It supports various renormalization schemes for the sbottom sector and the bottom Yukawa coupling, as well as resummation effects of higher order tanβ-enhanced sbottom contributions. SusHi provides a link to FeynHiggs for the calculation of the Higgs masses. Program SummaryProgram title: SusHi Catalogue identifier: AEOY_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOY_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 test data, etc.: 47725 No. of bytes in distributed program, including test data, etc.: 338380 Distribution format: tar.gz Programming language: Fortran 77. Computer: Personal computer. Operating system: Unix/Linux, Mac OS. RAM: A few 100 MB Classification: 11.1. External routines: LHAPDF (http://lhapdf.hepforge.org), FeynHiggs (http://www.feynhiggs.de) Nature of problem: Calculation of inclusive and exclusive Higgs production cross sections in gluon fusion and bottom-quark annihilation in the Standard Model and the MSSM through next-to-leading order QCD, includes next-to-next-to-leading order top-(s)quark contributions and electro-weak effects Solution method: Numerical Monte Carlo integration
Collective Flow signals the Quark Gluon Plasma
Bratkovskaya, E.L.; Bleicher, M.; Greiner, C.; Muronga, A.; Paech, K.; Reiter, M.; Scherer, S.; Soff, S.; Xu, Z.; Zeeb, G.; Zschiesche, D.; Tavares, B.; Portugal, L.; Aguiar, C.; Kodama, T.; Grassi, F.; Hama, Y.; Osada, T.; Sokolowski, O.; Werner, K.
2004-12-02
A critical discussion of the present status of the CERN experiments on charm dynamics and hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 A{center_dot}GeV: here the hydrodynamic model has predicted the collapse of the v1-flow and of the v2-flow at {approx} 10 A{center_dot}GeV; at 40 A{center_dot}GeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as potential evidence for a first order phase transition at high baryon density {rho}B. A detailed discussion of the collective flow as a barometer for the equation of state (EoS) of hot dense matter at RHIC follows. Additionally, detailed transport studies show that the away-side jet suppression can only partially (< 50%) be due to hadronic rescattering. We, finally, propose upgrades and second generation experiments at RHIC which inspect the first order phase transition in the fragmentation region, i.e. at {mu}B {approx_equal} 400 MeV (y {approx_equal} 4 - 5), where the collapse of the proton flow should be seen in analogy to the 40 A{center_dot}GeV data. The study of Jet-Wake-riding potentials and Bow shocks - caused by jets in the QGP formed at RHIC - can give further information on the equation of state (EoS) and transport coefficients of the Quark Gluon Plasma (QGP)
AdS/QCD, Light-Front Holography, and Sublimated Gluons
Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.
2012-02-16
The gauge/gravity duality leads to a simple analytical and phenomenologically compelling nonperturbative approximation to the full light-front QCD Hamiltonian - 'Light-Front Holography', which provides a Lorentz-invariant first-approximation to QCD, and successfully describes the spectroscopy of light-quark meson and baryons, their elastic and transition form factors, and other hadronic properties. The bound-state Schroedinger and Dirac equations of the soft-wall AdS/QCD model predict linear Regge trajectories which have the same slope in orbital angular momentum L and radial quantum number n for both mesons and baryons. Light-front holography connects the fifth-dimensional coordinate of AdS space z to an invariant impact separation variable {zeta} in 3+1 space at fixed light-front time. A key feature is the determination of the frame-independent light-front wavefunctions of hadrons - the relativistic analogs of the Schroedinger wavefunctions of atomic physics which allow one to compute form factors, transversity distributions, spin properties of the valence quarks, jet hadronization, and other hadronic observables. One thus obtains a one-parameter color-confining model for hadron physics at the amplitude level. AdS/QCD also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function with an infrared fixed point which agrees with the effective coupling a{sub g1} (Q{sup 2}) extracted from measurements of the Bjorken sum rule below Q{sup 2} < 1 GeV{sup 2}. This is consistent with a flux-tube interpretation of QCD where soft gluons with virtualities Q{sup 2} < 1 GeV{sup 2} are sublimated into a color-confining potential for quarks. We discuss a number of phenomenological hadronic properties which support this picture.
NASA Technical Reports Server (NTRS)
Siemers, P. M., III; Henry, M. W.
1986-01-01
Pressure distribution test data obtained on a 0.10-scale model of the forward fuselage of the Space Shuttle Orbiter are presented without analysis. The tests were completed in the Ames Unitary Wind Tunnel (UPWT). The UPWT tests were conducted in two different test sections operating in the continuous mode, the 8 x 7 feet and 9 x 7 feet test sections. Each test section has its own Mach number range, 1.6 to 2.5 and 2.5 to 3.5 for the 9 x 7 feet and 8 x 7 feet test section, respectively. The test Reynolds number ranged from 1.6 to 2.5 x 10 to the 6th power ft and 0.6 to 2.0 x 10 to the 6th power ft, respectively. The tests were conducted in support of the development of the Shuttle Entry Air Data System (SEADS). In addition to modeling the 20 SEADS orifices, the wind-tunnel model was also instrumented with orifices to match Development Flight Instrumentation (DFI) port locations that existed on the Space Shuttle Columbia (OV-102) during the Orbiter Flight test program. This DFI simulation has provided a means for comparisons between reentry flight pressure data and wind-tunnel and computational data.
Conformal symmetry and differential regularization of the three-gluon vertex
NASA Astrophysics Data System (ADS)
Freedman, Daniel Z.; Grignani, Gianluca; Johnson, Kenneth; Rius, Nuria
1992-08-01
The conformal symmetry of the QCD Lagrangian for massless quarks is broken both by renormalization effects and the gauge fixing procedure. Renormalized primitive divergent amplitudes have the property that their form away from the overall coincident point singularity is fully determined by the bare Lagrangian, and scale dependence is restricted to δ-functions at the singularity. If gauge fixing could be ignored, one would expect these amplitudes to be conformal invariant for non-coincident points. We find that the one-loop three-gluon vertex function Г μvp(x, y, z) is conformal invariant in this sense, if calculated in the background field formalism using the Feynman gauge for internal gluons. It is not vet clear why the expected breaking due to gauge fixing is absent. The conformal property implies that the gluon, ghost, and quark loop contributions to Г μvp are each purely numerical combinations of two universal conformal tensors Dμvp( x, y, z) and Cμvp( x, y, z) whose explicit form is given in the text. Only Dμvp has an ultraviolet divergence, although Cμvp requires a careful definition to resolve the expected ambiguity of a formally linearly divergent quantity. Regularization is straightforward and leads to a renormalized vertex function which satisfies the required Ward identity, and from which the beta function is easily obtained. Exact conformal invariance is broken in higher-loop orders, but we outline a speculative scenario in which the perturbative structure of the vertex function is determined from a conformal invariant primitive core by interplay of the renormalization group equation and Ward identities. Other results which are relevant to the conformal property include the following: (1) An analytic calculation shows that the linear deviation from the Feynman gauge is not conformal invariant, and a separate computation using symbolic manipulation confirms that among Dμbμ background gauges, only the Feynman gauge is conformal invariant. (2
All one-loop NMHV gluon amplitudes in = 1 SYM
NASA Astrophysics Data System (ADS)
Ochirov, Alexander
2013-12-01
We compute the next-to-maximally-helicity-violating one-loop n-gluon amplitudes in = 1 super-Yang-Mills theory. These amplitudes contain three negative-helicity gluons and an arbitrary number of positive-helicity gluons, and constitute the first infinite series of amplitudes beyond the simplest, MHV, amplitudes. We assemble ingredients from the = 4 NMHV tree super-amplitude into previously unwritten double cuts and use the spinor integration technique to calculate all bubble coefficients. We also derive the missing box coefficients from quadruple cuts. Together with the known formula for three-mass triangles, this completes the set of NMHV one-loop master integral coefficients in = 1 SYM. To facilitate further use of our results, we provide their Mathematica implementation.
To What Extent is Gluon Confinement an Empirical Fact?
NASA Astrophysics Data System (ADS)
Delgado, R. L.; Hidalgo-Duque, Carlos; Llanes-Estrada, Felipe J.
2013-11-01
Experimental verifications of confinement in hadron physics have established the absence of charges with a fraction of the electron's charge by studying the energy deposited in ionization tracks at high energies, and performing Millikan experiments with charged droplets at rest. These experiments test only the absence of particles with fractional charge in the asymptotic spectrum, and thus "Quark" Confinement. However what theory suggests is that Color is confined, that is, all asymptotic particles are color singlets. Since QCD is a non-Abelian theory, the gluon force carriers (indirectly revealed in hadron jets) are colored. We empirically examine what can be said about gluon confinement based on the lack of detection of appropriate events, aiming at an upper bound for high-energy free-gluon production.
Low-momentum ghost dressing function and the gluon mass
Boucaud, Ph.; Leroy, J. P.; Le Yaouanc, A.; Micheli, J.; Pene, O.; Gomez, M. E.; Rodriguez-Quintero, J.
2010-09-01
We study the low-momentum ghost propagator Dyson-Schwinger equation in the Landau gauge, assuming for the truncation a constant ghost-gluon vertex, as it is extensively done, and a simple model for a massive gluon propagator. Then, regular Dyson-Schwinger equation solutions (the zero-momentum ghost dressing function not diverging) appear to emerge, and we show the ghost propagator to be described by an asymptotic expression reliable up to the order O(q{sup 2}). That expression, depending on the gluon mass and the zero-momentum Taylor-scheme effective charge, is proven to fit pretty well some low-momentum ghost propagator data [I. L. Bogolubsky, E. M. Ilgenfritz, M. Muller-Preussker, and A. Sternbeck, Phys. Lett. B 676, 69 (2009); Proc. Sci., LAT2007 (2007) 290] from big-volume lattice simulations where the so-called ''simulated annealing algorithm'' is applied to fix the Landau gauge.
Impact factors for Reggeon-gluon transition in N=4 SYM with large number of colours
NASA Astrophysics Data System (ADS)
Fadin, V. S.; Fiore, R.
2014-06-01
We calculate impact factors for Reggeon-gluon transition in supersymmetric Yang-Mills theory with four supercharges at large number of colours Nc. In the next-to-leading order impact factors are not uniquely defined and must accord with BFKL kernels and energy scales. We obtain the impact factor corresponding to the kernel and the energy evolution parameter, which is invariant under Möbius transformation in momentum space, and show that it is also Möbius invariant up to terms taken into account in the BDS ansatz.
The hard gluon component of the QCD Pomeron
White, A.R.
1996-10-20
The authors argue that deep-inelastic diffractive scaling provides fundamental insight into the QCD Pomeron. The logarithmic scaling violations seen experimentally are in conflict with the scale-invariance of the BFKL Pomeron and with phenomenological two-gluon models. Instead the Pomeron appears as a single gluon at short-distances, indicating the appearance of a Super-Critical phase of Reggeon Field Theory. That the color compensation takes place at a longer distance is consistent with the Pomeron carrying odd color charge parity.
Viscous quark-gluon plasma model through fluid QCD approach
Djun, T. P.; Soegijono, B.; Mart, T.; Handoko, L. T. E-mail: Laksana.tri.handoko@lipi.go.id
2014-09-25
A Lagrangian density for viscous quark-gluon plasma has been constructed within the fluid-like QCD framework. Gauge symmetry is preserved for all terms inside the Lagrangian, except for the viscous term. The transition mechanism from point particle field to fluid field, and vice versa, are discussed. The energy momentum tensor that is relevant to the gluonic plasma having the nature of fluid bulk of gluon sea is derived within the model. By imposing conservation law in the energy momentum tensor, shear viscosity appears as extractable from the equation.
Further evidence for zero crossing on the three gluon vertex
NASA Astrophysics Data System (ADS)
Duarte, Anthony G.; Oliveira, Orlando; Silva, Paulo J.
2016-10-01
The three gluon one particle irreducible function is investigated using lattice QCD simulations over a large region of momentum in the Landau gauge for four-dimensional pure Yang-Mills equations and the SU(3) gauge group. The results favor a zero crossing of the gluon form factor for momenta in the range 220-260 MeV. This zero crossing is required to happen in order to have a properly defined set of Dyson-Schwinger equations. It is also shown that in the high momentum region the lattice results are compatible with the predictions of renormalization group improved perturbation theory.
NASA Astrophysics Data System (ADS)
Nahon, Laurent; Garcia, Gustavo A.; Soldi-Lose, Héloïse; Daly, Steven; Powis, Ivan
2010-09-01
As an intermediate state of matter between the free monomeric gas phase and the solid state, clusters may exhibit a specific electronic structure and photoionization dynamics that can be unraveled by different types of electron spectroscopies. From mass-selected ion yield scans measured for photoionization of (R)-camphor, the ionization potentials (IPs) of the monomer (8.66±0.01 eV), and of the homochiral dimer (⩽8.37±0.01 eV) and trimer (⩽8.30±0.01 eV) were obtained. These spectra, combined with threshold photoelectron spectroscopy and velocity map ion imaging, allow us to show that the camphor monomer and dimer photoionization channels are decoupled, i.e., that the highest occupied molecular orbital (HOMO) of the dimer does not undergo a dissociative ionization process that would lead to a spurious contribution to the monomer ion channel. Therefore mass selection, as achieved in our imaging photoelectron-photoion coincidence experiments, leads to size selection of the nascent monomer or dimer species. Since both the monomer and dimer are chiral, their photoelectron angular distribution (PAD) not only involves the usual β anisotropy parameter but also a chiral asymmetry parameter b1 that can generate a forward-backward asymmetry in the PAD. This has been investigated using circularly polarized light (CPL) to record the photoelectron circular dichroism (PECD) in the near-threshold vacuum-ultraviolet (VUV) photoionization region. Analysis of size-selected electron images recorded with left- and right-handed CPL shows that over the first 1.5 eV above the HOMO orbital ionization potentials (IPs), the β parameter is not affected by the dimerization process, while the chiral b1 parameter shows clear differences between the monomer and the dimer, confirming that PECD is a subtle long-range probe of the molecular potential.
NASA Astrophysics Data System (ADS)
Sumlin, B.; Arnott, W. P.; Moosmuller, H.
2012-12-01
The MODIS instruments aboard the Aqua and Terra satellites provide aerosol optical depth information for the entire Earth on a daily basis. Ideally, satellite measurements should correlate with ground-based measurements in order to be useful for air quality applications. Reno, Nevada, USA is a high desert city situated in the Great Basin. Its unique geography and proximity to urban and biomass burning aerosol sources make it an ideal candidate for aerosol research. In August 2011, the Reno Aerosol Characterization Experiment measured atmospheric aerosols with a ground-based Cimel CE-318 sun-photometer and in situ photoacoustic instrumentation to quantify aerosol concentrations at the surface and in the column. However, the results of these measurements indicated the existence of a more complex system of aerosol mixing above the atmospheric boundary layer than previously thought. In order to validate these measurements, an autonomous suite of instrumentation has been developed. This device is carried aloft by a weather balloon and utilizes a reciprocal nephelometer to obtain a high-resolution profile of the vertical distribution of aerosol light scattering coefficient, as well as instrumentation to record atmospheric variables such as temperature, pressure, relative humidity, and dew point. Position, course, speed, and altitude are logged with an onboard GPS module and correlated with atmospheric and aerosol measurements. Presented is the design and development of this new instrument, its comparison with proven laboratory instruments, data gathered from flights during August-November 2012, and its comparison to ground-based measurements and satellite data from the MODIS instruments.
NASA Astrophysics Data System (ADS)
Pagnoni, G.; Tinti, S.; Armigliato, A.; Tonini, R.; Gallazzi, S.; Manucci, A.; Zaniboni, F.
2006-12-01
study the run-up heights. In both cases, we divide the earthquake fault in a given number of sub-faults, and then compute the tsunami generated by each sub-fault by means of two different codes: a finite-difference code implementing the linear shallow-water equations for the ocean-wide domain, and a finite-element code solving the non-linear version of the same equations in the local domain. In the case of the altimeter data, the adopted inversion technique is an implementation of the classical generalized linear least-squares theory. A more sophisticated technique, allowing one to determine also different amplification factors along different coastal segments, is employed to invert run-up data. We discuss the slip distributions obtained separately in the two approaches, and compare the results with those retrieved by modeling seismic and geodetic data.
Structure functions and parton distributions
Olness, F.; Tung, Wu-Ki
1991-04-01
Activities of the structure functions and parton distributions group is summarized. The impact of scheme-dependence of parton distributions (especially sea-quarks and gluons) on the quantitative formulation of the QCD parton model is highlighted. Recent progress on the global analysis of parton distributions is summarized. Issues on the proper use of the next-to-leading parton distributions are stressed.
NASA Astrophysics Data System (ADS)
Bleibel, J.; Bravina, L. V.; Zabrodin, E. E.
2016-06-01
Multiplicity, rapidity and transverse momentum distributions of hadrons produced both in inelastic and nondiffractive p p collisions at energies from √{s }=200 GeV to 14 TeV are studied within the Monte Carlo quark-gluon string model. Good agreement with the available experimental data up to √{s }=13 TeV is obtained, and predictions are made for the collisions at top LHC energy √{s }=14 TeV . The model indicates that Feynman scaling and extended longitudinal scaling remain valid in the fragmentation regions, whereas strong violation of Feynman scaling is observed at midrapidity. The Koba-Nielsen-Olesen (KNO) scaling in multiplicity distributions is violated at LHC also. The origin of both maintenance and violation of the scaling trends is traced to short range correlations of particles in the strings and interplay between the multistring processes at ultrarelativistic energies.
Gluon condensate in a pion superfluid beyond the mean-field approximation
Jiang Yin; Zhuang Pengfei
2011-03-15
We study gluon condensate in a pion superfluid by calculating the equation of state of the system in the Nambu-Jona-Lasinio model. While in mean-field approximation the growing pion condensate leads to an increasing gluon condensate, meson fluctuations reduce the gluon condensate, and the broken scalar symmetry can be smoothly restored at finite isospin density.
Direct Photon Production and Gluon Polarization Measurements in Proton-Proton Collisions at PHENIX
NASA Astrophysics Data System (ADS)
Feege, Nils; Phenix Collaboration
2015-10-01
Direct photons probe the hard scattering process in proton-proton collisions. The channel that dominates their production in these collisions is ``the inverse QCD Compton effect,'' g + q --> γ + q . Calculating this process requires no photon fragmentation function, which facilitates comparisons between theories and experiments. In polarized p+p collisions, direct photons help determine the proton spin structure. At leading order, the longitudinal double-spin asymmetry ALL is directly proportional to the product of quark and gluon polarizations. The polarized quark distributions are known from polarized lepton-proton scattering experiments. Using them together with ALL measurements allows to access both the magnitude and sign of the polarized gluon distribution. The PHENIX experiment has collected data from polarized p+p collisions at RHIC at center of mass energies of 200 GeV and 500 GeV. This talk presents the status of direct photon cross section measurements and ALL measurements at midrapidity (| η | < 0 . 35) using these data.
NASA Astrophysics Data System (ADS)
Shurshakov, Vyacheslav; Nikolaev, Igor; Kartsev, Ivan; Tolochek, Raisa; Lyagushin, Vladimir
The tissue-equivalent spherical phantom (32 kg mass, 35 cm diameter and 10 cm central spherical cave) made in Russia has been used on board the ISS in Matroshka-R experiment for more than 10 years. Both passive and active space radiation detectors can be located inside the phantom and on its surface. Due to the specially chosen phantom shape and size, the chord length distributions of the detector locations are attributed to self-shielding properties of the critical organs in a human body. Originally the spherical phantom was installed in the star board crew cabin of the ISS Service Module, then in the Piers-1, MIM-2, and MIM-1 modules of the ISS Russian segment, and finally in JAXA Kibo module. Total duration of the detector exposure is more than 2000 days in 9 sessions of the space experiment. In the first phase of the experiment with the spherical phantom the dose measurements were realized with only passive detectors (thermoluminescent and solid state track detectors). The detectors are placed inside the phantom along the axes of 20 containers and on the phantom outer surface in 32 pockets of the phantom jacket. After each session the passive detectors are returned to the ground. The results obtained show the dose difference on the phantom surface as much as a factor of 2, the highest dose being usually observed close to the outer wall of the compartment, and the lowest dose being in the opposite location along the phantom diameter. However, because of the ISS module shielding properties an inverse dose distribution in a human body can be observed when the dose rate maximum is closer to the geometrical center of the module. Maximum dose rate measured in the phantom is obviously due to the action of two radiation sources, namely, galactic cosmic rays (GCR) and Earth’ radiation belts. Minimum dose rate is produced mainly by the strongly penetrating GCR particles and is mostly observed behind more than 5 g/cm2 tissue shielding. Critical organ doses, mean
Synchrotron contribution to photon emission from quark-gluon plasma
NASA Astrophysics Data System (ADS)
Zakharov, B. G.
2016-08-01
We study the inuence of the magnetic field on the photon emission from the quark-gluon plasma created in AA collisions. We find that even for very optimistic assumption on the magnitude of the magnetic field for noncentral AA collisions the effect of magnetic field is very small.
Note on permutation sum of color-ordered gluon amplitudes
NASA Astrophysics Data System (ADS)
Du, Yi-Jian; Feng, Bo; Fu, Chih-Hao
2012-01-01
In this Letter we show that under BCFW-deformation the large-z behavior of permutation sum of color-ordered gluon amplitudes found by Boels and Isermann in arxiv:arxiv:1109.5888 can be simply understood from the well known Kleiss-Kuijf relation and Bern-Carrasco-Johansson relation.
Parton distributions from SMC and SLAC data
Ramsey, G.P. |; Goshtasbpour, M. |
1996-01-04
We have extracted spin-weighted parton distributions in a proton from recent data at CERN and SLAC. The valence, sea quark and Antiquark spin-weighted distributions are determined separately. The data are all consistent with a small to moderate polarized gluon distribution, so that the anomaly term is not significant in the determination of the constituent contributions to the spin of the proton. We have analyzed the consistency of the results obtained from various sets of data and the Biorken sum rule. Although all data are consistent with the sum rule, the polarized distributions from different experiments vary, even with higher order QCD corrections taken into account. Results split into two models, one set implying a large polarized strange sea which violates the positivity bound, and the other set yielding a smaller polarized strange sea. Only further experiments which extract information about the polarized sea will reconcile these differences. We suggest specific experiments which can be performed to determine the size of the polarized sea and gluons.
QCD in the nuclear medium and effects due to Cherenkov gluons
Dremin, I. M.
2010-04-15
The equations of in-medium gluodynamics are proposed. Their classical lowest-order solution is explicitly shown for a color charge moving with constant speed. For chromopermittivity larger than 1 it describes emission of Cherenkov gluons resembling results of classical electrodynamics. The values of the real and imaginary parts of the chromopermittivity are obtained from the fits to experimental data on the double-humped structure around the away-side jet obtained at RHIC. The dispersion of the chromopermittivity is predicted by comparing the RHIC, SPS, and cosmic-ray data. This is important for LHC experiments. Cherenkov gluons may be responsible for the asymmetry of dilepton mass spectra near {rho} meson observed in the SPS experiment with excess in the low-mass wing of the resonance. This feature is predicted to be common for all resonances. The 'color rainbow' quantum effect might appear according to higher-order terms of in-medium QCD if the chromopermittivity depends on color.
Interpretation of vector-like quark searches: heavy gluons in composite Higgs models
NASA Astrophysics Data System (ADS)
Araque, Juan Pedro; Castro, Nuno Filipe; Santiago, José
2015-11-01
Pair production of new vector-like quarks in pp collisions is considered model independent as it is usually dominated by QCD production. We discuss the interpretation of vector-like quark searches in the case that QCD is not the only relevant production mechanism for the new quarks. In particular we consider the effect of a new massive color octet vector boson with sizeable decay branching ratio into the new quarks. We pay special attention to the sensitivity of the Large Hadron Collider experiments, both in run-1 and early run-2, to differences in the kinematical distributions from the different production mechanisms. We have found that even though there can be significant differences in some kinematical distributions at the parton level, the differences are washed out at the reconstruction level. Thus, the published experimental results can be reinterpreted in models with heavy gluons by simply rescaling the production cross section.
Investigating GPDs in the framework of the double distribution model
NASA Astrophysics Data System (ADS)
Nazari, F.; Mirjalili, A.
2016-06-01
In this paper, we construct the generalized parton distribution (GPD) in terms of the kinematical variables x, ξ, t, using the double distribution model. By employing these functions, we could extract some quantities which makes it possible to gain a three-dimensional insight into the nucleon structure function at the parton level. The main objective of GPDs is to combine and generalize the concepts of ordinary parton distributions and form factors. They also provide an exclusive framework to describe the nucleons in terms of quarks and gluons. Here, we first calculate, in the Double Distribution model, the GPD based on the usual parton distributions arising from the GRV and CTEQ phenomenological models. Obtaining quarks and gluons angular momenta from the GPD, we would be able to calculate the scattering observables which are related to spin asymmetries of the produced quarkonium. These quantities are represented by AN and ALS. We also calculate the Pauli and Dirac form factors in deeply virtual Compton scattering. Finally, in order to compare our results with the existing experimental data, we use the difference of the polarized cross-section for an initial longitudinal leptonic beam and unpolarized target particles (ΔσLU). In all cases, our obtained results are in good agreement with the available experimental data.
NASA Technical Reports Server (NTRS)
Olbert, S.; Jessen, J.; Belcher, J. W.; Lazarus, A.
1978-01-01
The main sensor of the Vogager plasma experiment consists of a cluster of three, modulated-grid Faraday cups whose normals are arranged symmetrically about the symmetry axis of the cluster at an angle of 20 degrees to that axis. In interplanetary space, each cup explores the positive ion distribution by accepting particles from contiguous slices in velocity space. The slices are narrow in the direction of the normal to the modulating grid but are broad in planes parallel to that grid. The resulting three sets of measurements can be combined to yield the three-dimensional distribution function in the following way: the distribution function is assumed to be gyrotropic. For each value of speed in a frame of reference moving with the bulk velocity of the solar wind, the variation of the distribution function with angle from the field direction is represented by a series of Legendre polynomials. Effects such as double-streaming and heat flow can be well represented by using only the first three terms of the series which are fully specified by the measurements. Examples of the use of this method in the analysis of Voyager data are shown.
ERIC Educational Resources Information Center
Rayner, Keith; Juhasz, Barbara J.; Brown, Sarah J.
2007-01-01
Two experiments tested predictions derived from serial lexical processing and parallel distributed models of eye movement control in reading. The boundary paradigm (K. Rayner, 1975) was used, and the boundary location was set either at the end of word n - 1 (the word just to the left of the target word) or at the end of word n - 2. Serial lexical…
Wallace, A.; Romney, E.M.; Kinnear, J.
1982-07-01
Baseline measurements were made of mineral composition of alfalfa (Medicago sativa L.) and sugar beets (Beta vulgaris L.) from one field each in the Imperial Valley of California. The fields are in a geothermal area being developed for energy production, and the purpose of the investigation was to ascertain variablility within a relatively large number of samples from a common area, so that subsequent samplings could be made to satisfactorily detect whether there were changes resulting from the geothermal activity. Means, standard deviations, frequency distribution, correlations, cluster trees, and other statistics were examined for over 20 elements at each site.Most elements were normally distributed, but there was three- to fourfold range in the concentration for each.
NASA Astrophysics Data System (ADS)
Wongpratat, Unchista; Maensiri, Santi; Swatsitang, Ekaphan
2016-09-01
Effect of cations distribution upon EXAFS analysis on magnetic properties of Co1-xNixFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1.0) nanoparticles prepared by the hydrothermal method in aloe vera extract solution were studied. XRD analysis confirmed a pure phase of cubic spinel ferrite of all samples. Changes in lattice parameter and particle size depended on the Ni content with partial substitution and site distributions of Co2+, Ni2+ ions of different ionic radii at both tetrahedral and octahedral sites in the crystal structure. Particle sizes of samples estimated by TEM images were found to be in the range of 10.87-62.50 nm. The VSM results at room temperature indicated the ferrimagnetic behavior of all samples. Superparamagnetic behavior was observed in NiFe2O4 sample. The coercivity (Hc) and remanance (Mr) values were related to the particle sizes of samples. The saturation magnetization (Ms) was increased by a factor of 1.4 to a value of 57.57 emu/g, whereas the coercivity (Hc) was decreased by a factor of 20 to a value of 63.15 Oe for a sample with x = 0.75. In addition to the cations distribution, the increase of aspect ratio (surface to volume ratio) due to the decrease of particle size could significantly affect the magnetic properties of the materials.
Spin, masses and other baryonic observables in a chiral model of quark and gluon confinement
NASA Astrophysics Data System (ADS)
Stern, Jacqueline; Clément, Gérard
1989-11-01
The structure of non-strange baryons is investigated in a field-theoretical model which minimally incorporates soft confinement of quarks and gluons and approximate chiral symmetry. Baryonic states are recovered from the mean-field hedgehog solutions by the coherent cranking procedure, which generates mean chromomagnetic fields, modelling gluon exchange between quarks. The cranking method allows for a non-perturbative, self-consistent computation of gluonic effects on the nucleon and delta masses, corrected for spurious translational and rotational fluctuations, on the contribution Δu + Δd of the non-strange quark helicities to the proton spin, and on various other baryonic observables. For the physical values of the pion parameters mπ = 139.6 MeV, Fπ = 93 MeV, and the effective strong fine structure constant α s ⋍ 0.5 , the results which we obtain for these observables, including Δu + Δd ⋍ 0.26, are in good agreement with experiment.
Quark-Gluon Soup -- The Perfectly Liquid Phase of QCD
NASA Astrophysics Data System (ADS)
Heinz, Ulrich
2015-03-01
At temperatures above about 150 MeV and energy densities exceeding 500 MeV/fm3, quarks and gluons exist in the form of a plasma of free color charges that is about 1000 times hotter and a billion times denser than any other plasma ever created in the laboratory. This quark-gluon plasma (QGP) turns out to be strongly coupled, flowing like a liquid. About 35 years ago, the nuclear physics community started a program of relativistic heavy-ion collisions with the goal of producing and studying QGP under controlled laboratory conditions. This article recounts the story of its successful creation in collider experiments at Brookhaven National Laboratory and CERN and the subsequent discovery of its almost perfectly liquid nature, and reports on the recent quantitatively precise determination of its thermodynamic and transport properties.
The physics of hot and dense quark-gluon matter
Kharzeev, Dmitri E
2012-05-10
This technical report describes the work done under the DOE grant DE-FG-88ER41723 (final award number DE-SC0005645), "The physics of hot and dense quark-gluon matter", during the year of 12/01/2010 through 11/30/2011. As planned in the proposal, the performed research focused along two main thrusts: 1) topological effects in hot quark-gluon matter and 2) phenomenology of relativistic heavy ion collisions. The results of research are presented in 12 papers published in reputable refereed journals (Physical Review Letters, Physical Review, Physics Letters and Nuclear Physics). All of the performed research is directly related to the experimental programs of DOE, especially at the Relativistic Heavy Ion Collider. Much of it also has broader interdisciplinary implications - for example, the work on the non-dissipative chiral magnetic current is directly relevant for quantum computing. The attached report describes the performed work in detail.
Bottomonia in the Quark Gluon Plasma
NASA Astrophysics Data System (ADS)
Strickland, Michael
2013-04-01
I review recent calculations of the suppression of bottomonium states in heavy ion collisions. A non-relativistic potential is used which is complex valued. This allows one to extract the binding energies and decay widths of the ground and excited states of bottomonium as a function of the typical plasma particle momentum and momentum-space anisotropy. The decay widths determined are used as input and integrated over space-time taking into account the dynamical evolution of the typical particle momentum and momentum-space anisotropy. The suppression of Upsilon(1s), Upsilon(2s), Upsilon(3s), χb1, and χb2 is obtained as a function of centrality, rapidity, and transverse momentum. The obtained results are compared with data from the STAR and CMS collaborations.
Tests of QCD at HERA: determination of the gluon density
Repond, J.
1996-12-31
An overview is given of the various methods available to the colliding beam experiments at HERA to determine the gluon density of the proton. The article includes a description of fits to the structure function F{sub 2}, of studies of dijet and open charm production in deep inelastic scattering, of elastic and inelastic {psi} photoproduction, and of inclusive diffractive scattering. 13 refs., 8 figs.
Angular correlations in gluon production at high energy
Kovner, Alex; Lublinsky, Michael
2011-02-01
We present a general, model independent argument demonstrating that gluons produced in high energy hadronic collision are necessarily correlated in rapidity and also in the emission angle. The strength of the correlation depends on the process and on the structure/model of the colliding particles. In particular we argue that it is strongly affected (and underestimated) by factorized approximations frequently used to quantify the effect.
RHIC AND THE PURSUIT OF THE QUARK-GLUON PLASMA.
MITCHELL,J.T.
2001-07-25
There is a fugitive on the loose. Its name is Quark-Gluon Plasma, alias the QGP. The QGP is a known informant with knowledge about the fundamental building blocks of nature that we wish to extract. This briefing will outline the status of the pursuit of the elusive QGP. We will cover what makes the QGP tick, its modus operandi, details on how we plan to hunt the fugitive down, and our level of success thus far.
NASA Astrophysics Data System (ADS)
Canal, G. P.; Luna, H.; Galvão, R. M. O.; Castell, R.
2009-07-01
Plasma diagnostics using the optical emission spectroscopy (OES) technique is often based on the assumption of Maxwellian distribution functions. Whenever the equilibrium condition is not fulfilled, the electron energy distribution function (EEDF) is no longer Maxwellian and there appear discrepancies between the electron temperature obtained via the spectral line ratio (e.g. Saha equation) and the effective temperature obtained from the EEDF, measured by a Langmuir probe. In this work we derive a modified version of the Saha equation by assuming a Druyvesteyn energy distribution function for the electrons. We apply the modified Saha equation to a low pressure argon plasma produced in an inductive RF discharge to obtain the electron temperature. We show that the modified version introduces substantial corrections in the measured values of the electron temperature given by OES, which approach those given by the second derivative method of Langmuir probe analysis.
Double distributions and evolution equations
A.V. Radyushkin
1998-05-01
Applications of perturbative QCD to deeply virtual Compton scattering and hard exclusive meson electroproduction processes require a generalization of usual parton distributions for the case when long-distance information is accumulated in nonforward matrix elements < p{prime} {vert_bar}O(0,z){vert_bar}p > of quark and gluon light-cone operators. In their previous papers the authors used two types of nonperturbative functions parameterizing such matrix elements: double distributions F(x,y;t) and nonforward distribution functions F{sub {zeta}}(X;t). Here they discuss in more detail the double distributions (DD's) and evolution equations which they satisfy. They propose simple models for F(x,y;t=0) DD's with correct spectral and symmetry properties which also satisfy the reduction relations connecting them to the usual parton densities f(x). In this way, they obtain self-consistent models for the {zeta}-dependence of nonforward distributions. They show that, for small {zeta}, one can easily obtain nonforward distributions (in the X > {zeta} region) from the parton densities: F{sub {zeta}} (X;t=0) {approx} f(X{minus}{zeta}/2).
