Double parton scattering: Impact of nonperturbative parton correlations
NASA Astrophysics Data System (ADS)
Ostapchenko, Sergey; Bleicher, Marcus
2016-02-01
We apply the phenomenological Reggeon field theory framework to investigate the relative importance of perturbative and nonperturbative multiparton correlations for the treatment of double parton scattering in proton-proton collisions. We obtain a significant correction to the so-called effective cross section for double parton scattering due to nonperturbative parton splitting. When combined with the corresponding perturbative contribution, this results in a rather weak energy and transverse momentum dependence of the effective cross section, in agreement with experimental observations at the Tevatron and the Large Hadron Collider. In addition, we observe that color fluctuations have a sizable impact on the calculated rate of double parton scattering and on the relative importance of the perturbative parton splitting mechanism.
NASA Astrophysics Data System (ADS)
Kutak, Krzysztof; Maciuła, Rafał; Serino, Mirko; Szczurek, Antoni; van Hameren, Andreas
2016-07-01
In the present paper, we discuss how to maximize the double-parton scattering (DPS) contribution in four-jet production by selecting kinematical cuts. Here both single-parton and double-parton scattering effects are calculated in the kT -factorization approach, following our recent developments of relevant methods and tools. Several differential distributions are shown and discussed in the context of future searches for DPS effects, such as rapidity of jets, rapidity distance, and azimuthal correlations between jets. The dependence of the relative DPS amount is studied as a function of those observables. The regions with an enhanced DPS contribution are identified. Future experimental explorations could extract more precise values of σeff and its potential dependence on kinematical variables.
All orders results for self-crossing Wilson loops mimicking double parton scattering
Dixon, Lance J.; Esterlis, Ilya
2016-07-21
Loop-level scattering amplitudes for massless particles have singularities in regions where tree amplitudes are perfectly smooth. For example, a 2 → 4 gluon scattering process has a singularity in which each incoming gluon splits into a pair of gluons, followed by a pair of 2 → 2 collisions between the gluon pairs. This singularity mimics double parton scattering because it occurs when the transverse momentum of a pair of outgoing gluons vanishes. The singularity is logarithmic at fixed order in perturbation theory. We exploit the duality between scattering amplitudes and polygonal Wilson loops to study six-point amplitudes in this limitmore » to high loop order in planar N = 4 super-Yang-Mills theory. The singular configuration corresponds to the limit in which a hexagonal Wilson loop develops a self-crossing. The singular terms are governed by an evolution equation, in which the hexagon mixes into a pair of boxes; the mixing back is suppressed in the planar (large N c) limit. Because the kinematic dependence of the box Wilson loops is dictated by (dual) conformal invariance, the complete kinematic dependence of the singular terms for the self-crossing hexagon on the one nonsingular variable is determined to all loop orders. The complete logarithmic dependence on the singular variable can be obtained through nine loops, up to a couple of constants, using a correspondence with the multi-Regge limit. As a byproduct, we obtain a simple formula for the leading logs to all loop orders. Furthermore, we also show that, although the MHV six-gluon amplitude is singular, remarkably, the transcendental functions entering the non-MHV amplitude are finite in the same limit, at least through four loops.« less
All orders results for self-crossing Wilson loops mimicking double parton scattering
NASA Astrophysics Data System (ADS)
Dixon, Lance J.; Esterlis, Ilya
2016-07-01
Loop-level scattering amplitudes for massless particles have singularities in regions where tree amplitudes are perfectly smooth. For example, a 2 → 4 gluon scattering process has a singularity in which each incoming gluon splits into a pair of gluons, followed by a pair of 2 → 2 collisions between the gluon pairs. This singularity mimics double parton scattering because it occurs when the transverse momentum of a pair of outgoing gluons vanishes. The singularity is logarithmic at fixed order in perturbation theory. We exploit the duality between scattering amplitudes and polygonal Wilson loops to study six-point amplitudes in this limit to high loop order in planar {N} = 4 super-Yang-Mills theory. The singular configuration corresponds to the limit in which a hexagonal Wilson loop develops a self-crossing. The singular terms are governed by an evolution equation, in which the hexagon mixes into a pair of boxes; the mixing back is suppressed in the planar (large N c) limit. Because the kinematic dependence of the box Wilson loops is dictated by (dual) conformal invariance, the complete kinematic dependence of the singular terms for the self-crossing hexagon on the one nonsingular variable is determined to all loop orders. The complete logarithmic dependence on the singular variable can be obtained through nine loops, up to a couple of constants, using a correspondence with the multi-Regge limit. As a byproduct, we obtain a simple formula for the leading logs to all loop orders. We also show that, although the MHV six-gluon amplitude is singular, remarkably, the transcendental functions entering the non-MHV amplitude are finite in the same limit, at least through four loops.
Chatrchyan, Serguei
2014-03-05
Double parton scattering is investigated in proton-proton collisions at √s = 7 TeV where the final state includes a W boson, which decays into a muon and a neutrino, and two jets. The data sample corresponds to an integrated luminosity of 5 fb–1, collected with the CMS detector at the LHC. Observables sensitive to double parton scattering are investigated after being corrected for detector effects and selection efficiencies. The fraction of W + 2-jet events due to double parton scattering is measured to be 0.055 +/- 0.002 (stat.) +/- 0.014 (syst.). Finally, the effective cross section, σeff, characterizing the effectivemore » transverse area of hard partonic interactions in collisions between protons is measured to be 20.7 +/- 0.8 (stat.) +/- 6.6 (syst.) mb.« less
Chatrchyan, Serguei
2014-03-05
Double parton scattering is investigated in proton-proton collisions at √s = 7 TeV where the final state includes a W boson, which decays into a muon and a neutrino, and two jets. The data sample corresponds to an integrated luminosity of 5 fb^{–1}, collected with the CMS detector at the LHC. Observables sensitive to double parton scattering are investigated after being corrected for detector effects and selection efficiencies. The fraction of W + 2-jet events due to double parton scattering is measured to be 0.055 +/- 0.002 (stat.) +/- 0.014 (syst.). Finally, the effective cross section, σ_{eff}, characterizing the effective transverse area of hard partonic interactions in collisions between protons is measured to be 20.7 +/- 0.8 (stat.) +/- 6.6 (syst.) mb.