NASA Astrophysics Data System (ADS)
Gökçe, M.; Uslu, D. Koçyiǧit; Ertunç, C.; Karalı, T.
2016-03-01
The aim of this study is to compare Intensity Modulated Radiation Therapy (IMRT) plan of prostate cancer patients with different dose verification systems in dosimetric aspects and to compare these systems with each other in terms of reliability, applicability and application time. Dosimetric control processes of IMRT plan of three prostate cancer patients were carried out using thermoluminescent dosimeter (TLD), ion chamber (IC) and 2D Array detector systems. The difference between the dose values obtained from the dosimetric systems and treatment planning system (TPS) were found to be about % 5. For the measured (TLD) and calculated (TPS) doses %3 percentage differences were obtained for the points close to center while percentage differences increased at the field edges. It was found that TLD and IC measurements will increase the precision and reliability of the results of 2D Array.
Bouchard, Andréanne; Jovanović, Natasa; de Boer, Anne H; Martín, Angel; Jiskoot, Wim; Crommelin, Daan J A; Hofland, Gerard W; Witkamp, Geert-Jan
2008-09-01
In the perspective of production of dry therapeutic protein formulations, spray drying of lysozyme (as a model protein) into supercritical carbon dioxide was studied. The effects of the nozzle (i.e., co-current coaxial converging and converging-diverging, and T-mixer impinging) and process conditions (i.e., flow rates, pressure) on the drying of the lysozyme prepared in aqueous solution dried with supercritical carbon dioxide enriched with ethanol were investigated. The particle size distribution, width of particle size distribution and morphology were used to determine the effect of the various parameters assessed. Particles with a median size of approximately 1.5, approximately 5 or approximately 25 microns were produced depending of the nozzle selected. A basic comparative study of the nozzle was done by computational fluid dynamics, but the differences in particle size could not be depicted by these computations. The proportional increase of the flow rates (up to fivefold) caused a decrease in particle size (7- to 12-fold), and doubling the pressure caused a moderate decrease of the size (5-20%). The individual effect of the supercritical carbon dioxide, ethanol and solution streams was explained with a mass transfer model. Changing the ratio between flow rates slightly affected the particle size in various ways because of the swelling and shrinking stages of the drying droplet in supercritical carbon dioxide enriched with ethanol. PMID:18534833
NASA Astrophysics Data System (ADS)
Zhou, Li-Juan; Zheng, Bo; Zhong, Hong-Wei; Ma, Wei-Xing
2015-03-01
Based on the Dyson-Schwinger Equations (DSEs), the two-quark vacuum condensate, the four-quark vacuum condensate, and the quark gluon mixed vacuum condensate in the non-perturbative QCD vacuum state are investigated by solving the DSEs with rainbow truncation at zero- and finite- temperature, respectively. These condensates are important input parameters in QCD sum rule with zero and finite temperature, and in studying hadron physics, as well as predicting the quark mean squared momentum m20- also called quark virtuality in the QCD vacuum state. The present calculated results show that these physical quantities are almost independent of the temperature below the critical point temperature Tc = 131 MeV, and above Tc the chiral symmetry is restored. For comparison we calculate the temperature dependence of the “in-hadron condensate” for pion. At the same time, we also calculate the ratio of the quark gluon mixed vacuum condensate to the two-quark vacuum condensate by using these condensates, and the unknown quark mean squared momentum in the QCD vacuum state has been obtained. The results show that the ratio m20(T) is almost flat in the temperature region from 0 to Tc, although there are drastic changes of the quark vacuum condensate and the quark gluon mixed vacuum condensate at the region. Our predicted ratio comes out to be m20(T)=2.41 GeV2 at the Chiral limit, which is consistent with other theory model predictions, and strongly indicates the significance that the quark gluon mixed vacuum condensate has played in the virtuality calculations. Supported by National Natural Science Foundation of China (11365002), Guangxi Natural Science Foundation for Young Researchers (2013GXNSFBB053007, 2011GXNSFA018140), Guangxi Education Department (2013ZD049), Guangxi Grant for Excellent Researchers (2011-54), and Guangxi University of Science and Technology Foundation for PhDs (11Z16)
Singh, Warsha; Örnólfsdóttir, Erla B.; Stefansson, Gunnar
2014-01-01
An approach is developed to estimate size of Iceland scallop shells from AUV photos. A small-scale camera based AUV survey of Iceland scallops was conducted at a defined site off West Iceland. Prior to height estimation of the identified shells, the distortions introduced by the vehicle orientation and the camera lens were corrected. The average AUV pitch and roll was and deg that resulted in error in ground distance rendering these effects negligible. A quadratic polynomial model was identified for lens distortion correction. This model successfully predicted a theoretical grid from a frame photographed underwater, representing the inherent lens distortion. The predicted shell heights were scaled for the distance from the bottom at which the photos were taken. This approach was validated by height estimation of scallops of known sizes. An underestimation of approximately cm was seen, which could be attributed to pixel error, where each pixel represented cm. After correcting for this difference the estimated heights ranged from cm. A comparison of the height-distribution from a small-scale dredge survey carried out in the vicinity showed non-overlapping peaks in size distribution, with scallops of a broader size range visible in the AUV survey. Further investigations are necessary to evaluate any underlying bias and to validate how representative these surveys are of the true population. The low resolution images made identification of smaller scallops difficult. Overall, the observations of very few small scallops in both surveys could be attributed to low recruitment levels in the recent years due to the known scallop parasite outbreak in the region. PMID:25303243
Singh, Warsha; Örnólfsdóttir, Erla B; Stefansson, Gunnar
2014-01-01
An approach is developed to estimate size of Iceland scallop shells from AUV photos. A small-scale camera based AUV survey of Iceland scallops was conducted at a defined site off West Iceland. Prior to height estimation of the identified shells, the distortions introduced by the vehicle orientation and the camera lens were corrected. The average AUV pitch and roll was 1.3 and 2.3 deg that resulted in <2% error in ground distance rendering these effects negligible. A quadratic polynomial model was identified for lens distortion correction. This model successfully predicted a theoretical grid from a frame photographed underwater, representing the inherent lens distortion. The predicted shell heights were scaled for the distance from the bottom at which the photos were taken. This approach was validated by height estimation of scallops of known sizes. An underestimation of approximately 0.5 cm was seen, which could be attributed to pixel error, where each pixel represented 0.24 x 0.27 cm. After correcting for this difference the estimated heights ranged from 3.8-9.3 cm. A comparison of the height-distribution from a small-scale dredge survey carried out in the vicinity showed non-overlapping peaks in size distribution, with scallops of a broader size range visible in the AUV survey. Further investigations are necessary to evaluate any underlying bias and to validate how representative these surveys are of the true population. The low resolution images made identification of smaller scallops difficult. Overall, the observations of very few small scallops in both surveys could be attributed to low recruitment levels in the recent years due to the known scallop parasite outbreak in the region.
Singh, Warsha; Örnólfsdóttir, Erla B; Stefansson, Gunnar
2014-01-01
An approach is developed to estimate size of Iceland scallop shells from AUV photos. A small-scale camera based AUV survey of Iceland scallops was conducted at a defined site off West Iceland. Prior to height estimation of the identified shells, the distortions introduced by the vehicle orientation and the camera lens were corrected. The average AUV pitch and roll was 1.3 and 2.3 deg that resulted in <2% error in ground distance rendering these effects negligible. A quadratic polynomial model was identified for lens distortion correction. This model successfully predicted a theoretical grid from a frame photographed underwater, representing the inherent lens distortion. The predicted shell heights were scaled for the distance from the bottom at which the photos were taken. This approach was validated by height estimation of scallops of known sizes. An underestimation of approximately 0.5 cm was seen, which could be attributed to pixel error, where each pixel represented 0.24 x 0.27 cm. After correcting for this difference the estimated heights ranged from 3.8-9.3 cm. A comparison of the height-distribution from a small-scale dredge survey carried out in the vicinity showed non-overlapping peaks in size distribution, with scallops of a broader size range visible in the AUV survey. Further investigations are necessary to evaluate any underlying bias and to validate how representative these surveys are of the true population. The low resolution images made identification of smaller scallops difficult. Overall, the observations of very few small scallops in both surveys could be attributed to low recruitment levels in the recent years due to the known scallop parasite outbreak in the region. PMID:25303243
Nonperturbative parton distributions and the proton spin problem
NASA Astrophysics Data System (ADS)
Simonov, Yu. A.
2016-05-01
The Lorentz contracted form of the static wave functions is used to calculate the valence parton distributions for mesons and baryons, boosting the rest frame solutions of the path integral Hamiltonian. It is argued that nonperturbative parton densities are due to excitedmultigluon baryon states. A simplemodel is proposed for these states ensuring realistic behavior of valence and sea quarks and gluon parton densities at Q 2 = 10 (GeV/ c)2. Applying the same model to the proton spin problem one obtains Σ3 = 0.18 for the same Q 2.
Observation of tree-level B decays with ss production from gluon radiation.
Aubert, B; Bona, M; Boutigny, D; Karyotakis, Y; Lees, J P; Poireau, V; Prudent, X; Tisserand, V; Zghiche, A; Garra Tico, J; Grauges, E; Lopez, L; Palano, A; Eigen, G; Stugu, B; Sun, L; Abrams, G S; Battaglia, M; Brown, D N; Button-Shafer, J; Cahn, R N; Groysman, Y; Jacobsen, R G; Kadyk, J A; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lopes Pegna, D; Lynch, G; Mir, L M; Orimoto, T J; Ronan, M T; Tackmann, K; Wenzel, W A; Del Amo Sanchez, P; Hawkes, C M; Watson, A T; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Schroeder, T; Steinke, M; Walker, D; Asgeirsson, D J; Cuhadar-Donszelmann, T; Fulsom, B G; Hearty, C; Mattison, T S; McKenna, J A; Khan, A; Saleem, M; Teodorescu, L; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Bondioli, M; Curry, S; Eschrich, I; Kirkby, D; Lankford, A J; Lund, P; Mandelkern, M; Martin, E C; Stoker, D P; Abachi, S; Buchanan, C; Foulkes, S D; Gary, J W; Liu, F; Long, O; Shen, B C; Zhang, L; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Kovalskyi, D; Richman, J D; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Schalk, T; Schumm, B A; Seiden, A; Williams, D C; Wilson, M G; Winstrom, L O; Chen, E; Cheng, C H; Fang, F; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Andreassen, R; Mancinelli, G; Meadows, B T; Mishra, K; Sokoloff, M D; Blanc, F; Bloom, P C; Chen, S; Ford, W T; Hirschauer, J F; Kreisel, A; Nagel, M; Nauenberg, U; Olivas, A; Smith, J G; Ulmer, K A; Wagner, S R; Zhang, J; Gabareen, A M; Soffer, A; Toki, W H; Wilson, R J; Winklmeier, F; Zeng, Q; Altenburg, D D; Feltresi, E; Hauke, A; Jasper, H; Merkel, J; Petzold, A; Spaan, B; Wacker, K; Brandt, T; Klose, V; Kobel, M J; Lacker, H M; Mader, W F; Nogowski, R; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Volk, A; Bernard, D; Bonneaud, G R; Latour, E; Lombardo, V; Thiebaux, Ch; Verderi, M; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Robertson, A I; Xie, Y; Andreotti, M; Bettoni, D; Bozzi, C; Calabrese, R; Cecchi, A; Cibinetto, G; Franchini, P; Luppi, E; Negrini, M; Petrella, A; Piemontese, L; Prencipe, E; Santoro, V; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Pacetti, S; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Buzzo, A; Contri, R; Lo Vetere, M; Macri, M M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Chaisanguanthum, K S; Morii, M; Wu, J; Dubitzky, R S; Marks, J; Schenk, S; Uwer, U; Bard, D J; Dauncey, P D; Flack, R L; Nash, J A; Nikolich, M B; Panduro Vazquez, W; Tibbetts, M; Behera, P K; Chai, X; Charles, M J; Mallik, U; Meyer, N T; Ziegler, V; Cochran, J; Crawley, H B; Dong, L; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Gritsan, A V; Guo, Z J; Lae, C K; Denig, A G; Fritsch, M; Schott, G; Arnaud, N; Béquilleux, J; Davier, M; Grosdidier, G; Höcker, A; Lepeltier, V; Le Diberder, F; Lutz, A M; Pruvot, S; Rodier, S; Roudeau, P; Schune, M H; Serrano, J; Sordini, V; Stocchi, A; Wang, W F; Wormser, G; Lange, D J; Wright, D M; Bingham, I; Chavez, C A; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; Hutchcroft, D E; Payne, D J; Schofield, K C; Touramanis, C; Bevan, A J; George, K A; Di Lodovico, F; Menges, W; Sacco, R; Cowan, G; Flaecher, H U; Hopkins, D A; Paramesvaran, S; Salvatore, F; Wren, A C; Brown, D N; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Chia, Y M; Edgar, C L; Lafferty, G D; West, T J; Yi, J I; Anderson, J; Chen, C; Jawahery, A; Roberts, D A; Simi, G; Tuggle, J M; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Li, X; Moore, T B; Salvati, E; Saremi, S; Cowan, R; Dujmic, D; Fisher, P H; Koeneke, K; Sciolla, G; Sekula, S J; Spitznagel, M; Taylor, F; Yamamoto, R K; Zhao, M; Zheng, Y; McLachlin, S E; Patel, P M; Robertson, S H; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Simard, M; Taras, P; Viaud, F B; Nicholson, H; De Nardo, G; Fabozzi, F; Lista, L; Monorchio, D; Sciacca, C; Baak, M A; Raven, G; Snoek, H L; Jessop, C P; Losecco, J M; Benelli, G; Corwin, L A; Honscheid, K; Kagan, H; Kass, R; Morris, J P; Rahimi, A M; Regensburger, J J; Wong, Q K; Blount, N L; Brau, J; Frey, R; Igonkina, O; Kolb, J A; Lu, M; Rahmat, R; Sinev, N B; Strom, D; Strube, J; Torrence, E; Gagliardi, N; Gaz, A; Margoni, M; Morandin, M; Pompili, A; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Ben-Haim, E; Briand, H; Calderini, G; Chauveau, J; David, P; Del Buono, L; de la Vaissière, Ch; Hamon, O; Leruste, Ph; Malclès, J; Ocariz, J; Perez, A; Gladney, L; Biasini, M; Covarelli, R; Manoni, E; Angelini, C; Batignani, G; Bettarini, S; Carpinelli, M; Cenci, R; Cervelli, A; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Mazur, M A; Morganti, M; Neri, N; Paoloni, E; Rizzo, G; Walsh, J J; Haire, M; Biesiada, J; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Baracchini, E; Bellini, F; Cavoto, G; D'Orazio, A; Del Re, D; Di Marco, E; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Jackson, P D; Li Gioi, L; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Renga, F; Voena, C; Ebert, M; Hartmann, T; Schröder, H; Waldi, R; Adye, T; Castelli, G; Franek, B; Olaiya, E O; Ricciardi, S; Roethel, W; Wilson, F F; Aleksan, R; Emery, S; Escalier, M; Gaidot, A; Ganzhur, S F; Hamel de Monchenault, G; Kozanecki, W; Vasseur, G; Yèche, Ch; Zito, M; Chen, X R; Liu, H; Park, W; Purohit, M V; Wilson, J R; Allen, M T; Aston, D; Bartoldus, R; Bechtle, P; Berger, N; Claus, R; Coleman, J P; Convery, M R; Dingfelder, J C; Dorfan, J; Dubois-Felsmann, G P; Dunwoodie, W; Field, R C; Glanzman, T; Gowdy, S J; Graham, M T; Grenier, P; Hast, C; Hryn'ova, T; Innes, W R; Kaminski, J; Kelsey, M H; Kim, H; Kim, P; Kocian, M L; Leith, D W G S; Li, S; Luitz, S; Luth, V; Lynch, H L; Macfarlane, D B; Marsiske, H; Messner, R; Muller, D R; O'Grady, C P; Ofte, I; Perazzo, A; Perl, M; Pulliam, T; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Stelzer, J; Su, D; Sullivan, M K; Suzuki, K; Swain, S K; Thompson, J M; Va'vra, J; van Bakel, N; Wagner, A P; Weaver, M; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Yi, K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Wilden, L; Ahmed, S; Alam, M S; Bula, R; Ernst, J A; Jain, V; Pan, B; Saeed, M A; Wappler, F R; Zain, S B; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Ritchie, J L; Ruland, A M; Schilling, C J; Schwitters, R F; Izen, J M; Lou, X C; Ye, S; Bianchi, F; Gallo, F; Gamba, D; Pelliccioni, M; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Lanceri, L; Vitale, L; Azzolini, V; Lopez-March, N; Martinez-Vidal, F; Milanes, D A; Oyanguren, A; Albert, J; Banerjee, Sw; Bhuyan, B; Hamano, K; Kowalewski, R; Nugent, I M; Roney, J M; Sobie, R J; Back, J J; Harrison, P F; Ilic, J; Latham, T E; Mohanty, G B; Pappagallo, M; Band, H R; Chen, X; Dasu, S; Flood, K T; Hollar, J J; Kutter, P E; Pan, Y; Pierini, M; Prepost, R; Wu, S L; Neal, H
2008-05-01
We report on our search for decays proceeding via a tree-level b-->c quark transition in which a gluon radiates into an ss[over ] pair. We present observations of the decays B;{-}-->D_{s};{+}K;{-}pi;{-} and B[over ];{0}-->D_{s};{+}K_{S};{0}pi;{-} and evidence for B;{-}-->D_{s};{+}K;{-}K;{-} and set upper limits on the branching fractions for B[over ];{0}-->D_{s};{+}K_{S};{0}pi;{-} and B;{-}-->D_{s};{+}K;{-}K;{-} using 383x10;{6} Upsilon(4S)-->BB[over ] events collected by the BABAR detector at SLAC. We present evidence that the invariant mass distributions of D_{s};{+}K;{-} pairs from B;{-}-->D_{s};{+}K;{-}pi;{-} decays are inconsistent with the phase-space model, suggesting the presence of charm resonances lying below the D_{s};{+}K;{-} threshold. PMID:18518280
Nonplanar 4-Jets in Quarkonium Decays as a Probe for 3-Gluon Coupling
NASA Astrophysics Data System (ADS)
Muta, T.; Niuya, T.
1982-11-01
We calculate the acoplanarity (à la Fox-Wolfram) distribution of 4 jets generated by orthoquarkonium decays: 3S1(Qbar{Q})→ GGGG, GGqbar{q}. The result shows that the deviation from planar event due to 4 jets is significantly large showing the importance of the effect of 3-gluon couplings in quantum chromodynamics. The average acoplanarity
Higgs pair production via gluon fusion in the Two-Higgs-Doublet Model
NASA Astrophysics Data System (ADS)
Hespel, Benoît; López-Val, David; Vryonidou, Eleni
2014-09-01
We study the production of Higgs boson pairs via gluon fusion at the LHC in the Two-Higgs-Doublet Model. We present predictions at NLO accuracy in QCD, matched to parton showers through the MC@NLO method. A dedicated reweighting technique is used to improve the NLO calculation upon the infinite top-mass limit. We perform our calculation within the MadGraph5 aMC@NLO framework, along with the 2HDM implementation based on the NLOCT package. The inclusion of the NLO corrections leads to large K-factors and significantly reduced theoretical uncertainties. We examine the seven 2HDM Higgs pair combinations using a number of representative 2HDM scenarios. We show how the model-specific features modify the Higgs pair total rates and distribution shapes, leading to trademark signatures of an extended Higgs sector.
Gluons to Diphotons via New Particles with Half the Signal's Invariant Mass
NASA Astrophysics Data System (ADS)
Chway, Dongjin; Dermíšek, Radovan; Jung, Tae Hyun; Kim, Hyung Do
2016-08-01
Any new particle charged under S U (3 )C and carrying an electric charge will leave an imprint in the diphoton invariant mass spectrum, as it can mediate the g g →γ γ process through loops. The combination of properties of loop functions, threshold resummation, and gluon parton distribution functions can result in a peaklike feature in the diphoton invariant mass around twice the mass of a given particle even if the particle is short lived, and thus it does not form a narrow bound state. Using a recent ATLAS analysis, we set upper limits on the combined S U (3 )C and electric charge of new particles and indicate future prospects. We also discuss the possibility that the excess of events in the diphoton invariant mass spectrum around 750 GeV originates from loops of a particle with a mass of around 375 GeV.
NASA Astrophysics Data System (ADS)
Snyder, Douglas
For a pair of entangled signal-idler photons, one may ``lose'' the idler photon (that provides which-way information to the entangled signal photon) in many other photons with similar characteristics to the idler photon before the signal photon is detected, thereby losing the which-way information supplied to the signal photon and eliminating the entanglement. The experiment allows for a delayed choice on the idler photons (whether or not to lose the idler photon before the signal photon is detected) to determine the distribution of distant signal photons (either overall which-way or overall interference) without making correlations between signal and idler photon detections. When the idler photon is lost, it is lost in an optical microcavity filled with photons in the same mode as the idler photon. The experiment could provide the basis for a useful quantum communications device. It might be possible to use a micropost coated with a material such as Vantablack in place of the optical microcavity.
Mochalski, Paweł; Unterkofler, Karl; Španěl, Patrik; Smith, David; Amann, Anton
2014-01-01
Product ion distributions for the reactions of NO+ with 22 aldehydes involved in human physiology have been determined under the prevailing conditions of a selective reagent ionization time of flight mass spectrometry (SRI-TOF-MS) at an E/N in the flow/drift tube reactor of 130 Td. The chosen aldehydes were fourteen alkanals (the C2–C11 n-alkanals, 2-methyl propanal, 2-methyl butanal, 3-methyl butanal, and 2-ethyl hexanal), six alkenals (2-propenal, 2-methyl 2-propenal, 2-butenal, 3-methyl 2-butenal, 2-methyl 2-butenal, and 2-undecenal), benzaldehyde, and furfural. The product ion fragmentations patterns were determined for both dry air and humid air (3.5% absolute humidity) used as the matrix buffer/carrier gas in the drift tube of the SRI-TOF-MS instrument. Hydride ion transfer was seen to be a common ionization mechanism in all these aldehydes, thus generating (M−H)+ ions. Small fractions of the adduct ion, NO+M, were also seen for some of the unsaturated alkenals, in particular 2-undecenal, and heterocyclic furfural for which the major reactive channel was non-dissociative charge transfer generating the M+ parent ion. Almost all of the reactions resulted in partial fragmentation of the aldehyde molecules generating hydrocarbon ions; specifically, the alkanal reactions resulted in multiple product ions, whereas, the alkenals reactions produced only two or three product ions, dissociation of the nascent excited product ion occurring preferentially at the 2-position. The findings of this study are of particular importance for data interpretation in studies of aldehydes reactions employing SRI-TOF-MS in the NO+ mode. PMID:25844049
Evidence for the Absence of Gluon Orbital Angular Momentum in the Nucleon
Brodsky, S.J.; Gardner, S.
2006-08-23
The Sivers mechanism for the single-spin asymmetry in unpolarized lepton scattering from a transversely polarized nucleon is driven by the orbital angular momentum carried by its quark and gluon constituents, combined with QCD final-state interactions. Both quark and gluon mechanisms can generate such a single-spin asymmetry, though only the quark mechanism can explain the small single-spin asymmetry measured by the COMPASS collaboration on the deuteron, suggesting the gluon mechanism is small relative to the quark mechanism. We detail empirical studies through which the gluon and quark orbital angular momentum contributions, quark-flavor by quark-flavor, can be elucidated.
Infrared behavior of the ghost-gluon vertex in Landau gauge Yang-Mills theory
Schleifenbaum, W.; Maas, A.; Wambach, J.; Alkofer, R.
2005-07-01
A semiperturbative calculation of the ghost-gluon vertex in Landau-gauge Yang-Mills theory in four and three Euclidean space-time dimensions is presented. Nonperturbative gluon and ghost propagators are employed, which have previously been calculated from a truncated set of Dyson-Schwinger equations and which are in qualitative and quantitative agreement with corresponding lattice results. Our results for the ghost-gluon vertex show only relatively small deviations from the tree-level one in agreement with recent lattice data. In particular, we do not see any sign for a singular behavior of the ghost-gluon vertex in the infrared.
How perfect can a gluon plasma be in perturbative QCD?
Chen, Jiunn-Wei; Deng Jian; Dong Hui; Wang Qun
2011-02-01
The shear viscosity to entropy density ratio, {eta}/s, characterizes how perfect a fluid is. We calculate the leading order {eta}/s of a gluon plasma in perturbation using the kinetic theory. The leading order contribution only involves the elastic gg{r_reversible}gg (22) process and the inelastic gg{r_reversible}ggg (23) process. The hard-thermal-loop (HTL) treatment is used for the 22 matrix element, while the exact matrix element in vacuum is supplemented by the gluon Debye mass insertion for the 23 process. Also, the asymptotic mass is used for the external gluons in the kinetic theory. The errors from not implementing HTL and the Landau-Pomeranchuk-Migdal effect in the 23 process, and from the uncalculated higher order corrections, are estimated. Our result smoothly connects the two different approximations used by Arnold, Moore, and Yaffe (AMY) and Xu and Greiner (XG). At small {alpha}{sub s} ({alpha}{sub s}<<1), our result is closer to AMY's collinear result while at larger {alpha}{sub s} the finite angle noncollinear configurations become more important and our result is closer to XG's soft bremsstrahlung result. In the region where perturbation is reliable ({alpha}{sub s} < or approx. 0.1), we find no indication that the proposed perfect fluid limit {eta}/s{approx_equal}1/(4{pi}) can be achieved by perturbative QCD alone. Whether this can be achieve for {alpha}{sub s} > or approx. 0.1 is still an open question.
Eikonal gluon bremsstrahlung at finite Nc beyond two loops
NASA Astrophysics Data System (ADS)
Delenda, Yazid; Khelifa-Kerfa, Kamel
2016-03-01
We present a general formalism for computing the matrix-element squared for the emission of soft energy-ordered gluons beyond two loops in QCD perturbation theory at finite Nc. Our formalism is valid in the eikonal approximation. A Mathematica program has been developed for the automated calculation of all real/virtual eikonal squared amplitudes needed at a given loop order. For the purpose of illustration, we show the explicit forms of the eikonal squared amplitudes up to the fifth-loop order. In the large-Nc limit, our results coincide with those previously reported in literature.
Attractive Casimir effect in an infrared modified gluon bag model
Oxman, L.E.; Amaral, R.L.P.G.
2005-12-15
In this work, we are motivated by previous attempts to derive the vacuum contribution to the bag energy in terms of familiar Casimir energy calculations for spherical geometries. A simple infrared modified model is introduced which allows studying the effects of the analytic structure as well as the geometry in a clear manner. In this context, we show that if a class of infrared vanishing effective gluon propagators is considered, then the renormalized vacuum energy for a spherical bag is attractive, as required by the bag model to adjust hadron spectroscopy.
Scaling, decoupling and transversality of the gluon propagator
Fischer, Christian S.; Smekal, Lorenz von
2011-05-23
In this note we discuss a couple of technical issues relevant to solving the Dyson-Schwinger equation for the gluon propagator in Landau gauge Yang-Mills theory. In the deep infrared functional methods extract a one-parameter family of solutions generically showing a massive behavior referred to as 'decoupling' but also including the so-called 'scaling' solution with a conformal infrared behavior as a limiting case. We emphasize that the latter cannot be ruled out by technical arguments related to the removal of quadratic divergencies and transversality.
Heavy quarks, gluons and the confinement potential in Coulomb gauge
Popovici, Carina; Watson, Peter; Reinhardt, Hugo
2011-05-23
We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.
Quarks and gluons in the nucleon: Proceedings. Volume 6
1997-12-31
The purpose of the symposium was to discuss the quark and gluon structure of the nucleon as probed experimentally by hard processes with lepton and hadron beams and studied theoretically by perturbative QCD, lattice QCD and effective models on the one hand and to stimulate research activities in the fields related to RHIC and RHIC-SPIN projects on the other hand. There were 18 talks and 2 discussion sessions. About 50, including 5 from abroad participated in the symposium. An excellent summary in the form of 5 most important transparencies and a one-page explanation is included for each of the invited talks.
Threshold resummation of soft gluons in hadronic reactions - an introduction.
Berger, E. L.
1998-02-17
The authors discuss the motivation for resummation of the effects of initial-state soft gluon radiation, to all orders in the strong coupling strength, for processes in which the near-threshold region in the partonic subenergy is important. The author summarizes the method of perturbative resummation and its application to the calculation of the total cross section for top quark production at hadron colliders. Comments are included on the differences between the treatment of subleading logarithmic terms in this method and in other approaches.
Interactions of quarks and gluons with nuclei at intermediate energies
Mueller, A.H.
1994-04-01
Some processes involving the interaction of medium energy quarks and gluons with nuclear matter are described. Possible mechanisms for the A-dependence of the energy loss of leading protons produced in proton-nucleus collisions are given, and an experiment which may help to distinguish these mechanisms is described. A possible color transparency experiment at CEBAF is described. Experiments to measure energy loss of quarks in nuclear matter and the formation time of hadrons are discussed along with the possibilities of measuring {sigma}{sub J}/{psi} and {sigma}{sub {psi}{prime}} at CEBAF.
Heavy quarks, gluons and the confinement potential in Coulomb gauge
NASA Astrophysics Data System (ADS)
Popovici, Carina; Watson, Peter; Reinhardt, Hugo
2011-05-01
We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.
An improved global analysis of nuclear parton distribution functions including RHIC data
NASA Astrophysics Data System (ADS)
Eskola, Kari J.; Paukkunen, Hannu; Salgado, Carlos A.
2008-07-01
We present an improved leading-order global DGLAP analysis of nuclear parton distribution functions (nPDFs), supplementing the traditionally used data from deep inelastic lepton-nucleus scattering and Drell-Yan dilepton production in proton-nucleus collisions, with inclusive high-pT hadron production data measured at RHIC in d+Au collisions. With the help of an extended definition of the χ2 function, we now can more efficiently exploit the constraints the different data sets offer, for gluon shadowing in particular, and account for the overall data normalization uncertainties during the automated χ2 minimization. The very good simultaneous fit to the nuclear hard process data used demonstrates the feasibility of a universal set of nPDFs, but also limitations become visible. The high-pT forward-rapidity hadron data of BRAHMS add a new crucial constraint into the analysis by offering a direct probe for the nuclear gluon distributions—a sector in the nPDFs which has traditionally been very badly constrained. We obtain a strikingly stronger gluon shadowing than what has been estimated in previous global analyses. The obtained nPDFs are released as a parametrization called EPS08.
Xu Zhe; Greiner, Carsten
2007-08-15
To describe momentum isotropization of gluon matter produced in ultrarelativistic heavy-ion collisions, the transport rate of gluon drift and the transport collision rates of elastic (gg{r_reversible}gg) as well as inelastic (gg{r_reversible}ggg) perturbative quantum chromodynamics- (pQCD) scattering processes are introduced and calculated within the kinetic parton cascade Boltzmann approach of multiparton scatterings (BAMPS), which simulates the space-time evolution of partons. We define isotropization as the development of an anisotropic system as it reaches isotropy. The inverse of the introduced total transport rate gives the correct time scale of the momentum isotropization. The contributions of the various scattering processes to the momentum isotropization can be separated into the transport collision rates. In contrast to the transport cross section, the transport collision rate has an indirect but correctly implemented relationship with the collision-angle distribution. Based on the calculated transport collision rates from BAMPS for central Au+Au collisions at Relativistic Heavy Ion Collider energies, we show that pQCD gg{r_reversible}ggg bremsstrahlung processes isotropize the momentum five times more efficiently than elastic scatterings. The large efficiency of the bremsstrahlung stems mainly from its large momentum deflection. Due to kinematics, 2{yields}N (N>2) production processes allow more particles to become isotropic in momentum space and thus kinetically equilibrate more quickly than their back reactions or elastic scatterings. We also show that the relaxation time in the relaxation time approximation, which is often used, is strongly momentum dependent and thus cannot serve as a global quantity that describes kinetic equilibration.
High precision determination of the gluon fusion Higgs boson cross-section at the LHC
NASA Astrophysics Data System (ADS)
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Lazopoulos, Achilleas; Mistlberger, Bernhard
2016-05-01
We present the most precise value for the Higgs boson cross-section in the gluon-fusion production mode at the LHC. Our result is based on a perturbative expansion through N3LO in QCD, in an effective theory where the top-quark is assumed to be infinitely heavy, while all other Standard Model quarks are massless. We combine this result with QCD corrections to the cross-section where all finite quark-mass effects are included exactly through NLO. In addition, electroweak corrections and the first corrections in the inverse mass of the top-quark are incorporated at three loops. We also investigate the effects of threshold resummation, both in the traditional QCD framework and following a SCET approach, which resums a class of π2 contributions to all orders. We assess the uncertainty of the cross-section from missing higher-order corrections due to both perturbative QCD effects beyond N3LO and unknown mixed QCD-electroweak effects. In addition, we determine the sensitivity of the cross-section to the choice of parton distribution function (PDF) sets and to the parametric uncertainty in the strong coupling constant and quark masses. For a Higgs mass of m H = 125 GeV and an LHC center-of-mass energy of 13 TeV, our best prediction for the gluon fusion cross-section is σ =48.58{pb}_{-3.27pb}^{+2.22pb}(theory)± 1.56pb(3.20%)(PDF+{α}_s).
Pre-equilibrium dilepton production from an anisotropic quark-gluon plasma
Martinez, Mauricio; Strickland, Michael
2008-09-15
We calculate leading-order dilepton yields from a quark-gluon plasma that has a time-dependent anisotropy in momentum space. Such anisotropies can arise during the earliest stages of quark-gluon plasma evolution due to the rapid longitudinal expansion of the created matter. Two phenomenological models for the proper-time dependence of the parton hard momentum scale, p{sub hard}, and the plasma anisotropy parameter, {xi}, are constructed that describe the transition of the plasma from its initial nonequilibrium state to an isotropic thermalized state. The first model constructed interpolates between 1+1 dimensional free streaming at early times and 1+1 dimensional ideal hydrodynamical expansion at late times. In the second model we include the effect of collisional broadening of the parton distribution functions in the early-time pre-equilibrium stage of plasma evolution. We find for both cases that for fixed initial conditions high-energy dilepton production is enhanced by pre-equilibrium emission. When the models are constrained to fixed final pion multiplicity the dependence of the resulting spectra on the assumed plasma isotropization time is reduced. Using our most realistic collisionally broadened model we find that high-transverse-momentum dilepton production would be enhanced by at most 40% at the Relativistic Heavy Ion Collider and 50% at the CERN Large Hadron Collider if one assumes an isotropization/thermalization time of 2 fm/c. Given sufficiently precise experimental data this enhancement could be used to determine the plasma isotropization time experimentally.
The parton distributions in nuclei and in polarized nucleons
Close, F.E.
1988-01-01
The emerging information was reviewed on the way quark and anti-quark, and gluon distributions are modified in nuclei relative to free nucleons. Some implications of the recent data on polarized leptoproduction are discussed. 27 refs., 6 figs.