NASA Astrophysics Data System (ADS)
Gaunt, Jonathan R.; Maciuła, Rafał; Szczurek, Antoni
2014-09-01
The double parton distributions (dPDF), both conventional (i.e. double ladder) and those corresponding to 1→2 ladder splitting, are calculated and compared for different two-parton combinations. The conventional and splitting dPDFs have very similar shape in x1 and x2. We make a first quantitative evaluation of the single-ladder-splitting contribution to double parton scattering (DPS) production of two S- or P-wave quarkonia, two Higgs bosons and cc ¯cc ¯. The ratio of the single-ladder-splitting to conventional (i.e. double ladder against double ladder) contributions is discussed as a function of center-of-mass energy, mass of the produced system and other kinematical variables. Using a simple model for the dependence of the conventional two-parton distribution on transverse parton separation (Gaussian and independent of xi and scales), we find that the single-ladder-splitting (or 2v1) contribution is as big as the conventional (or 2v2) contribution discussed in recent years in the literature. In many experimental studies of DPS, one extracts the quantity 1/σeff=σDPS/(σSPS ,1σSPS,2), with σSPS ,1 and σSPS ,2 being the single scattering cross sections for the two subprocesses in the DPS process. Many past phenomenological studies of DPS have only considered the conventional contribution and have obtained values a factor of ˜2 too small for 1/σeff. Our analysis shows that it is important also to consider the ladder-splitting mechanism, and that this might resolve the discrepancy (this was also pointed out in a recent study by Blok et al.). The differential distributions in rapidity and transverse momenta calculated for conventional and single-ladder-splitting DPS processes are however very similar which causes their experimental separation to be rather difficult, if not impossible. The direct consequence of the existence of the two components (conventional and splitting) is the energy and process dependence of the empirical parameter σeff. This is
NASA Astrophysics Data System (ADS)
Aaij, R.; Abellán Beteta, C.; Adeva, B.; Adinolfi, M.; Affolder, A.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.; Anderson, J.; Andreassi, G.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Aquines Gutierrez, O.; Archilli, F.; d'Argent, P.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Bachmann, S.; Back, J. J.; Badalov, A.; Baesso, C.; Baldini, W.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Batozskaya, V.; Battista, V.; Bay, A.; Beaucourt, L.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Bel, L. J.; Bellee, V.; Belloli, N.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Benton, J.; Berezhnoy, A.; Bernet, R.; Bertolin, A.; Bettler, M.-O.; van Beuzekom, M.; Bien, A.; Bifani, S.; Billoir, P.; Bird, T.; Birnkraut, A.; Bizzeti, A.; Blake, T.; Blanc, F.; Blouw, J.; Blusk, S.; Bocci, V.; Bondar, A.; Bondar, N.; Bonivento, W.; Borghi, S.; Borisyak, M.; Borsato, M.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Braun, S.; Britsch, M.; Britton, T.; Brodzicka, J.; Brook, N. H.; Buchanan, E.; Burr, C.; Bursche, A.; Buytaert, J.; Cadeddu, S.; Calabrese, R.; Calvi, M.; Calvo Gomez, M.; Campana, P.; Campora Perez, D.; Capriotti, L.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carniti, P.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Cassina, L.; Castillo Garcia, L.; Cattaneo, M.; Cauet, Ch.; Cavallero, G.; Cenci, R.; Charles, M.; Charpentier, Ph.; Chefdeville, M.; Chen, S.; Cheung, S.-F.; Chiapolini, N.; Chrzaszcz, M.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Coco, V.; Cogan, J.; Cogneras, E.; Cogoni, V.; Cojocariu, L.; Collazuol, G.; Collins, P.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coombes, M.; Coquereau, S.; Corti, G.; Corvo, M.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Crocombe, A.; Cruz Torres, M.; Cunliffe, S.; Currie, R.; D'Ambrosio, C.; Dall'Occo, E.; Dalseno, J.; David, P. N. Y.; Davis, A.; De Aguiar Francisco, O.; De Bruyn, K.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Simone, P.; Dean, C.-T.; Decamp, D.; Deckenhoff, M.; Del Buono, L.; Déléage, N.; Demmer, M.; Derkach, D.; Deschamps, O.; Dettori, F.; Dey, B.; Di Canto, A.; Di Ruscio, F.; Dijkstra, H.; Donleavy, S.; Dordei, F.; Dorigo, M.; Dosil Suárez, A.; Dossett, D.; Dovbnya, A.; Dreimanis, K.; Dufour, L.; Dujany, G.; Durante, P.; Dzhelyadin, R.; Dziurda, A.; Dzyuba, A.; Easo, S.; Egede, U.; Egorychev, V.; Eidelman, S.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; El Rifai, I.; Elsasser, Ch.; Ely, S.; Esen, S.; Evans, H. M.; Evans, T.; Falabella, A.; Färber, C.; Farley, N.; Farry, S.; Fay, R.; Ferguson, D.; Fernandez Albor, V.; Ferrari, F.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fiore, M.; Fiorini, M.; Firlej, M.; Fitzpatrick, C.; Fiutowski, T.; Fohl, K.; Fol, P.; Fontana, M.; Fontanelli, F.; Forshaw, D. C.; Forty, R.; Frank, M.; Frei, C.; Frosini, M.; Fu, J.; Furfaro, E.; Gallas Torreira, A.; Galli, D.; Gallorini, S.; Gambetta, S.; Gandelman, M.; Gandini, P.; Gao, Y.; García Pardiñas, J.; Garra Tico, J.; Garrido, L.; Gascon, D.; Gaspar, C.; Gauld, R.; Gavardi, L.; Gazzoni, G.; Gerick, D.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gianì, S.; Gibson, V.; Girard, O. G.; Giubega, L.; Gligorov, V. V.; Göbel, C.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gotti, C.; Grabalosa Gándara, M.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graverini, E.; Graziani, G.; Grecu, A.; Greening, E.; Gregson, S.; Griffith, P.; Grillo, L.; Grünberg, O.; Gui, B.; Gushchin, E.; Guz, Yu.; Gys, T.; Hadavizadeh, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Haines, S. C.; Hall, S.; Hamilton, B.; Han, X.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Harrison, J.; He, J.; Head, T.; Heijne, V.; Hennessy, K.; Henrard, P.; Henry, L.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hill, D.; Hoballah, M.; Hombach, C.; Hulsbergen, W.; Humair, T.; Hussain, N.; Hutchcroft, D.; Hynds, D.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jaeger, A.; Jalocha, J.; Jans, E.; Jawahery, A.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kandybei, S.; Kanso, W.; Karacson, M.; Karbach, T. M.; Karodia, S.; Kecke, M.; Kelsey, M.; Kenyon, I. R.; Kenzie, M.; Ketel, T.; Khairullin, E.; Khanji, B.; Khurewathanakul, C.; Klaver, S.; Klimaszewski, K.; Kochebina, O.; Kolpin, M.; Komarov, I.; Koopman, R. F.; Koppenburg, P.; Kozeiha, M.; Kravchuk, L.; Kreplin, K.; Kreps, M.; Krocker, G.; Krokovny, P.; Kruse, F.; Krzemien, W.; Kucewicz, W.; Kucharczyk, M.; Kudryavtsev, V.; Kuonen, A. K.; Kurek, K.; Kvaratskheliya, T.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lambert, D.; Lanfranchi, G.; Langenbruch, C.; Langhans, B.; Latham, T.; Lazzeroni, C.; Le Gac, R.; van Leerdam, J.; Lees, J.-P.; Lefèvre, R.; Leflat, A.; Lefrançois, J.; Lemos Cid, E.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, Y.; Likhomanenko, T.; Liles, M.; Lindner, R.; Linn, C.; Lionetto, F.; Liu, B.; Liu, X.; Loh, D.; Longstaff, I.; Lopes, J. H.; Lucchesi, D.; Lucio Martinez, M.; Luo, H.; Lupato, A.; Luppi, E.; Lupton, O.; Lusiani, A.; Machefert, F.; Maciuc, F.; Maev, O.; Maguire, K.; Malde, S.; Malinin, A.; Manca, G.; Mancinelli, G.; Manning, P.; Mapelli, A.; Maratas, J.; Marchand, J. F.; Marconi, U.; Marin Benito, C.; Marino, P.; Marks, J.; Martellotti, G.; Martin, M.; Martinelli, M.; Martinez Santos, D.; Martinez Vidal, F.; Martins Tostes, D.; Massafferri, A.; Matev, R.; Mathad, A.; Mathe, Z.; Matteuzzi, C.; Mauri, A.; Maurin, B.; Mazurov, A.; McCann, M.; McCarthy, J.; McNab, A.; McNulty, R.; Meadows, B.; Meier, F.; Meissner, M.; Melnychuk, D.; Merk, M.; Michielin, E.; Milanes, D. A.; Minard, M.