Global NLO Analysis of Nuclear Parton Distribution Functions
Hirai, M.; Kumano, S.; Nagai, T.-H.
2008-02-21
Nuclear parton distribution functions (NPDFs) are determined by a global analysis of experimental measurements on structure-function ratios F{sub 2}{sup A}/F{sub 2}{sup A{sup '}} and Drell-Yan cross section ratios {sigma}{sub DY}{sup A}/{sigma}{sub DY}{sup A{sup '}}, and their uncertainties are estimated by the Hessian method. The NPDFs are obtained in both leading order (LO) and next-to-leading order (NLO) of {alpha}{sub s}. As a result, valence-quark distributions are relatively well determined, whereas antiquark distributions at x>0.2 and gluon distributions in the whole x region have large uncertainties. The NLO uncertainties are slightly smaller than the LO ones; however, such a NLO improvement is not as significant as the nucleonic case.
Quark mean field model with pion and gluon corrections
NASA Astrophysics Data System (ADS)
Xing, Xueyong; Hu, Jinniu; Shen, Hong
2016-10-01
The properties of nuclear matter and finite nuclei are studied within the quark mean field (QMF) model by taking the effects of pions and gluons into account at the quark level. The nucleon is described as the combination of three constituent quarks confined by a harmonic oscillator potential. To satisfy the spirit of QCD theory, the contributions of pions and gluons on the nucleon structure are treated in second-order perturbation theory. In a nuclear many-body system, nucleons interact with each other by exchanging mesons between quarks. With different constituent quark mass, mq, we determine three parameter sets for the coupling constants between mesons and quarks, named QMF-NK1, QMF-NK2, and QMF-NK3, by fitting the ground-state properties of several closed-shell nuclei. It is found that all of the three parameter sets can give a satisfactory description of properties of nuclear matter and finite nuclei, moreover they also predict a larger neutron star mass around 2.3 M⊙ without hyperon degrees of freedom.
Introduction to quantum chromo transport theory for quark-gluon plasmas
Gyulassy, M.; Elze, H.Th.; Iwazaki, A.; Vasak, D.
1986-08-01
Upcoming heavy ion experiments at the AGS and SPS are aimed at producing and diagnosing a primordial form of matter, the quark-gluon plasma. In these lectures some recent developments on formulating a quantum transport theory for quark-gluon plasmas are introduced. 46 refs.
On the color factor of n-gluon decay from quarkonium
Biyajima, M.; Kawabe, T.; Suzuki, N.
1987-02-01
A method for evaluating the weight of the color factor necessary for gluon decay in the context of quantum chromodynamics (QCD) is presented. As concrete examples, the method is applied to the three- and four-gluon decays from heavy quarkonium.
NASA Astrophysics Data System (ADS)
Wolin, Scott Justin
The PHENIX experiment is one of two detectors located at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in Upton, NY. Understanding the spin structure of the proton is a central goal at RHIC, the only polarized proton-on-proton collider in existence. The PHENIX spin program has two primary objectives. The first is to improve the constraints on the polarized parton distributions of the anti-u and anti-d quarks within the proton. The second objective is to improve the constraint on the gluon spin contribution to the proton spin, DeltaG. The focus of this thesis is the second objective. PHENIX experiment has been successful at providing the first meaningful constraints on DeltaG, along with STAR, the other detector located at RHIC. These constraints have, in fact, eliminated the extreme scenarios for gluon polarization through measurements of the double spin asymmetry, ALL, between the cross section of like and unlike sign helicity pp interactions. ALL measurements can be performed with a variety of final states at PHENIX. Until 2009, these final states were only measured for pseudo-rapidities of |eta| < 0.35. This range of eta is referred to as mid-rapidity. These mid-rapidity measurements, like the polarized DIS measurements, suffer from a limited kinematic reach. Final states containing a measured particle with pT [special character omitted] 1 GeV/c are considered to have occurred in the hard scattering domain where the pp interaction is well approximated as an interaction of a quark or gluon in one proton and a quark or gluon in the second proton. Each of these interacting particles has a momentum fraction, x, of its parent proton's momentum. The gluon polarization is dependent on the momentum fraction and the net gluon polarization can be written as the integral of the momentum fraction dependent polarization: DeltaG = f(1,0)Delta g(x)dx. The momentum fractions of the two interacting particles give information about the final state
A measurement of quark and gluon jet differences at the Z{sup 0} resonance
Iwasaki, Yoshihito
1994-08-01
The authors have studied differences between quark and gluon jets using 3-jet events in hadronic decays of Z{sup 0} bosons collected by the SLD experiment at SLAC. Gluon jets were identified in symmetric 3-jet events containing one jet tagged as a heavy quark jet and compared with a mixed sample of quark and gluon jets and also with a mixed sample of light quark (u, d and s) and gluon jets. Their preliminary results show that the particle multiplicity in gluon jets is higher than that in light quark jets. These results are in qualitative agreement with QCD expectations. Differences are also observed in particle energy spectra and the jet widths, consistent with QCD expectations.
Agaev, S.S.; Stefanis, N.G.
2004-09-01
We compute power-suppressed corrections to the {eta}{gamma} and {eta}{sup '}{gamma} transition form factors Q{sup 2}F{sub {eta}}{sub ({eta}}{sub {sup '}}{sub {gamma}}(Q{sup 2}) arising from the end point regions x{yields}0,1 by employing the infrared-renormalon approach. The contribution to the form factors from the quark and gluon content of the {eta},{eta}{sup '} mesons is taken into account using for the {eta}-{eta}{sup '} mixing the SU{sub f}(3) singlet {eta}{sub 1} and octet {eta}{sub 8} basis. The theoretical predictions obtained this way are compared with the corresponding CLEO data and restrictions on the input parameters (Gegenbauer coefficients) B{sub 2}{sup q}({eta}{sub 1}), B{sub 2}{sup g}({eta}{sub 1}), and B{sub 2}{sup q}({eta}{sub 8}) in the distribution amplitudes for the {eta}{sub 1},{eta}{sub 8} states with one nonasymptotic term are deduced. Comparison is made with the results from QCD perturbation theory.
NASA Astrophysics Data System (ADS)
Kłusek-Gawenda, Mariola; Schäfer, Wolfgang; Szczurek, Antoni
2016-10-01
We discuss the two-gluon exchange contribution (formally three-loops) to elastic photon-photon scattering in the high-energy approximation. The elastic γγ → γγ amplitude is given in the impact-factor representation for all helicity configurations and finite quark masses. We discuss the importance of including the charm quark, which contribution, due to interference, can enhance the cross section considerably. We investigate the contribution to the γγ → γγ amplitude from the soft region, by studying its dependence on nonperturbative gluon mass. Helicity-flip contributions are shown to be much smaller than helicity-conserving ones. We identify region(s) of phase space where the two-gluon exchange contribution becomes important ingredient compared to box and nonperturbative VDM-Regge mechanisms considered in the literature. Consequences for the AA → AAγγ reaction are discussed. Several differential distributions are shown. A feasibility study to observe the effect of two-gluon exchange is presented. We perform a similar analysis for the pp → ppγγ reaction. Only by imposing severe cuts on Mγγ and a narrow window on photon transverse momenta the two gluon contribution becomes comparable to the box contribution but the corresponding cross section is rather small.
Gluon-fusion contributions to {Phi}+2 jet production
Campanario, F.; Zeppenfeld, D.; Kubocz, M.
2011-11-01
In high energy hadronic collisions, a scalar or pseudoscalar Higgs boson, {Phi}=H, A, can be efficiently produced via gluon fusion, which is mediated by heavy quark loops. In this paper, we consider double real emission corrections to {Phi}=A production, which lead to a Higgs plus two-jet final state, at order {alpha}{sub s}{sup 4}. Full quark mass effects are considered in the calculation of scattering amplitudes for the CP-odd Higgs boson A, as induced by quark triangle-, box-, and pentagon-diagrams. They complement the analogous results for a CP-even Higgs boson H in Ref. [1]. Interference effects between loops with top and bottom quarks as well as between CP-even and CP-odd couplings of the heavy quarks are fully taken into account.
LONGITUDINAL GLUON POLARIZATION IN RHIC DOUBLE-SPIN ASYMMETRIES.
JAGER,B.; STRATMANN,M.; KRETZER,S.; VOGELSANG,W.
2004-04-14
The longitudinally polarized gluon density is probed sensitively in hard collisions of polarized protons under the condition that the dominant dynamics are perturbative and of leading twist origin. First data have recently been presented by PHENIX on the double-spin asymmetry A{sub LL}{sup {pi}} for {pi}{sup 0} production at moderate transverse momentum p {perpendicular} {approx_equal} 1 {divided_by} 4 GeV and central rapidity. By means of a systematic investigation of the relevant degrees of freedom we show that the perturbative QCD framework at leading power in p{perpendicular} produces an asymmetry that is basically positive definite in this kinematic range, i.e. A{sub LL}{sup {pi}} {approx}> {Omicron}(-10{sup -3}).
Experimental Studies of Quark Gluon Plasma at RHIC
NASA Astrophysics Data System (ADS)
Esumi, ShinIchi
2010-05-01
A new state of matter, Quark Gluon Plasma (QGP) is supposed to exist under extreme temperature and/or density conditions just as a beginning of this early universe after the Big Bang. High energy nucleus-nucleus collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) has been used to form the QGP and to study the properties of QGP. The recent progress on the experimental research of QGP at RHIC experiments and the understanding of the properties are discussed. Major discoveries at RHIC experiments are very strong energy loss of high energy partons in central Au+Au collisions and very large elliptic and collective expansion given by the initial almond geometry in non-central Au+Au collisions. Those two finding and related physics explanations as well as future plans are presented.
Experimental Studies of Quark Gluon Plasma at RHIC
Esumi, ShinIchi
2010-05-12
A new state of matter, Quark Gluon Plasma (QGP) is supposed to exist under extreme temperature and/or density conditions just as a beginning of this early universe after the Big Bang. High energy nucleus-nucleus collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) has been used to form the QGP and to study the properties of QGP. The recent progress on the experimental research of QGP at RHIC experiments and the understanding of the properties are discussed. Major discoveries at RHIC experiments are very strong energy loss of high energy partons in central Au+Au collisions and very large elliptic and collective expansion given by the initial almond geometry in non-central Au+Au collisions. Those two finding and related physics explanations as well as future plans are presented.
Shock-like hadronization of a quark gluon plasma
Suhonen, E.; Stalnacke, J.
1995-07-20
The effect of a sharp front separating the quark-gluon plasma phase from the hadronic phase is studied. Energy-momentum conservation and baryon number conservation constrain the possible temperature jump across the front. Assuming the temperature in the hadronic phase to be fixed from experiments one can determine the corresponding temperature in the plasma. In addition to the standard space-like discontinuities sudden transitions across a time-like front are also considered. The calculations reveal that the quark phase had to be expanded to a substantially supercooled state for a shock transition to happen. The supercooling is weaker if the hadronization occurs simultaneously across a time-like front than in the case of a space-like shock hadronization. If the initial phase is not pure but contains an admixture of hadronic matter slightly less supercooling is needed. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}.
NASA Astrophysics Data System (ADS)
Wolin, Scott Justin
The PHENIX experiment is one of two detectors located at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in Upton, NY. Understanding the spin structure of the proton is a central goal at RHIC, the only polarized proton-on-proton collider in existence. The PHENIX spin program has two primary objectives. The first is to improve the constraints on the polarized parton distributions of the anti-u and anti-d quarks within the proton. The second objective is to improve the constraint on the gluon spin contribution to the proton spin, DeltaG. The focus of this thesis is the second objective. PHENIX experiment has been successful at providing the first meaningful constraints on DeltaG, along with STAR, the other detector located at RHIC. These constraints have, in fact, eliminated the extreme scenarios for gluon polarization through measurements of the double spin asymmetry, ALL, between the cross section of like and unlike sign helicity pp interactions. ALL measurements can be performed with a variety of final states at PHENIX. Until 2009, these final states were only measured for pseudo-rapidities of |eta| < 0.35. This range of eta is referred to as mid-rapidity. These mid-rapidity measurements, like the polarized DIS measurements, suffer from a limited kinematic reach. Final states containing a measured particle with pT [special character omitted] 1 GeV/c are considered to have occurred in the hard scattering domain where the pp interaction is well approximated as an interaction of a quark or gluon in one proton and a quark or gluon in the second proton. Each of these interacting particles has a momentum fraction, x, of its parent proton's momentum. The gluon polarization is dependent on the momentum fraction and the net gluon polarization can be written as the integral of the momentum fraction dependent polarization: DeltaG = f(1,0)Delta g(x)dx. The momentum fractions of the two interacting particles give information about the final state
Lee, HyeongJin; Ahn, SeungHyun; Bonassar, Lawrence J.; Chun, Wook
2013-01-01
Generally, solid-freeform fabricated scaffolds show a controllable pore structure (pore size, porosity, pore connectivity, and permeability) and mechanical properties by using computer-aided techniques. Although the scaffolds can provide repeated and appropriate pore structures for tissue regeneration, they have a low biological activity, such as low cell-seeding efficiency and nonuniform cell density in the scaffold interior after a long culture period, due to a large pore size and completely open pores. Here we fabricated three different poly(ɛ-caprolactone) (PCL)/alginate scaffolds: (1) a rapid prototyped porous PCL scaffold coated with an alginate, (2) the same PCL scaffold coated with a mixture of alginate and cells, and (3) a multidispensed hybrid PCL/alginate scaffold embedded with cell-laden alginate struts. The three scaffolds had similar micropore structures (pore size=430–580 μm, porosity=62%–68%, square pore shape). Preosteoblast cells (MC3T3-E1) were used at the same cell density in each scaffold. By measuring cell-seeding efficiency, cell viability, and cell distribution after various periods of culturing, we sought to determine which scaffold was more appropriate for homogeneously regenerated tissues. PMID:23469894
Lee, HyeongJin; Ahn, SeungHyun; Bonassar, Lawrence J; Chun, Wook; Kim, GeunHyung
2013-10-01
Generally, solid-freeform fabricated scaffolds show a controllable pore structure (pore size, porosity, pore connectivity, and permeability) and mechanical properties by using computer-aided techniques. Although the scaffolds can provide repeated and appropriate pore structures for tissue regeneration, they have a low biological activity, such as low cell-seeding efficiency and nonuniform cell density in the scaffold interior after a long culture period, due to a large pore size and completely open pores. Here we fabricated three different poly(ɛ-caprolactone) (PCL)/alginate scaffolds: (1) a rapid prototyped porous PCL scaffold coated with an alginate, (2) the same PCL scaffold coated with a mixture of alginate and cells, and (3) a multidispensed hybrid PCL/alginate scaffold embedded with cell-laden alginate struts. The three scaffolds had similar micropore structures (pore size = 430-580 μm, porosity = 62%-68%, square pore shape). Preosteoblast cells (MC3T3-E1) were used at the same cell density in each scaffold. By measuring cell-seeding efficiency, cell viability, and cell distribution after various periods of culturing, we sought to determine which scaffold was more appropriate for homogeneously regenerated tissues.
Description of gluon propagation in the presence of an A{sup 2} condensate
Li Xiangdong; Shakin, C.M.
2005-04-01
There is a good deal of current interest in the condensate which has been seen to play an important role in calculations which make use of the operator product expansion. That development has led to the publication of a large number of papers which discuss how that condensate could play a role in a gauge-invariant formulation. In the present work we consider gluon propagation in the presence of such a condensate which we assume to be present in the vacuum. We show that the gluon propagator has no on-mass-shell pole and, therefore, a gluon cannot propagate over extended distances. That is, the gluon is a nonpropagating mode in the gluon condensate. In the present work we discuss the properties of both the Euclidean-space and Minkowski-space gluon propagator. In the case of the Euclidean-space propagator we can make contact with the results of QCD lattice calculations of the propagator in the Landau gauge. With an appropriate choice of normalization constants, we present a unified representation of the gluon propagator that describes both the Minkowski-space and Euclidean-space dynamics in which the condensate plays an important role.
Alkofer, Reinhard; Fischer, Christian S. Llanes-Estrada, Felipe J.; Schwenzer, Kai
2009-01-15
The infrared behavior of the quark-gluon vertex of quenched Landau gauge QCD is studied by analyzing its Dyson-Schwinger equation. Building on previously obtained results for Green functions in the Yang-Mills sector, we analytically derive the existence of power-law infrared singularities for this vertex. We establish that dynamical chiral symmetry breaking leads to the self-consistent generation of components of the quark-gluon vertex forbidden when chiral symmetry is forced to stay in the Wigner-Weyl mode. In the latter case the running strong coupling assumes an infrared fixed point. If chiral symmetry is broken, either dynamically or explicitly, the running coupling is infrared divergent. Based on a truncation for the quark-gluon vertex Dyson-Schwinger equation which respects the analytically determined infrared behavior, numerical results for the coupled system of the quark propagator and vertex Dyson-Schwinger equation are presented. The resulting quark mass function as well as the vertex function show only a very weak dependence on the current quark mass in the deep infrared. From this we infer by an analysis of the quark-quark scattering kernel a linearly rising quark potential with an almost mass independent string tension in the case of broken chiral symmetry. Enforcing chiral symmetry does lead to a Coulomb type potential. Therefore, we conclude that chiral symmetry breaking and confinement are closely related. Furthermore, we discuss aspects of confinement as the absence of long-range van der Waals forces and Casimir scaling. An examination of experimental data for quarkonia provides further evidence for the viability of the presented mechanism for quark confinement in the Landau gauge.
Equation of state and initial temperature of quark gluon plasma at RHIC
NASA Astrophysics Data System (ADS)
Csanád, Máté; Májer, Imre
2012-08-01
In gold-gold collisions of the Relativistic Heavy Ion Collider a perfect fluid of strongly interacting quark gluon plasma (sQGP) is created. The time evolution of this fluid can be described by hydrodynamical models. After an expansion, hadrons are created during the freeze-out period. Their distribution reveals information about the final state. To investigate the time evolution one needs to analyze penetrating probes: e.g. direct photon observations. In this paper we analyze a 1+3 dimensional solution of relativistic hydrodynamics. We calculate momentum distribution, azimuthal asymmetry and momentum correlations of direct photons. Based on earlier fits to hadronic spectra, we compare photon calculations to measurements to determine the equations of state and the initial temperature of sQGP. We find that the initial temperature in the center of the fireball is 507±12 MeV, while for the sound speed we get c s=0.36±0.02. We also estimate a systematic error of these results. We find that the measured azimuthal asymmetry is also compatible with this model. We also predict a photon source that is significantly larger in the out direction than in the side direction.
Equation of state and initial temperature of quark gluon plasma at RHIC
NASA Astrophysics Data System (ADS)
Csanád, Máté; Májer, Imre
2012-08-01
In gold-gold collisions of the Relativistic Heavy Ion Collider a perfect fluid of strongly interacting quark gluon plasma (sQGP) is created. The time evolution of this fluid can be described by hydrodynamical models. After an expansion, hadrons are created during the freeze-out period. Their distribution reveals information about the final state. To investigate the time evolution one needs to analyze penetrating probes: e.g. direct photon observations. In this paper we analyze a 1+3 dimensional solution of relativistic hydrodynamics. We calculate momentum distribution, azimuthal asymmetry and momentum correlations of direct photons. Based on earlier fits to hadronic spectra, we compare photon calculations to measurements to determine the equations of state and the initial temperature of sQGP. We find that the initial temperature in the center of the fireball is 507±12 MeV, while for the sound speed we get c s =0.36±0.02. We also estimate a systematic error of these results. We find that the measured azimuthal asymmetry is also compatible with this model. We also predict a photon source that is significantly larger in the out direction than in the side direction.
Gluon transport equation with effective mass and dynamical onset of Bose–Einstein condensation
Blaizot, Jean-Paul; Jiang, Yin; Liao, Jinfeng
2016-05-01
In this paper we study the transport equation describing a dense system of gluons, in the small scattering angle approximation, taking into account medium-generated effective masses of the gluons. We focus on the case of overpopulated systems that are driven to Bose–Einstein condensation on their way to thermalization. Lastly, the presence of a mass modifies the dispersion relation of the gluon, as compared to the massless case, but it is shown that this does not change qualitatively the scaling behavior in the vicinity of the onset.
Polarization effects in hadron structure functions and in quark and gluon fragmentation
Einhorn, M.B.
1986-07-20
The predictions of QCD for the evolution of the quark and gluon structure functions of a polarized proton are discussed. In fact, the parton polarizations increase with energy, for fixed Feynman x. Thus, polarized protons may be useful for the discovery or investigation of new physical phenomena at very high energy, especially if there are new interactions or particles whose behavior violates one of the natural symmetries of QCD, such as parity. The mean gluon asymmetry grows as l-scriptnQ/sup 2/, which implies that the orbital angular momentum of the gluons grows similarly.
J/ψ-PRODUCTION Mechanisms and Determination of the Gluon Density at Hera
NASA Astrophysics Data System (ADS)
Jung, H.; Schuler, G. A.; Terron, J.
We discuss photo- and leptoproduction of J/ψ mesons at energies ranging from those of fixed-target experiments up to those of HERA. Elastic and diffractive production as well as various inelastic processes are studied. We investigate the range in which J/ψ production is described by photon-gluon fusion in the color-singlet model. We show how inelastic J/ψ production at HERA can be used to extract the gluon density. We estimate an accessible range of 3×10-4
Probing transverse momentum dependent parton distributions in charmonium and bottomonium production
NASA Astrophysics Data System (ADS)
Mukherjee, Asmita; Rajesh, Sangem
2016-03-01
We propose the study of unpolarized transverse momentum dependent gluon parton distributions as well as the effect of linearly polarized gluons on transverse momentum and rapidity distributions of J /ψ and ϒ production within the framework of transverse momentum dependent factorization employing a color evaporation model (CEM) in an unpolarized proton-proton collision. We estimate the transverse momentum and rapidity distributions of J /ψ and ϒ at LHCb, RHIC and AFTER energies using TMD evolution formalism.
Effect of the gluon condensate on the holographic heavy quark potential
Kim, Youngman; Lee, Bum-Hoon; Park, Chanyong; Sin, Sang-Jin
2009-11-15
The gluon condensate is very sensitive to the QCD deconfinement transition since its value changes drastically with the deconfinement transition. We calculate the gluon condensate dependence of the heavy quark potential in AdS/CFT to study how the property of the heavy quarkonium is affected by a relic of the deconfinement transition. We observe that the heavy quark potential becomes deeper as the value of the gluon condensate decreases. We interpret this as a dropping of the heavy quarkonium mass just above the deconfinement transition. We finally argue that dropping of the gluon condensate and the pure thermal effect are competing with each other in the physics of heavy quarkonium at high temperature.
Sound Produced by a Fast Parton in the Quark-Gluon Plasma is a ``Crescendo''
NASA Astrophysics Data System (ADS)
Neufeld, R. B.; Müller, B.
2009-07-01
We calculate the total energy deposited into the medium per unit length by fast partons traversing a quark-gluon plasma. The medium excitation due to collisions is taken to be given by the well-known expression for the collisional drag force. The radiative energy loss of the parton contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. We derive a differential equation which governs how the spectrum of radiated gluons is modified when this energy loss is taken into account. This modified spectrum is then used to calculate the additional energy deposition due to the interactions of radiated gluons with the medium. Numerical results are presented for the medium response for the case of two energetic back-to-back partons created in a hard interaction.
Sound produced by a fast parton in the quark-gluon plasma is a "crescendo".
Neufeld, R B; Müller, B
2009-07-24
We calculate the total energy deposited into the medium per unit length by fast partons traversing a quark-gluon plasma. The medium excitation due to collisions is taken to be given by the well-known expression for the collisional drag force. The radiative energy loss of the parton contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. We derive a differential equation which governs how the spectrum of radiated gluons is modified when this energy loss is taken into account. This modified spectrum is then used to calculate the additional energy deposition due to the interactions of radiated gluons with the medium. Numerical results are presented for the medium response for the case of two energetic back-to-back partons created in a hard interaction.
Semirelativistic potential model for low-lying three-gluon glueballs
Mathieu, Vincent; Semay, Claude; Silvestre-Brac, Bernard
2006-09-01
The three-gluon glueball states are studied with the generalization of a semirelativistic potential model giving good results for two-gluon glueballs. The Hamiltonian depends only on 3 parameters fixed on two-gluon glueball spectra: the strong coupling constant, the string tension, and a gluon size which removes singularities in the potential. The Casimir scaling determines the structure of the confinement. Low-lying J{sup PC} states are computed and compared with recent lattice calculations. A good agreement is found for 1{sup --} and 3{sup --} states, but our model predicts a 2{sup --} state much higher in energy than the lattice result. The 0{sup -+} mass is also computed.
Measurement of the Gluon Polarization {delta}g/g from Open Charm at COMPASS
Kunne, Fabienne
2009-08-04
We have measured the gluon polarization in the nucleon by detecting charm production via D{sup 0} meson decay to charged K and {pi} in polarized muon scattering off a longitudinally polarized deuteron target. The dominant process for charm production is the photon gluon fusion into a charm anti-charm quark pair. By using all deuteron statistics from COMPASS accumulated between 2002 and 2006, we extract double spin asymmetries in bins of the transverse momentum and the energy of the D{sup 0} meson and we perform a leading order analysis of the data to extract the gluon polarization <{delta}g/g> = -0.49{+-}0.27(stat){+-}0.11(syst) at a Quantum Chromodynamics (QCD) scale {mu}{sup 2} = 13 GeV{sup 2} and at a gluon momentum fraction
Probing the twist-3 multi-gluon correlation functions by p↑p → DX
NASA Astrophysics Data System (ADS)
Koike, Yuji; Yoshida, Shinsuke
2011-05-01
We study the single spin asymmetry (SSA) for the D-meson production ADN in the pp collision, p↑p → DX in the framework of the collinear factorization. Since the charm quark is mainly produced through the cbar c-pair creation from the gluon-fusion process, this is an ideal process to probe the twist-3 triple-gluon correlation functions in the polarized nucleon. We derive the corresponding cross section formula for the contribution of the triple-gluon correlation function to ADN in p↑p → DX, applying the method developed for ep↑ → eDX in our previous study. As in the case of ep↑ → eDX, our result differs from a previous study in the literature.We will also present a simple estimate of the triple-gluon correlation functions based on the preliminary data on ADN by RHIC.
Check of the gluon-reggeization condition in the next-to-leading order: Quark part
Kozlov, M. G. Reznichenko, A. V. Fadin, V. S.
2011-05-15
The bootstrap condition for gluon production in multi-Regge kinematics is considered in the next-to-leading order. Bootstrap conditions follow fromthe requirement that the Regge formof amplitudes in QCD be consistent with s-channel unitarity and are nonlinear relations between the Reggeized-gluon trajectory and vertex functions. Their fulfillment ensures the Reggeization of gluons-that is, the Regge form of both elastic and inelastic amplitudes. This condition is the only one that has not yet been verified. The demonstration of its fulfillment is the ultimate step in proving the Reggeization of gluons in the next-to-leading logarithmic approximation. In the present article, this is done for the quark part of the bootstrap condition.
Stopping Distance for High Energy Jets in Weakly-Coupled Quark-Gluon Plasmas
NASA Astrophysics Data System (ADS)
Xiao, Wei
Quark-gluon plasmas (QGPs) are hot dense media created in relativistic heavy ion collisions, and jet quenching makes it possible to study the properties of QGP medium, through observing changes in the jet fragmentation functions as compared to the unquenched case. Therefore, it has long been of interest to study the jet energy loss and stopping processes in relativistic QCD media. In weakly-coupled quark-gluon plasmas, a high energy parton's energy loss is dominated by medium induced gluon bremsstrahlung and pair production. However, the calculation of gluon bremsstrahlung is complicated by the Landau-Pomeranchuk-Migdal (LPM) effect, in which the gluon formation time becomes longer than the mean free path between scatterings and successive scattering cannot be treated as independent. Arnold, Moore, and Yaffe (AMY) proposed a formalism to solve the LPM effect in uniform, infinite QCD mediums. In this thesis, gluon emission rates in the AMY formalism are reviewed, and the transport coefficient q̂, which characterizes the scattering power of the medium, is calculated to the leading order in the weak coupling limit, and then is used to generalize the previous analytic results on the gluon bremsstrahlung and pair production rates at next-to-leading logarithmic order in weakly-coupled QGP. Stopping distance is a more general idea, for unlike the bremsstrahlung rate, it can be generalized to strongly-coupled situations, in which we cannot talk about individual partons. In this thesis, stopping distances are defined, and by using the gluon emission rates studied earlier, the analytic expressions for high energy jet's stopping distance is calculated in weak coupling, we will see that the stopping distance has a E1/2/ lnE dependence on the initial parton's energy E in the high energy limit.
J/{Psi} suppression as an evidence for quark gluon matter
Kharzeev, D.
1998-08-10
The J/{psi} suppression was originally proposed as a signature of the quark-gluon plasma. Strong suppression of J/{psi} production was indeed observed recently by the NA50 Collaboration at CERN SPS. Is it the first signature of a long-awaited quark-gluon matter, or just a peculiar combination of ''conventional'' effects acting together to produce the puzzling pattern observed experimentally? In this lecture, I am trying to summarize the existing theoretical explanations.
Measurement of the Gluon Contribution to the Nucleon Spin at COMPASS
Dedek, N.
2005-10-26
The measurement of the gluon contribution to the nucleon spin {delta}G is one of the main goals of the COMPASS experiment located at the CERN Super Proton Synchrotron. The key reaction is the photon gluon fusion to D (D-bar) -mesons. The status of the analysis of the D0- and D*-events is shown as well as the expected statistical error of {delta}G/G from the first 3 years of data taking.
Chiral electric separation effect in the quark-gluon plasma
Jiang, Yin; Liao, Jinfeng; Huang, Xu-Guang
2015-02-02
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient σχe, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current JA that is generated in response to an externally applied electric field eE: JA=σχe(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure σχe∝μμ5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density μ5 ≠ 0. Using the Hard-Thermal-Loop framework, the CESEmore » conductivity for the QGP is found to be σχe = (#)TTrfQeQA/g⁴ln(1/g) μμ5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.« less
Linear polarization of gluons and photons in unpolarized collider experiments
Pisano, Cristian; Boer, Daniël; Brodsky, Stanley J.; Buffing, Maarten G. A.; Mulders, Piet J.
2013-10-01
We study azimuthal asymmetries in heavy quark pair production in unpolarized electron-proton and proton-proton collisions, where the asymmetries originate from the linear polarization of gluons inside unpolarized hadrons. We provide cross section expressions and study the maximal asymmetries allowed by positivity, for both charm and bottom quark pair production. The upper bounds on the asymmetries are shown to be very large depending on the transverse momentum of the heavy quarks, which is promising especially for their measurements at a possible future Electron-Ion Collider or a Large Hadron electron Collider. We also study the analogous processes and asymmetries in muon pair production as a means to probe linearly polarized photons inside unpolarized protons. For increasing invariant mass of the muon pair the asymmetries become very similar to the heavy quark pair ones. Finally, we discuss the process dependence of the results that arises due to differences in color flow and address the problem with factorization in case of proton-proton collisions.
Chiral electric separation effect in the quark-gluon plasma
Jiang, Yin; Liao, Jinfeng; Huang, Xu-Guang
2015-02-02
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient σ_{χe}, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current J_{A} that is generated in response to an externally applied electric field eE: J_{A}=σ_{χe}(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure σ_{χe}∝μμ5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density μ5 ≠ 0. Using the Hard-Thermal-Loop framework, the CESE conductivity for the QGP is found to be σ_{χe} = (#)TT_{rf}Q_{e}Q_{A}/g⁴ln(1/g) μμ5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.
Measuring the aspect ratio renormalization of anisotropic-lattice gluons
Alford, M.; Drummond, I. T.; Horgan, R. R.; Shanahan, H.; Peardon, M.
2001-04-01
Using tadpole-improved actions we investigate the consistency between different methods of measuring the aspect ratio renormalization of anisotropic-lattice gluons for bare aspect ratios {chi}{sub 0}=4,6,10 and inverse lattice spacing in the range a{sub s}{sup -1}=660--840 MeV. The tadpole corrections to the action, which are established self-consistently, are defined for two cases, mean link tadpoles in the Landau gauge and gauge invariant mean plaquette tadpoles. Parameters in the latter case exhibited no dependence on the spatial lattice size L, while in the former, parameters showed only a weak dependence on L easily extrapolated to L={infinity}. The renormalized anisotropy {chi}{sub R} was measured using both the torelon dispersion relation and the sideways potential method. There is general agreement between these approaches, but there are discrepancies which are evidence for the presence of lattice artifact contributions. For the torelon these are estimated to be O({alpha}{sub S}a{sub s}{sup 2}/R{sup 2}), where R is the flux-tube radius. We also present some new data that suggest that rotational invariance is established more accurately for the mean-link action than the plaquette action.
Resolving gluon fusion loops at current and future hadron colliders
NASA Astrophysics Data System (ADS)
Azatov, Aleksandr; Grojean, Christophe; Paul, Ayan; Salvioni, Ennio
2016-09-01
Inclusive Higgs measurements at the LHC have limited resolution on the gluon fusion loops, being unable to distinguish the long-distance contributions mediated by the top quark from possible short-distance new physics effects. Using an Effective Field Theory (EFT) approach we compare several proposed methods to lift this degeneracy, including toverline{t}h and boosted, off-shell and double Higgs production, and perform detailed projections to the High-Luminosity LHC and a future hadron collider. In addition, we revisit off-shell Higgs production. Firstly, we point out its sensitivity to modifications of the top- Z couplings, and by means of a general analysis we show that the reach is comparable to that of tree-level processes such as toverline{t}Z production. Implications for composite Higgs models are also discussed. Secondly, we assess the regime of validity of the EFT, performing an explicit comparison for a simple extension of the Standard Model containing one vector-like quark.
Nondiagonal parton distributions at small x
NASA Astrophysics Data System (ADS)
Frankfurt, L. L.; Freund, A.; Guzey, V.; Strikman, M.
1997-04-01
In this paper we make predictions for nondiagonal parton distributions in a proton in the LLA. We calculate the DGLAP-type evolution kernels in the LLA, solve the nondiagonal GLAP evolution equations with a modified version of the CTEQ-package and comment on the range of applicability of the LLA in the asymmetric regime. We show that the nondiagonal gluon distribution x2G(x1,x2,Q2) can be well approximated at small x by the conventional gluon density xG(x,Q2) and explain that the cross sections of hard diffractive processes are determined by x2G(x1,x2).
Suppression of Baryon Diffusion and Transport in a Baryon Rich Strongly Coupled Quark-Gluon Plasma.
Rougemont, Romulo; Noronha, Jorge; Noronha-Hostler, Jacquelyn
2015-11-13
Five dimensional black hole solutions that describe the QCD crossover transition seen in (2+1)-flavor lattice QCD calculations at zero and nonzero baryon densities are used to obtain predictions for the baryon susceptibility, baryon conductivity, baryon diffusion constant, and thermal conductivity of the strongly coupled quark-gluon plasma in the range of temperatures 130 MeV≤T≤300 MeV and baryon chemical potentials 0≤μ(B)≤400 MeV. Diffusive transport is predicted to be suppressed in this region of the QCD phase diagram, which is consistent with the existence of a critical end point at larger baryon densities. We also calculate the fourth-order baryon susceptibility at zero baryon chemical potential and find quantitative agreement with recent lattice results. The baryon transport coefficients computed in this Letter can be readily implemented in state-of-the-art hydrodynamic codes used to investigate the dense QGP currently produced at RHIC's low energy beam scan.
Heavy quark diffusion with relativistic Langevin dynamics in the quark-gluon fluid
Akamatsu, Yukinao; Hatsuda, Tetsuo; Hirano, Tetsufumi
2009-05-15
The relativistic diffusion process of heavy quarks is formulated on the basis of the relativistic Langevin equation in Ito discretization scheme. The drag force inside the quark-gluon plasma (QGP) is parametrized according to the formula for the strongly coupled plasma obtained by the anti-de-Sitter space/conformal field theory (AdS/CFT) correspondence. The diffusion dynamics of charm and bottom quarks in QGP is described by combining the Langevin simulation under the background matter described by the relativistic hydrodynamics. Theoretical calculations of the nuclear modification factor R{sub AA} and the elliptic flow v{sub 2} for the single electrons from the charm and bottom decays are compared with the experimental data from the relativistic heavy-ion collisions. The R{sub AA} for electrons with large transverse momentum (p{sub T}>3 GeV) indicates that the drag force from the QGP is as strong as the AdS/CFT prediction.
Hydrodynamic transport coefficients for the non-conformal quark-gluon plasma from holography
NASA Astrophysics Data System (ADS)
Finazzo, Stefano I.; Rougemont, Romulo; Marrochio, Hugo; Noronha, Jorge
2015-02-01
In this paper we obtain holographic formulas for the transport coefficients κ and τ π present in the second-order derivative expansion of relativistic hydrodynamics in curved spacetime associated with a non-conformal strongly coupled plasma described holographically by an Einstein+Scalar action in the bulk. We compute these coefficients as functions of the temperature in a bottom-up non-conformal model that is tuned to reproduce lattice QCD thermodynamics at zero baryon chemical potential. We directly compute, besides the speed of sound, 6 other transport coefficients that appear at second-order in the derivative expansion. We also give an estimate for the temperature dependence of 11 other transport coefficients taking into account the simplest contribution from non-conformal effects that appear near the QCD crossover phase transition. Using these results, we construct an Israel-Stewart-like theory in flat spacetime containing 13 of these 17 transport coefficients that should be suitable for phenomenological applications in the context of numerical hydrodynamic simulations of the strongly-coupled, non-conformal quark-gluon plasma. Using several different approximations, we give parametrizations for the temperature dependence of all the second-order transport coefficients that appear in this theory in a format that can be easily implemented in existing numerical hydrodynamic codes.
Suppression of Baryon Diffusion and Transport in a Baryon Rich Strongly Coupled Quark-Gluon Plasma.
Rougemont, Romulo; Noronha, Jorge; Noronha-Hostler, Jacquelyn
2015-11-13
Five dimensional black hole solutions that describe the QCD crossover transition seen in (2+1)-flavor lattice QCD calculations at zero and nonzero baryon densities are used to obtain predictions for the baryon susceptibility, baryon conductivity, baryon diffusion constant, and thermal conductivity of the strongly coupled quark-gluon plasma in the range of temperatures 130 MeV≤T≤300 MeV and baryon chemical potentials 0≤μ(B)≤400 MeV. Diffusive transport is predicted to be suppressed in this region of the QCD phase diagram, which is consistent with the existence of a critical end point at larger baryon densities. We also calculate the fourth-order baryon susceptibility at zero baryon chemical potential and find quantitative agreement with recent lattice results. The baryon transport coefficients computed in this Letter can be readily implemented in state-of-the-art hydrodynamic codes used to investigate the dense QGP currently produced at RHIC's low energy beam scan. PMID:26613433
Generalized parton distributions in nuclei
Vadim Guzey
2009-12-01
Generalized parton distributions (GPDs) of nuclei describe the distribution of quarks and gluons in nuclei probed in hard exclusive reactions, such as e.g. deeply virtual Compton scattering (DVCS). Nuclear GPDs and nuclear DVCS allow us to study new aspects of many traditional nuclear effects (nuclear shadowing, EMC effect, medium modifications of the bound nucleons) as well as to access novel nuclear effects. In my talk, I review recent theoretical progress in the area of nuclear GPDs.
Borowka, S; Greiner, N; Heinrich, G; Jones, S P; Kerner, M; Schlenk, J; Schubert, U; Zirke, T
2016-07-01
We present the calculation of the cross section and invariant mass distribution for Higgs boson pair production in gluon fusion at next-to-leading order (NLO) in QCD. Top-quark masses are fully taken into account throughout the calculation. The virtual two-loop amplitude has been generated using an extension of the program GoSam supplemented with an interface to Reduze for the integral reduction. The occurring integrals have been calculated numerically using the program SecDec. Our results, including the full top-quark mass dependence for the first time, allow us to assess the validity of various approximations proposed in the literature, which we also recalculate. We find substantial deviations between the NLO result and the different approximations, which emphasizes the importance of including the full top-quark mass dependence at NLO.
NASA Astrophysics Data System (ADS)
Borowka, S.; Greiner, N.; Heinrich, G.; Jones, S. P.; Kerner, M.; Schlenk, J.; Schubert, U.; Zirke, T.
2016-07-01
We present the calculation of the cross section and invariant mass distribution for Higgs boson pair production in gluon fusion at next-to-leading order (NLO) in QCD. Top-quark masses are fully taken into account throughout the calculation. The virtual two-loop amplitude has been generated using an extension of the program GoSam supplemented with an interface to Reduze for the integral reduction. The occurring integrals have been calculated numerically using the program SecDec. Our results, including the full top-quark mass dependence for the first time, allow us to assess the validity of various approximations proposed in the literature, which we also recalculate. We find substantial deviations between the NLO result and the different approximations, which emphasizes the importance of including the full top-quark mass dependence at NLO.
Borowka, S; Greiner, N; Heinrich, G; Jones, S P; Kerner, M; Schlenk, J; Schubert, U; Zirke, T
2016-07-01
We present the calculation of the cross section and invariant mass distribution for Higgs boson pair production in gluon fusion at next-to-leading order (NLO) in QCD. Top-quark masses are fully taken into account throughout the calculation. The virtual two-loop amplitude has been generated using an extension of the program GoSam supplemented with an interface to Reduze for the integral reduction. The occurring integrals have been calculated numerically using the program SecDec. Our results, including the full top-quark mass dependence for the first time, allow us to assess the validity of various approximations proposed in the literature, which we also recalculate. We find substantial deviations between the NLO result and the different approximations, which emphasizes the importance of including the full top-quark mass dependence at NLO. PMID:27419563
Dynamical chiral symmetry breaking and confinement with an infrared-vanishing gluon propagator
Roberts, C.D.; Hawes, F.T.; Williams, A.G.
1995-08-01
We have studied a model Dyson-Schwinger equation for the quark propagator, constructed using an Ansatz for the gluon propagator of the form D(q) {approximately} q{sup 2}/[(q{sup 2}){sup 2} + b{sup 4}] and two Ansatze for the quark-gluon vertex: the minimal Ball-Chiu and the modified form suggested by Curtis and Pennington. The aim was to determine whether such a form of the gluon propagator, which was suggested by a number of authors and which recent lattice simulations of QCD suggest may be plausible, can support dynamical chiral symmetry breaking and ensure quark confinement. The form of the gluon propagator at small space-like momenta is crucial to the nature of the strong interaction spectrum but is presently unknown and information gathered in such studies is invaluable in supporting or invalidating given hypotheses. It was found that there is a critical value of b = b{sub c} such that the model does not support dynamical chiral symmetry breaking for b > b{sub c}. Further, it was shown that this form of gluon propagator cannot confine quarks. As a consequence this form represents a physically unreasonable model. In addition, these results formed the basis for an invited presentation at a workshop on quantum infrared physics and will be published in the proceedings.
Unified description of seagull cancellations and infrared finiteness of gluon propagators
NASA Astrophysics Data System (ADS)
Aguilar, A. C.; Binosi, D.; Figueiredo, C. T.; Papavassiliou, J.
2016-08-01
We present a generalized theoretical framework for dealing with the important issue of dynamical mass generation in Yang-Mills theories, and, in particular, with the infrared finiteness of the gluon propagators, observed in a multitude of recent lattice simulations. Our analysis is manifestly gauge invariant, in the sense that it preserves the transversality of the gluon self-energy, and gauge independent, given that the conclusions do not depend on the choice of the gauge-fixing parameter within the linear covariant gauges. The central construction relies crucially on the subtle interplay between the Abelian Ward identities satisfied by the nonperturbative vertices and a special integral identity that enforces a vast number of "seagull cancellations" among the one- and two-loop dressed diagrams of the gluon Schwinger-Dyson equation. The key result of these considerations is that the gluon propagator remains rigorously massless, provided that the vertices do not contain (dynamical) massless poles. When such poles are incorporated into the vertices, under the pivotal requirement of respecting the gauge symmetry of the theory, the terms comprising the Ward identities conspire in such a way as to still enforce the total annihilation of all quadratic divergences, inducing, at the same time, residual contributions that account for the saturation of gluon propagators in the deep infrared.
Gulyás, Balázs; Spenger, Christian; Beliczai, Zsuzsa; Gulya, Károly; Kása, Péter; Jahan, Mahabuba; Jia, Zhisheng; Weber, Urs; Pfeifer, Andrea; Muhs, Andreas; Willbold, Dieter; Halldin, Christer
2012-01-01
One of the major pathological landmarks of Alzheimer's disease and other neurodegenerative diseases is the presence of amyloid deposits in the brain. The early non-invasive visualization of amyloid is a major objective of recent diagnostic neuroimaging approaches, including positron emission tomography (PET), with an eye on follow-up of disease progression and/or therapy efficacy. The development of molecular imaging biomarkers with binding affinity to amyloid in the brain is therefore in the forefront of imaging biomarker and radiochemistry research. Recently, a dodecamer peptide (amino acid sequence=QSHYRHISPAQV; denominated D1 or ACI-80) was identified as a prospective ligand candidate, binding with high ex vivo affinity to L-Aβ-amyloid (K(d): 0.4 μM). In order to assess the ligand's capacity to visualize amyloid in Alzheimer's disease (AD), two (125)I labeled and three (18)F labeled analogues of the peptide were synthesized and tested in post mortem human autoradiography experiments using whole hemisphere brain slices obtained from deceased AD patients and age matched control subjects. The (18)F-labeled radioligands showed more promising visualization capacity of amyloid that the (125)I-labeled radioligands. In the case of each (18)F radioligands the grey matter uptake in the AD brains was significantly higher than that in control brains. Furthermore, the grey matter: white matter uptake ratio was over ~2, the difference being significant for each (18)F-radioligands. The regional distribution of the uptake of the various radioligands systematically shows a congruent pattern between the high uptake regions and spots in the autoradiographic images and the disease specific signals obtained in adjacent or identical brain slices labeled with histological, immunohistochemical or autoradiographic stains for amyloid deposits or activated astrocytes. The present data, using post mortem human brain autoradiography in whole hemisphere human brains obtained from deceased
Running coupling from the four-gluon vertex in Landau gauge Yang-Mills theory
Kellermann, Christian; Fischer, Christian S.
2008-07-15
We consider the running coupling from the four-gluon vertex in Landau gauge, SU(N{sub c}) Yang-Mills theory as given by a combination of dressing functions of the vertex and the gluon propagator. We determine these functions numerically from a coupled set of Dyson-Schwinger equations. We reproduce asymptotic freedom in the ultraviolet momentum region and find a coupling of order one at mid-momenta. In the infrared we find a nontrivial (i.e. nonzero) fixed point which is 3 orders of magnitude smaller than the corresponding fixed point in the coupling of the ghost-gluon vertex. This result explains why the Dyson-Schwinger and the functional renormalization group equations for the two point functions can agree in the infrared, although their structure is quite different. Our findings also support Zwanziger's notion of an infrared effective theory driven by the Faddeev-Popov determinant.
Guan Nana; Li Jianwei; He Zejun; Long Jiali; Cai Xiangzhou; Ma Yugang; Shen Wenqing
2009-07-15
By considering the effect of shear viscosity we have investigated the evolution of a chemically equilibrating quark-gluon plasma at finite baryon density. Based on the evolution of the system we have performed a complete calculation for the dilepton production from the following processes: qq{yields}ll, qq{yields}gll, Compton-like scattering (qg{yields}qll,qg{yields}qll), gluon fusion (gg{yields}cc), annihilation (qq{yields}cc), as well as the multiple scattering of quarks. We have found that quark-antiquark annihilation, Compton-like scatterring, gluon fusion, and multiple scattering of quarks give important contributions. Moreover, we have also found that the dilepton yield is an increasing function of the initial quark chemical potential, and the increase of the quark phase lifetime because of the viscosity also obviously raises the dilepton yield.
Resummation of soft gluon logarithms in the DGLAP evolution of fragmentation functions
Albino, S.; Kniehl, B.A.; Kramer, G.; Ochs, W.
2006-03-01
We define a general scheme for the evolution of fragmentation functions which resums both soft gluon logarithms and mass singularities in a consistent manner and to any order, and requires no additional theoretical assumptions. Using the double logarithmic approximation and the known perturbative results for the splitting functions, we present our scheme with the complete contribution from the double logarithms, being the largest soft gluon logarithms. We show that the resulting approximation is more complete than the modified leading logarithm approximation even with the fixed order contribution calculated to leading order only, and find, after using it to fit quark and gluon fragmentation functions to experimental data, that this approximation in our scheme gives a good description of the data from the largest x{sub p} values to the peak region in {xi}=ln(1/x{sub p}), in contrast to other approximations. In addition, we develop a treatment of hadron mass effects which gives additional improvements at large {xi}.
First study of the three-gluon static potential in lattice QCD
NASA Astrophysics Data System (ADS)
Cardoso, M.; Bicudo, P.
2008-10-01
We estimate the potential energy for a system of three static gluons in lattice QCD. This is relevant for the different models of three-body glueballs that have been proposed in the literature, either for gluons with a constituent mass, or for massless ones. A Wilson loop adequate to the static hybrid three-body system is developed. We study different spacial geometries, to compare the starfish model with the triangle model, for the three-gluon potential. We also study two different color structures, symmetric and antisymmetric, and compare the respective static potentials. A first simulation is performed in a 243×48 periodic Lattice, with β=6.2 and ã0.072fm.
Probing the Anomalous Couplings of the Top Quark with Gluon at the Lhc and Tevatron
NASA Astrophysics Data System (ADS)
Hesari, Hoda; Najafabadi, Mojtaba Mohammadi
2013-11-01
In this paper, we study the sensitivity of the fraction of t\\bar {t} events arising from gluon-gluon fusion to the chromoelectric and chromomagnetic dipole moments (CEDM and CMDM) as well as the total and differential t\\bar {t} cross-sections at the LHC and Tevatron. The sensitivity of measured charged asymmetry at the LHC to CEDM and CMDM is also studied. We find that at the Tevatron and the LHC, nonzero values of CMDM could suppress the t\\bar {t} production rate. It is shown that the ratio of σ (gg-> t\\bar {t})/σ (p\\bar {p}-> t\\bar {t}) at the Tevatron is more sensitive to CEDM and CMDM than the LHC case. The presence of CEDM always increases the contribution of gluon-gluon fusion process in top pair rate at the Tevatron and LHC. Except for a small range of CMDM, the presence of CEDM and CMDM can increase the fraction of gluon-gluon fusion at the Tevatron and LHC. The measured ratio of σ (gg-> t\\bar {t})/σ (p\\bar {p}-> t\\bar {t}) at the Tevatron is used to derive bounds on the chromoelectric and chromomagnetic dipole moments as well as the total and differential (dσ /dmt\\bar {t}) cross-sections at the LHC and Tevatron, and the measured charged asymmetry at the LHC. The combination of dσ TeV/dmt\\bar {t} and σLHC provides stringent limits on CMDM and CEDM.
Open-beauty production in pPb collisions at √{sNN}=5 TeV: Effect of the gluon nuclear densities
NASA Astrophysics Data System (ADS)
Conesa del Valle, Z.; Ferreiro, E. G.; Fleuret, F.; Lansberg, J. P.; Rakotozafindrabe, A.
2014-06-01
We present our results on open-beauty production in proton-nucleus collisions for the recent LHC pPb run at √{sNN}=5 TeV. We have analyzed the effect of the modification of the gluon PDFs in a nucleus at the level of the nuclear modification factor. Because of the absence of measurements in pp collisions at the same collision energy, √{sNN}, we also propose the study of the forward-to-backward yield ratio in which the unknown proton-proton yield cancels. Our results are compared with the data obtained by the LHCb collaboration and show a good agreement.
Model independent determination of the gluon condensate in four dimensional SU(3) gauge theory.
Bali, Gunnar S; Bauer, Clemens; Pineda, Antonio
2014-08-29
We determine the nonperturbative gluon condensate of four-dimensional SU(3) gauge theory in a model-independent way. This is achieved by carefully subtracting high-order perturbation theory results from nonperturbative lattice QCD determinations of the average plaquette. No indications of dimension-two condensates are found. The value of the gluon condensate turns out to be of a similar size as the intrinsic ambiguity inherent to its definition. We also determine the binding energy of a B meson in the heavy quark mass limit. PMID:25215978
The rational parts of one-loop QCD amplitudes III: The six-gluon case
NASA Astrophysics Data System (ADS)
Xiao, Zhi-Guang; Yang, Gang; Zhu, Chuan-Jie
2006-12-01
The rational parts of 6-gluon one-loop amplitudes with scalars circulating in the loop are computed by using the newly developed method for computing the rational parts directly from Feynman integrals. We present the analytic results for the two MHV helicity configurations: (123456) and (123456), and the two NMHV helicity configurations: (123456) and (123456). Combined with the previously computed results for the cut-constructible part, our results are the last missing pieces for the complete partial helicity amplitudes of the 6-gluon one-loop QCD amplitude.
Lam, C.S.; Li, B.A.
1980-05-01
A way to detect experimentally the existence of triple gluon coupling and the Adler-Bell-Jackiw anomaly is to measure the Q/sup 2/-dependence of polarized deep inelastic scattering. These effects lead to a ln ln Q/sup 2/ term which we calculate by introducing a new gluon operator in the Wilson expansion.
Relating q ̂, η /s , and Δ E in an expanding quark-gluon plasma
NASA Astrophysics Data System (ADS)
Ayala, Alejandro; Dominguez, Isabel; Jalilian-Marian, Jamal; Tejeda-Yeomans, Maria Elena
2016-08-01
We use linear viscous hydrodynamics to describe the energy and momentum deposited by a fast moving parton in a quark gluon plasma. This energy-momentum is in turn used to compute the probability density for the production of soft partons by means of the Cooper-Frye formula. We use this probability density to render manifest a relation between the average transverse momentum given to the fast moving parton from the medium q ̂, the shear viscosity to entropy density ratio η /s , and the energy lost by the fast moving parton Δ E in an expanding medium under similar conditions to those generated in nucleus-nucleus collisions at the CERN Large Hadron Collider. We find that q ̂ increases linearly with Δ E for both trigger and away side partons that have been produced throughout the medium. On the other hand, η /s is more stable with Δ E . We also study how these transport coefficients vary with the geometrical location of the hard scattering that produces the fast moving partons. The behavior of q ̂, with Δ E , is understood as arising from the length of medium the parton traverses from the point where it is produced. However, since η /s is proportional to the ratio of the length of medium traversed by the fast parton and the average number of scatterings it experiences, it has a milder dependence on the energy it loses. This study represents a tool to obtain a direct connection between transport coefficients and the description of in-medium energy loss within a linear viscous hydrodynamical evolution of the bulk.
Energy loss, equilibration, and thermodynamics of a baryon rich strongly coupled quark-gluon plasma
NASA Astrophysics Data System (ADS)
Rougemont, Romulo; Ficnar, Andrej; Finazzo, Stefano I.; Noronha, Jorge
2016-04-01
Lattice data for the QCD equation of state and the baryon susceptibility near the crossover phase transition (at zero baryon density) are used to determine the input parameters of a 5-dimensional Einstein-Maxwell-Dilaton holographic model that provides a consistent holographic framework to study both equilibrium and out-of-equilibrium properties of a hot and baryon rich strongly coupled quark-gluon plasma (QGP). We compare our holographic equation of state computed at nonzero baryon chemical potential, μ B , with recent lattice calculations and find quantitative agreement for the pressure and the speed of sound for μ B ≤ 400 MeV. This holographic model is used to obtain holographic predictions for the temperature and μ B dependence of the drag force and the Langevin diffusion coefficients associated with heavy quark jet propagation as well as the jet quenching parameter q and the shooting string energy loss of light quarks in the baryon dense plasma. We find that the energy loss of heavy and light quarks generally displays a nontrivial, fast-varying behavior as a function of the temperature near the crossover. Moreover, energy loss is also found to generally increase due to nonzero baryon density effects even though this strongly coupled liquid cannot be described in terms of well defined quasiparticle excitations. Furthermore, to get a glimpse of how thermalization occurs in a hot and baryon dense QGP, we study how the lowest quasinormal mode of an external massless scalar disturbance in the bulk is affected by a nonzero baryon charge. We find that the equilibration time associated with the lowest quasinormal mode decreases in a dense medium.
NCG gluon fusion for the Higgs production at large hadron colliders
Chadou, I.; Mebarki, N.; Bekli, M. R.
2012-06-27
A pure NCG gluon fusion contribution to the Higgs production at large hadron colliders is discussed. It is shown that the NCG results become relevant at very high energies. This can be a good signal for the space-time non commutativity events.
Dynamical chiral symmetry breaking and confinement with an infrared-vanishing gluon propagator
Hawes, F.T. ); Roberts, C.D. ); Williams, A.G. )
1994-05-01
We study a model Dyson-Schwinger equation for the quark propagator closed using an [ital Ansatz] for the gluon propagator of the form [ital D]([ital q])[similar to][ital q][sup 2]/[([ital q][sup 2])[sup 2]+[ital b][sup 4
Bulk viscosity of quark-gluon matter in a magnetic field
Agasian, N. O.
2013-11-15
On the basis of low-energy QCD theorems, the bulk viscosity {zeta}(T, Micro-Sign , H) is expressed in terms of basic thermodynamic quantities that characterizes quark-gluon matter at finite temperature and a finite baryon density in a magnetic field. Various limiting cases are considered.
Maximal Wavelength of Confined Quarks and Gluons and Properties of Quantum Chromodynamics
Brodsky, Stanley J.; Shrock, Robert; /YITP, Stony Brook
2008-08-01
Because quarks and gluons are confined within hadrons, they have a maximum wavelength of order the confinement scale. Propagators, normally calculated for free quarks and gluons using Dyson-Schwinger equations, are modified by bound-state effects in close analogy to the calculation of the Lamb shift in atomic physics. Because of confinement, the effective quantum chromodynamic coupling stays finite in the infrared. The quark condensate which arises from spontaneous chiral symmetry breaking in the bound state Dyson-Schwinger equation is the expectation value of the operator {bar q}q evaluated in the background of the fields of the other hadronic constituents, in contrast to a true vacuum expectation value. Thus quark and gluon condensates reside within hadrons. The effects of instantons are also modified. We discuss the implications of the maximum quark and gluon wavelength for phenomena such as deep inelastic scattering and annihilation, the decay of heavy quarkonia, jets, and dimensional counting rules for exclusive reactions. We also discuss implications for the zero-temperature phase structure of a vectorial SU(N) gauge theory with a variable number N{sub f} of massless fermions.
A New Phase of Matter: Quark-Gluon Plasma Beyond the Hagedorn Critical Temperature
NASA Astrophysics Data System (ADS)
Müller, Berndt
I retrace the developments from Hagedorn's concept of a limiting temperature for hadronic matter to the discovery and characterization of the quark-gluon plasma as a new state of matter. My recollections begin with the transformation more than 30 years ago of Hagedorn's original concept into its modern interpretation as the "critical" temperature separating the hadron gas and quark-gluon plasma phases of strongly interacting matter. This was followed by the realization that the QCD phase transformation could be studied experimentally in high-energy nuclear collisions. I describe here my personal effort to help develop the strangeness experimental signatures of quark and gluon deconfinement and recall how the experimental program proceeded soon to investigate this idea, at first at the SPS, then at RHIC, and finally at LHC. As is often the case, the experiment finds more than theory predicts, and I highlight the discovery of the "perfectly" liquid quark-gluon plasma at RHIC. I conclude with an outline of future opportunities, especially the search for a critical point in the QCD phase diagram.
Aguilar, A. C.; Papavassiliou, J.; Binosi, D.
2008-07-15
We show that the application of a novel gauge-invariant truncation scheme to the Schwinger-Dyson equations of QCD leads, in the Landau gauge, to an infrared finite gluon propagator and a divergent ghost propagator, in qualitative agreement with recent lattice data.
Probing Sea Quarks and Gluons: The Electron-Ion Collider Project
NASA Astrophysics Data System (ADS)
Horn, Tanja
2014-03-01
The 21st century holds great promise for reaching a new era for unlocking the mysteries of the structure of the atomic nucleus and the nucleons inside it governed by the theory of strong interactions (QCD). In particular, much remains to be learned about the dynamical basis of the structure of hadrons and nuclei in terms of the fundamental quarks and gluons. One of the main goals of existing and nearly completed facilities is to map out the spin flavor structure of the nucleons in the valence region. A future Electron-Ion Collider (EIC) would be the world's first polarized electron-proton collider, and the world's first e-A collider, and would seek the QCD foundation of nucleons and nuclei in terms of the sea quarks and gluons, matching to these valence quark studies. The EIC will provide a versatile range of kinematics and beam polarization, as well as beam species, to allow for mapping the spin and spatial structure of the quark sea and gluons, to discover the collective effects of gluons in atomic nuclei, and to understand the emergence of hadronic matter from color charge.
Nondiagonal parton distributions in the leading logarithmic approximation
NASA Astrophysics Data System (ADS)
Frankfurt, L. L.; Freund, A.; Guzey, V.; Strikman, M.
1998-02-01
In this paper we make predictions for nondiagonal parton distributions in a proton in the LLA. We calculate the DGLAP-type evolution kernels in the LLA, solve the nondiagonal GLAP evolution equations with a modified version of the CTEQ-package and comment on the range of applicability of the LLA in the asymmetric regime. We show that the nondiagonal gluon distribution g(x1,x2,t,μ2) can be well approximated at small x by the conventional gluon density xG(x,μ2).
Obtaining and maintaining funding
Beverly Hartline
1996-04-01
Obtaining and maintaining funding is important for individuals, groups, institutions, and fields. This challenge is easier during times of abundant and growing resources than it is now, when funding is tight and shrinking. Thus, to obtain and maintain funding will require: maintaining healthy funding levels for all of science; maintaining healthy funding levels for the field(s) you work in; and competing successfully for the available funds. Everyone should pay attention to the overall prospects for science funding and dedicate some effort to working with others to grow the constituency for science. Public support is likely an important prerequisite for keeping future science budgets high. In this context, researchers should share with society at large the benefits of their research, so that taxpayers can see and appreciate some return from the federal investment in science. Assuming this effort is successful, and there continue to be government and private organizations with substantial resources to invest in research, what can the individual investigator do to improve her chances? She can be clear about her goal(s) and carefully plan her effort to make maximum progress for minimum resources, especially early in her career while she is establishing a solid professional reputation. Specific useful strategies include: brainstorm funding options and select the most promising one(s); be persistent but flexible, responsive to new information and changing circumstances; provide value and assistance to prospective funding sources both before and after receiving funding; know the funding agents and what their goals are, they are the customers; promise a lot and always deliver more; build partnerships and collaboration to leverage interest and resources; and develop capabilities and ideas with a promising, irresistible future. There is no guarantee of success. For the best chances, consistently contribute positively and productively in all your efforts, and continue to
Parton and valon distributions in the nucleon
Hwa, R.C.; Sajjad Zahir, M.
1981-06-01
Structure functions of the nucleon are analyzed in the valon model in which a nucleon is assumed to be a bound state of three valence quark clusters (valons). At high Q/sup 2/ the structure of the valons is described by leading-order results in the perturbative quantum chromodynamics. From the experimental data on deep-inelastic scattering off protons and neutrons, the flavor-dependent valon distributions in the nucleon are determined. Predictions for the parton distributions are then made for high Q/sup 2/ without guesses concerning the quark and gluon distributions at low Q/sup 2/. The sea-quark and gluon distributions are found to have a sharp peak at very small x. Convenient parametrization is provided which interpolates between different numbers of flavors.
NASA Technical Reports Server (NTRS)
Butler, Thomas G.
1990-01-01
In modeling a complex structure the researcher was faced with a component that would have logical appeal if it were modeled as a beam. The structure was a mast of a robot controlled gantry crane. The structure up to this point already had a large number of degrees of freedom, so the idea of conserving grid points by modeling the mast as a beam was attractive. The researcher decided to make a separate problem of of the mast and model it in three dimensions with plates, then extract the equivalent beam properties by setting up the loading to simulate beam-like deformation and constraints. The results could then be used to represent the mast as a beam in the full model. A comparison was made of properties derived from models of different constraints versus manual calculations. The researcher shows that the three-dimensional model is ineffective in trying to conform to the requirements of an equivalent beam representation. If a full 3-D plate model were used in the complete representation of the crane structure, good results would be obtained. Since the attempt is to economize on the size of the model, a better way to achieve the same results is to use substructuring and condense the mast to equivalent end boundary and intermediate mass points.
Dudal, D.; Vandersickel, N.; Verschelde, H.; Sorella, S. P.
2008-04-01
So far, the infrared behavior of the gluon and ghost propagator based on the Gribov-Zwanziger approach predicted a positivity violating gluon propagator vanishing at zero momentum, and an infrared enhanced ghost propagator. However, recent data based on huge lattices have revealed a positivity violating gluon propagator which turns out to attain a finite nonvanishing value very close to zero momentum. At the same time the ghost propagator does not seem to be infrared enhanced anymore. We point out that these new features can be accounted for by yet unexploited dynamical effects within the Gribov-Zwanziger approach, leading to an infrared behavior in qualitatively good agreement with the new data.
Transverse-momentum-dependent parton distributions in a spectator diquark model
F Conti, A Bacchetta, M Radici
2009-09-01
Within the framework of a spectator diquark model of the nucleon, involving both scalar and axial-vector diquarks, we calculate all the leading-twist transverse-momentum-dependent parton distribution functions (TMDs). Naive Time-odd densities are generated through a one-gluon-loop rescattering mechanism, simulating the final state interactions required for these functions to exist. Analytic results are obtained for all the TMDs, and a connection with the light-cone wave functions formalism is also established. The model parameters are fixed by reproducing the phenomenological parametrizations of unpolarized and helicity parton distributions at the lowest available scale. Predictions for the other parton densities are given and, whenever possible, compared with available parametrizations.
Generalized parton distributions and rapidity gap survival in exclusive diffractive pp scattering
Frankfurt, L.; Hyde, C. E.; Strikman, M.; Weiss, C.