-N.; Mitzel, D. S.; Molina Rodriguez, J.; Monroy, I. A.; Monteil, S.; Morandin, M.; Morawski, P.; Mordà, A.; Morello, M. J.; Moron, J.; Morris, A. B.; Mountain, R.; Muheim, F.; Müller, D.; Müller, J.; Müller, K.; Müller, V.; Mussini, M.; Muster, B.; Naik, P.; Nakada, T.; Nandakumar, R.; Nandi, A.; Nasteva, I.; Needham, M.; Neri, N.; Neubert, S.; Neufeld, N.; Neuner, M.; Nguyen, A. D.; Nguyen, T. D.; Nguyen-Mau, C.; Niess, V.; Niet, R.; Nikitin, N.; Nikodem, T.; Novoselov, A.; O'Hanlon, D. P.; Oblakowska-Mucha, A.; Obraztsov, V.; Ogilvy, S.; Okhrimenko, O.; Oldeman, R.; Onderwater, C. J. G.; Osorio Rodrigues, B.; Otalora Goicochea, J. M.; Otto, A.; Owen, P.; Oyanguren, A.; Palano, A.; Palombo, F.; Palutan, M.; Panman, J.; Papanestis, A.; Pappagallo, M.; Pappalardo, L. L.; Pappenheimer, C.; Parker, W.; Parkes, C.; Passaleva, G.; Patel, G. D.; Patel, M.; Patrignani, C.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perret, P.; Pescatore, L.; Petridis, K.; Petrolini, A.; Petruzzo, M.; Picatoste Olloqui, E.; Pietrzyk, B.; Pilař, T.; Pinci, D.; Pistone, A.; Piucci, A.; Playfer, S.; Plo Casasus, M.; Poikela, T.; Polci, F.; Poluektov, A.; Polyakov, I.; Polycarpo, E.; Popov, A.; Popov, D.; Popovici, B.; Potterat, C.; Price, E.; Price, J. D.; Prisciandaro, J.; Pritchard, A.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Punzi, G.; Qian, W.; Quagliani, R.; Rachwal, B.; Rademacker, J. H.; Rama, M.; Ramos Pernas, M.; Rangel, M. S.; Raniuk, I.; Rauschmayr, N.; Raven, G.; Redi, F.; Reichert, S.; Reid, M. M.; dos Reis, A. C.; Ricciardi, S.; Richards, S.; Rihl, M.; Rinnert, K.; Rives Molina, V.; Robbe, P.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Lopez, J. A.; Rodriguez Perez, P.; Roiser, S.; Romanovsky, V.; Romero Vidal, A.; Ronayne, J. W.; Rotondo, M.; Ruf, T.; Ruiz Valls, P.; Saborido Silva, J. J.; Sagidova, N.; Sail, P.; Saitta, B.; Salustino Guimaraes, V.; Sanchez Mayordomo, C.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santimaria, M.; Santovetti, E.; Sarti, A.; Satriano, C.; Satta, A.; Saunders, D. M.; Savrina, D.; Schiller, M.; Schindler, H.; Schlupp, M.; Schmelling, M.; Schmelzer, T.; Schmidt, B.; Schneider, O.; Schopper, A.; Schubiger, M.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Semennikov, A.; Serra, N.; Serrano, J.; Sestini, L.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, V.; Shires, A.; Siddi, B. G.; Silva Coutinho, R.; Silva de Oliveira, L.; Simi, G.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, E.; Smith, E.; Smith, I. T.; Smith, J.; Smith, M.; Snoek, H.; Sokoloff, M. D.; Soler, F. J. P.; Soomro, F.; Souza, D.; Souza De Paula, B.; Spaan, B.; Spradlin, P.; Sridharan, S.; Stagni, F.; Stahl, M.; Stahl, S.; Stefkova, S.; Steinkamp, O.; Stenyakin, O.; Stevenson, S.; Stoica, S.; Stone, S.; Storaci, B.; Stracka, S.; Straticiuc, M.; Straumann, U.; Sun, L.; Sutcliffe, W.; Swientek, K.; Swientek, S.; Syropoulos, V.; Szczekowski, M.; Szumlak, T.; T'Jampens, S.; Tayduganov, A.; Tekampe, T.; Teklishyn, M.; Tellarini, G.; Teubert, F.; Thomas, C.; Thomas, E.; van Tilburg, J.; Tisserand, V.; Tobin, M.; Todd, J.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Topp-Joergensen, S.; Torr, N.; Tournefier, E.; Tourneur, S.; Trabelsi, K.; Tran, M. T.; Tresch, M.; Trisovic, A.; Tsaregorodtsev, A.; Tsopelas, P.; Tuning, N.; Ukleja, A.; Ustyuzhanin, A.; Uwer, U.; Vacca, C.; Vagnoni, V.; Valenti, G.; Vallier, A.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vázquez Sierra, C.; Vecchi, S.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Vesterinen, M.; Viaud, B.; Vieira, D.; Vieites Diaz, M.; Vilasis-Cardona, X.; Volkov, V.; Vollhardt, A.; Volyanskyy, D.; Voong, D.; Vorobyev, A.; Vorobyev, V.; Voß, C.; de Vries, J. A.; Waldi, R.; Wallace, C.; Wallace, R.; Walsh, J.; Wandernoth, S.; Wang, J.; Ward, D. R.; Watson, N. K.; Websdale, D.; Weiden, A.; Whitehead, M.; Wilkinson, G.; Wilkinson, M.; Williams, M.; Williams, M. P.; Williams, M.; Williams, T.; Wilson, F. F.; Wimberley, J.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wright, S.; Wyllie, K.; Xie, Y.; Xu, Z.; Yang, Z.; Yu, J.; Yuan, X.; Yushchenko, O.; Zangoli, M.; Zavertyaev, M.; Zhang, L.; Zhang, Y.; Zhelezov, A.; Zhokhov, A.; Zhong, L.; Zucchelli, S.
2016-07-01
Associated production of bottomonia and open charm hadrons in pp collisions at √{s}=7 and 8 TeV is observed using data corresponding to an integrated luminosity of 3 fb-1 accumulated with the LHCb detector. The observation of five combinations, Y(1S)D0, Y(2S)D0, Y(1S)D+, Y(2S)D+ and Y(1S)D s + , is reported. Production crosssections are measured for Y(1S)D0 and Y(1S)D+ pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism. [Figure not available: see fulltext.
Parton-parton elastic scattering and rapidity gaps at SSC and LHC energies
Duca, V.D.
1993-08-01
The theory of the perturbative pomeron, due to Lipatov and collaborators, is used to compute the probability of observing parton-parton elastic scattering and rapidity gaps between jets in hadron collisions at SSC and LHC energies.
Triple parton scattering in collinear approximation of perturbative QCD
NASA Astrophysics Data System (ADS)
Snigirev, A. M.
2016-08-01
Revised formulas for the inclusive cross section of a triple parton scattering process in a hadron collision are suggested based on the modified collinear three-parton distributions. The possible phenomenological issues are discussed.
Double parton effects for jets with large rapidity separation
Szczurek, Antoni; Cisek, Anna; Maciuła, Rafal
2015-04-10
We discuss production of four jets pp → jjjjX with at least two jets with large rapidity separation in proton-proton collisions at the LHC through the mechanism of double-parton scattering (DPS). The cross section is calculated in a factorizaed approximation. Each hard subprocess is calculated in LO collinear approximation. The LO pQCD calculations are shown to give a reasonably good descritption of CMS and ATLAS data on inclusive jet production. It is shown that relative contribution of DPS is growing with increasing rapidity distance between the most remote jets, center-of-mass energy and with decreasing (mini)jet transverse momenta. We show also result for angular azimuthal dijet correlations calculated in the framework of k{sub t} -factorization approximation.
Double Parton Fragmentation Function and its Evolution in Quarkonium Production
NASA Astrophysics Data System (ADS)
Kang, Zhong-Bo
2014-01-01
We summarize the results of a recent study on a new perturbative QCD factorization formalism for the production of heavy quarkonia of large transverse momentum pT at collider energies. Such a new factorization formalism includes both the leading power (LP) and next-to-leading power (NLP) contributions to the cross section in the mQ2/p_T^2 expansion for heavy quark mass mQ. For the NLP contribution, the so-called double parton fragmentation functions are involved, whose evolution equations have been derived. We estimate fragmentation functions in the non-relativistic QCD formalism, and found that their contribution reproduce the bulk of the large enhancement found in explicit NLO calculations in the color singlet model. Heavy quarkonia produced from NLP channels prefer longitudinal polarization, in contrast to the single parton fragmentation function. This might shed some light on the heavy quarkonium polarization puzzle.
Generalized parton distributions from deep virtual compton scattering at CLAS
Guidal, M.
2010-04-24
Here, we have analyzed the beam spin asymmetry and the longitudinally polarized target spin asymmetry of the Deep Virtual Compton Scattering process, recently measured by the Jefferson Lab CLAS collaboration. Our aim is to extract information about the Generalized Parton Distributions of the proton. By fitting these data, in a largely model-independent procedure, we are able to extract numerical values for the two Compton Form Factors $H_{Im}$ and $\\tilde{H}_{Im}$ with uncertainties, in average, of the order of 30%.