2007-03-01
We study rapidity gap survival (RGS) in the production of high-mass systems (H=dijet, heavy quarkonium, Higgs boson) in double-gap exclusive diffractive pp scattering, pp{yields}p+(gap)+H+(gap)+p. Our approach is based on the idea that hard and soft interactions are approximately independent because they proceed over widely different time and distance scales. We implement this idea in a partonic description of proton structure, which allows for a model-independent treatment of the interplay of hard and soft interactions. The high-mass system is produced in a hard scattering process with exchange of two gluons between the protons, whose amplitude is calculable in terms of the gluon generalized parton distribution (GPD), measured in exclusive ep scattering. The hard scattering process is modified by soft spectator interactions, which we calculate neglecting correlations between hard and soft interactions (independent interaction approximation). We obtain an analytic expression for the RGS probability in terms of the phenomenological pp elastic scattering amplitude, without reference to the eikonal approximation. Contributions from inelastic intermediate states are suppressed. The onset of the black-disk limit in pp scattering at TeV energies strongly suppresses diffraction at small impact parameters and is the main factor in determining the RGS probability. Correlations between hard and soft interactions (e.g. due to scattering from the long-range pion field of the proton or due to possible short-range transverse correlations between partons) further decrease the RGS probability. We also investigate the dependence of the diffractive cross section on the transverse momenta of the final-state protons ('diffraction pattern'). By measuring this dependence one can perform detailed tests of the interplay of hard and soft interactions and even extract information about the gluon GPD in the proton. Such studies appear to be feasible with the planned forward detectors at the
Adare, A; Afanasiev, S; Aidala, C; Ajitanand, N N; Akiba, Y; Al-Bataineh, H; Alexander, J; Aoki, K; Aphecetche, L; Asai, J; Atomssa, E T; Averbeck, R; Awes, T C; Azmoun, B; Babintsev, V; Bai, M; Baksay, G; Baksay, L; Baldisseri, A; Barish, K N; Barnes, P D; Bassalleck, B; Basye, A T; Bathe, S; Batsouli, S; Baublis, V; Baumann, C; Bazilevsky, A; Belikov, S; Bennett, R; Berdnikov, A; Berdnikov, Y; Bickley, A A; Boissevain, J G; Borel, H; Boyle, K; Brooks, M L; Buesching, H; Bumazhnov, V; Bunce, G; Butsyk, S; Camacho, C M; Campbell, S; Chand, P; Chang, B S; Chang, W C; Charvet, J-L; Chernichenko, S; Chi, C Y; Chiu, M; Choi, I J; Choudhury, R K; Chujo, T; Chung, P; Churyn, A; Cianciolo, V; Citron, Z; Cole, B A; Constantin, P; Csanád, M; Csörgo, T; Dahms, T; Dairaku, S; Das, K; David, G; Denisov, A; d'Enterria, D; Deshpande, A; Desmond, E J; Dietzsch, O; Dion, A; Donadelli, M; Drapier, O; Drees, A; Drees, K A; Dubey, A K; Durum, A; Dutta, D; Dzhordzhadze, V; Efremenko, Y V; Egdemir, J; Ellinghaus, F; Engelmore, T; Enokizono, A; En'yo, H; Esumi, S; Eyser, K O; Fadem, B; Fields, D E; Finger, M; Finger, M; Fleuret, F; Fokin, S L; Fraenkel, Z; Frantz, J E; Franz, A; Frawley, A D; Fujiwara, K; Fukao, Y; Fusayasu, T; Garishvili, I; Glenn, A; Gong, H; Gonin, M; Gosset, J; Goto, Y; de Cassagnac, R Granier; Grau, N; Greene, S V; Perdekamp, M Grosse; Gunji, T; Gustafsson, H-A; Henni, A Hadj; Haggerty, J S; Hamagaki, H; Han, R; Hartouni, E P; Haruna, K; Haslum, E; Hayano, R; Heffner, M; Hemmick, T K; Hester, T; He, X; Hill, J C; Hohlmann, M; Holzmann, W; Homma, K; Hong, B; Horaguchi, T; Hornback, D; Huang, S; Ichihara, T; Ichimiya, R; Ikeda, Y; Imai, K; Imrek, J; Inaba, M; Isenhower, D; Ishihara, M; Isobe, T; Issah, M; Isupov, A; Ivanischev, D; Jacak, B V; Jia, J; Jin, J; Johnson, B M; Joo, K S; Jouan, D; Kajihara, F; Kametani, S; Kamihara, N; Kamin, J; Kang, J H; Kapustinsky, J; Kawall, D; Kazantsev, A V; Kempel, T; Khanzadeev, A; Kijima, K M; Kikuchi, J; Kim, B I; Kim, D H; Kim, D J; Kim, E; Kim, S H; Kinney, E; Kiriluk, K; Kiss, A; Kistenev, E; Klay, J; Klein-Boesing, C; Kochenda, L; Kochetkov, V; Komkov, B; Konno, M; Koster, J; Kozlov, A; Král, A; Kravitz, A; Kunde, G J; Kurita, K; Kurosawa, M; Kweon, M J; Kwon, Y; Kyle, G S; Lacey, R; Lai, Y S; Lajoie, J G; Layton, D; Lebedev, A; Lee, D M; Lee, K B; Lee, T; Leitch, M J; Leite, M A L; Lenzi, B; Liebing, P; Liska, T; Litvinenko, A; Liu, H; Liu, M X; Li, X; Love, B; Lynch, D; Maguire, C F; Makdisi, Y I; Malakhov, A; Malik, M D; Manko, V I; Mannel, E; Mao, Y; Masek, L; Masui, H; Matathias, F; McCumber, M; McGaughey, P L; Means, N; Meredith, B; Miake, Y; Mikes, P; Miki, K; Milov, A; Mishra, M; Mitchell, J T; Mohanty, A K; Morino, Y; Morreale, A; Morrison, D P; Moukhanova, T V; Mukhopadhyay, D; Murata, J; Nagamiya, S; Nagle, J L; Naglis, M; Nagy, M I; Nakagawa, I; Nakamiya, Y; Nakamura, T; Nakano, K; Newby, J; Nguyen, M; Niita, T; Nouicer, R; Nyanin, A S; O'Brien, E; Oda, S X; Ogilvie, C A; Okada, H; Okada, K; Oka, M; Onuki, Y; Oskarsson, A; Ouchida, M; Ozawa, K; Pak, R; Palounek, A P T; Pantuev, V; Papavassiliou, V; Park, J; Park, W J; Pate, S F; Pei, H; Peng, J-C; Pereira, H; Peresedov, V; Peressounko, D Yu; Pinkenburg, C; Purschke, M L; Purwar, A K; Qu, H; Rak, J; Rakotozafindrabe, A; Ravinovich, I; Read, K F; Rembeczki, S; Reuter, M; Reygers, K; Riabov, V; Riabov, Y; Roach, D; Roche, G; Rolnick, S D; Rosati, M; Rosendahl, S S E; Rosnet, P; Rukoyatkin, P; Ruzicka, P; Rykov, V L; Sahlmueller, B; Saito, N; Sakaguchi, T; Sakai, S; Sakashita, K; Samsonov, V; Sato, T; Sawada, S; Sedgwick, K; Seele, J; Seidl, R; Semenov, A Yu; Semenov, V; Seto, R; Sharma, D; Shein, I; Shibata, T-A; Shigaki, K; Shimomura, M; Shoji, K; Shukla, P; Sickles, A; Silva, C L; Silvermyr, D; Silvestre, C; Sim, K S; Singh, B K; Singh, C P; Singh, V; Slunecka, M; Soldatov, A; Soltz, R A; Sondheim, W E; Sorensen, S P; Sourikova, I V; Staley, F; Stankus, P W; Stenlund, E; Stepanov, M; Ster, A; Stoll, S P; Sugitate, T; Suire, C; Sukhanov, A; Sziklai, J; Takagui, E M; Taketani, A; Tanabe, R; Tanaka, Y; Taneja, S; Tanida, K; Tannenbaum, M J; Taranenko, A; Tarján, P; Themann, H; Thomas, T L; Togawa, M; Toia, A; Tomásek, L; Tomita, Y; Torii, H; Towell, R S; Tram, V-N; Tserruya, I; Tsuchimoto, Y; Vale, C; Valle, H; van Hecke, H W; Veicht, A; Velkovska, J; Vertesi, R; Vinogradov, A A; Virius, M; Vrba, V; Vznuzdaev, E; Walker, D; Wang, X R; Watanabe, Y; Wei, F; Wessels, J; White, S N; Williamson, S; Winter, D; Woody, C L; Wysocki, M; Xie, W; Yamaguchi, Y L; Yamaura, K; Yang, R; Yanovich, A; Ying, J; Yokkaichi, S; Young, G R; Younus, I; Yushmanov, I E; Zajc, W A; Zaudtke, O; Zhang, C; Zhou, S; Zolin, L
2009-07-01
The double helicity asymmetry in neutral pion production for pT=1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, DeltaG, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of micro2=4 GeV2 a next to leading order QCD analysis gives DeltaG[0.02,0.3]=0.2, with a constraint of -0.7
NASA Astrophysics Data System (ADS)
Ivanov, I. P.; Nikolaev, N. N.
2002-03-01
The differential gluon structure function of the proton F(x,Q2) introduced by Fadin, Kuraev, and Lipatov in 1975 is used in many applications of small-x QCD. We report here ready-to-use parametrizations of F(x,Q2) from the κ-factorization phenomenology of the experimental data on the small-x proton structure function F2p(x,Q2). These parametrizations are based partly on the available Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution fits [Glück-Reya-Vogt, Coordinated Theoretical/Experimental Project on QCD Phenomenology (CTEQ), and Martin-Roberts-Stirling] to parton distribution functions and on realistic extrapolations into a soft region. We discuss the impact of soft gluons on various observables. The x dependence of the F(x,Q2) so determined varies strongly with Q2 and does not exhibit simple Regge properties. Nonetheless, the hard-to-soft diffusion is found to give rise to a viable approximation of the proton structure function F2p(x,Q2) by the soft and hard Regge components with intercepts Δsoft=0 and Δhard~0.4.
Blaizot, Jean-Paul; Liao, Jinfeng; Mehtar-Tani, Yacine
2016-12-01
We analyze the interplay of elastic and inelastic collisions in the thermalization of the quark-gluon plasma, using kinetic theory. Our main focus is the dynamics and equilibration of long wavelength modes.
Jean-Paul Blaizot; Liao, Jinfeng; Mehtar-Tani, Yacine
2016-01-01
We analyze the interplay of elastic and inelastic collisions in the thermalization of the quark-gluon plasma, using kinetic theory. Our main focus is the dynamics and equilibration of long wavelength modes.
Probing gluon number fluctuation effects in future electron-hadron colliders
NASA Astrophysics Data System (ADS)
Amaral, J. T.; Gonçalves, V. P.; Kugeratski, M. S.
2014-10-01
The description of the QCD dynamics in the kinematical range which will be probed in the future electron-hadron colliders is still an open question. Although phenomenological studies indicate that the gluon number fluctuations, which are related to discreteness in the QCD evolution, are negligible at HERA, the magnitude of these effects for the next generation of colliders still should be estimated. In this paper we investigate inclusive and diffractive ep observables considering a model for the physical scattering amplitude which describes the HERA data. Moreover, we estimate, for the first time, the contribution of the fluctuation effects for the nuclear structure functions. Our results indicate that the study of these observables in the future colliders can be useful to constrain the presence of gluon number fluctuations.
Anti pp searches for quark-gluon plasma at TeV I
Turkot, F.
1986-06-01
Three experiments that have been approved to run at TeV I are discussed from the viewpoint of their capability to search for evidence of the QCD phase transition in proton-antiproton collisions at 1.6 TeV. One of these experiments, E-735, was proposed as a dedicated search for quark-gluon plasma effects with a detector designed to study large total E/sub T/, low P/sub T/ individual particles. The other two, E-741 (CDF) and E-740 (DO), embody general purpose four-pi detectors designed primarily to study the physics of W and Z bosons and other large P/sub T/ phenomena. The detectors and their quark-gluon plasma signals are compared. 8 refs., 6 figs., 4 tabs. (LEW)
Propagation of cosmic rays through the atmosphere in the quark-gluon strings model
NASA Technical Reports Server (NTRS)
Erlykin, A. D.; Krutikova, N. P.; Shabelski, Y. M.
1985-01-01
The quark-gluon strings model succeeds in the description of multiple hadron production in the central rapidity region of nucleon-nucleon interctions. This model was developed for hadron-nucleus interactions and used for calculation of the cosmic ray propagation through the atmosphere. It is shown that at energies 10 to the 11th power to the 12th power eV, this model gives a satisfactory description of experimental data. But with the increase of the energy up to approximately 10 to the 14th power eV, results of calculations and of experiments begin to differ and this difference rises with the energy. It may indicate that the scaling violation in the fragmentation region of inclusive spectra for hadron-nucleus interactions is stronger than in the quark-gluon strings model.
The sound generated by a fast parton in the quark-gluon plasma is a crescendo
NASA Astrophysics Data System (ADS)
Neufeld, R. B.; Müller, B.
2009-11-01
The total energy deposited into the medium per unit length by a fast parton traversing a quarkgluon plasma is calculated. We take the medium excitation due to collisions to be given by the well known expression for the collisional drag force. The parton's radiative energy loss contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. In our model, this leads to a length dependence on the differential energy loss due to the interactions of radiated gluons with the medium. The final result, which is a sum of the primary and the secondary contributions, is then treated as the coefficient of a local hydrodynamic source term. Results are presented for energy density wave induced by two fast, back-to-back partons created in an initial hard interaction.
Momentum broadening of a fast parton in a perturbative quark-gluon plasma
Majumder, Abhijit; Mueller, Berndt; Mrowczynski, Stanislaw
2009-12-15
The average transverse momentum transfer per unit path length to a fast parton scattering elastically in a perturbative quark-gluon plasma is related to the radiative energy loss of the parton. We first calculate the momentum transfer coefficient q-circumflex in terms of a classical Langevin problem and then define it quantum mechanically through a scattering matrix element. After treating the well-known case of a quark-gluon plasma in equilibrium, we consider an off-equilibrium unstable plasma. As a specific example, we treat the two-stream plasma with unstable modes of longitudinal chromoelectric field. In the presence of the instabilities, q-circumflex is shown to exponentially grow in time.
Dimension-two gluon condensate from large-N{sub c} Regge models
Ruiz Arriola, Enrique; Broniowski, Wojciech
2006-05-01
It is shown that in the large-N{sub c} limit radial, Regge trajectories give rise in a natural way to the presence of the dimension-2 gluon condensate in meson correlators. We match these models to QCD and provide estimates for in terms of other physical quantities. In particular, in the simplest strictly linear radial Regge model with equal residues is proportional to the pion decay constant squared. However, the linear model fails a consistency condition based on matching the short- and long-distance string tensions, nor does it reproduce the phenomenological values of the gluon condensates. On the contrary, in Regge models departing from strict linearity one may reproduce both the consistency condition and the signs of condensates. We demonstrate this in a simple explicit model.
Gluon Schwinger-Dyson equation in the PT-BFM scheme
NASA Astrophysics Data System (ADS)
Narciso Ferreira, A. M. S.; Aguilar, A. C.
2016-04-01
Schwinger-Dyson equations provide an appropriate framework for tackling non-perturbative QCD phenomena requiring a continuum treatment. However, an inadequate truncation of this tower of integral equations can compromise the symmetries underlying the theory in question. The synthesis of the Pinch Technique and the Background Field method provides a framework where it is possible to devise a self-consistent truncation scheme, exploiting the Ward identities satisfied by the effective Green’s functions that emerge. In this work we review how this truncation scheme is implemented, and show that the new series of dressed diagrams for the background gluon propagator organizes itself in characteristic subsets that are individually transverse. In addition, we discuss how the Background Quantum identity connects the background gluon propagator with the conventional one, computed in the lattice simulations.
Gluon Self-Interaction in the Position Space in Landau Gauge
NASA Astrophysics Data System (ADS)
Cvetič, Gorazd; Kondrashuk, Igor
We propose a method to treat the three-gluon self-interaction vertex in the position space in D = 4 - 2ɛ dimensions. As an example, we calculate a two-loop contribution to auxiliary Lcc vertex in the Landau gauge which contains the three-gluon vertex for SU(N) Yang-Mills theory. We represent the integral expression as a sum of separate contributions so that each of the contributions is a double finite integral or single integral (singular or finite) in the position space. In each double finite integral, we use the freedom to shift exponents in powers in the denominator of integrands by some multiples of ɛ, in order to perform at least one of the integrations by the uniqueness technique without corrupting the first term of the decomposition in ɛ.
Quark-gluon soup — The perfectly liquid phase of QCD
NASA Astrophysics Data System (ADS)
Heinz, Ulrich
2015-01-01
At temperatures above about 150 MeV and energy densities exceeding 500 MeV/fm3, quarks and gluons exist in the form of a plasma of free color charges that is about 1000 times hotter and a billion times denser than any other plasma ever created in the laboratory. This quark-gluon plasma (QGP) turns out to be strongly coupled, flowing like a liquid. About 35 years ago, the nuclear physics community started a program of relativistic heavy-ion collisions with the goal of producing and studying QGP under controlled laboratory conditions. This article recounts the story of its successful creation in collider experiments at Brookhaven National Laboratory and CERN and the subsequent discovery of its almost perfectly liquid nature, and reports on the recent quantitatively precise determination of its thermodynamic and transport properties.
Can antibaryons signal the formation of a quark-gluon plasma
Heinz, U.; Subramanian, P.R.; Greiner, W.
1985-01-01
We report on recent work which indicates that an enhancement of antibaryons produced in the hadronization phase transition can signal the existence of a transient quark-gluon plasma phase formed in a heavy-ion collision. The basis of the enhancement mechanism is the realization that antiquark densities are typically a factor 3 higher in the quark-gluon plasma phase than in hadronic matter at the same temperature and baryon density. The signal is improved by studying larger clusters of antimatter, i.e., light antinuclei like anti ..cap alpha.., in the central rapidity region. The effects of the transition dynamics and of the first order nature of the phase transition on the hadronization process are discussed.
Energy change of a heavy quark in a viscous quark-gluon plasma with fluctuations
NASA Astrophysics Data System (ADS)
Jiang, Bing-feng; Hou, De-fu; Li, Jia-rong
2016-09-01
When a heavy quark travels through the quark-gluon plasma, the polarization and fluctuating chromoelectric fields will be produced simultaneously in the plasma. The drag force due to those fields exerting in return on the moving heavy quark will cause energy change to it. Based on the dielectric functions derived from the viscous chromohydrodynamics, we have studied the collisional energy change of a heavy quark traversing the viscous quark-gluon plasma including fluctuations of chromoelectric field. Numerical results indicate that the chromoelectric field fluctuations lead to an energy gain of the moving heavy quark. Shear viscosity suppresses the fluctuation-induced energy gain and the viscous suppression effect for the charm quark is much more remarkable than that for the bottom quark. While, the fluctuation energy gain is much smaller than the polarization energy loss in magnitude and the net energy change for the heavy quark is at loss.
Next-to-leading order static gluon self-energy for anisotropic plasmas
Carrington, M. E.; Rebhan, A.
2009-01-15
In this paper the structure of the next-to-leading order static gluon self-energy for an anisotropic plasma is investigated in the limit of a small momentum space anisotropy. Using the Ward identities for the static hard-loop (HL) gluon polarization tensor and the (nontrivial) static HL vertices, we derive a comparatively compact form for the complete next-to-leading order correction to the structure function containing the spacelike pole associated with magnetic instabilities. On the basis of a calculation without HL vertices, it has been conjectured that the imaginary part of this structure function is nonzero, rendering the spacelike poles integrable. We show that there are both positive and negative contributions when HL vertices are included, highlighting the necessity of a complete numerical evaluation, for which the present work provides the basis.
Phenomenological analysis of Higgs boson production through gluon fusion in association with jets
Greiner, Nicolas; Hoeche, Stefan; Luisoni, Gionata; Schonherr, Marek; Winter, Jan -Christopher; Yundin, Valery
2016-01-27
We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. We consider the gluon fusion channel using an effective theory in the large top-quark mass limit. Higgs boson production in gluon fusion constitutes an irreducible background to the vector boson fusion (VBF) process; hence the precise knowledge of its characteristics is a prerequisite for any measurement in the VBF channel. The calculation is carried out at next-to-leading order (NLO) in QCD in a fully automated way by combining the two programs GoSAM and SHERPA. We present numerical resultsmore » for a large variety of observables for both standard cuts and VBF selection cuts.« less
Gluon scattering in N = 4 Super Yang-Mills at finite temperature
Ito, Katsushi; Iwasaki, Koh; Nastase, Horatiu
2008-11-23
We extend the AdS/CFT prescription of Alday and Maldacena to finite temperature T, defining an amplitude for gluon scattering in N = 4 Super Yang-Mills at strong coupling from string theory. It is defined by a lightlike 'Wilson loop' living at the horizon of the T-dual to the black hole in AdS space. Unlike the zero temperature case, this is different from the Wilson loop contour defined at the boundary of the AdS black hole metric, thus at nonzero T there is no relation between gluon scattering amplitudes and the Wilson loop. We calculate a gauge theory observable that can be interpreted as the amplitude at strong coupling in both cut-off and generalized dimensional regularization.
{lambda}{sub c} Enhancement from Strongly Coupled Quark-Gluon Plasma
Lee, Su Houng; Ohnishi, Kazuaki; Yasui, Shigehiro; Yoo, In-Kwon; Ko, Che Ming
2008-06-06
We propose the enhancement of {lambda}{sub c} as a novel quark-gluon plasma signal in heavy ion collisions at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider. Assuming a stable bound diquark state in the strongly coupled quark-gluon plasma near the critical temperature, we argue that the direct two-body collision between a c quark and a [ud] diquark would lead to an enhanced {lambda}{sub c} production in comparison with the normal three-body collision among independent c, u, and d quarks. In the coalescence model, we find that the {lambda}{sub c}/D yield ratio is enhanced substantially due to the diquark correlation.
Higgs Boson Production via Gluon Fusion in the Standard Model with four Generations
Li Qiang; Spira, Michael; Gao, Jun; Li Chongsheng
2011-05-01
Higgs bosons can be produced copiously at the LHC via gluon fusion induced by top and bottom quark loops, and can be enhanced strongly if extra heavy quarks exist. We present results for Higgs+zero-, one- and two-jet production at the LHC operating at 7 and 14 TeV collision energy, in both the standard model and the 4th generation model, by evaluating the corresponding heavy quark triangle, box, and pentagon Feynman diagrams. We compare the results by using the effective Higgs-gluon interactions in the limit of heavy quarks with the cross sections including the full mass dependences. NLO effects on Higgs+zero-jet production rate with full mass dependence are presented for the first time consistently in the 4th generation model. Our results improve the theoretical basis for fourth generation effects on the Higgs boson search at the LHC.
Searching for gluon number fluctuations effects in eA collisions
Kugeratski, M. S.; Gonçalves, V. P.; Santana Amaral, J. T. de
2014-11-11
We propose to investigate the gluon number fluctuations effects in deep inelastic electron-ion scattering at high energies. We estimate the nuclear structure function F{sub 2}{sup A}(x,Q{sup 2}), as well the longitudinal and charm contributions, using a generalization for nuclear targets of the Golec-Biernat-Wusthoff (GBW) model which describes the electron proton HERA data. Here we consider that the nucleus at high energies acts as an amplifier of the physics of high parton densities. For a first investigation we study the scattering with Ca and Pb nuclei. Our preliminary results predict that the effects of gluon number fluctuations are small in the region of the future electron ion collider.
Deconfining Phase Transition to a Quark-Gluon Plasma in Different SU(3) Color Representations
NASA Astrophysics Data System (ADS)
Mezouar, K.; Ait El Djoudi, A.; Ghenam, L.
2016-10-01
For a statistical description of the quark gluon plasma (QGP) considering its internal symmetry, we calculate its partition function using the group theoretical projection method. We project out the partition function of a QGP consisting of gluons, massless up and down quarks, and massive strange quarks onto the singlet representation of the SU(3) color group, as well as onto the color octet and the color 27-plet representations. A comparison of these color representations is done, by studying their effects on the behavior of some thermodynamical quantities characterizing the mixed hadronic gas-QGP system undergoing a thermal deconfining phase transition on one side, and on the free energy during the formation of a QGP droplet from the hot hadronic gas on another side.
From quarks and gluons to hadrons: Chiral symmetry breaking in dynamical QCD
NASA Astrophysics Data System (ADS)
Braun, Jens; Fister, Leonard; Pawlowski, Jan M.; Rennecke, Fabian
2016-08-01
We present an analysis of the dynamics of two-flavor QCD in the vacuum. Special attention is paid to the transition from the high-energy quark-gluon regime to the low-energy regime governed by hadron dynamics. This is done within a functional renormalization group approach to QCD amended by dynamical hadronization techniques. These techniques allow us to describe conveniently the transition from the perturbative high-energy regime to the nonperturbative low-energy limit without suffering from a fine-tuning of model parameters. In the present work, we apply these techniques to two-flavor QCD with physical quark masses and show how the dynamics of the dominant low-energy degrees of freedom emerge from the underlying quark-gluon dynamics.
Thermal charm and charmonium production in quark gluon plasma
NASA Astrophysics Data System (ADS)
Zhou, Kai; Chen, Zhengyu; Greiner, Carsten; Zhuang, Pengfei
2016-07-01
We study the effect of thermal charm production on charmonium regeneration in high energy nuclear collisions. By solving the kinetic equations for charm quark and charmonium distributions in Pb+Pb collisions, we calculate the global and differential nuclear modification factors RAA (Npart) and RAA (pt) for J / ψ s. Due to the thermal charm production in hot medium, the charmonium production source changes from the initially created charm quarks at SPS, RHIC and LHC to the thermally produced charm quarks at Future Circular Collider (FCC), and the J / ψ suppression (RAA < 1) observed so far will be replaced by a strong enhancement (RAA > 1) at FCC at low transverse momentum.
Deep-inelastic diffraction and the pomeron as a single gluon
White, A.R.
1997-09-03
Deep-inelastic diffractive scaling provides fundamental insight into the QCD pomeron. It is argued that single gluon domination of the structure function, together with the well-known Regge pole property, determines that the pomeron carries color-change parity C{sub c} = {minus}1 and, at short distances, is in a super-critical phase of Reggeon Field Theory. The main purpose of the talk is to describe the relationship of the super-critical pomeron to QCD.
3D imaging of sea quarks and gluons at an electron-ion collider
Vadim Guzey
2011-11-01
We outline key objectives and capabilities of an Electron-Ion Collider (EIC) — a high-energy and high-luminosity electron-proton/nucleus collider with polarized electron and proton beams. One of goals of a future EIC is to map the 3D (in configuration and momentum spaces) structure of sea quarks and gluons in the nucleon and nuclei. We briefly present and discuss key observables and measurements pertaining to the program of 3D imaging at an EIC.
Cancellation of Glauber Gluon Exchange in the Double Drell-Yan Process
NASA Astrophysics Data System (ADS)
Diehl, Markus; Gaunt, Jonathan R.; Ostermeier, Daniel; Plößl, Peter; Schäfer, Andreas
2016-06-01
For any factorisation proof, a crucial step is a demonstration of the cancellation of so-called Glauber gluons. We summarise a recent paper in which we demonstrated this cancellation for double Drell-Yan production (the double parton scattering process in which a pair of electroweak gauge bosons is produced), both for the integrated cross section and for the cross section differential in the boson transverse momenta.
Asymptotic freedom and IR freezing in QCD: the role of gluon paramagnetism
Simonov, Yu. A.
2011-08-15
Paramagnetism of gluons is shown to play the basic role in establishing main properties of QCD: IR freezing and asymptotic freedom (AF). Starting with Polyakov background field approach the first terms of background perturbation theory are calculated and shown to ensure not only the classical result of AF but also IR freezing. For the latter only the confining property of the background is needed, and the effective mass entering the IR freezing logarithms is calculated in good agreement with phenomenology and lattice data.
Imaginary part of the static gluon propagator in an anisotropic (viscous) QCD plasma
Dumitru, Adrian; Guo, Yun; Strickland, Michael
2009-06-01
We determine viscosity corrections to the retarded, advanced and symmetric gluon self-energies and to the static propagator in the weak-coupling ''hard loop'' approximation to high-temperature QCD. We apply these results to calculate the imaginary part of the heavy-quark potential which is found to be smaller (in magnitude) than at vanishing viscosity. This implies a smaller decay width of quarkonium bound states in an anisotropic plasma.
Event-by-event hydrodynamics: A better tool to study the Quark-Gluon plasma
Grassi, Frederique
2013-03-25
Hydrodynamics has been established as a good tool to describe many data from relativistic heavyion collisions performed at RHIC and LHC. More recently, it has become clear that it is necessary to use event-by-event hydrodynamics (i.e. describe each collision individually using hydrodynamics), an approach first developed in Brazil. In this paper, I review which data require the use of event-by-event hydrodynamics and what more we may learn on the Quark-Gluon Plasma with this.
The Investigation of Bose Excitations in Quark-Gluon Plasma in Lightcone Gauge
Veliev, Elsen Veli; Suengue, Jale Y.; Bozkir, Guelsah; Aksit, Nurcan
2007-04-23
We investigate collective excitations in quark-gluon plasma at high temperatures. Ultrarelativistic plasmas are of importance in cosmology, astrophysics, and high energy nucleus-nucleus collisions. One of the fundamental properties of a thermal field theory at finite temperatures is the collective excitations, which are characterized by dispersion law {omega}(p) giving their energy as a function of their momenta p. Collective modes appear mathematically as poles of propagators with well-defined quantum numbers in the complex plane of the energy: the real part of the pole gives the dispersion law, while the imaginary part gives the damping rate. In this paper, Bose excitations in quark-gluon plasma are investigated in the lightcone gauge. In order to remove non-physical singularities, which appear in non-covariant gauges in non-abelian gauge field theories, we used the Mandelstam-Leibbrandt prescription. Gluon self-energy in the one-loop approximation is calculated using standard Thermal QCD diagram technique. Bose excitation spectrum is found in the high-temperature limit and the dispersion equation is shown to be gauge invariant.
Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation
Matevosyan, Hrayr H.; Thomas, Anthony W.; Tandy, Peter C.
2007-04-15
We include a generalized infinite class of quark-gluon vertex dressing diagrams in a study of how dynamics beyond the ladder-rainbow truncation influences the Bethe-Salpeter description of light-quark pseudoscalar and vector mesons. The diagrammatic specification of the vertex is mapped into a corresponding specification of the Bethe-Salpeter kernel, which preserves chiral symmetry. This study adopts the algebraic format afforded by the simple interaction kernel used in previous work on this topic. The new feature of the present work is that in every diagram summed for the vertex and the corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be the self-consistent vertex solution. We also adopt from previous work the effective accounting for the role of the explicitly non-Abelian three-gluon coupling in a global manner through one parameter determined from recent lattice-QCD data for the vertex. Within the current model, the more consistent dressed vertex limits the ladder-rainbow truncation error for vector mesons to be never more than 10% as the current quark mass is varied from the u/d region to the b region.
Viscosities of gluon dominated QGP model within relativistic non-Abelian hydrodynamics
NASA Astrophysics Data System (ADS)
Djun, T. P.; Handoko, L. T.; Soegijono, B.; Mart, T.
2015-04-01
Based on the first principle calculation, a Lagrangian for the system describing quarks, gluons, and their interactions, is constructed. Ascribed to the existence of dissipative behavior as a consequence of strong interaction within quark-gluon plasma (QGP) matter, auxiliary terms describing viscosities are constituted into the Lagrangian. Through a "kind" of phase transition, gluon field is redefined as a scalar field with four-vector velocity inherently attached. Then, the Lagrangian is elaborated further to produce the energy-momentum tensor of dissipative fluid-like system and the equation of motion (EOM). By imposing the law of energy and momentum conservation, the values of shear and bulk viscosities are analytically calculated. Our result shows that, at the energy level close to hadronization, the bulk viscosity is bigger than shear viscosity. By making use of the conjectured values η/s 1/4π and ζ/s 1, the ratio of bulk to shear viscosity is found to be ζ/η>4π.
Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation
Hrayr Matevosyan; Anthony Thomas; Peter Tandy
2007-04-01
We include a generalized infinite class of quark-gluon vertex dressing diagrams in a study of how dynamics beyond the ladder-rainbow truncation influences the Bethe-Salpeter description of light quark pseudoscalar and vector mesons. The diagrammatic specification of the vertex is mapped into a corresponding specification of the Bethe-Salpeter kernel, which preserves chiral symmetry. This study adopts the algebraic format afforded by the simple interaction kernel used in previous work on this topic. The new feature of the present work is that in every diagram summed for the vertex and the corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be the self-consistent vertex solution. We also adopt from previous work the effective accounting for the role of the explicitly non-Abelian three gluon coupling in a global manner through one parameter determined from recent lattice-QCD data for the vertex. With the more consistent vertex used here, the error in ladder-rainbow truncation for vector mesons is never more than 10% as the current quark mass is varied from the u/d region to the b region.
Do Gluons Carry Proton Spin? - Toward Resolving the Spin Crisis (445th Brookhaven Lecture)
Bazilevsky, Alexander
2009-01-21
Just as Earth and other planets spin within the solar system, subatomic quark and gluon particles spin within the protons and neutrons that spin within the nucleus of an atom. Quantum Chromodynamics (QCD) is a theory that describes interactions between subatomic particles and it has played a defining role in understanding the spin of protons and neutrons, which make up most of the visible mass in the universe. Experiments first completed at CERN and furthered at several other laboratories around the world revealed that surprisingly, quarks and their partnering anti-quarks are responsible for only 20 to 30 percent of proton spin. These findings pointed to what would become known as "spin crisis." More recent experiments at BNL's Relativistic Heavy Ion Collider (RHIC), the first collider to smash protons that are "polarized," or made to spin in the same orientation, have helped to isolate the role of the gluon's spin within the spinning proton in hopes of resolving this crisis. In his lecture, Bazilevsky will explain how data from RHIC's PHENIX and STAR detectors help to reveal the role of gluons in the proton's spin. Bazilevsky will also discuss long- and short-term plans to attain a deeper look into the proton spin structure, utilizing RHIC and its future upgrades
Effects of dynamical masses of gluons and quarks on hadronic B decays
Zanetti, C. M.; Natale, A. A.
2010-11-12
We study hadronic annihilation decays of B mesons within the perturbative QCD at collinear approximation. The regulation of endpoint divergences is performed with the help of an infrared finite gluon propagator characterized by a non-perturbative dynamical gluon mass. The divergences at twist-3 are regulated by a dynamical quark mass. Our results fit quite well the existent data of B{sup 0}{yields}D{sub s}{sup -}K{sup +} and B{sup 0}{yields}D{sub s}{sup -*}K{sup +} for the expected range of dynamical gluon masses. We also make predictions for the rare decays B{sup 0}{yields}K{sup -}K{sup +}, B{sub s}{sup 0}{yields}{pi}{sup -}{pi}{sup +}, {pi}{sup 0}{pi}{sup 0}, B{sup +}{yields}D{sub s}{sup (*)+}K-bar{sup 0}, B{sup 0}{yields}D{sub s}{sup {+-}(*)}K{sup {+-}} and B{sub s}{sup 0}{yields}D{sup {+-}(*)}{pi}{sup {+-}}, D{sup 0}{pi}{sup 0}.
NASA Astrophysics Data System (ADS)
Thilker, David A.; Vinsen, K.; Galaxy Properties Key Project, PS1
2014-01-01
To measure resolved galactic physical properties unbiased by the mask of recent star formation and dust features, we are conducting a citizen-scientist enabled nearby galaxy survey based on the unprecedented optical (g,r,i,z,y) imaging from Pan-STARRS1 (PS1). The PS1 Optical Galaxy Survey (POGS) covers 3π steradians (75% of the sky), about twice the footprint of SDSS. Whenever possible we also incorporate ancillary multi-wavelength image data from the ultraviolet (GALEX) and infrared (WISE, Spitzer) spectral regimes. For each cataloged nearby galaxy with a reliable redshift estimate of z < 0.05 - 0.1 (dependent on donated CPU power), publicly-distributed computing is being harnessed to enable pixel-by-pixel spectral energy distribution (SED) fitting, which in turn provides maps of key physical parameters such as the local stellar mass surface density, crude star formation history, and dust attenuation. With pixel SED fitting output we will then constrain parametric models of galaxy structure in a more meaningful way than ordinarily achieved. In particular, we will fit multi-component (e.g. bulge, bar, disk) galaxy models directly to the distribution of stellar mass rather than surface brightness in a single band, which is often locally biased. We will also compute non-parametric measures of morphology such as concentration, asymmetry using the POGS stellar mass and SFR surface density images. We anticipate studying how galactic substructures evolve by comparing our results with simulations and against more distant imaging surveys, some of which which will also be processed in the POGS pipeline. The reliance of our survey on citizen-scientist volunteers provides a world-wide opportunity for education. We developed an interactive interface which highlights the science being produced by each volunteer’s own CPU cycles. The POGS project has already proven popular amongst the public, attracting about 5000 volunteers with nearly 12,000 participating computers, and is
The quark and gluon structure of the proton.