Generalized parton distributions from deep virtual compton scattering at CLAS
Guidal, M.
2010-04-24
Here, we have analyzed the beam spin asymmetry and the longitudinally polarized target spin asymmetry of the Deep Virtual Compton Scattering process, recently measured by the Jefferson Lab CLAS collaboration. Our aim is to extract information about the Generalized Parton Distributions of the proton. By fitting these data, in a largely model-independent procedure, we are able to extract numerical values for the two Compton Form Factorsmore » $$H_{Im}$$ and $$\\tilde{H}_{Im}$$ with uncertainties, in average, of the order of 30%.« less
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
Generalized Parton Distributions And Deeply Virtual Compton Scattering At Clas
De Masi, Rita
2007-09-01
The deeply virtual Compton scattering is the simplest process to access the generalized parton distributions of the nucleon. A dedicated large statistics experiment for the measurement of deeply virtual Compton scattering with a 6 GeV polarized electron beam on a proton target has been performed at the Hall-B of Jefferson Laboratory with the CLAS spectrometer. The experiment covered a wide kinematic range, allowing the study of the beam spin asymmetry as function of the Bjorken variable xB, the Mandelstam variable t, the virtual photon four-momentum squared Q2 and the angle phi between leptonic and hadronic planes. The preliminary results are in agreement with previous measurements and with the predicted twist-2 dominance.
D0 results on diphoton direct production and double parton interactions in photon + 3 jet events
Sawyer, Lee; /Louisiana Tech. U.
2010-01-01
We report the measurement of differential diphoton direct production cross sections and a study of photon + 3-jet events with double parton (DP) interactions, based on data taken with the D0 experiment at the Fermilab Tevatron proton-antiproton collider. We measure single differential cross sections as a function of the diphoton mass, the transverse momentum of the diphoton system, the azimuthal angle between the photons, and the polar scattering angle of the photons. In addition, we measure double differential cross sections considering the last three kinematic variables in three diphoton mass bins. The results are compared with different perturbative QCD predictions and event generators. We have used a sample of photon + 3-jet events collected by the D0 experiment with an integrated luminosity of about 1 fb{sup -1} to determine the fraction of events with double parton scattering (f{sub DP}) in a single p{bar p} collision at {radical}s = 1.96 TeV. The DP fraction and effective cross section ({sigma}{sub eff}), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p{sub T}) jet transverse momentum p{sub T}{sup jet2} within the range 15 < p{sub T}{sup jet} < 30 GeV. In this range, f{sub DP} varies between 0.23 < f{sub DP} < 0.47, while {sigma}{sub eff} has the average value {sigma}{sub eff}{sup ave} = 16.4 {+-} 0.3(stat) {+-} 2.3(syst) mb.
NASA Astrophysics Data System (ADS)
Seng, Chien-Yeah; Ramsey-Musolf, Michael J.
2013-07-01
We study the effect of parton angular momentum on the twist-four correction to the left-right asymmetry in the electron-deuteron parity-violating deep-inelastic scattering (PVDIS). We show that this higher-twist correction is transparent to the dynamics of parton angular momentum needed to account for the Sivers and Boer-Mulders functions and spin-independent parton distribution functions. A sufficiently precise measurement of the PVDIS asymmetry may, thus, provide additional information about the parton dynamics responsible for nucleon spin.
Deeply virtual Compton scattering and generalized parton distributions at CLAS
Niccolai, Silvia
2008-11-01
The exclusive electroproduction of real photons and mesons at high momentum transfer allows us to access the Generalized Parton Distributions (GPDs). The formalism of the GPDs provides a unified description of the hadronic structure in terms of quark and gluonic degrees of freedom. In particular, the Deeply Virtual Compton Scattering (DVCS), ep â e2p2Å , is one of the key reactions to determine the GPDs experimentally, as it is the simplest process that can be described in terms of GPDs. A dedicated experiment to study DVCS has been carried out in Hall B at Jefferson Lab. Beam-spin asymmetries, resulting from the interference of the Bethe-Heitler process and DVCS have been extracted over the widest kinematic range ever accessed for this reaction ( 1.2 < Q 2 < 3.7 (GeV/c 2, 0.09 < - t < 1.3 (GeV/c 2, 0.13 < x B < 0.46 . In this paper, the results obtained experimentally are shown and compared to GPD parametrizations.
Nuclear and partonic dynamics in high energy elastic nucleus-nucleus scattering
NASA Astrophysics Data System (ADS)
Małecki, Andrzej
1991-10-01
A hybrid description of diffraction which combines a geometrical modeling of multiple scattering with many-channel effects resulting from intrinsic dynamics on the nuclear and subnuclear level is presented. The application to 4-4He elastic scattering is satisfactory. Our analysis suggests that, at large momentum transfers, the parton constituents of nucleons immersed in nuclei are deconfined.
Nuclear and partonic dynamics in high energy elastic nucleus-nucleus scattering
Malecki, A. )
1991-10-01
A hybrid description of diffraction which combines a geometrical modeling of multiple scattering with many-channel effects resulting from intrinsic dynamics on the nuclear and subnuclear level is presented. The application to {sup 4}He-{sup 4}He elastic scattering is satisfactory. Our analysis suggests that, at large momentum transfers, the parton constituents of nucleons immersed in nuclei are deconfined.
Ma, Guo -Liang; Bzdak, Adam
2014-11-04
In this study, we show that the incoherent elastic scattering of partons, as present in a multi-phase transport model (AMPT), with a modest parton–parton cross-section of σ = 1.5 – 3 mb, naturally explains the long-range two-particle azimuthal correlation as observed in proton–proton and proton–nucleus collisions at the Large Hadron Collider.
QCD CORRECTIONS TO DILEPTON PRODUCTION NEAR PARTONIC THRESHOLD IN PP SCATTERING.
SHIMIZU, H.; STERMAN, G.; VOGELSANG, W.; YOKOYA, H.
2005-10-02
We present a recent study of the QCD corrections to dilepton production near partonic threshold in transversely polarized {bar p}p scattering, We analyze the role of the higher-order perturbative QCD corrections in terms of the available fixed-order contributions as well as of all-order soft-gluon resummations for the kinematical regime of proposed experiments at GSI-FAIR. We find that perturbative corrections are large for both unpolarized and polarized cross sections, but that the spin asymmetries are stable. The role of the far infrared region of the momentum integral in the resummed exponent and the effect of the NNLL resummation are briefly discussed.
Double parton interactions as a background to associated HW production at the Tevatron
Bandurin, Dmitry; Golovanov, Georgy; Skachkov, Nikolai
2010-11-01
In this paper we study events with W+jets final state, produced in double parton (DP) interactions, as a background to the associated Higgs boson (H) and W production, with H {yields} b{bar b} decay, at the Tevatron. We have found that the event yield from the DP background can be quite sizable, what necessitates a choice of selection criteria to separate the HW and DP production processes. We suggest a set of variables sensitive to the kinematics of DP and HW events. We show that these variables, being used as an input to the artificial neural network, allow one to significantly improve a sensitivity to the Higgs boson production.
Hard scattering of partons as a probe of collisions at RHIC using the STAR detector system
Christie, W.B.
1995-07-15
Presented here is the current state of the author`s investigations into the use of hard probes to study pp, pA, and AA collisions at the Relativistic Heavy Ion Collider (RHIC) being built at Brookhaven National Laboratory. The overall goal of the RHIC program is the discovery and study of the Quark-Gluon Plasma (QGP), which is predicted to be formed at the high energy densities reached at RHIC in high energy AA collisions. The term {open_quotes}Hard probes{close_quotes} as used in this document includes those particles whose origin is the result of a direct hard parton scatter (i.e qq, qg, or gg). The final states of these hard parton scatters which the author proposes to study include dijets, gamma-jet coincidences, and inclusive high P{sub t} particle spectra. A brief discussion of the physics objectives is given in section 1. This is followed by an introduction to the STAR detector system in section 2, with particular details given for the proposed STAR Electromagnetic Calorimeter (EMC). The present simulation studies and results are given in section 3. The author concludes with a summary and a discussion of future plans in section 4.