Perez, E; Rizvi, E
2013-04-01
In this paper we present a review of the structure of the proton and the current status of our knowledge of the parton distribution functions (PDFs). The lepton-nucleon scattering experiments which provide the main constraints in PDF extractions are introduced and their measurements are discussed. Particular emphasis is given to the HERA data which cover a wide kinematic region. Hadron-hadron scattering measurements which provide supplementary information are also discussed. The methods used by various groups to extract the PDFs in QCD analyses of hard scattering data are presented and their results are compared. The use of existing measurements allows predictions for cross sections at the LHC to be made. A comparison of these predictions for selected processes is given. First measurements from the LHC experiments are compared to predictions and some initial studies of the impact of this new data on the PDFs are presented. PMID:23503469
Exploring the Quark-Gluon Content of Hadrons: From Mesons to Nuclear Matter
Matevosyan, Hrayr
2007-08-01
Even though Quantum Chromodynamics (QCD) was formulated over three decades ago, it poses enormous challenges for describing the properties of hadrons from the underlying quark-gluon degrees of freedom. Moreover, the problem of describing the nuclear force from its quark-gluon origin is still open. While a direct solution of QCD to describe the hadrons and nuclear force is not possible at this time, we explore a variety of developed approaches ranging from phenomenology to first principle calculations at one or other level of approximation in linking the nuclear force to QCD. The Dyson Schwinger formulation (DSE) of coupled integral equations for the QCD Green’s functions allows a non-perturbative approach to describe hadronic properties, starting from the level of QCD n-point functions. A significant approximation in this method is the employment of a finite truncation of the system of DSEs, that might distort the physical picture. In this work we explore the effects of including a more complete truncation of the quark-gluon vertex function on the resulting solutions for the quark 2-point functions as well as the pseudoscalar and vector meson masses. The exploration showed strong indications of possibly large contributions from the explicit inclusion of the gluon 3- and 4-point functions that are omitted in this and previous analyses. We then explore the possibility of extrapolating state of the art lattice QCD calculations of nucleon form factors to the physical regime using phenomenological models of nucleon structure. Finally, we further developed the Quark Meson Coupling model for describing atomic nuclei and nuclear matter, where the quark-gluon structure of nucleons is modeled by the MIT bag model and the nucleon many body interaction is mediated by the exchange of scalar and vector mesons. This approach allows us to formulate a fully relativistic theory, which can be expanded in the nonrelativistic limit to reproduce the well known phenomenological Skyrme
Jet-vetoed Higgs cross section in gluon fusion at N3LO+NNLL with small-R resummation
NASA Astrophysics Data System (ADS)
Banfi, Andrea; Caola, Fabrizio; Dreyer, Frédéric A.; Monni, Pier Francesco; Salam, Gavin P.; Zanderighi, Giulia; Dulat, Falko
2016-04-01
We present new results for the jet-veto efficiency and zero-jet cross section in Higgs production through gluon fusion. We incorporate the N3LO corrections to the total cross section, the NNLO corrections to the 1-jet rate, NNLL resummation for the jet p t and LL resummation for the jet radius dependence. Our results include known finite-mass corrections and are obtained using the jet-veto efficiency method, updated relative to earlier work to take into account what has been learnt from the new precision calculations that we include. For 13 TeV collisions and using our default choice for the renormalisation and factorisation scales, μ 0 = m H /2, the matched prediction for the jet-veto efficiency increases the pure N3LO prediction by about 2% and the two have comparable uncertainties. Relative to NNLO+NNLL results, the new prediction is 2% smaller and the uncertainty reduces from about 10% to a few percent. Results are also presented for the central scale μ 0 = m H .
Quarks, Gluons and Color are sufficient, but are they necessary?
NASA Astrophysics Data System (ADS)
Bartlett, David
2016-03-01
John Stewart Bell died in 1990. Two experiments in the last year have made one appreciate Bell's support for instantaneous action at a distance (``quantum spookiness'') and his disdain for ``hidden variables''. R. Hanson et al constructed an entangled state with electrons in two labs 1.3 km apart. At NIST, C.W. Clark et al gave a free neutron orbital angular momentum. The neutron joins the electron and photon as particles that can be given L. Who knows how the up and down quarks enjoyed this experience. Quarks are the most obvious hidden variable in physics. No person has isolated even one. Consequently, the standard model features ``Quark Confinement''. Unfortunately confinement complicates the comparison of QED and QCD.. The alternatives to quarks are scattering lengths, resonances, octets, decuplets, and singlets. This talk will elucidate some of the pre LHC tensions in the standard model. Why is strangeonium qualitatively different from charmonium and bottomonium . Why does the process γ + γ --> η + η (Belle 2010) have a resonance at just the mass of the J/psi, but with a forward & backward peaked angular distribution that contrasts with the isotropy of the J/psi(1S)(1974)? What is needed to show that it is really the off-diagonal elements in the K-mass matrix that are responsible for CP violation (CPLEAR 1999). My colleague John Cumalat MAY submit something. If so, please call either him (303) 492-8604 or me (303) 492-6960.
Suppression and energy loss in Quark-Gluon Plasma
NASA Astrophysics Data System (ADS)
Djordjevic, M.
2016-01-01
High momentum suppression of light and heavy flavor observables is considered to be an excellent probe of jet-medium interactions in QCD matter created at RHIC and LHC. Utilizing this tool requires accurate suppression predictions for different experiments, probes and experimental conditions, and their unbiased comparison with experimental data. We developed the dynamical energy loss formalism which takes into account both radiative and collision energy loss computed within the same theoretical framework, dynamical (as opposed to static) scattering centers, finite magnetic mass, running coupling and uses no free parameters in comparison with experimental data. Within this formalism, we provide predictions, and a systematic comparison with the experimental data, for a diverse set of probes, various centrality ranges and various collision energies at RHIC and LHC. We also provide clear qualitative and quantitative predictions for the upcoming LHC experiments. A comprehensive agreement between our predictions and experimental results suggests that our dynamical energy loss formalism can well explain the jet-medium interactions in QGP, which will be further tested by the obtained predictions for the upcoming data.
The four-loop six-gluon NMHV ratio function
Dixon, Lance J.; von Hippel, Matt; McLeod, Andrew J.
2016-01-11
We use the hexagon function bootstrap to compute the ratio function which characterizes the next-to-maximally-helicity-violating (NMHV) six-point amplitude in planar N=4 super-Yang-Mills theory at four loops. A powerful constraint comes from dual superconformal invariance, in the form of a Q¯ differential equation, which heavily constrains the first derivatives of the transcendental functions entering the ratio function. At four loops, it leaves only a 34-parameter space of functions. Constraints from the collinear limits, and from the multi-Regge limit at the leading-logarithmic (LL) and next-to-leading-logarithmic (NLL) order, suffice to fix these parameters and obtain a unique result. We test the result againstmore » multi-Regge predictions at NNLL and N3LL, and against predictions from the operator product expansion involving one and two flux-tube excitations; all cross-checks are satisfied. We study the analytical and numerical behavior of the parity-even and parity-odd parts on various lines and surfaces traversing the three-dimensional space of cross ratios. As part of this program, we characterize all irreducible hexagon functions through weight eight in terms of their coproduct. As a result, we also provide representations of the ratio function in particular kinematic regions in terms of multiple polylogarithms.« less
Hyperfine meson splittings: chiral symmetry versus transverse gluon exchange
Felipe J. Llanes-Estrada; Stephen R. Cotanch; Adam P. Szczepaniak; Eric S. Swanson
2004-02-01
Meson spin splittings are examined within an effective Coulomb gauge QCD Hamiltonian incorporating chiral symmetry and a transverse hyperfine interaction necessary for heavy quarks. For light and heavy quarkonium systems the pseudoscalar-vector meson spectrum is generated by approximate BCS-RPA diagonalizations. This relativistic formulation includes both S and D waves for the vector mesons which generates a set of coupled integral equations. A smooth transition from the heavy to the light quark regime is found with chiral symmetry dominating the /pi-/rho mass difference. A good, consistent description of the observed meson spin splittings and chiral quantities, such as the quark condensate and the /pi mass, is obtained. Similar comparisons with TDA diagonalizations, which violate chiral symmetry, are deficient for light pseudoscalar mesons indicating the need to simultaneously include both chiral symmetry and a hyperfine interaction. The /eta{sub b} mass is predicted to be around 9400 MeV consistent with other theoretical expectations and above the unconfirmed 9300 MeV candidate. Finally, for comparison with lattice results, the J reliability parameter is also evaluated.
NASA Astrophysics Data System (ADS)
Lacey, Roy A.; Reynolds, D.; Taranenko, A.; Ajitanand, N. N.; Alexander, J. M.; Liu, Fu-Hu; Gu, Yi; Mwai, A.
2016-10-01
It is shown that the acoustic scaling patterns of anisotropic flow for different event shapes at a fixed collision centrality (shape-engineered events), provide robust constraints for the event-by-event fluctuations in the initial-state density distribution from ultrarelativistic heavy ion collisions. The empirical scaling parameters also provide a dual-path method for extracting the specific shear viscosity {(η /s)}{QGP} of the quark-gluon plasma (QGP) produced in these collisions. A calibration of these scaling parameters via detailed viscous hydrodynamical model calculations, gives {(η /s)}{QGP} estimates for the plasma produced in collisions of Au + Au (\\sqrt{{s}{NN}}=0.2 {TeV}) and Pb + Pb (\\sqrt{{s}{NN}}=2.76 {TeV}). The estimates are insensitive to the initial-state geometry models considered.
How do quarks and gluons lose energy in the QGP?
NASA Astrophysics Data System (ADS)
Tannenbaum, M. J.
2015-03-01
. Thus an apparent hard scattering component for A+A multiplicity distributions based on a popular formula, dNAAch/dη = [(1 - x) langleNpartrangle dNppch/dη/2 + x langleNcollrangledNppch/dη], seems to be an unphysical way to understand the deviation from Npart scaling. Based on recent p-p and d+A measurements, a more physical way is presented along with several other stimulating results and ideas from recent d+Au (p+Pb) measurements.
How do quarks and gluons lose energy in the QGP?
Tannenbaum, M. J.
2015-03-10
multiplicity or transverse energy production in p-p collisions–soft particles, with ρT < 2 GeV/c, predominate. Thus an apparent hard scattering component for A+A multiplicity distributions based on a popular formula, dNAAch/dη = [(1 - x) (Npart)dNppch/dη2 + x (NcolldNppch/dη], seems to be an unphysical way to understand the deviation from Npart scaling. Based on recent p-p and d+A measurements, a more physical way is presented along with several other stimulating results and ideas from recent d+Au (p+Pb) measurements.« less
How do quarks and gluons lose energy in the QGP?
Tannenbaum, M. J.
2015-03-10
k_{T}-effect. Another issue well known from experiments at the CERN ISR, SpS and SpS collider is that parton-parton hard-collisions make negligible contribution to multiplicity or transverse energy production in p-p collisions–soft particles, with ρ_{T} < 2 GeV/c, predominate. Thus an apparent hard scattering component for A+A multiplicity distributions based on a popular formula, dN^{AA}_{ch}/dη = [(1 - x) (N_{part})dN^{pp}_{ch}/dη2 + x (N_{coll}dN^{pp}_{ch}/dη], seems to be an unphysical way to understand the deviation from N_{part} scaling. Based on recent p-p and d+A measurements, a more physical way is presented along with several other stimulating results and ideas from recent d+Au (p+Pb) measurements.
NASA Astrophysics Data System (ADS)
Vovchenko, V.; Gorenstein, M. I.; Satarov, L. M.; Mishustin, I. N.; Csernai, L. P.; Kisel, I.; Stöcker, H.
2016-01-01
We study the possibility that partonic matter produced at an early stage of ultrarelativistic heavy-ion collisions is out of chemical equilibrium. It is assumed that initially this matter is mostly composed of gluons, but quarks and antiquarks are produced at later times. The dynamical evolution of partonic system is described by the Bjorken-like ideal hydrodynamics with a time-dependent quark fugacity. The results of this model are compared with those obtained by assuming the complete chemical equilibrium of partons already at the initial stage. It is shown that in a chemically nonequilibrium scenario the entropy gradually increases, and about 25% of the total final entropy is generated during the hydrodynamic evolution of deconfined matter. We argue that the (anti)quark suppression included in this approach may be responsible for reduced (anti)baryon-to-meson ratios observed in heavy-ion collisions at energies available at the CERN Large Hadron Collider.
NASA Astrophysics Data System (ADS)
Gómez-Rocha, M.; Hilger, T.; Krassnigg, A.
2016-04-01
We extend earlier investigations of heavy-light pseudoscalar mesons to the vector case, using a simple model in the context of the Dyson-Schwinger-Bethe-Salpeter approach. We investigate the effects of a dressed quark-gluon vertex in a systematic fashion and illustrate and attempt to quantify corrections beyond the phenomenologically very useful and successful rainbow-ladder truncation. In particular we investigate the dressed quark-photon vertex in such a setup and make a prediction for the experimentally as yet unknown mass of the Bc* , which we obtain at 6.334 GeV well in line with predictions from other approaches. Furthermore, we combine a comprehensive set of results from the theoretical literature. The theoretical average for the mass of the Bc* meson is 6.336 ±0.002 GeV .
NASA Astrophysics Data System (ADS)
Tarasov, Yu. A.
1998-11-01
Hard π0 and η production is investigated in Landau and Bjorken hydrodynamical models taking into account great number of hadronic resonances (16 and 42) in hadronic phase. We consider two different scenario: with quark-gluon plasma (QGP) formation and with only hadronic gas one without QGP. The Cronin effect and hard direct pions emission are taken into account. It is shown that these two scenario give similar p⊥ spectra which agrees with experimental data obtained by WA80 collaboration. Therefore we conclude that from hadronic spectra it is difficult to extract the proof of QGP formation. However we calculate also the η/π0 ratio. We show that this value agrees with experiment only for scenario with QGP and phase transition to hadrons. The hadronic gas scenario without QGP disagrees with experimental data.
Where are we in the search for the Quark Gluon Plasma?
Ullrich, Thomas
2006-02-08
The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory was completed in 1999, with the first data-taking runs in the summer of 2000. Since then the measurements at RHIC have yielded a wealth of data from four independent detectors: BRAHMS, PHENIX, PHOBOS, and STAR. For the first time, collisions of heavy nuclei have been carried out with colliding-beam energies that have previously been accessible only to high-energy physics experiments. It is at these high energies that the predictions of QCD come into play and new phenomena are sought that may illuminate our view of the basic structure of matter.The RHIC experiments have recorded data from collisions of gold nuclei from {radical}(S{sub NN}) = 19 GeV up to the highest energy of 200 GeV, as well as reference data in proton-proton and deuteron-gold collisions. These collisions result in final states of unprecedented complexity, with thousands of produced particles radiating from the nuclear collision.The early measurements have revealed compelling evidence for the existence of a new form of nuclear matter at extremely high density and temperature. This medium allows for the predictions of QCD to be tested, and new phenomena explored, under conditions where the relevant degrees of freedom, over nuclear volumes, are expected to be those of quarks and gluons, rather than of hadrons. This is the realm of the quark gluon plasma.However, detailed analyses of the data also make it clear that this hot, dense medium has properties that are surprising, and not yet fully understood in terms of the early expectations for the quark gluon plasma. In this paper I review the major findings of the RHIC experiments to date and discuss the current understanding of the state of matter created.
A Secular Quark Gluon Plasma Phase Preceding Black HoleFormation
Mitra, Abhas; Glendenning, Norman K.
2006-01-13
As spherical collapse of very massive stars would tend to the formation of Black Holes with an Event Horion having a gravitational red-shift of z = {infinity}, the pressure of gravitationally trapped radiation would increase as {approx} (1 + z){sup 2}. Consequently catastrophic collapse must change into a secular collapse as the radioactive luminosity would attain its Eddington value. Since the local temperature of the collapsing body is found to be {approx} 250 MeV, the stellar mass Black Hole Candidates could be in this intermediate state of a hot Quark Gluon Plasma.
Electromagnetic field and the chiral magnetic effect in the quark-gluon plasma
NASA Astrophysics Data System (ADS)
Tuchin, Kirill
2015-06-01
Time evolution of an electromagnetic field created in heavy-ion collisions strongly depends on the electromagnetic response of the quark-gluon plasma, which can be described by the Ohmic and chiral conductivities. The latter is intimately related to the chiral magnetic effect. I argue that a solution to the classical Maxwell equations at finite chiral conductivity is unstable due to the soft modes k <σχ that grow exponentially with time. In the kinematical region relevant for the relativistic heavy-ion collisions, I derive analytical expressions for the magnetic field of a point charge. I show that finite chiral conductivity causes oscillations of magnetic field at early times.
Jet flavor tomography of quark gluon plasmas at RHIC and LHC.
Buzzatti, Alessandro; Gyulassy, Miklos
2012-01-13
A new Monte Carlo model of jet quenching in nuclear collisions, CUJET1.0, is applied to predict the jet flavor dependence of the nuclear modification factor for fragments f=π,D,B,e(-) from quenched jet flavors g,u,c,b in central collisions at RHIC and LHC. The nuclear modification factors for different flavors are predicted to exhibit a novel level crossing pattern over a transverse momentum range 5
gluon plasmas.
Higgs boson gluon-fusion production beyond threshold in N3LO QCD
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard
2015-03-18
In this study, we compute the gluon fusion Higgs boson cross-section at N3LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N3LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N3LO in perturbative QCD.
RHIC PHYSICS: THE QUARK GLUON PLASMA AND THE COLOR GLASS CONDENSATE: 4 LECTURES
MCLERRAN,L.
2003-01-01
The purpose of these lectures is to provide an introduction to the physics issues which are being studied in the RHIC heavy ion program. These center around the production of new states of matter. The Quark Gluon Plasma is thermal matter which once existed in the big bang which may be made at RHIC. The Color Glass Condensate is a universal form of matter which controls the high energy limit of strong interactions. Both such forms of matter might be produced and probed at RHIC.
The thermal width of heavy quarkonia moving in quark-gluon plasma
Wong, Cheuk-Yin; Song, Taesoo; Park, Yongjae; Lee, Su Houng
2008-01-01
The velocity dependence of the thermal width of heavy quarkonia traveling with respect to the quark-gluon plasma is calculated up to the NLO in perturbative QCD. At the LO, the width decreases with increasing speed, whereas at the NLO it increases with a magnitude approximately proportional to the expectation value of the relative velocity between the quarkonium and a parton in thermal equilibrium. Such an asymptotic behavior is due to the NLO dissociation cross section converging to a nonvanishing value in the high energy limit.
Gluon scattering in N=4 super-Yang-Mills theory fromweak to strong coupling
Dixon, Lance J.; /SLAC
2008-03-25
I describe some recent developments in the understanding of gluon scattering amplitudes in N = 4 super-Yang-Mills theory in the large-N{sub c} limit. These amplitudes can be computed to high orders in the weak coupling expansion, and also now at strong coupling using the AdS/CFT correspondence. They hold the promise of being solvable to all orders in the gauge coupling, with the help of techniques based on integrability. They are intimately related to expectation values for polygonal Wilson loops composed of light-like segments.
QCD Evolution of Naive-Time Quark-Gluon Correlation Functions
NASA Astrophysics Data System (ADS)
Kang, Zhong-Bo; Qiu, Jian-Wei
In this talk, we examine the existing calculations of QCD evolution kernels for the scale dependence of two sets of twist-3 quark-gluon correlation functions, Tq,F(x, x) and T(σ ){q, F}(x, x), which are the first transverse-momentum-moment of the naive-time-reversal-odd Sivers and Boer-Mulders function, respectively. The evolution kernels at the leading order in strong coupling constant αs were derived by several groups with apparent differences. We identify the sources of discrepancies and are able to reconcile the results from various groups.
Transport coefficients of Quark-Gluon Plasma in a Kinetic Theory approach
NASA Astrophysics Data System (ADS)
Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V.
2014-07-01
One of the main results of heavy ions collision at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound η/s = 1/4π for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green- Kubo relations give us an exact expression to compute these coefficients. We computed shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigated different cases of particles, for one component system (gluon matter), interacting via isotropic or anisotropic cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. Another transport coefficient of interest is the electric conductivity σel which determines the response of QGP to the electromagnetic fields present in the early stage of the collision. We study the σel dependence on microscopic details of interaction and we find also in this case that Relaxation Time Approximation is a good approximation only for isotropic cross-section.
Kaluza-Klein gluon + jets associated production at the Large Hadron Collider
NASA Astrophysics Data System (ADS)
Iyer, A. M.; Mahmoudi, F.; Manglani, N.; Sridhar, K.
2016-08-01
The Kaluza-Klein excitations of gluons offer the exciting possibility of probing bulk Randall-Sundrum (RS) models. In these bulk models either a custodial symmetry or a deformation of the metric away from AdS is invoked in order to deal with electroweak precision tests. Addressing both these models, we suggest a new channel in which to study the production of KK-gluons (gKK): one where it is produced in association with one or more hard jets. The cross-section for the gKK + jets channel is significant because of several contributing sub-processes. In particular, the 1-jet and the 2-jet associated processes are important because at these orders in QCD the qg and the gg initial states respectively come into play. We have performed a hadron-level simulation of the signal and present strategies to effectively extract the signal from what could potentially be a huge background. We present results for the kinematic reach of the LHC Run-II for different gKK masses in bulk-RS models.
Energy dependence of jet transport parameter and parton saturationin quark-gluon plasma
Casalderrey-Solana, Jorge; Wang, Xin-Nian
2007-06-24
We study the evolution and saturation of the gluondistribution function in the quark-gluon plasma as probed by apropagating parton and its effect on the computation of jet quenching ortransport parameter $\\hat q $. For thermal partons, the saturation scale$Q2_s$ is found to be proportional to the Debye screening mass $\\mu_D2$.For hard probes, evolution at small $x=Q2_s/6ET$ leads to jet energydependence of hat q. We study this dependence for both a conformal gaugetheory in weak and strong coupling limit and for (pure gluon) QCD. Theenergy dependence can be used to extract the shear viscosity $\\eta$ ofthe medium since $\\eta$ can be related to the transport parameter forthermal partons in a transport description. We also derive upper boundson the transport parameter for both energetic and thermal partons. Thelater leads to a lower bound on shear viscosity-to-entropy density ratiowhich is consistent with the conjectured lower bound $\\eta/s\\geq 1/4\\pi$.Implications on the study of jet quenching at RHIC and LHC and the bulkproperties of the dense matter are discussed.
Malheiro, M.; Dey, M.; Delfino, A.; Dey, J. |||
1997-01-01
It is known now that chiral symmetry restoration requires the meson-nucleon couplings to be density-dependent in nuclear-matter mean-field models. We further show that, quite generally, the quark and gluon condensates in medium are related to the trace of the energy-momentum tensor of nuclear matter and in these models the incompressibility K must be less than 3 times the chemical potential {mu}. In the critical density {rho}{sub c}, the gluon condensate is only reduced by 20{percent}, indicating a larger effective nucleon mass. {copyright} {ital 1997} {ital The American Physical Society}
Dai, Lingyun; Prokudin, Alexei; Kang, Zhong-Bo; Vitev, Ivan
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.
Rebyakova, V.; Strikman, M.; Zhalov, M.
2010-02-01
We argue that already the first year LHC run at {radical}(s)=7 TeV will provide a quick and effective way to test the dynamics of the color dipole-gluon interactions and the small x behavior of the gluon density in the proton by studying vector meson photoproduction in ultraperipheral proton-proton collisions.
Hirai, M.; Kumano, S.; Nagai, T.-H.
2007-12-15
Nuclear parton distribution functions (NPDFs) are determined by global analyses of experimental data on structure-function ratios F{sub 2}{sup A}/F{sub 2}{sup A'} and Drell-Yan cross-section ratios {sigma}{sub DY}{sup A}/{sigma}{sub DY}{sup A'}. The analyses are done in the leading order (LO) and next-to-leading order (NLO) of running coupling constant {alpha}{sub s}. Uncertainties of the NPDFs are estimated in both LO and NLO for finding possible NLO improvement. Valence-quark distributions are well determined, and antiquark distributions are also determined at x<0.1. However, the antiquark distributions have large uncertainties at x>0.2. Gluon modifications cannot be fixed at this stage. Although the advantage of the NLO analysis, in comparison with the LO one, is generally the sensitivity to the gluon distributions, gluon uncertainties are almost the same in the LO and NLO. It is because current scaling-violation data are not accurate enough to determine precise nuclear gluon distributions. Modifications of the PDFs in the deuteron are also discussed by including data on the proton-deuteron ratio F{sub 2}{sup D}/F{sub 2}{sup p} in the analysis. A code is provided for calculating the NPDFs and their uncertainties at given x and Q{sup 2} in the LO and NLO.
Quark-gluon plasma in the early Universe and in ultra-relativistic heavy-ion collisions
Greco, V.
2014-05-09
We briefly give an elementary introduction to the expansion of the Early Universe till when the phase transition of the quark-gluon plasma to a hadronic matter takes place. Then we describe some main element of the study of QGP by mean of ultra-relativistic heavy-ion collisions (uRHIC's)
Direct and indirect constraints on CP-violating Higgs-quark and Higgs-gluon interactions
NASA Astrophysics Data System (ADS)
Chien, Y. T.; Cirigliano, V.; Dekens, W.; de Vries, J.; Mereghetti, E.
2016-02-01
We investigate direct and indirect constraints on the complete set of anomalous CP-violating Higgs couplings to quarks and gluons originating from dimension-6 operators, by studying their signatures at the LHC and in electric dipole moments (EDMs). We show that existing uncertainties in hadronic and nuclear matrix elements have a significant impact on the interpretation of EDM experiments, and we quantify the improvements needed to fully exploit the power of EDM searches. Currently, the best bounds on the anomalous CP-violating Higgs interactions come from a combination of EDM measurements and the data from LHC Run 1. We argue that Higgs production cross section and branching ratios measurements at the LHC Run 2 will not improve the constraints significantly. On the other hand, the bounds on the couplings scale roughly linearly with EDM limits, so that future theoretical and experimental EDM developments can have a major impact in pinning down interactions of the Higgs.
Equilibration Rates in a Strongly Coupled Nonconformal Quark-Gluon Plasma.
Buchel, Alex; Heller, Michal P; Myers, Robert C
2015-06-26
We initiate the study of equilibration rates of strongly coupled quark-gluon plasmas in the absence of conformal symmetry. We primarily consider a supersymmetric mass deformation within N=2^{*} gauge theory and use holography to compute quasinormal modes of a variety of scalar operators, as well as the energy-momentum tensor. In each case, the lowest quasinormal frequency, which provides an approximate upper bound on the thermalization time, is proportional to temperature, up to a prefactor with only a mild temperature dependence. We find similar behavior in other holographic plasmas, where the model contains an additional scale beyond the temperature. Hence, our study suggests that the thermalization time is generically set by the temperature, irrespective of any other scales, in strongly coupled gauge theories.
Note on cyclic sum and combination sum of color-ordered gluon amplitudes
NASA Astrophysics Data System (ADS)
Du, Yi-Jian; Feng, Bo; Fu, Chih-Hao
2012-03-01
Continuing our previous study [22] of permutation sum of color ordered tree amplitudes of gluons, in this note, we prove the large- z behavior of their cyclic sum and the combination of cyclic and permutation sums under BCFW deformation. Unlike the permutation sum, the study of cyclic sum and the combination of cyclic and permutation sums is much more difficult. By using the generalized Bern-Carrasco-Johansson (BCJ) relation, we have proved the boundary behavior of cyclic sum with nonadjacent BCFW deformation. The proof of cyclic sum with adjacent BCFW deformation is a little bit simpler, where only Kleiss-Kuijf (KK) relations are needed. Finally we have presented a new observation for partial-ordered permutation sum and applied it to prove the boundary behavior of combination sum with cyclic and permutation.
What does low energy physics tell us about the zero momentum gluon propagator?
Costa, P.; Oliveira, O.; Silva, P. J.
2011-05-23
The connection between QCD, a nonlocal Nambu-Jona-Lasinio type model and the Landau gauge gluon propagator is explored. This two point function is parameterized by a functional form which is compatible with Dyson-Schwinger and lattice QCD results. Demanding the nonlocal model to reproduce the experimental values for the pion mass, the pion decay constant, {Gamma}{sub {pi}{yields}{gamma}{gamma}} and the light quark condensate we conclude that low energy physics does not distinguish between the so-called decoupling and scaling solutions of the Dyson-Schwinger equations. This result means that, provided that the model parameters are chosen appropriately, one is free to choose any of the above scenarios. Furthermore, the nonlocal Nambu-Jona-Lasinio quark model considered here is chiral invariant and satisfies the GMOR relation at the 1% level of precision.
Classical strongly coupled quark-gluon plasma. II. Screening and equation of state
Gelman, Boris A.; Shuryak, Edward V.; Zahed, Ismail
2006-10-15
We analyze the screening and bulk energy of a classical and strongly interacting plasma of color charges, a model we recently introduced for the description of a quark-gluon plasma at T=(1-3)T{sub c}. The partition function is organized around the Debye-Hueckel limit. The linear Debye-Hueckel limit is corrected by a virial expansion. For the pressure, the expansion is badly convergent even in the dilute limit. The nonlinear Debye-Hueckel theory is studied numerically as an alternative for moderately strong plasmas. We use the Debye theory of solid to extend the analysis to the crystal phase at very strong coupling. The analytical results for the bulk energy per particle compare well with the numerical results from molecular dynamics simulations for all couplings.
Comparison of models of critical opacity in the quark-gluon plasma
Li Xiangdong; Shakin, C.M.
2004-12-01
In this work we discuss two methods of calculation of quark propagation in the quark-gluon plasma. Both methods make use of the Nambu-Jona-Lasinio model. The essential difference of these calculations is the treatment of deconfinement. A model of confinement is not included in the work of Gastineau, Blanquier, and Aichelin (e-print hep-ph/0404207), however, the meson states they consider are still bound for temperatures greater than the deconfinement temperature T{sub c}. On the other hand, our model deals with unconfined quarks and includes a description of the qq resonances found in lattice QCD studies that make use of the maximum entropy method. We compare the qq cross sections calculated in these models.
Renormalization group evolution of multi-gluon correlators in high energy QCD
NASA Astrophysics Data System (ADS)
Dumitru, A.; Jalilian-Marian, J.; Lappi, T.; Schenke, B.; Venugopalan, R.
2011-12-01
Many-body QCD in leading high energy Regge asymptotics is described by the Balitsky-JIMWLK hierarchy of renormalization group equations for the x evolution of multi-point Wilson line correlators. These correlators are universal and ubiquitous in final states in deeply inelastic scattering and hadronic collisions. For instance, recently measured di-hadron correlations at forward rapidity in deuteron-gold collisions at the Relativistic Heavy Ion Collider (RHIC) are sensitive to four and six point correlators of Wilson lines in the small x color fields of the dense nuclear target. We evaluate these correlators numerically by solving the functional Langevin equation that describes the Balitsky-JIMWLK hierarchy. We compare the results to mean-field Gaussian and large Nc approximations used in previous phenomenological studies. We comment on the implications of our results for quantitative studies of multi-gluon final states in high energy QCD.
Higgs production via gluon fusion in k{sub T} factorisation
Hautmann, F.; Jung, H.; Pandis, V.
2011-07-15
Theoretical studies of Higgs production via gluon fusion are frequently carried out in the limit where the top quark mass is much larger than the Higgs mass, an approximation which reduces the top quark loop to an effective vertex. We present a numerical analysis of the error thus introduced by performing a Monte Carlo calculation for gg{yields}h in k{sub T}-factorisation, using the parton shower generator CASCADE. By examining both inclusive and exclusive quantities, we find that retaining the top-mass dependence results in only a small enhancement of the cross-section. We then proceed to compare CASCADE to the collinear Monte Carlos PYTHIA, MC-NLO and POWHEG.
The Two-loop Anomalous Dimension Matrix for Soft Gluon Exchange
Aybat, S.Mert; Dixon, Lance J.; Sterman, George
2006-06-27
The resummation of soft gluon exchange for QCD hard scattering requires a matrix of anomalous dimensions. We compute this matrix directly for arbitrary 2 {yields} n massless processes for the first time at two loops. Using color generator notation, we show that it is proportional to the one-loop matrix. This result reproduces all pole terms in dimensional regularization of the explicit calculations of massless 2 {yields} 2 amplitudes in the literature, and it predicts all poles at next-to-leading order in any 2 {yields} n process that has been computed at next-to-leading order. The proportionality of the one- and two-loop matrices makes possible the resummation in closed form of the next-to-next-to-leading logarithms and poles in dimensional regularization for the 2 {yields} n processes.
Quark-gluon vertex from the Landau gauge Curci-Ferrari model
NASA Astrophysics Data System (ADS)
Peláez, Marcela; Tissier, Matthieu; Wschebor, Nicolás
2015-08-01
We investigate the quark-gluon three-point correlation function within a one-loop computation performed in the Curci-Ferrari massive extension of the Faddeev-Popov gauge-fixed action. The mass term is used as a minimal way for taking into account the influence of the Gribov ambiguity. Our results, with renormalization-group improvement, are compared with lattice data. We show that the comparison is, in general, very satisfactory for the functions which are compatible with chiral symmetry, except for one. We argue that this may be due to large systematic errors when extracting this function from lattice simulations. The quantities which break chiral symmetry are more sensitive to the details of the renormalization scheme. We, however, manage to reproduce some of them with good precision. The chosen parameters allow us to simultaneously fit the quark mass function coming from the quark propagator with reasonable agreement.
The shear viscosity of a chemically equilibrating quark-gluon plasma at finite baryon density
NASA Astrophysics Data System (ADS)
Guan, Nana; Long, Jiali; Ma, Yugang; Yuan, Ying
2013-09-01
Taking account of elastic gg{\\rightarrow}gg and bremsstrahlung gg{\\leftrightarrow}ggg processes, as well as quark elastic scattering, we calculated the shear viscous coefficient of a chemically equilibrating quark-gluon plasma at finite baryon density. We found that the inelastic bremsstrahlung processes make the shear viscosity remarkably lower, and the ratio of shear viscosity to entropy density \\eta/s increases with increasing initial quark chemical potential. Considering the effect of shear viscosity the evolution of the QGP system was investigated. We found that the evolution of the system becomes slower owing to viscosity compared to the one in the ideal case, and the inelastic bremsstrahlung processes make the slower rate of the system not as much as in our previous calculations.
NASA Astrophysics Data System (ADS)
Cao, Shanshan; Luo, Tan; Qin, Guang-You; Wang, Xin-Nian
2016-07-01
A linearized Boltzmann transport (LBT) model coupled with hydrodynamical background is established to describe the evolution of jet shower partons and medium excitations in high energy heavy-ion collisions. We extend the LBT model to include both elastic and inelastic processes for light and heavy partons in the quark-gluon plasma. A hybrid model of fragmentation and coalescence is developed for the hadronization of heavy quarks. Within this framework, we investigate how heavy flavor observables depend on various ingredients, such as different energy loss and hadronization mechanisms, the momentum and temperature dependences of the transport coefficients, and the radial flow of the expanding fireball. Our model calculations show good descriptions of the D meson suppression and elliptic flow observed at the Larege Hadron Collider and the Relativistic Heavy-Ion Collider. The prediction for the Pb-Pb collisions at √{sN N}=5.02 TeV is provided.