Analytical Expressions for the Hard-Scattering Production of Massive Partons
Wong, Cheuk-Yin
2016-01-01
We obtain explicit expressions for the two-particle differential cross section $E_c E_\\kappa d\\sigma (AB \\to c\\kappa X) /d\\bb c d \\bb \\kappa$ and the two-particle angular correlation function \\break $d\\sigma(AB$$ \\to$$ c\\kappa X)/d\\Delta \\phi \\, d\\Delta y$ in the hard-scattering production of massive partons in order to exhibit the ``ridge" structure on the away side in the hard-scattering process. The single-particle production cross section $d\\sigma(AB \\to cX) /dy_c c_T dc_T $ is also obtained and compared with the ALICE experimental data for charm production in $pp$ collisions at 7 TeV at LHC.
Generalized parton distributions and Deeply Virtual Compton Scattering on proton at CLAS
R. De Masi
2007-12-01
Two measurements of target and beam spin asymmetries for the reaction ep→epγ were performed with CLAS at Jefferson Laboratory. Polarized 5.7 GeV electrons were impinging on a longitudinally polarized ammonia and liquid hydrogen target respectively. These measurements are sensitive to Generalized Parton Distributions. Sizable sin phi azimuthal angular dependences were observed in both experiments, indicating the dominance of leading twist terms and the possibility of extracting combinations of Generalized Parton Distributions on the nucleon.
CT14QED parton distribution functions from isolated photon production in deep inelastic scattering
NASA Astrophysics Data System (ADS)
Schmidt, Carl; Pumplin, Jon; Stump, Daniel; Yuan, C.-P.
2016-06-01
We describe the implementation of quantum electrodynamic (QED) evolution at leading order (LO) along with quantum chromodynamic (QCD) evolution at next-to-leading order (NLO) in the CTEQ-TEA global analysis package. The inelastic contribution to the photon parton distribution function (PDF) is described by a two-parameter ansatz, coming from radiation off the valence quarks, and based on the CT14 NLO PDFs. Setting the two parameters to be equal allows us to completely specify the inelastic photon PDF in terms of the inelastic momentum fraction carried by the photon, p0γ, at the initial scale Q0=1.295 GeV . We obtain constraints on the photon PDF by comparing with ZEUS data [S. Chekanov et al. (ZEUS Collaboration), Phys. Lett. B 687, 16 (2010)] on the production of isolated photons in deep inelastic scattering, e p →e γ +X . For this comparison we present a new perturbative calculation of the process that consistently combines the photon-initiated contribution with the quark-initiated contribution. Comparison with the data allows us to put a constraint at the 90% confidence level of p0γ≲0.14 % for the inelastic photon PDF at the initial scale of Q0=1.295 GeV in the one-parameter radiative ansatz. The resulting inelastic CT14QED PDFs will be made available to the public. In addition, we also provide CT14QEDinc PDFs, in which the inclusive photon PDF at the scale Q0 is defined by the sum of the inelastic photon PDF and the elastic photon distribution obtained from the equivalent photon approximation.
Abazov, Victor Mukhamedovich
2016-03-01
We use a sample of diphoton+dijet events to measure the effective cross section of double parton interactions, which characterizes the area containing the interacting partons in proton-antiproton collisions, and find it to be σeff=19.3±1.4(stat)±7.8(syst) mb. The sample was collected by the D0 detector at the Fermilab Tevatron collider inmore » $$p\\bar{p}$$ collisions at $$\\sqrt{s} = 1.96$$ TeV and corresponds to an integrated luminosity of 8.7 fb-1.« less
Study of double parton interactions in diphoton +dijet events in p p ¯ collisions at √{s }=1.96 TeV
NASA Astrophysics Data System (ADS)
Abazov, V. M.; Abbott, B.; Acharya, B. S.; Adams, M.; Adams, T.; Agnew, J. P.; Alexeev, G. D.; Alkhazov, G.; Alton, A.; Askew, A.; Atkins, S.; Augsten, K.; Aushev, V.; Aushev, Y.; Avila, C.; Badaud, F.; Bagby, L.; Baldin, B.; Bandurin, D. V.; Banerjee, S.; Barberis, E.; Baringer, P.; Bartlett, J. F.; Bassler, U.; Bazterra, V.; Bean, A.; Begalli, M.; Bellantoni, L.; Beri, S. B.; Bernardi, G.; Bernhard, R.; Bertram, I.; Besançon, M.; Beuselinck, R.; Bhat, P. C.; Bhatia, S.; Bhatnagar, V.; Blazey, G.; Blessing, S.; Bloom, K.; Boehnlein, A.; Boline, D.; Boos, E. E.; Borissov, G.; Borysova, M.; Brandt, A.; Brandt, O.; Brock, R.; Bross, A.; Brown, D.; Bu, X. B.; Buehler, M.; Buescher, V.; Bunichev, V.; Burdin, S.; Buszello, C. P.; Camacho-Pérez, E.; Casey, B. C. K.; Castilla-Valdez, H.; Caughron, S.; Chakrabarti, S.; Chan, K. M.; Chandra, A.; Chapon, E.; Chen, G.; Cho, S. W.; Choi, S.; Choudhary, B.; Cihangir, S.; Claes, D.; Clutter, J.; Cooke, M.; Cooper, W. E.; Corcoran, M.; Couderc, F.; Cousinou, M.-C.; Cuth, J.; Cutts, D.; Das, A.; Davies, G.; de Jong, S. J.; De La Cruz-Burelo, E.; Déliot, F.; Demina, R.; Denisov, D.; Denisov, S. P.; Desai, S.; Deterre, C.; DeVaughan, K.; Diehl, H. T.; Diesburg, M.; Ding, P. F.; Dominguez, A.; Dubey, A.; Dudko, L. V.; Duperrin, A.; Dutt, S.; Eads, M.; Edmunds, D.; Ellison, J.; Elvira, V. D.; Enari, Y.; Evans, H.; Evdokimov, A.; Evdokimov, V. N.; Fauré, A.; Feng, L.; Ferbel, T.; Fiedler, F.; Filthaut, F.; Fisher, W.; Fisk, H. E.; Fortner, M.; Fox, H.; Franc, J.; Fuess, S.; Garbincius, P. H.; Garcia-Bellido, A.; García-González, J. A.; Gaspar, P.; Gavrilov, V.; Geng, W.; Gerber, C. E.; Gershtein, Y.; Ginther, G.; Gogota, O.; Golovanov, G.; Grannis, P. D.; Greder, S.; Greenlee, H.; Grenier, G.; Gris, Ph.; Grivaz, J.-F.; Grohsjean, A.; Grünendahl, S.; Grünewald, M. W.; Guillemin, T.; Gutierrez, G.; Gutierrez, P.; Haley, J.; Han, L.; Harder, K.; Harel, A.; Hauptman, J. M.; Hays, J.; Head, T.; Hebbeker, T.; Hedin, D.; Hegab, H.; Heinson, A. P.; Heintz, U.; Hensel, C.; Heredia-De La Cruz, I.; Herner, K.; Hesketh, G.; Hildreth, M. D.; Hirosky, R.; Hoang, T.; Hobbs, J. D.; Hoeneisen, B.; Hogan, J.; Hohlfeld, M.; Holzbauer, J. L.; Howley, I.; Hubacek, Z.; Hynek, V.; Iashvili, I.; Ilchenko, Y.; Illingworth, R.; Ito, A. S.; Jabeen, S.; Jaffré, M.; Jayasinghe, A.; Jeong, M. S.; Jesik, R.; Jiang, P.; Johns, K.; Johnson, E.; Johnson, M.; Jonckheere, A.; Jonsson, P.; Joshi, J.; Jung, A. W.; Juste, A.; Kajfasz, E.; Karmanov, D.; Katsanos, I.; Kaur, M.; Kehoe, R.; Kermiche, S.; Khalatyan, N.; Khanov, A.; Kharchilava, A.; Kharzheev, Y. N.; Kiselevich, I.; Kohli, J. M.; Kozelov, A. V.; Kraus, J.; Kumar, A.; Kupco, A.; Kurča, T.; Kuzmin, V. A.; Lammers, S.; Lebrun, P.; Lee, H. S.; Lee, S. W.; Lee, W. M.; Lei, X.; Lellouch, J.; Li, D.; Li, H.; Li, L.; Li, Q. Z.; Lim, J. K.; Lincoln, D.; Linnemann, J.; Lipaev, V. V.; Lipton, R.; Liu, H.; Liu, Y.; Lobodenko, A.; Lokajicek, M.; Lopes de Sa, R.; Luna-Garcia, R.; Lyon, A. L.; Maciel, A. K. A.; Madar, R.; Magaña-Villalba, R.; Malik, S.; Malyshev, V. L.; Mansour, J.; Martínez-Ortega, J.; McCarthy, R.; McGivern, C. L.; Meijer, M. M.; Melnitchouk, A.; Menezes, D.; Mercadante, P. G.; Merkin, M.; Meyer, A.; Meyer, J.; Miconi, F.; Mondal, N. K.; Mulhearn, M.; Nagy, E.; Narain, M.; Nayyar, R.; Neal, H. A.; Negret, J. P.; Neustroev, P.; Nguyen, H. T.; Nunnemann, T.; Orduna, J.; Osman, N.; Osta, J.; Pal, A.; Parashar, N.; Parihar, V.; Park, S. K.; Partridge, R.; Parua, N.; Patwa, A.; Penning, B.; Perfilov, M.; Peters, Y.; Petridis, K.; Petrillo, G.; Pétroff, P.; Pleier, M.-A.; Podstavkov, V. M.; Popov, A. V.; Prewitt, M.; Price, D.; Prokopenko, N.; Qian, J.; Quadt, A.; Quinn, B.; Ratoff, P. N.; Razumov, I.; Ripp-Baudot, I.; Rizatdinova, F.; Rominsky, M.; Ross, A.; Royon, C.; Rubinov, P.; Ruchti, R.; Sajot, G.; Sánchez-Hernández, A.; Sanders, M. P.; Santos, A. S.; Savage, G.; Savitskyi, M.; Sawyer, L.; Scanlon, T.; Schamberger, R. D.; Scheglov, Y.; Schellman, H.; Schott, M.; Schwanenberger, C.; Schwienhorst, R.; Sekaric, J.; Severini, H.; Shabalina, E.; Shary, V.; Shaw, S.; Shchukin, A. A.; Simak, V.; Skubic, P.; Slattery, P.; Smirnov, D.; Snow, G. R.; Snow, J.; Snyder, S.; Söldner-Rembold, S.; Sonnenschein, L.; Soustruznik, K.; Stark, J.; Stefaniuk, N.; Stoyanova, D. A.; Strauss, M.; Suter, L.; Svoisky, P.; Titov, M.; Tokmenin, V. V.; Tsai, Y.-T.; Tsybychev, D.; Tuchming, B.; Tully, C.; Uvarov, L.; Uvarov, S.; Uzunyan, S.; Van Kooten, R.; van Leeuwen, W. M.; Varelas, N.; Varnes, E. W.; Vasilyev, I. A.; Verkheev, A. Y.; Vertogradov, L. S.; Verzocchi, M.; Vesterinen, M.; Vilanova, D.; Vokac, P.; Wahl, H. D.; Wang, M. H. L. S.; Warchol, J.; Watts, G.; Wayne, M.; Weichert, J.; Welty-Rieger, L.; Williams, M. R. J.; Wilson, G. W.; Wobisch, M.; Wood, D. R.; Wyatt, T. R.; Xie, Y.; Yamada, R.; Yang, S.; Yasuda, T.; Yatsunenko, Y. A.; Ye, W.; Ye, Z.; Yin, H.; Yip, K.; Youn, S. W.; Yu, J. M.; Zennamo, J.; Zhao, T. G.; Zhou, B.; Zhu, J.; Zielinski, M.; Zieminska, D.; Zivkovic, L.; D0 Collaboration
2016-03-01
We use a sample of diphoton+dijet events to measure the effective cross section of double parton interactions, which characterizes the area containing the interacting partons in proton-antiproton collisions, and find it to be σeff=19.3 ±1.4 (stat)±7.8 (syst) mb . The sample was collected by the D0 detector at the Fermilab Tevatron collider in p p ¯ collisions at √{s }=1.96 TeV and corresponds to an integrated luminosity of 8.7 fb-1 .
Measurement of partonic nuclear effects in deep-inelastic neutrino scattering using MINERvA
Mousseau, J.
2016-04-19
Here, the MINERvA Collaboration reports a novel study of neutrino-nucleus charged-current deep inelastic scattering (DIS) using the same neutrino beam incident on targets of polystyrene, graphite, iron, and lead. Results are presented as ratios of C, Fe, and Pb to CH. The ratios of total DIS cross sections as a function of neutrino energy and flux-integrated differential cross sections as a function of the Bjorken scaling variable x are presented in the neutrino-energy range of 5–50 GeV. Based on the predictions of charged-lepton scattering ratios, good agreement is found between the data and prediction at medium x and low neutrino energy.more » However, the ratios appear to be below predictions in the vicinity of the nuclear shadowing region, x < 0.1. This apparent deficit, reflected in the DIS cross-section ratio at high Eν, is consistent with previous MINERvA observations [B. Tice (MINERvA Collaboration), Phys. Rev. Lett. 112, 231801 (2014).] and with the predicted onset of nuclear shadowing with the axial-vector current in neutrino scattering.« less
Measurement of partonic nuclear effects in deep-inelastic neutrino scattering using MINERvA
NASA Astrophysics Data System (ADS)
Mousseau, J.; Wospakrik, M.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Devan, J.; Dytman, S. A.; Díaz, G. A.; Eberly, B.; Felix, J.; Fields, L.; Fine, R.; Gago, A. M.; Galindo, R.; Gallagher, H.; Ghosh, A.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Hurtado, K.; Kiveni, M.; Kleykamp, J.; Kordosky, M.; Le, T.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; Martinez Caicedo, D. A.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Naples, D.; Nelson, J. K.; Norrick, A.; Nuruzzaman; Osta, J.; Paolone, V.; Park, J.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ransome, R. D.; Ray, H.; Ren, L.; Rimal, D.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Schmitz, D. W.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Zavala, G.; Zhang, D.; Minerν A Collaboration
2016-04-01
The MINERvA Collaboration reports a novel study of neutrino-nucleus charged-current deep inelastic scattering (DIS) using the same neutrino beam incident on targets of polystyrene, graphite, iron, and lead. Results are presented as ratios of C, Fe, and Pb to CH. The ratios of total DIS cross sections as a function of neutrino energy and flux-integrated differential cross sections as a function of the Bjorken scaling variable x are presented in the neutrino-energy range of 5-50 GeV. Based on the predictions of charged-lepton scattering ratios, good agreement is found between the data and prediction at medium x and low neutrino energy. However, the ratios appear to be below predictions in the vicinity of the nuclear shadowing region, x <0.1 . This apparent deficit, reflected in the DIS cross-section ratio at high Eν, is consistent with previous MINERvA observations [B. Tice et al. (MINERvA Collaboration), Phys. Rev. Lett. 112, 231801 (2014).] and with the predicted onset of nuclear shadowing with the axial-vector current in neutrino scattering.
Summing threshold logs in a parton shower
NASA Astrophysics Data System (ADS)
Nagy, Zoltán; Soper, Davison E.
2016-10-01
When parton distributions are falling steeply as the momentum fractions of the partons increases, there are effects that occur at each order in α s that combine to affect hard scattering cross sections and need to be summed. We show how to accomplish this in a leading approximation in the context of a parton shower Monte Carlo event generator.
Guegan, Baptiste
2012-11-01
The exclusive leptoproduction of a real photon is considered to be the "cleanest" way to access the Generalized Parton Distribution (GPD). This process is called Deeply Virtual Compton Scattering (DVCS) lN {yields} lN{gamma} , and is sensitive to all the four GPDs. Measuring the DVCS cross section is one of the main goals of this thesis. In this thesis, we present the work performed to extract on a wide phase-space the DVCS cross-section from the JLab data at a beam energy of 6 GeV.