Probing the Quark Sea and Gluons: the Electron-Ion Collider Projects
Rolf Ent
2012-04-01
EIC is the generic name for the nuclear science-driven Electron-Ion Collider presently considered in the US. Such an EIC would be the world’s first polarized electron-proton collider, and the world’s first e-A collider. Very little remains known about the dynamical basis of the structure of hadrons and nuclei in terms of the fundamental quarks and gluons of Quantum Chromodynamics (QCD). A large community effort to sharpen a compelling nuclear science case for an EIC occurred during a ten-week program taking place at the Institute for Nuclear Theory (INT) in Seattle from September 13 to November 19, 2010. The critical capabilities of a stage-I EIC are a range in center-of-mass energies from 20 to 70 GeV and variable, full polarization of electrons and light ions (the latter both longitudinal and transverse), ion species up to A=200 or so, multiple interaction regions, and a high luminosity of about 10{sup 34} electron-nucleons per cm{sup 2} and per second. The physics program of such a stage-I EIC encompass inclusive measurements (ep/A{yields}e'+X), which require detection of the scattered lepon and/or the full scattered hadronic debris with high precision, semi-inclusive processes (ep/A{yields}e'+h+X), which require detection in coincidence with the scattered lepton of at least one (current or target region) hadron; and exclusive processes (ep/A{yields}e'+N'/A'+{gamma}/m), which require detection of all particles in the reaction. The main science themes of an EIC are to i) map the spin and spatial structure of quarks and gluons in nucleons, ii) discover the collective effects of gluons in atomic nuclei, and (iii) understand the emergence of hadronic matter from color charge. In addition, there are opportunities at an EIC for fundamental symmetry and nucleon structure measurements using the electroweak probe. To truly make headway to image the sea quarks and gluons in nucleons and nuclei, the EIC needs high luminosity over a range of energies as more exclusive
Time-Dependence of the Survival Probability of Quarkonia in Quark-Gluon Plasma
NASA Astrophysics Data System (ADS)
Mah Hussin, Noor Sabrina; Shalaby, Asmaa; Petridis, Athanasios
2015-10-01
The time-dependent Schrödinger equation is used to study the formation of quarkonia and their propagation in Quark-Gluon Plasma (QGP). The initial bound (ground) state is computed using imaginary-time propagation in a confining potential. The QGP is simulated with a confining potential of an extended asymptotic freedom region. The interior of the QGP potential may correspond to a vacuum that differs from that of the exterior region. The initial state propagates through this potential in real time. The survival probability is calculated versus time for various potential parameters and relative momenta of the quarkonium by projecting the interacting wavefunction onto its freely-propagating counterpart. In these calculations the staggered-leap frog method is used with special attention paid to the issue of stability. It is found that quarkonium decay is typically non-exponential. Fast moving states decay faster. Connection with experimental results is done by means of cross-section ratios.
Higgs-gluon coupling in warped extra dimensional models with brane kinetic terms
NASA Astrophysics Data System (ADS)
Dey, Ujjal Kumar; Ray, Tirtha Sankar
2016-01-01
Warped models with the Higgs confined to the weak brane and the gauge and matter fields accessing the AdS5 bulk provide a viable setting to address the gauge hierarchy problem. Brane kinetic terms for the bulk fields are known to ease some of the tensions of these models with precision electroweak observables and flavor constraints. We study the loop-driven Higgs coupling to the gluons that are relevant to the Higgs program at the LHC, in this scenario. We demonstrate a partial cancellation in the contribution of the fermionic Kaluza-Klein (KK) towers within such framework relatively independent of the 5D parameters. The entire dependence of this coupling on the new physics arises from the mixing between the Standard Model states and the KK excitations. We find that the present precision in measurement of these couplings can lead to a constraint on the KK scale up to 1.2 TeV at 95% confidence level.
Soliton in the global color model with a sophisticated effective gluon propagator
Wang Bin; Chen Huan; Chang Lei; Liu Yuxin
2007-08-15
With a sophisticated effective gluon propagator, Maris-Tandy model, we solve the Dyson-Schwinger equation to get the quark propagator and then study the soliton solution in the global color model (GCM). Along the constraints on the parameters fitted to the pion decay constant, we take several sets of parameters and find that some of the properties of soliton can be produced in the GCM soliton model with a special choice of parameters. We also discuss the influences of the parameters and the ultraviolet perturbative term on the property of the soliton. We find that the interaction among quarks is the one with self-adjusting characteristic and only the fine-tuned interaction can generate an appropriate solition, but not that much stronger attraction produces more stable soliton.
5th International conference on Physics and Astrophysics of Quark Gluon Plasma
NASA Astrophysics Data System (ADS)
Sinha, Bikash; Alam, Jan-E.; Nayak, Tapan K.
2006-11-01
The 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2005) was held on 8 - 12 February 2005 at the Variable Energy Cyclotron Centre and Saha Institute of Nuclear Physics campus, Kolkata, India. The conference was enriched by the august presence of about 300 participants representing 18 countries across the globe. It had plenary talks and oral presentations, which form a part of these proceedings. Besides invited and contributed talks there were also a large number of poster presentations. The conference was energized by discussions of fresh experimental data from RHIC on strong elliptic flow, jet quenching, single photon spectra etc. Moreover, new theoretical results were brought to the discussion forum during this conference. Colour glass condensates, hydrodynamical flow, jet quenching and sQGP were intensely debated by the participants. The highlight of ICPAQGP 2005 was the presentation of fresh experimental results from the RHIC-IV run. The ICPAQGP series, since its inception in 1988, has placed emphasis on the role of quark matter in the fields of astrophysics and cosmology. The subsequent conferences held in 1993, 1997, 2001 and 2005 had also retained this focus. The conference was preceded by a Fest Colloquium in honour of Professor Bikash Sinha. Professor Sinha, regarded as the pioneer in establishing quark gluon plasma research in India, has successfully encouraged a group of young Indian researchers to devote themselves wholeheartedly to QGP research - both theoretical and experimental. Members of the International Advisory Committee played a pivotal role mainly in the selection of speakers. The contributions of the Organizing Committee in all aspects, from selecting the contributory talks posters down to arranging local hospitality, were much appreciated. We thank the members of both committees for making ICPAQGP 2005 an interesting platform for scientific deliberation. The ICPAQGP 2005 was supported financially by
Employment Obtaining and Business Starting
ERIC Educational Resources Information Center
Lan, Jian
2009-01-01
The implementation of business starting education in higher vocational colleges is of important and realistic meanings for cultivating advanced technology application-type talents and for releasing the employment obtaining pressure of higher vocational students. Based on the analysis on the employment situation of higher vocational graduates, this…
Obtaining Public Records: Reporter Guide
ERIC Educational Resources Information Center
Hammond, Betsy
2013-01-01
Obtaining public records is essential to covering public education. Fortunately, the law is on the side of reporters: Public agencies generally must disclose their records to the public and to the media--with important exceptions. Public agencies are often reluctant to hand over records, however, even when the law clearly says they should.…
NASA Astrophysics Data System (ADS)
Chang, Ning-Bo; Qin, Guang-You
2016-08-01
We study the evolution of the full jet shower in quark-gluon plasma by solving a set of coupled differential transport equations for the three-dimensional momentum distributions of quarks and gluons contained in full jets. In our jet evolution equations, we include all partonic splitting processes as well as the collisional energy loss and transverse momentum broadening for both the leading and radiated partons of the full jets. Combining with a realistic (2 +1 )-dimensional viscous hydrodynamic simulation for the spacetime profiles of the hot and dense nuclear medium produced in heavy-ion collisions, we apply our formalism to calculate the nuclear modification of single inclusive full jet spectra, the momentum imbalance of photon-jet and dijet pairs, and the jet shape function (at partonic level) in Pb+Pb collisions at 2.76 A TeV. The roles of various jet-medium interaction mechanisms on the full jet modification are studied. We find that the nuclear modification of jet shape is sensitive to the interplay of different interaction mechanisms as well as the energies of the full jets.
Uncertainties in determining parton distributions at large x
Alberto Accardi, Wolodymyr Melnitchouk, Jeff Owens, Michael Christy, Cynthia Keppel, Lingyan Zhu, Jorge Morfin
2011-07-01
We critically examine uncertainties in parton distribution functions (PDFs) at large x arising from nuclear effects in deuterium F2 structure function data. Within a global PDF analysis, we assess the impact on the PDFs from uncertainties in the deuteron wave function at short distances and nucleon off-shell effects, the use of relativistic kinematics, as well as the use of less a restrictive parametrization of the d/u ratio. We find that in particular the d-quark and gluon PDFs vary significantly with the choice of nuclear model. We highlight the impact of these uncertainties on the determination of the neutron structure function, and on W boson production and parton luminosity at the Tevatron and the LHC. Finally, we discuss prospects for new measurements sensitive to the d-quark and gluon distributions but insensitive to nuclear corrections.
Adare, A.; Awes, Terry C; Cianciolo, Vince; Enokizono, Akitomo; Read Jr, Kenneth F; Silvermyr, David O; Sorensen, Soren P; Stankus, Paul W; Young, Glenn R; PHENIX, Collaboration
2009-01-01
The double helicity asymmetry in neutral pion production for p{sub T} = 1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, {Delta}G, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of {mu}{sup 2} = 4 GeV{sup 2} a next to leading order QCD analysis gives {Delta}G{sup [0.02,0.3]} = 0.2, with a constraint of -0.7 < {Delta}G{sup [0.02,0.3]} < 0.5 at {Delta}{chi}{sup 2} = 9 (-3{sigma}) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the {Delta}G constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.
QCD sum rule calculation of quark-gluon three-body components in the B-meson wave function
NASA Astrophysics Data System (ADS)
Nishikawa, Tetsuo; Tanaka, Kazuhiro
2011-10-01
We discuss the QCD sum rule calculation of the heavy-quark effective theory parameters λE and λH, which represent quark-gluon three-body components in the B-meson wave function. We update the sum rules for λE,H calculating the new higher-order contributions to the operator product expansion for the corresponding correlator, i.e., the order αs radiative corrections to the Wilson coefficients associated with the dimension-5 quark-gluon mixed condensate, and the power corrections due to the dimension-6 vacuum condensates. We find that the new radiative corrections significantly improve stability of the corresponding Borel sum rules, modifying the values of λE,H.
Impact factor for gluon production in multi-Regge kinematics in the next-to-leading order
Kozlov, M. G. Reznichenko, A. V. Fadin, V. S.
2012-07-15
The one-loop correction to the impact factor for gluon production upon the transition of a one-Reggeon state in the t channel to a two-Reggeon state is found. This impact factor is an element of multiparticle amplitudes in multi-Regge kinematics. The correction in question is necessary for developing the theory of Regge and multi-Regge processes. In particular, it is necessary for proving the multi-Regge form of the amplitude in the next-to-leading-logarithm approximation. This correction also makes it possible to complete the verification of the last of the unproven bootstrap conditions for gluon Reggeization and to prove, in this approximation, the validity of the multi-Regge form of the amplitude. All necessary calculations are presented, and an explicit expression for the impact factor in front of all possible color states in the t channel is given.
QCD sum rule calculation of quark-gluon three-body components in the B-meson wave function
Nishikawa, Tetsuo; Tanaka, Kazuhiro
2011-10-21
We discuss the QCD sum rule calculation of the heavy-quark effective theory parameters {lambda}{sub E} and {lambda}{sub H}, which represent quark-gluon three-body components in the B-meson wave function. We update the sum rules for {lambda}{sub E,H} calculating the new higher-order contributions to the operator product expansion for the corresponding correlator, i.e., the order {alpha}{sub s} radiative corrections to the Wilson coefficients associated with the dimension-5 quark-gluon mixed condensate, and the power corrections due to the dimension-6 vacuum condensates. We find that the new radiative corrections significantly improve stability of the corresponding Borel sum rules, modifying the values of {lambda}{sub E,H}.
Kang, Hyejoo
2002-01-30
We present production measurements of the charged hadrons {pi}{sup {+-}}, K{sup {+-}} and p/{bar p} in e{sup +}e{sup -} interactions at the Z{sup 0} pole. The excellent particle identification capability of the SLC Large Detector (SLD) at the Stanford Linear Collider (SLC) are used. In addition to studies over a wide momentum range in hadronic Z{sup 0} events of all five flavors, we have made the most precise measurements in light (uds), c and b flavor events separately. Unambiguous flavor dependencies have been observed, and the results have been compared with the predictions of several QCD fragmentation models. We have also exploited the unique feature of electron beam polarization in our experiment to compare hadron production separately in quark and antiquark jets. Direct evidence that higher momentum hadrons are more likely to contain the primary quark and antiquark is seen, with precision sufficient to provide new model tests. Finally, we have studied hard gluon jets in detail. We have confirmed that gluon jets have a higher multiplicity of softer particles than light quark jets, and found this enhancement to be the same for {pi}{sup {+-}}, K{sup {+-}} and p/{bar p} at the few percent level at all momenta. Any overall difference in the hadron fractions is limited to 0.018 at the 95% confidence level, indicating that there are no differences at the hadronization stage in jet formation between gluons and quarks.
Xu Zhe; Greiner, Carsten
2005-06-01
We develop a new 3 + 1 dimensional Monte Carlo cascade solving the kinetic on-shell Boltzmann equations for partons including the inelastic gg{r_reversible}ggg pQCD processes. The back reaction channel is treated - for the first time - fully consistently within this scheme. An extended stochastic method is used to solve the collision integral. The frame dependence and convergency are studied for a fixed tube with thermal initial conditions. The detailed numerical analysis shows that the stochastic method is fully covariant and that convergency is achieved more efficiently than within a standard geometrical formulation of the collision term, especially for high gluon interaction rates. The cascade is then applied to simulate parton evolution and to investigate thermalization of gluons for a central Au+Au collision at RHIC energy. For this study the initial conditions are assumed to be generated by independent minijets with p{sub T}>p{sub 0}=2 GeV. With that choice it is demonstrated that overall kinetic equilibration is driven mainly by the inelastic processes and is achieved on a scale of 1 fm/c. The further evolution of the expanding gluonic matter in the central region then shows almost an ideal hydrodynamical behavior. In addition, full chemical equilibration of the gluons follows on a longer time scale of about 3 fm/c.
Shear viscosity of the quark-gluon plasma in a kinetic theory approach
Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V.
2014-05-09
One of the main results of heavy ions collision (HIC) at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound η/s=1/4π for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green-Kubo relations give us an exact expression to compute these coefficients. We compute shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigate a system of particles interacting via anisotropic and energy dependent cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. The correct analytic formula for shear viscosity can be used to develop a transport theory with a fixed η/s and have a comparison with physical observables like elliptic flow.
Heller, Michal P; Janik, Romuald A; Spaliński, Michał; Witaszczyk, Przemysław
2014-12-31
Relativistic hydrodynamics simulations of quark-gluon plasma play a pivotal role in our understanding of heavy ion collisions at RHIC and LHC. They are based on a phenomenological description due to Müller, Israel, Stewart (MIS) and others, which incorporates viscous effects and ensures a well-posed initial value problem. Focusing on the case of conformal plasma we propose a generalization which includes, in addition, the dynamics of the least damped far-from-equilibrium degree of freedom found in strongly coupled plasmas through the AdS/CFT correspondence. We formulate new evolution equations for general flows and then test them in the case of N=4 super Yang-Mills plasma by comparing their solutions alongside solutions of MIS theory with numerical computations of isotropization and boost-invariant flow based on holography. In these tests the new equations reproduce the results of MIS theory when initialized close to the hydrodynamic stage of evolution, but give a more accurate description of the dynamics when initial conditions are set in the preequilibrium regime.
Shear viscosity of the quark-gluon plasma in a kinetic theory approach
NASA Astrophysics Data System (ADS)
Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V.
2014-05-01
One of the main results of heavy ions collision (HIC) at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound η/s=1/4π for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green-Kubo relations give us an exact expression to compute these coefficients. We compute shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigate a system of particles interacting via anisotropic and energy dependent cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. The correct analytic formula for shear viscosity can be used to develop a transport theory with a fixed η/s and have a comparison with physical observables like elliptic flow.
Hadron production in relativistic heavy ion interactions and the search for the quark-gluon plasma
Tannenbaum, M.J.
1989-12-01
The course starts with an introduction, from the experimentalist's point of view, of the challenge of measuring Relativistic Heavy Ion interactions. A review of some theoretical predictions for the expected signatures of the quark gluon plasma will be made, with a purpose to understand how they relate to quantities which may be experimentally measured. A short exposition of experimental techniques and details is given including charged particles in matter, momentum resolution, kinematics and Lorentz Transformations, calorimetry. Principles of particle identification including magnetic spectrometers, time of flight measurement. Illustrations using the E802 spectrometer and other measured results. Resolution smearing of spectra, and binning effects. Parent to daughter effects in decay, with {pi}{sup 0} {yields} {gamma} {gamma} as an example. The experimental situation from the known data in p -- p collisions and proton-nucleus reactions is reviewed and used as a basis for further discussions. The Cronin Effect'' and the Seagull Effect'' being two arcana worth noting. Then, selected experiments from the BNL and CERN heavy ion programs are discussed in detail. 118 refs., 45 figs.
A rotation/magnetism analogy for the quark-gluon plasma
NASA Astrophysics Data System (ADS)
McInnes, Brett
2016-10-01
In peripheral heavy ion collisions, the Quark-Gluon Plasma that may be formed often has a large angular momentum per unit energy. This angular momentum may take the form of (local) rotation. In many physical systems, rotation can have effects analogous to those produced by a magnetic field; thus, there is a risk that the effects of local rotation in the QGP might be mistaken for those of the large genuine magnetic fields which are also known to arise in these systems. Here we use the gauge-gravity duality to investigate this, and we find indeed that, with realistic parameter values, local rotation has effects on the QGP (at high values of the baryonic chemical potential) which are not only of the same kind as those produced by magnetic fields, but which can in fact be substantially larger. Furthermore, the combined effect of rotation and magnetism is to change the shape of the main quark matter phase transition line in an interesting way, reducing the magnitude of its curvature; again, local rotation contributes to this phenomenon at least as strongly as magnetism.
Debye Layers in Plasmas Generalized to Hadron Confinement of Nuclei and Quark-Gluon-Plasmas
NASA Astrophysics Data System (ADS)
Hora, Heinrich; Miley, George H.
2005-10-01
. A new theory for the nuclear forces for confining the hadrons in a nucleus has been derived from a generalization of the Debye layer as known from the plasma ablation at laser irradiation where the temperature is substituted by the Fermi energy of the nucleons [1]. The first convincing proof is by using the empirical density of the nucleons defining their Fermi energy to arrive at a Debye length of about 3 fm as measured by Hofstadter for the decay of the nucleon density at the surface of heavy nuclei. This decay is interpreted as Wigner scattering and the Goos-Haenchen effect. With the same steps of substitutions, the surface energy of nuclei is always too small against the nucleon enthalpy to confine the hadrons until the density reaches such high values reproducing the empirical known radii of nuclei. By this way nuclei are possible only until uranium or curium by a Boltzmann equilibrium process explaining the endothermic generation of heavy nuclei in the Universe [2]. At and about six times higher nucleon density, the Fermi statistics changes into its relativistic branch excluding nucleation in neutron stars and explaining the quark-gluon plasma. [1] Edward Teller Lectures, H. Hora and G.H. Miley eds. (Imperial College Press London 2005) p. 103. [2] H. Hora, G.H. Miley, F. Osman, Astrophysics and Space Science, 298, 247 (2005)
ConnesFusionTensorProduct/Photon GluonFusion in Mitochondria
NASA Astrophysics Data System (ADS)
Wh-Maksoed, Prodi Of Physics Ui, Depok 16415-Indonesia; Ssi, Wh-Maksoed
2016-05-01
As in AJ Wassermann distinguished of classical invariant theory & quantum invariant theory subfactor, in S. Palcoux:``From Neveu-Schwarz Subfactors & Connes Fusion'' described the subfactor theory & Witt-algebra whereas Andreas Thom's explanation about ConnesFusionTensorProduct/CFTP related Connes fusion to composition of homomorphism (i). classical tensor product O-X adds the changes,(ii). Relative tensor product H-X preserve the changes. For photonGluonFusion/PGF defined:''photon is the gauge boson of QED, the simplest of all boson'' devotes to CFT as ``quantum field theory which are invariant under conformal transformation & in 2D there are infinite dimensional algebra. Alain Connes states theirselves Connes fusion as ``associative tensor operation'' to be in coincidences with ``their dynamic behavior driven by the balance in mitochondrial fusion & fission (Carveney, 2007) from Peter Alexander Williams: ``Retinal neuronal remodeling in a model of Optic Atrophy'', Dec, 2011. Great acknowledged to the VicePresident of the R.I, HE.Mr. Drs. M. JUSUF KALLA.
NASA Astrophysics Data System (ADS)
Heller, Michal P.; Janik, Romuald A.; Spaliński, Michał; Witaszczyk, Przemysław
2014-12-01
Relativistic hydrodynamics simulations of quark-gluon plasma play a pivotal role in our understanding of heavy ion collisions at RHIC and LHC. They are based on a phenomenological description due to Müller, Israel, Stewart (MIS) and others, which incorporates viscous effects and ensures a well-posed initial value problem. Focusing on the case of conformal plasma we propose a generalization which includes, in addition, the dynamics of the least damped far-from-equilibrium degree of freedom found in strongly coupled plasmas through the AdS/CFT correspondence. We formulate new evolution equations for general flows and then test them in the case of N =4 super Yang-Mills plasma by comparing their solutions alongside solutions of MIS theory with numerical computations of isotropization and boost-invariant flow based on holography. In these tests the new equations reproduce the results of MIS theory when initialized close to the hydrodynamic stage of evolution, but give a more accurate description of the dynamics when initial conditions are set in the preequilibrium regime.
Perturbative and nonperturbative aspects of jet quenching in near-critical quark-gluon plasmas
NASA Astrophysics Data System (ADS)
Xu, Jiechen
In this thesis, we construct two QCD based energy loss models to perform quantitative analysis of jet quenching observables in ultra-relativistic nucleus-nucleus collisions at RHIC and the LHC. We first build up a perturbative QCD based CUJET2.0 jet flavor tomography model that couples the dynamical running coupling DGLV opacity series to bulk data constrained relativistic viscous hydrodynamic backgrounds. It solves the strong heavy quark energy loss puzzle at RHIC and explains the surprising transparency of the quark-gluon plasma (QGP) at the LHC. The observed azimuthal anisotropy of hard leading hadrons requires a path dependent jet-medium coupling in CUJET2.0 that implies physics of nonperturbative origin. To explore the nonperturbative chromo-electric and chromo-magnetic structure of the strongly-coupled QGP through jet probes, we build up a new CUJET3.0 framework that includes in CUJET2.0 both Polyakov loop suppressed semi-QGP chromo-electric charges and emergent chromo-magnetic monopoles in the critical transition regime. CUJET3.0 quantitatively describes the anisotropic hadron suppression at RHIC and the LHC. More significantly, it provides a robust connection between the long wavelength ``perfect fluidity'' of the QGP and the short distance jet transport in the QGP. This framework paves the way for ``measuring'' both perturbative and nonperturbative properties of the QGP, and more importantly for probing color confinement through jet quenching.
NASA Astrophysics Data System (ADS)
Petersen, Hannah
2012-03-01
Recent measurements of higher order flow coefficients offer a more complete understanding of how hot and dense QCD matter is created in relativistic heavy ion collisions and what its properties are. In addition to providing new constraints on the viscosity of the quark gluon plasma, anisotropic flow is sensitive to the structure of the initial state. As elliptic flow (v2) is generated by the difference in pressure gradients that result from the initial almond shape of the reaction region in non-central collisions, higher order coefficients encode more detailed information about the event-by-event fluctuating initial state profile. In my talk, I will present an overview of theoretical work aimed at understanding the correlations between initial state structures and final state correlations and their origin and discuss the current status of initial state models. I will outline how the new experimental findings at RHIC and LHC can be used towards characterize the dynamical evolution of relativistic heavy ion collisions with special emphasis on the role of event-by-event approaches and sophisticated multi-parameter fits to achieve this goal.
Gluon effects on the equation of state of color superconducting strange stars
NASA Astrophysics Data System (ADS)
Ferrer, E. J.; de la Incera, V.; Paulucci, L.
2015-08-01
Compact astrophysical objects are a window for the study of strongly interacting nuclear matter given the conditions in their interiors, which are not reproduced in a laboratory environment. Much has been debated about their composition with possibilities ranging from a simple mixture of mostly protons and neutrons to deconfined quark matter. Recent observations on the mass of two pulsars, PSR J 1614 -2230 and PSR J 0348 +0432 , have posed a great restriction on their composition, since the equation of state must be hard enough to support masses of about at least two solar masses. The onset of quarks tends to soften the equation of state, but it can get substantially stiffer since in the high-dense medium a repulsive vector interaction channel is opened. Nevertheless, we show that once gluon effects are considered, the equation of state of strange stars formed by quark matter in the color-flavor-locked (CFL) phase of color superconductivity becomes softer decreasing the maximum stellar mass that can be reached. This may indicate that strange stars made entirely of CFL matter can only be favored if other interactions, as the one corresponding to the vector channel, are taken into consideration and are large enough.
How to measure the size of the quark-gluon plasma? And why is it important?
NASA Astrophysics Data System (ADS)
Kisiel, Adam
2015-09-01
Heavy-ions are brought to ultrarelativistic energies in dedicated accelerators. When the ions collide, a system is produced with high temperature and energy density. Its size is initially comparable to the size of a nucleus. Theory predicts that a deconfined state of matter - a Quark-Gluon Plasma is produced in these conditions. However such description implicitly uses thermodynamic properties, such as temperature, chemical potentials etc. In physics such quantities are usually defined only for "large" systems. A question of the actual size of the system in the heavy-ion collision then becomes crucial. A methodology based on two-particle correlations, called "femtoscopy" is used to measure this size. In this work we briefly describe the technique, which is based on the quantum mechanical properties of particle pairs. We discuss examples of correlation functions and describe a procedure of extracting the "femtoscopic radii". We show selected recent experimental results for these radii. We also give the theoretical interpretation and consequences for the model description of the heavy-ion collision evolution.
Physic of the nucleon sea quark distributions
NASA Astrophysics Data System (ADS)
Vogt, R.
Sea quark distributions in the nucleon have naively been expected to be generated perturbatively by gluon splitting. In this case, there is no reason for the light quark and anti-quark sea distributions to be different. No asymmetries in the strange or heavy quark sea distributions are predicted in the improved parton model. However, recent experiments have called these naive expectations into question. A violation of the Gottfried sum rule has been measured in several experiments, suggesting that overlineu < overlined in the proton. Additionally, other measurements, while not definitive, show that there may be an asymmetry in the strange and anti-strange quark sea distributions. These effects may require nonperturbative explanations. In this review we first discuss the perturbative aspects of the sea quark distributions. We then describe the experiments that could point to nonperturbative contributions to the nucleon sea. Current phenomenological models that could explain some of these effects are reviewed.
Physics of the nucleon sea quark distributions
Vogt, R.
2000-03-10
Sea quark distributions in the nucleon have naively been expected to be generated perturbatively by gluon splitting. In this case, there is no reason for the light quark and anti-quark sea distributions to be different. No asymmetries in the strange or heavy quark sea distributions are predicted in the improved parton model. However,recent experiments have called these naive expectations into question. A violation of the Gottfried sum rule has been measured in several experiments, suggesting that (bar u) < (bar d) in the proton. Additionally, other measurements, while not definitive, show that there may be an asymmetry in the strange and anti-strange quark sea distributions. These effects may require nonperturbative explanations. In this review we first discuss the perturbative aspects of the sea quark distributions. We then describe the experiments that could point to nonperturbative contributions to the nucleon sea. Current phenomenological models that could explain some of these effects are reviewed.
Gluon and charm content of the {eta}{sup {prime}} meson and instantons
Shuryak, E.V. |; Zhitnitsky, A.R. |
1998-02-01
Motivated by recent CLEO measurements of the B{r_arrow}{eta}{sup {prime}}K decay, we evaluate the gluon and charm content of the {eta}{sup {prime}} meson using the interacting instanton liquid model of the QCD vacuum. Our main result is {l_angle}0{vert_bar}g{sup 3}f{sup abc}G{sub {mu}{nu}}{sup a}{tilde G}{sub {nu}{alpha}}{sup b}G{sub {alpha}{mu}}{sup c}{vert_bar}{eta}{sup {prime}}{r_angle}={minus}(2.3{endash}3.3) GeV{sup 2}{times}{l_angle}0{vert_bar}g{sup 2}G{sub {mu}{nu}}{sup a}{tilde G}{sub {mu}{nu}}{sup a}{vert_bar}{eta}{sup {prime}}{r_angle}. It is very large due to the strong field of small-size instantons. We show that it provides quantitative explanations of the CLEO data on the B{r_arrow}{eta}{sup {prime}}K decay rate (as well as the inclusive process B{r_arrow}{eta}{sup {prime}}+X), via a virtual Cabibbo-unsuppressed decay into a {bar c}c pair which then becomes {eta}{sup {prime}}. If so, a significant charm component may be present in other hadrons also: We briefly discuss the contribution of the charmed quark to the {ital polarized} deep-inelastic scattering on a proton. {copyright} {ital 1998} {ital The American Physical Society}
Obtaining information by dynamic (effortful) touching
Turvey, M. T.; Carello, Claudia
2011-01-01
Dynamic touching is effortful touching. It entails deformation of muscles and fascia and activation of the embedded mechanoreceptors, as when an object is supported and moved by the body. It is realized as exploratory activities that can vary widely in spatial and temporal extents (a momentary heft, an extended walk). Research has revealed the potential of dynamic touching for obtaining non-visual information about the body (e.g. limb orientation), attachments to the body (e.g. an object's height and width) and the relation of the body both to attachments (e.g. hand's location on a grasped object) and surrounding surfaces (e.g. places and their distances). Invariants over the exploratory activity (e.g. moments of a wielded object's mass distribution) seem to ground this ‘information about’. The conception of a haptic medium as a nested tensegrity structure has been proposed to express the obtained information realized by myofascia deformation, by its invariants and transformations. The tensegrity proposal rationalizes the relative indifference of dynamic touch to the site of mechanical contact (hand, foot, torso or probe) and the overtness of exploratory activity. It also provides a framework for dynamic touching's fractal nature, and the finding that its degree of fractality may matter to its accomplishments. PMID:21969694
Obtaining information by dynamic (effortful) touching.
Turvey, M T; Carello, Claudia
2011-11-12
Dynamic touching is effortful touching. It entails deformation of muscles and fascia and activation of the embedded mechanoreceptors, as when an object is supported and moved by the body. It is realized as exploratory activities that can vary widely in spatial and temporal extents (a momentary heft, an extended walk). Research has revealed the potential of dynamic touching for obtaining non-visual information about the body (e.g. limb orientation), attachments to the body (e.g. an object's height and width) and the relation of the body both to attachments (e.g. hand's location on a grasped object) and surrounding surfaces (e.g. places and their distances). Invariants over the exploratory activity (e.g. moments of a wielded object's mass distribution) seem to ground this 'information about'. The conception of a haptic medium as a nested tensegrity structure has been proposed to express the obtained information realized by myofascia deformation, by its invariants and transformations. The tensegrity proposal rationalizes the relative indifference of dynamic touch to the site of mechanical contact (hand, foot, torso or probe) and the overtness of exploratory activity. It also provides a framework for dynamic touching's fractal nature, and the finding that its degree of fractality may matter to its accomplishments. PMID:21969694
Dai, Ling -Yun; Kang, Zhong -Bo; Prokudin, Alexei; Vitev, Ivan
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}^{2}α_{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 order 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.
Dai, Ling -Yun; Kang, Zhong -Bo; Prokudin, Alexei; Vitev, Ivan
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(αem2αs), 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 order calculation for themore » 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
Parton distributions with threshold resummation
NASA Astrophysics Data System (ADS)
Bonvini, Marco; Marzani, Simone; Rojo, Juan; Rottoli, Luca; Ubiali, Maria; Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Hartland, Nathan P.
2015-09-01
We construct a set of parton distribution functions (PDFs) in which fixed-order NLO and NNLO calculations are supplemented with soft-gluon (threshold) resummation up to NLL and NNLL accuracy respectively, suitable for use in conjunction with any QCD calculation in which threshold resummation is included at the level of partonic cross sections. These resummed PDF sets, based on the NNPDF3.0 analysis, are extracted from deep-inelastic scattering, Drell-Yan, and top quark pair production data, for which resummed calculations can be consistently used. We find that, close to threshold, the inclusion of resummed PDFs can partially compensate the enhancement in resummed matrix elements, leading to resummed hadronic cross-sections closer to the fixed-order calculations. On the other hand, far from threshold, resummed PDFs reduce to their fixed-order counterparts. Our results demonstrate the need for a consistent use of resummed PDFs in resummed calculations.
Higgs boson gluon-fusion production beyond threshold in N^{3}LO QCD
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard
2015-03-18
In this study, we compute the gluon fusion Higgs boson cross-section at N^{3}LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N^{3}LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N^{3}LO in perturbative QCD.
NASA Astrophysics Data System (ADS)
Kumar, Yogesh; Singh, S. Somorendro
2016-07-01
We extend the previous study of dilepton production using [S. Somorendro Singh and Y. Kumar, Can. J. Phys. 92 (2014) 31] based on a simple quasiparticle model of quark-gluon plasma (QGP). In this model, finite value of quark mass uses temperature dependent chemical potential the so-called Temperature Dependent Chemical Potential Quark Mass (TDCPQM). We calculate dilepton production in the relevant range of mass region. It is observed that the production rate is marginally enhanced from the earlier work. This is due to the effect of TDCPQM and its effect is highly significant in the production of dilepton.