Lidar measurements of rotational Raman and double scattering.
Cohen, A; Kleiman, M; Cooney, J
1978-06-15
The analysis of unusually strong Raman backscattering signals from clouds shows that such signals cannot be merely related to filter on-line leakage. Theoretical calculations of Raman double scattering in an atmosphere with high optical depth values are presented, and it is shown that the Raman multiple scattering effect is not negligible. The results of the calculations are in good agreement with the experimental data.
Accardi, A.; Brady, L. T.; Melnitchouk, W.; Owens, J. F.; Sato, N.
2016-06-20
Here, we present a new set of leading twist parton distribution functions, referred to as "CJ15", which take advantage of developments in the theoretical treatment of nuclear corrections as well as new data. The analysis includes for the first time data on the free neutron structure function from Jefferson Lab, and new high-precision charged lepton and W-boson asymmetry data from Fermilab, which significantly reduce the uncertainty on the d/u ratio at large values of x.
Energy distribution of elastically scattered electrons from double layer samples
NASA Astrophysics Data System (ADS)
Tőkési, K.; Varga, D.
2016-02-01
We present a theoretical description of the spectra of electrons elastically scattered from thin double layered Au-C samples. The analysis is based on the Monte Carlo simulation of the recoil and Doppler effects in reflection and transmission geometries of the scattering at a fixed angle of 44.3 ° and a primary energy of 40 keV. The relativistic correction is taken into account. Besides the experimentally measurable energy distributions the simulations give many partial distributions separately, depending on the number of elastic scatterings (single, and multiple scatterings of different types). Furthermore, we present detailed analytical calculations for the main parameters of the single scattering, taking into account both the ideal scattering geometry, i.e. infinitesimally small angular range, and the effect of the real, finite angular range used in the measurements. We show our results for intensity ratios, peak shifts and broadenings for four cases of measurement geometries and layer thicknesses. While in the peak intensity ratios of gold and carbon for transmission geometries were found to be in good agreement with the results of the single scattering model, especially large deviations were obtained in reflection geometries. The separation of the peaks, depending on the geometry and the thickness, generally smaller, and the peak width generally larger than it can be expected from the nominal values of the primary energy, scattering angle, and mean kinetic energy of the atoms. We also show that the peaks are asymmetric even for the case of the single scattering due to the finite solid angle. Finally, we present a qualitative comparison with the experimental data. We find our resulting energy distribution of elastically scattered electrons to be in good agreement with recent measurements.
A Double Scattering Analytical Model For Elastic Recoil Detection Analysis
Barradas, N. P.; Lorenz, K.; Alves, E.; Darakchieva, V.
2011-06-01
We present an analytical model for calculation of double scattering in elastic recoil detection measurements. Only events involving the beam particle and the recoil are considered, i.e. 1) an ion scatters off a target element and then produces a recoil, and 2) an ion produces a recoil which then scatters off a target element. Events involving intermediate recoils are not considered, i.e. when the primary ion produces a recoil which then produces a second recoil. If the recoil element is also present in the stopping foil, recoil events in the stopping foil are also calculated. We included the model in the standard code for IBA data analysis NDF, and applied it to the measurement of hydrogen in Si.
Xin Qian
2012-06-01
Parton distribution functions, which represent the flavor and spin structure of the nucleon, provide invaluable information in illuminating quantum chromodynamics in the confinement region. Among various processes that measure such parton distribution functions, semi-inclusive deep inelastic scattering is regarded as one of the golden channels to access transverse momentum dependent parton distribution functions, which provide a 3-D view of the nucleon structure in momentum space. The Jefferson Lab experiment E06-010 focuses on measuring the target single and double spin asymmetries in the 3He(e, e'pi+,-)X reaction with a transversely polarized 3He target in Hall A with a 5.89 GeV electron beam. A leading pion and the scattered electron are detected in coincidence by the left High-Resolution Spectrometer at 16{sup o} and the BigBite spectrometer at 30{sup o} beam right, respectively. The kinematic coverage concentrates in the valence quark region, x {approx} 0.1-0.4, at Q2 {approx}1-3 Gev{sub 2}. The Collins and Sivers asymmetries of 3He and neutron are extracted. In this review, an overview of the experiment and the final results are presented. Furthermore, an upcoming 12-GeV program with a large acceptance solenoidal device and the future possibilities at an electron-ion collider are discussed.
Bahar, E; El-Shenawee, M
2001-01-01
Full-wave solutions are given for the single- and double-scatter radar cross sections for two-dimensional random rough surfaces. High-frequency approximations are used for the double-scatter cross sections in order to express them as numerically tractable four-dimensional integrals. The major contributions to the double-scatter cross sections are associated with the quasi-parallel and quasi-antiparallel double-scatter paths. They come from the neighborhoods of specular points. The enhancement of the backscatter cross sections, which is associated with the quasi-antiparallel double-scatter paths, is observed for both the like- and cross-polarized cross sections.
Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Prum, Richard O.; Mochrie, Simon G.J.; Dufresne, Eric R.; Cao, Hui
2010-07-28
We measured the polarization- and angle-resolved optical scattering and reflection spectra of the quasiordered nanostructures in the bird feather barbs. In addition to the primary peak that originates from single scattering, we observed a secondary peak which exhibits depolarization and distinct angular dispersion. We explained the secondary peak in terms of double scattering, i.e., light is scattered successively twice by the structure. The two sequential single-scattering events are considered uncorrelated. Using the Fourier power spectra of the nanostructures obtained from the small-angle x-ray scattering experiment, we calculated the double scattering of light in various directions. The double-scattering spectrum is broader than the single-scattering spectrum, and it splits into two subpeaks at larger scattering angle. The good agreement between the simulation results and the experimental data confirms that double scattering of light makes a significant contribution to the structural color.
Nuclear Parton Distribution Functions
I. Schienbein, J.Y. Yu, C. Keppel, J.G. Morfin, F. Olness, J.F. Owens
2009-06-01
We study nuclear effects of charged current deep inelastic neutrino-iron scattering in the framework of a {chi}{sup 2} analysis of parton distribution functions (PDFs). We extract a set of iron PDFs which are used to compute x{sub Bj}-dependent and Q{sup 2}-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged-lepton--iron scattering. We find that, except for very high x{sub Bj}, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.
Generalized Parton Distributions and their Singularities
Anatoly Radyushkin
2011-04-01
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) Ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function $f(\\beta)/\\beta$ rather than with the usual parton density $f(\\beta)$. This results in a non-integrable singularity at $\\beta=0$ exaggerated by the fact that $f(\\beta)$'s, on their own, have a singular $\\beta^{-a}$ Regge behavior for small $\\beta$. It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs $H(x,\\xi)$ that are finite and continuous at the "border point'' $x=\\xi$. Using a simple input forward distribution, we illustrate the implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the $\\beta=0$ singularities is proposed that is based on the separation of the initial single DD $f(\\beta, \\alpha)$ into the "plus'' part $[f(\\beta,\\alpha)]_{+}$ and the $D$-term. It is demonstrated that the "DD+D'' separation method allows to (re)derive GPD sum rules that relate the difference between the forward distribution $f(x)=H(x,0)$ and the border function $H(x,x)$ with the $D$-term function $D(\\alpha)$.
Generalized parton distributions and their singularities
Radyushkin, A. V.
2011-04-01
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function f({beta})/{beta} rather than with the usual parton density f({beta}). This results in a nonintegrable singularity at {beta}=0 exaggerated by the fact that f({beta})'s, on their own, have a singular {beta}{sup -a} Regge behavior for small {beta}. It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs H(x,{xi}) that are finite and continuous at the 'border point' x={xi}. Using a simple input forward distribution, we illustrate implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the {beta}=0 singularities is proposed that is based on the separation of the initial single DD f({beta},{alpha}) into the 'plus' part [f({beta},{alpha})]{sub +} and the D term. It is demonstrated that the ''DD+D'' separation method allows one to (re)derive GPD sum rules that relate the difference between the forward distribution f(x)=H(x,0) and the border function H(x,x) with the D-term function D({alpha}).