SYSTEMATIC STUDIES OF HEAVY ION COLLISIONS TO SEARCH FOR QUARK-GLUON PLASMA
Fuqiang Wang
2007-11-29
This is the final technical report for DOE Outstanding Junior Investigator (OJI) Award, 'Systematic Studies of Heavy Ion Collisions to Search for Quark-Gluon Plasma', grant DE-FG02-02ER41219, Principal Investigator (PI) Fuqiang Wang. The research under the grant was divided into two phases. The first concentrated on systematic studies of soft hadron production at low transverse momentum (p{sub T}), in particular the production of (anti-)baryon and strangeness in heavy ion collisions at RHIC energies. The second concentrated on measurements of di-hadron and multi-hadron jet-correlations and investigations of medium response to jets. The research was conducted at the Relativistic Heavy-Ion Collider (RHIC) at BNL with the Solenoidal Tracker At RHIC (STAR) experiment. The total grant is $214,000. The grant established a PC farm solely used for this research. The PC farm consists of 8 nodes with a total of 16 CPUs and 3 disk servers of total 2 TB shared storage. The current balance of the grant is $19,985. The positive balance is because an initial purchase of $22,600 for the PC farm came out of the PI's start-up fund due to the lateness of the award. The PC farm is an integral part of the Purdue Physics Department's computer cluster. The grant supported two Ph.D. graduate students. Levente Molnar was supported from July 2002 to December 2003, and worked on soft hadron production. His thesis title is Systematics of Identified Particle Production in pp, d-Au and Au-Au Collisions at RHIC Energies. He graduated in 2006 and now is a Postdoctoral fellow at INFN Sezione di Bari, Italy working on the ALICE experiment at the LHC. Jason Ulery was supported from January 2004 to July 2007. His thesis title is Two- and Three-Particle Jet-Like Correlations. He defended his thesis in October 2007 and is moving to Frankfurt University, Germany to work on the ALICE experiment at the LHC. The research by this grant resulted in 7 journal publications (2 PRL, 1 PLB, 1 PRC, 2 submitted and
Testing the case for the creation of a strongly interacting quark gluon plasma at RHIC
NASA Astrophysics Data System (ADS)
Adil, Azfar
Recent data from the Relativistic Heavy Ion Collider (RHIC) has provided information regarding the creation of dense QCD matter in Heavy Ion Collisions (HIC). Two of the most puzzling issues raised are; (1) models using ideal hydrodynamics to describe bulk evolution have met with great success in reproducing data in HIC at RHIC, and (2) the recent data detailing the production of non-photonic electrons from heavy meson decays has shown a large quenching of heavy quark jets that is not explained by radiative energy loss calculations. These two surprising results lend credence to the claim that a Strongly Coupled Quark Gluon Plasma (sQGP) has been created at RHIC; with the strong coupling characteristics providing both the low viscosity needed by (1) and the large momentum transfers needed by (2). In order to properly quantify this, one needs to get a better understanding of the detailes of jet tomography so that one can truly adjudicate the need for sQGP creation. We consider the theoretical uncertainties stemming from the Poisson convolution assumption in energy loss calculations. We examine two different ways to account for the leakage of probabilities into unphysical regions and show that the evolution of the nuclear modification factor, RAA, with center of mass energy is sensitive to these differences. The success of ideal hydrodynamics in describing the evolution of bulk matter in the QGP phase is dependent on the choice of initial state that is fed into the evolution equations. The Participant Brodsk-Gunion-Kuhn initial conditions lead to a good agreement with the data while initial states inspired by Color Glass Condensate (CGC) models overestimate the data and seem to imply the need for viscous dissipative corrections to the dynamics. We propose 3D jet tomography as a probe to experimentally differentiate between the BGK and CGC initial state models. We find and induced non zero directed flow vl in the high p⊥ spectra in both BGK and CGC models that can be
Search for a heavy vector boson decaying to two gluons in pp̄ collisions at √s=1.96 TeV
Aaltonen, T.; Adelman, J.; Álvarez González, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; et al
2012-12-05
We present a search for a new heavy vector boson Z' that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of Z'→g*g. We study the case where the off-shell gluon g* converts to a pair of top quarks, leading to a final state of tt¯g. In a sample of events with exactly one charged lepton, large missing transverse momentum and at least five jets, corresponding to an integrated luminosity of 8.7 fb⁻¹ collected by the CDF II detector, we find the data to be consistent with the standard model. We set upper limitsmore » on the production cross section times branching ratio of this chromophilic Z' at 95% confidence level from 300 to 40 fb for Z' masses ranging from 400 to 1000 GeV/c², respectively.« less
Search for a heavy vector boson decaying to two gluons in pp̄ collisions at √s=1.96 TeV
Aaltonen, T.; Adelman, J.; Álvarez González, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; Arisawa, T.; Artikov, A.; Asaadi, J.; Ashmanskas, W.; Auerbach, B.; Aurisano, A.; Azfar, F.; Badgett, W.; Bae, T.; Barbaro-Galtieri, A.; Barnes, V. E.; Barnett, B. A.; Barria, P.; Bartos, P.; Bauce, M.; Bedeschi, F.; Behari, S.; Bellettini, G.; Bellinger, J.; Benjamin, D.; Beretvas, A.; Bhatti, A.; Bisello, D.; Bizjak, I.; Bland, K. R.; Blumenfeld, B.; Bocci, A.; Bodek, A.; Bortoletto, D.; Boudreau, J.; Boveia, A.; Brigliadori, L.; Bromberg, C.; Brucken, E.; Budagov, J.; Budd, H. S.; Burkett, K.; Busetto, G.; Bussey, P.; Buzatu, A.; Calamba, A.; Calancha, C.; Camarda, S.; Campanelli, M.; Campbell, M.; Canelli, F.; Carls, B.; Carlsmith, D.; Carosi, R.; Carrillo, S.; Carron, S.; Casal, B.; Casarsa, M.; Castro, A.; Catastini, P.; Cauz, D.; Cavaliere, V.; Cavalli-Sforza, M.; Cerri, A.; Cerrito, L.; Chen, Y. C.; Chertok, M.; Chiarelli, G.; Chlachidze, G.; Chlebana, F.; Cho, K.; Chokheli, D.; Chung, W. H.; Chung, Y. S.; Ciocci, M. A.; Clark, A.; Clarke, C.; Compostella, G.; Convery, M. E.; Conway, J.; Corbo, M.; Cordelli, M.; Cox, C. A.; Cox, D. J.; Crescioli, F.; Cuevas, J.; Culbertson, R.; Dagenhart, D.; d’Ascenzo, N.; Datta, M.; de Barbaro, P.; Dell’Orso, M.; Demortier, L.; Deninno, M.; Devoto, F.; d’Errico, M.; Di Canto, A.; Di Ruzza, B.; Dittmann, J. R.; D’Onofrio, M.; Donati, S.; Dong, P.; Dorigo, M.; Dorigo, T.; Ebina, K.; Elagin, A.; Eppig, A.; Erbacher, R.; Errede, S.; Ershaidat, N.; Eusebi, R.; Farrington, S.; Feindt, M.; Fernandez, J. P.; Field, R.; Flanagan, G.; Forrest, R.; Frank, M. J.; Franklin, M.; Freeman, J. C.; Funakoshi, Y.; Furic, I.; Gallinaro, M.; Garcia, J. E.; Garfinkel, A. F.; Garosi, P.; Gerberich, H.; Gerchtein, E.; Giagu, S.; Giakoumopoulou, V.; Giannetti, P.; Gibson, K.; Ginsburg, C. M.; Giokaris, N.; Giromini, P.; Giurgiu, G.; Glagolev, V.; Glenzinski, D.; Gold, M.; Goldin, D.; Goldschmidt, N.; Golossanov, A.; Gomez, G.; Gomez-Ceballos, G.; Goncharov, M.; González, O.; Gorelov, I.; Goshaw, A. T.; Goulianos, K.; Grinstein, S.; Grosso-Pilcher, C.; Group, R. C.; Guimaraes da Costa, J.; Hahn, S. R.; Halkiadakis, E.; Hamaguchi, A.; Han, J. Y.; Happacher, F.; Hara, K.; Hare, D.; Hare, M.; Harr, R. F.; Hatakeyama, K.; Hays, C.; Heck, M.; Heinrich, J.; Herndon, M.; Hewamanage, S.; Hocker, A.; Hopkins, W.; Horn, D.; Hou, S.; Hughes, R. E.; Hurwitz, M.; Husemann, U.; Hussain, N.; Hussein, M.; Huston, J.; Introzzi, G.; Iori, M.; Ivanov, A.; James, E.; Jang, D.; Jayatilaka, B.; Jeon, E. J.; Jindariani, S.; Jones, M.; Joo, K. K.; Jun, S. Y.; Junk, T. R.; Kamon, T.; Karchin, P. E.; Kasmi, A.; Kato, Y.; Ketchum, W.; Keung, J.; Khader, M.; Khotilovich, V.; Kilminster, B.; Kim, D. H.; Kim, H. S.; Kim, J. E.; Kim, M. J.; Kim, S. B.; Kim, S. H.; Kim, Y. K.; Kim, Y. J.; Kimura, N.; Kirby, M.; Klimenko, S.; Knoepfel, K.; Kondo, K.; Kong, D. J.; Konigsberg, J.; Kotwal, A. V.; Kreps, M.; Kroll, J.; Krop, D.; Kruse, M.; Krutelyov, V.; Kuhr, T.; Kurata, M.; Kwang, S.; Laasanen, A. T.; Lami, S.; Lammel, S.; Lancaster, M.; Lander, R. L.; Lannon, K.; Lath, A.; Latino, G.; LeCompte, T.; Lee, E.; Lee, H. S.; Lee, J. S.; Lee, S. W.; Leo, S.; Leone, S.; Lewis, J. D.; Limosani, A.; Lin, C.-J.; Lindgren, M.; Lipeles, E.; Lister, A.; Litvintsev, D. O.; Liu, C.; Liu, H.; Liu, Q.; Liu, T.; Lockwitz, S.; Loginov, A.; Lucchesi, D.; Lueck, J.; Lujan, P.; Lukens, P.; Lungu, G.; Lys, J.; Lysak, R.; Madrak, R.; Maeshima, K.; Maestro, P.; Malik, S.; Manca, G.; Manousakis-Katsikakis, A.; Margaroli, F.; Marino, C.; Martínez, M.; Mastrandrea, P.; Matera, K.; Mattson, M. E.; Mazzacane, A.; Mazzanti, P.; McFarland, K. S.; McIntyre, P.; McNulty, R.; Mehta, A.; Mehtala, P.; Mesropian, C.; Miao, T.; Mietlicki, D.; Mitra, A.; Miyake, H.; Moed, S.; Moggi, N.; Mondragon, M. N.; Moon, C. S.; Moore, R.; Morello, M. J.; Morlock, J.; Movilla Fernandez, P.; Mukherjee, A.; Muller, Th.; Murat, P.; Mussini, M.; Nachtman, J.; Nagai, Y.; Naganoma, J.; Nakano, I.; Napier, A.; Nett, J.; Neu, C.; Neubauer, M. S.; Nielsen, J.; Nodulman, L.; Noh, S. Y.; Norniella, O.; Oakes, L.; Oh, S. H.; Oh, Y. D.; Oksuzian, I.; Okusawa, T.; Orava, R.; Ortolan, L.; Pagan Griso, S.; Pagliarone, C.; Palencia, E.; Papadimitriou, V.; Paramonov, A. A.; Patrick, J.; Pauletta, G.; Paulini, M.; Paus, C.; Pellett, D. E.; Penzo, A.; Phillips, T. J.; Piacentino, G.; Pianori, E.; Pilot, J.; Pitts, K.; Plager, C.; Pondrom, L.; Poprocki, S.; Potamianos, K.; Prokoshin, F.; Pranko, A.; Ptohos, F.; Punzi, G.; Rahaman, A.; Ramakrishnan, V.; Ranjan, N.; Rao, K.; Redondo, I.; Renton, P.; Rescigno, M.; Riddick, T.; Rimondi, F.; Ristori, L.; Robson, A.; Rodrigo, T.; Rodriguez, T.; Rogers, E.; Rolli, S.; Roser, R.; Ruffini, F.; Ruiz, A.; Russ, J.; Rusu, V.; Safonov, A.; Sakumoto, W. K.; Sakurai, Y.; Santi, L.; Sato, K.; Saveliev, V.; Savoy-Navarro, A.; Schlabach, P.; Schmidt, A.; Schmidt, E. E.; Schwarz, T.; Scodellaro, L.; Scribano, A.; Scuri, F.; Seidel, S.; Seiya, Y.; Semenov, A.; Sforza, F.; Shalhout, S. Z.; Shears, T.; Shepard, P. F.; Shimojima, M.; Shochet, M.; Shreyber-Tecker, I.; Simonenko, A.; Sinervo, P.; Sliwa, K.; Smith, J. R.; Snider, F. D.; Soha, A.; Sorin, V.; Song, H.; Squillacioti, P.; Stancari, M.; St. Denis, R.; Stelzer, B.; Stelzer-Chilton, O.; Stentz, D.; Strologas, J.; Strycker, G. L.; Sudo, Y.; Sukhanov, A.; Suslov, I.; Takemasa, K.; Takeuchi, Y.; Tang, J.; Tecchio, M.; Teng, P. K.; Thom, J.; Thome, J.; Thompson, G. A.; Thomson, E.; Toback, D.; Tokar, S.; Tollefson, K.; Tomura, T.; Tonelli, D.; Torre, S.; Torretta, D.; Totaro, P.; Trovato, M.; Ukegawa, F.; Uozumi, S.; Varganov, A.; Vázquez, F.; Velev, G.; Vellidis, C.; Vidal, M.; Vila, I.; Vilar, R.; Vizán, J.; Vogel, M.; Volpi, G.; Wagner, P.; Wagner, R. L.; Wakisaka, T.; Wallny, R.; Wang, S. M.; Warburton, A.; Waters, D.; Wester, W. C.; Whiteson, D.; Wicklund, A. B.; Wicklund, E.; Wilbur, S.; Wick, F.; Williams, H. H.; Wilson, J. S.; Wilson, P.; Winer, B. L.; Wittich, P.; Wolbers, S.; Wolfe, H.; Wright, T.; Wu, X.; Wu, Z.; Yamamoto, K.; Yamato, D.; Yang, T.; Yang, U. K.; Yang, Y. C.; Yao, W.-M.; Yeh, G. P.; Yen, M.; Yi, K.; Yoh, J.; Yorita, K.; Yoshida, T.; Yu, G. B.; Yu, I.; Yu, S. S.; Yun, J. C.; Zanetti, A.; Zeng, Y.; Zhou, C.; Zucchelli, S.
2012-12-05
We present a search for a new heavy vector boson Z' that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of Z'→g*g. We study the case where the off-shell gluon g* converts to a pair of top quarks, leading to a final state of tt¯g. In a sample of events with exactly one charged lepton, large missing transverse momentum and at least five jets, corresponding to an integrated luminosity of 8.7 fb⁻¹ collected by the CDF II detector, we find the data to be consistent with the standard model. We set upper limits on the production cross section times branching ratio of this chromophilic Z' at 95% confidence level from 300 to 40 fb for Z' masses ranging from 400 to 1000 GeV/c², respectively.
Uncertainties in obtaining high reliability from stress-strength models
NASA Technical Reports Server (NTRS)
Neal, Donald M.; Matthews, William T.; Vangel, Mark G.
1992-01-01
There has been a recent interest in determining high statistical reliability in risk assessment of aircraft components. The potential consequences are identified of incorrectly assuming a particular statistical distribution for stress or strength data used in obtaining the high reliability values. The computation of the reliability is defined as the probability of the strength being greater than the stress over the range of stress values. This method is often referred to as the stress-strength model. A sensitivity analysis was performed involving a comparison of reliability results in order to evaluate the effects of assuming specific statistical distributions. Both known population distributions, and those that differed slightly from the known, were considered. Results showed substantial differences in reliability estimates even for almost nondetectable differences in the assumed distributions. These differences represent a potential problem in using the stress-strength model for high reliability computations, since in practice it is impossible to ever know the exact (population) distribution. An alternative reliability computation procedure is examined involving determination of a lower bound on the reliability values using extreme value distributions. This procedure reduces the possibility of obtaining nonconservative reliability estimates. Results indicated the method can provide conservative bounds when computing high reliability. An alternative reliability computation procedure is examined involving determination of a lower bound on the reliability values using extreme value distributions. This procedure reduces the possibility of obtaining nonconservative reliability estimates. Results indicated the method can provide conservative bounds when computing high reliability.
NASA Astrophysics Data System (ADS)
Echevarria, Miguel G.; Scimemi, Ignazio; Vladimirov, Alexey
2016-09-01
The transverse momentum dependent parton distribution/fragmentation functions (TMDs) are essential in the factorization of a number of processes like Drell-Yan scattering, vector boson production, semi-inclusive deep inelastic scattering, etc. We provide a comprehensive study of unpolarized TMDs at next-to-next-to-leading order, which includes an explicit calculation of these TMDs and an extraction of their matching coefficients onto their integrated analogues, for all flavor combinations. The obtained matching coefficients are important for any kind of phenomenology involving TMDs. In the present study each individual TMD is calculated without any reference to a specific process. We recover the known results for parton distribution functions and provide new results for the fragmentation functions. The results for the gluon transverse momentum dependent fragmentation functions are presented for the first time at one and two loops. We also discuss the structure of singularities of TMD operators and TMD matrix elements, crossing relations between TMD parton distribution functions and TMD fragmentation functions, and renormalization group equations. In addition, we consider the behavior of the matching coefficients at threshold and make a conjecture on their structure to all orders in perturbation theory.
NASA Astrophysics Data System (ADS)
Rosenberg, Leslie J.
We have made a high statistics study of QCD jets produced in e('+)e('-) annihilations at SQRT.(s) of 29 GeV and observed in the MAC detector located at the PEP storage ring at SLAC. The MAC detector uses calorimetry and provides a homogeneous response over much of its 98%(.)4(pi) sr instrumented solid angle. A data sample of well reconstructed hadronic events was selected by requiring that E(,vis) in the calorimeters be near SQRT.(s), and almost all the energy be deposited in the central calorimeters. Fits of the jet transverse energy flow are made to the data using String (STR) model and several types of Independent Jet (IJM) model hypotheses, where (alpha)(,s), the strong coupling constant, and (sigma)(,q), the width of the secondary quark P(,(PERP)) distribution, are free parameters. The fits to O((alpha)(,s)('2)) using MS renormalization yield (alpha)(,s) (TURN) 0.17 with the STR hypothesis, and (alpha)(,s) (TURN) 0.12 with the various IJM hypotheses. The correlations between (alpha)(,s) and (sigma)(,q) are examined. Detailed comparisons were made with other experimental results. The energy flow projected onto the event plane of 3-jet events selected from the above data sample was studied. The data shows an asymmetric energy flow around the thin jet. Such an asymmetry was predicted by the STR model, and a cluster model (Webber) incorporating soft gluon interference. The various IJM models show no such asymmetry. We associate this asymmetry with coherence effects during hadronization.
Rosenberg, L.J.
1985-11-01
We have made a high statistics study of QCD jets produced in e/sup +/e/sup -/ annihilations at ..sqrt..s of 29 GeV and observed in the MAC detector located at the PEP storage ring at SLAC. The MAC detector uses calorimetry and provides a homogeneous response over much of its 98% . 4..pi.. sr instrumented solid angle. A data sample of well reconstructed hadronic events was selected by requiring that E/sub vis/ in the calorimeters be near ..sqrt..s, and almost all the energy be deposited in the central calorimeters. Fits of the jet transverse energy flow are made to the data using String (STR) model and several types of Independent Jet (IJM) model hypotheses, where ..alpha../sub s/, the strong coupling constant, and sigma/sub q/, the width of the secondary quark P/sub perpendicular/ distribution, are free parameters. The fits to O(..alpha../sub s//sup 2/ using MS-bar renormalization yield ..alpha../sub s/ approx.0.17 with the STR hypothesis, and ..alpha../sub s/ approx.0.12 with the various IJM hypotheses. The correlations between ..alpha../sub s/ and sigma/sub q/ are examined. Detailed comparisons were made with other experimental results. The energy flow projected onto the event plane of 3-jet events selected from the above data sample was studied. The data shows an asymmetric energy flow around the thin jet. Such an asymmetry was predicted by the STR model, and a cluster model (Webber) incorporating soft gluon interference. The various IJM models show no such asymmetry. We associate this asymmetry with coherence effects during hadronization. 106 refs., 58 figs., 18 tabs.
Thermodynamics and jet-quenching in the quark-gluon plasma from an AdS/QCD model
NASA Astrophysics Data System (ADS)
Lilleskov, Elias; Bartz, Sean
2015-10-01
The Anti-de Sitter Space/Conformal Field Theory Correspondence (AdS/CFT) has been used to study both hadronic dynamics and the thermodynamics and jet quenching behavior of the quark-gluon plasma created in heavy ion collisions. We attempt to connect the two regimes by adapting an AdS/QCD model previously used to study meson spectra to apply to the quark-gluon plasma. The model includes three fields: a dilaton to introduce confinement, and chiral and glueball condensates to reflect the zero-temperature dynamics. We dynamically solve the Einstein field equations to numerically determine the metric, which asymptotically describes an anti-de Sitter-Schwarzschild black hole solution. We then numerically calculate the temperature as a function of the black hole horizon location. Next, we determine the behavior of the entropy density, the speed of sound, and the jet quenching parameter as functions of the temperature. These quantities approach the behavior of a conformal plasma in the high temperature limit. The minimum of the temperature-horizon plot is interpreted as the plasma's deconfinement temperature, found to be 104 MeV.
NASA Technical Reports Server (NTRS)
Takahashi, Y.; Eby, P. B.
1985-01-01
Possibilities of observing abundances of phi mesons and narrow hadronic pairs, as results of QGP and Chiral transitions, are considered for nucleus-nucleus interactions. Kinematical requirements in forming close pairs are satisfied in K+K decays of S(975) and delta (980) mesons with small phi, and phi (91020) mesons with large PT, and in pi-pi decays of familiar resonance mesons only in a partially restored chiral symmetry. Gluon-gluon dominance in QGP can enhance phi meson production. High hadronization rates of primordial resonance mesons which form narrow hadronic pairs are not implausible. Past cosmic ray evidences of anomalous phi production and narrow pair abundances are considered.
Product Distributions for Distributed Optimization. Chapter 1
NASA Technical Reports Server (NTRS)
Bieniawski, Stefan R.; Wolpert, David H.
2004-01-01
With connections to bounded rational game theory, information theory and statistical mechanics, Product Distribution (PD) theory provides a new framework for performing distributed optimization. Furthermore, PD theory extends and formalizes Collective Intelligence, thus connecting distributed optimization to distributed Reinforcement Learning (FU). This paper provides an overview of PD theory and details an algorithm for performing optimization derived from it. The approach is demonstrated on two unconstrained optimization problems, one with discrete variables and one with continuous variables. To highlight the connections between PD theory and distributed FU, the results are compared with those obtained using distributed reinforcement learning inspired optimization approaches. The inter-relationship of the techniques is discussed.
NASA Astrophysics Data System (ADS)
Caola, Fabrizio; Dowling, Matthew; Melnikov, Kirill; Röntsch, Raoul; Tancredi, Lorenzo
2016-07-01
We compute next-to-leading order (NLO) QCD corrections to the production of two massive electroweak bosons in gluon fusion. We consider both the prompt production process gg → V V and the production mediated by an exchange of an s-channel Higgs boson, gg → H ∗ → V V . We include final states with both on- and off-shell vector bosons with leptonic decays. The gluonic production of vector bosons is a loop-induced process, including both massless and massive quarks in the loop. For gg → ZZ production, we obtain the NLO QCD corrections to the massive loops through an expansion around the heavy top limit. This approximation is valid below the top production threshold, giving a broad range of invariant masses between the Higgs production and the top production thresholds in which our results are valid. We explore the NLO QCD effects in gg → ZZ focusing, in particular, on the interference between prompt and Higgs-mediated processes. We find that the QCD corrections to the interference are large and similar in size to the corrections to both the signal and the background processes. At the same time, we observe that corrections to the interference change rapidly with the four-lepton invariant mass in the region around the ZZ production threshold. We also study the interference effects in gg → W + W - production where, due to technical limitations, we only consider contributions of massless loops. We find that the QCD corrections to the interference in this case are somewhat larger than those for either the signal or the background.
Petersen, A.
1986-04-01
Results of inclusive charged particle distribution for gluon jets using nearly 3-fold symmetric 3-jet events taken at center of mass energies of 29 GeV in e/sup +/e/sup -/ annihilation are presented. The charged particle spectrum for these jets is observed to be softer than that of quark jets with the same jet energy.
Generalized parton distributions at CLAS
Silvia Pisano
2010-11-01
The understanding of the hadron structure in terms of QCD degrees of freedom is one of the main challenges of hadron physics. Indeed, despite the large amount of theoretical and experimental activity devoted to the subject in the last years, a full comprehension of mesons and baryons in terms of quark and gluon fields is still lacking. In order to operate a more detailed investigation of the hadron structure, new quantities have been introduced ten years ago, the Generalized Parton Distributions (GPDs), defined as bilocal, off-forward matrix elements of quark and gluon operators. From an experimental point of view, GPDs are accessible through two main processes: Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Electroproduction (DVMP). Depending on the polarization degrees of freedom acting in the process (like, for example, the simultaneous presence of a polarization in the beam and in the target, or the usage of a polarized beam with an unpolarized target), various combinations of GPDs can be accessed. In the case of DVCS, for example, the measurement of the Single Spin Asymmetry of processes like View the MathML source – realized by using a longitudinally polarized target - gives access to a combination of the GDPs H and H̃. The CEBAF Large Acceptance Spectrometer (CLAS) installed in the Hall-B at JLab, is particularly suited for the extraction of these quantities. Its large acceptance implies a good capability in the reconstruction of exclusive final states, allowing the investigation of the aforementioned processes in a wide range of kinematics. In this presentation, an overview of the main GPD measurements performed by CLAS will be given. In particular, the first DVCS measurements realized both with unpolarized and polarized target, together with the measurements of some exclusive meson electroproduction processes, will be described.
NASA Astrophysics Data System (ADS)
Duarte, Anthony G.; Oliveira, Orlando; Silva, Paulo J.
2016-07-01
The dependence of the Landau gauge two-point gluon and ghost correlation functions on the lattice spacing and on the physical volume are investigated for pure SU(3) Yang-Mills theory in four dimensions using lattice simulations. We present data from very large lattices up to 1284 and for two lattice spacings 0.10 fm and 0.06 fm corresponding to volumes of ˜(13 fm )4 and ˜(8 fm )4 , respectively. Our results show that, for sufficiently large physical volumes, both propagators have a mild dependence on the lattice volume. On the other hand, the gluon and ghost propagators change with the lattice spacing a in the infrared region, with the gluon propagator having a stronger dependence on a compared to the ghost propagator. In what concerns the strong coupling constant αs(p2), as defined from gluon and ghost two-point functions, the simulations show a sizeable dependence on the lattice spacing for the infrared region and for momenta up to ˜1 GeV .
Brown, William E.; Liu, James T.; Ren, Hai-cang
2000-09-01
At sufficiently high baryon densities, the physics of a dense quark-gluon plasma may be investigated through the tools of perturbative QCD. This approach has recently been successfully applied to the study of color superconductivity, where the dominant di-quark pairing interaction arises from one gluon exchange. Screening in the plasma leads to novel behavior, including a remarkable non-BCS scaling of T{sub C}, the transition temperature to the color superconducting phase. Radiative corrections to one gluon exchange were previously considered and found to affect T{sub C}. In particular, the quark self-energy in a plasma leads to non-Fermi liquid behavior and suppresses T{sub C}. However, at the same time, the quark-gluon vertex was shown not to modify the result at leading order. This dichotomy between the effects of the radiative corrections at first appears rather surprising, as the BRST identity connects the self-energy to the vertex corrections. Nevertheless, as we demonstrate, there is in fact no contradiction with the BRST identity, at least to leading logarithmic order. This clarifies some of the previous statements on the importance of the higher order corrections to the determination of T{sub C} and the zero temperature gap in color superconductivity. (c) 2000 The American Physical Society.
Production and elliptic flow of dileptons and photons in a matrix model of the quark-gluon plasma.
Gale, Charles; Hidaka, Yoshimasa; Jeon, Sangyong; Lin, Shu; Paquet, Jean-François; Pisarski, Robert D; Satow, Daisuke; Skokov, Vladimir V; Vujanovic, Gojko
2015-02-20
We consider a nonperturbative approach to the thermal production of dileptons and photons at temperatures near the critical temperature in QCD. The suppression of colored excitations at low temperature is modeled by including a small value of the Polyakov loop, in a "semi"-quark-gluon plasma (QGP). Comparing the semi-QGP to the perturbative QGP, we find a mild enhancement of thermal dileptons. In contrast, to leading logarithmic order in weak coupling there are far fewer hard photons from the semi-QGP than the usual QGP. To illustrate the possible effects on photon and dilepton production in heavy-ion collisions, we integrate the rate with a simulation using ideal hydrodynamics. Dileptons uniformly exhibit a small flow, but the strong suppression of photons in the semi-QGP tends to weight the elliptical flow of photons to that generated in the hadronic phase.
Das, Santosh K.; Alam, Jan-e; Mohanty, Payal
2010-07-15
The drag and diffusion coefficients of charm and bottom quarks propagating through quark gluon plasma (QGP) have been evaluated for conditions relevant to nuclear collisions at the Large Hadron Collider (LHC). The dead cone and Landau-Pomeronchuk-Migdal (LPM) effects on radiative energy loss of heavy quarks have been considered. Both radiative and collisional processes of energy loss are included in the effective drag and diffusion coefficients. With these effective transport coefficients, we solve the Fokker-Plank (FP) equation for the heavy quarks executing Brownian motion in the QGP. The solution of the FP equation has been used to evaluate the nuclear suppression factor, R{sub AA}, for the nonphotonic single-electron spectra resulting from the semileptonic decays of hadrons containing charm and bottom quarks. The effects of mass on R{sub AA} have also been highlighted.
Asymmetry distributions and mass effects in dijet events at a polarized HERA
NASA Astrophysics Data System (ADS)
Maul, M.; Schäfer, A.; Mirkes, E.; Rädel, G.
1998-09-01
The asymmetry distributions for several kinematic variables are considered for finding a systematic way to maximize the signal for the extraction of the polarized gluon density. The relevance of mass effects for the corresponding dijet cross section is discussed and the different approximations for including mass effects are compared. We also compare via the programs Pepsi and Mepjet two different Monte Carlo (MC) approaches for simulating the expected signal in the dijet asymmetry at a polarized HERA.
NASA Astrophysics Data System (ADS)
Grazzini, Massimiliano; Papaefstathiou, Andreas; Smillie, Jennifer M.; Webber, Bryan R.
2014-09-01
We compute the resummed hadronic transverse-energy ( E T ) distribution due to initial-state QCD radiation in the production of a Standard Model Higgs boson of mass 126 GeV by gluon fusion at the Large Hadron Collider, with matching to next-to-leading order calculations at large E T . Effects of hadronization, underlying event and limited detector acceptance are estimated using aMC@NLO with the Herwig++ and Pythia8 event generators.
High energy angular distribution measurements of the exclusive deuteron photodisintegration reaction
Elaine Schulte; et. Al.
2002-10-01
The first complete measurements of the angular distributions of the two-body deuteron photodisintegration differential cross section at photon energies above 1.6 GeV were performed at the Thomas Jefferson National Accelerator Facility. The results show a persistent forward-backward asymmetry up to Egamma = 2.4 GeV, the highest-energy measured in this experiment. The Hard Rescattering and the Quark-Gluon string models are in fair agreement with the results.
Jimenez-Delgado, P.; Reya, E.
2009-12-01
Based on our recent next-to-next-to-leading order (NNLO) dynamical parton distributions as obtained in the 'fixed flavor number scheme', we generate radiatively parton distributions in the 'variable flavor number scheme' where the heavy-quark flavors (c,b,t) also become massless partons within the nucleon. Only within this latter factorization scheme are NNLO calculations feasible at present, since the required partonic subprocesses are only available in the approximation of massless initial-state partons. The NNLO predictions for gauge boson production are typically larger (by more than 1{sigma}) than the next-to-leading order (NLO) ones, and rates at LHC energies can be predicted with an accuracy of about 5%, whereas at Tevatron they are more than 2{sigma} above the NLO ones. The NNLO predictions for standard model Higgs-boson production via the dominant gluon fusion process have a total (parton distribution function and scale) uncertainty of about 10% at LHC which almost doubles at the lower Tevatron energies; they are typically about 20% larger than the ones at NLO but the total uncertainty bands overlap.
Pion Electromagnetic Form Factor in Virtuality Distribution Formalism
Radyushkin, Anatoly V.
2016-01-01
We discuss two applications of the {\\it Virtuality Distribution Amplitudes} (VDA) formalism developed in our recent papers. We start with an overview of the main properties of the pion distribution amplitude emphasizing the quantitative measures of its width, and possibility to access them through the pion transition form factor studies. We formulate the basic concepts of the VDA approach and introduce the pion {\\it transverse momentum distribution amplitude} (TMDA) which plays, in a covariant Lagrangian formulation, a role similar to that of the pion wave function in the 3-dimensional Hamiltonian light-front approach. We propose simple factorized models for soft TMDAs, and use them to describe existing data on the pion transition form factor, thus fixing the scale determining the size of the transverse-momentum effects. Finally, we apply the VDA approach to the one-gluon exchange contribution for the pion electromagnetic form factor. We observe a very late $Q^2 \\gtrsim 20$ GeV$^2$ onset of transition to the asymptotic pQCD predictions and show that in the $Q^2 \\lesssim 10$ GeV$^2$ region there is essentially no sensitivity to the shape of the pion distribution amplitude. Furthermore, the magnitude of the one-gluon exchange contribution in this region is estimated to be an order of magnitude below the Jefferson Lab data, thus leaving the Feynman mechanism as the only one relevant to the pion electromagnetic form factor behavior for accessible $Q^2$.
NUCLEAR MODIFICATION TO PARTON DISTRIBUTION FUNCTIONS AND PARTON SATURATION.
QIU, J.-W.
2006-11-14
We introduce a generalized definition of parton distribution functions (PDFs) for a more consistent all-order treatment of power corrections. We present a new set of modified DGLAP evolution equations for nuclear PDFs, and show that the resummed {alpha}{sub s}A{sup 1/3}/Q{sup 2}-type of leading nuclear size enhanced power corrections significantly slow down the growth of gluon density at small-x. We discuss the relation between the calculated power corrections and the saturation phenomena.
Orbital angular momentum and generalized transverse momentum distribution
NASA Astrophysics Data System (ADS)
Zhao, Yong; Liu, Keh-Fei; Yang, Yi-Bo
2016-03-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of Chen et al. are the same as those whose matrix elements correspond to the moments of generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally and discuss the strategies of calculating them in lattice QCD.
40 CFR 35.6310 - Obtaining equipment.
Code of Federal Regulations, 2010 CFR
2010-07-01
... STATE AND LOCAL ASSISTANCE Cooperative Agreements and Superfund State Contracts for Superfund Response Actions Personal Property Requirements Under A Cooperative Agreement § 35.6310 Obtaining equipment....
SOFIA Observatory Obtains 'First Light' Images
NASA's Stratospheric Observatory for Infrared Astronomy, or SOFIA, successfully obtained its "First Light"" images during an overnight flight May 26. Scientists are now processing the data gathered...
Transverse momentum dependent quark distributions and polarized Drell-Yan processes
Zhou, J.; Yuan, F.; Liang, Z.-T.
2009-09-11
We study the spin-dependent quark distributions at large transverse momentum. We derive their transverse momentum behaviors in the collinear factorization approach in this region. We further calculate the angular distribution of the Drell-Yan lepton pair production with polarized beams and present the results in terms of the collinear twist-three quark-gluon correlation functions. In the intermediate transverse momentum region, we find that the two pproaches: the collinear factorization and the transverse momentum dependent factorization approaches are consistent in the description of the lepton pair angular distributions.
NASA Astrophysics Data System (ADS)
Binns, Lewis A.; Valachis, Dimitris; Anderson, Sean; Gough, David W.; Nicholson, David; Greenway, Phil
2002-07-01
Previously, we have developed techniques for Simultaneous Localization and Map Building based on the augmented state Kalman filter. Here we report the results of experiments conducted over multiple vehicles each equipped with a laser range finder for sensing the external environment, and a laser tracking system to provide highly accurate ground truth. The goal is simultaneously to build a map of an unknown environment and to use that map to navigate a vehicle that otherwise would have no way of knowing its location, and to distribute this process over several vehicles. We have constructed an on-line, distributed implementation to demonstrate the principle. In this paper we describe the system architecture, the nature of the experimental set up, and the results obtained. These are compared with the estimated ground truth. We show that distributed SLAM has a clear advantage in the sense that it offers a potential super-linear speed-up over single vehicle SLAM. In particular, we explore the time taken to achieve a given quality of map, and consider the repeatability and accuracy of the method. Finally, we discuss some practical implementation issues.
42 CFR 442.101 - Obtaining certification.
Code of Federal Regulations, 2010 CFR
2010-10-01
... section states the requirements for obtaining notice of an ICF/MR's certification before a Medicaid agency... Secretary for an ICF/MR located on an Indian reservation. (c) The agency must obtain notice of certification... provisions pertains to the ICF/MR: (1) An ICF/MR meets the conditions of participation set forth in subpart...