Pion double charge exchange scattering above the delta resonance
Burleson, G.R.
1989-01-01
Data are presented on pion-nucleus double-charge-exchange scattering at energies between 300 and 500 MeV, the highest energies measured so far, together with a review of results at lower energies. The small-angle excitation functions disagree with predictions based on a sex-quark cluster model and on an optical model consistent with single-charge-exchange scattering at these energies, but they are consistent with a distorted-wave calculation. Data on f{sub 7/2}-shell nuclei are in partial agreement with a two-amplitude model which is successful at lower energies. In order to achieve good understanding of this process at these energies, more work; both experimental and theoretical, is needed. 16 refs., 6 figs.
Chaotic dephasing in a double-slit scattering experiment.
Levnajić, Zoran; Prosen, Tomaz
2010-12-01
We design a computational experiment in which a quantum particle tunnels into a billiard of variable shape and scatters out of it through a double-slit opening on the billiard's base. The interference patterns produced by the scattered probability currents for a range of energies are investigated in relation to the billiard's geometry which is connected to its classical integrability. Four billiards with hierarchical integrability levels are considered: integrable, pseudointegrable, weak-mixing, and strongly chaotic. In agreement with the earlier result by Casati and Prosen [Phys. Rev. A 72, 032111 (2005)], we find the billiard's integrability to have a crucial influence on the properties of the interference patterns. In the integrable case, most experiment outcomes are found to be consistent with the constructive interference occurring in the usual double-slit experiment. In contrast to this, nonintegrable billiards typically display asymmetric interference patterns of smaller visibility characterized by weakly correlated wave function values at the two slits. Our findings indicate an intrinsic connection between the classical integrability and the quantum dephasing, which is responsible for the destruction of interference.
Guzey, V.; Teckentrup, T.
2006-09-01
We develop the minimal model of a new leading order parametrization of generalized parton distributions (GPDs) introduced by Polyakov and Shuvaev. The model for GPDs H and E is formulated in terms of the forward quark distributions, the Gegenbauer moments of the D-term, and the forward limit of the GPD E. The model is designed primarily for small and medium-size values of x{sub B}, x{sub B}{<=}0.2. We examine two different models of the t dependence of the GPDs: the factorized exponential model and the nonfactorized Regge-motivated model. Using our model, we successfully described the deeply virtual Compton scattering (DVCS) cross section measured by H1 and ZEUS, the moments of the beam-spin A{sub LU}{sup sin{phi}}, the beam-charge A{sub C}{sup cos{phi}}, and the transversely polarized target A{sub UT}{sup sin{phi}}{sup cos{phi}} DVCS asymmetries measured by HERMES and A{sub LU}{sup sin{phi}} measured by CLAS. The data on A{sub C}{sup cos{phi}} prefer the Regge-motivated model of the t dependence of the GPDs. The data on A{sub UT}{sup sin{phi}}{sup cos{phi}} indicate that the u and d quarks carry only a small fraction of the proton total angular momentum.
Disentangling correlations in multiple parton interactions
Calucci, G.; Treleani, D.
2011-01-01
Multiple Parton Interactions are the tool to obtain information on the correlations between partons in the hadron structure. Partons may be correlated in all degrees of freedom and all different correlation terms contribute to the cross section. The contributions due to the different parton flavors can be isolated, at least to some extent, by selecting properly the final state. In the case of high energy proton-proton collisions, the effects of correlations in the transverse coordinates and in fractional momenta are, on the contrary, unavoidably mixed in the final observables. The standard way to quantify the strength of double parton interactions is by the value of the effective cross section and a small value of the effective cross section may be originated both by the relatively short transverse distance between the pairs of partons undergoing the double interaction and by a large dispersion of the distribution in multiplicity of the multiparton distributions. The aim of the present paper is to show how the effects of longitudinal and transverse correlations may be disentangled by taking into account the additional information provided by double parton interactions in high energy proton-deuteron collisions.
Bahar, E; El-Shenawee, M
2001-01-01
Full-wave solutions are given for the single- and double-scatter radar cross sections for two-dimensional random rough surfaces. High-frequency approximations are used for the double-scatter cross sections in order to express them as numerically tractable four-dimensional integrals. The major contributions to the double-scatter cross sections are associated with the quasi-parallel and quasi-antiparallel double-scatter paths. They come from the neighborhoods of specular points. The enhancement of the backscatter cross sections, which is associated with the quasi-antiparallel double-scatter paths, is observed for both the like- and cross-polarized cross sections. PMID:11151986
Excited nucleon as a van der Waals system of partons
Jenkovszky, L. L.; Muskeyev, A. O. Yezhov, S. N.
2012-06-15
Saturation in deep inelastic scattering (DIS) and deeply virtual Compton scattering (DVCS) is associated with a phase transition between the partonic gas, typical of moderate x and Q{sup 2}, and partonic fluid appearing at increasing Q{sup 2} and decreasing Bjorken x. We suggest the van der Waals equation of state to describe properly this phase transition.
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.
Structure functions and parton distributions
Martin, A.D.; Stirling, W.J.; Roberts, R.G.
1995-07-01
The MRS parton distribution analysis is described. The latest sets are shown to give an excellent description of a wide range of deep-inelastic and other hard scattering data. Two important theoretical issues-the behavior of the distributions at small x and the flavor structure of the quark sea-are discussed in detail. A comparison with the new structure function data from HERA is made, and the outlook for the future is discussed.
NASA Astrophysics Data System (ADS)
Bellm, Johannes; Plätzer, Simon; Richardson, Peter; Siódmok, Andrzej; Webster, Stephen
2016-08-01
We report on the possibility of reweighting parton-shower Monte Carlo predictions for scale variations in the parton-shower algorithm. The method is based on a generalization of the Sudakov veto algorithm. We demonstrate the feasibility of this approach using example physical distributions. Implementations are available for both of the parton-shower modules in the Herwig 7 event generator.
Modeling Nucleon Generalized Parton Distributions
Radyushkin, Anatoly V.
2013-05-01
We discuss building models for nucleon generalized parton distributions (GPDs) H and E that are based on the formalism of double distributions (DDs). We find that the usual "DD+D-term'' construction should be amended by an extra term, generated by GPD E(x,\\xi). Unlike the $D$-term, this function has support in the whole -1 < x< 1 region, and in general does not vanish at the border points|x|=\\xi.
Accardi, Alberto; Owens, Jeff F.
2013-07-01
Three new sets of next-to-leading order parton distribution functions (PDFs) are presented, determined by global fits to a wide variety of data for hard scattering processes. The analysis includes target mass and higher twist corrections needed for the description of deep-inelastic scattering data at large x and low Q^2, and nuclear corrections for deuterium targets. The PDF sets correspond to three different models for the nuclear effects, and provide a more realistic uncertainty range for the d quark PDF compared with previous fits. Applications to weak boson production at colliders are also discussed.
Extractions of polarized and unpolarized parton distribution functions
Jimenez-Delgado, Pedro
2014-01-01
An overview of our ongoing extractions of parton distribution functions of the nucleon is given. First JAM results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering are presented first, and followed by a short report on the status of the JR unpolarized parton distributions. Different aspects of PDF analysis are briefly discussed, including effects of the nuclear structure of targets, target-mass corrections and higher twist contributions to the structure functions.
Self-Organizing Maps and Parton Distribution Functions
K. Holcomb, Simonetta Liuti, D. Z. Perry
2011-05-01
We present a new method to extract parton distribution functions from high energy experimental data based on a specific type of neural networks, the Self-Organizing Maps. We illustrate the features of our new procedure that are particularly useful for an anaysis directed at extracting generalized parton distributions from data. We show quantitative results of our initial analysis of the parton distribution functions from inclusive deep inelastic scattering.
Transverse nucleon structure and diagnostics of hard parton-parton processes at LHC
L. Frankfurt, M. Strikman, C. Weiss
2011-03-01
We propose a new method to determine at what transverse momenta particle production in high-energy pp collisions is governed by hard parton-parton processes. Using information on the transverse spatial distribution of partons obtained from hard exclusive processes in ep/\\gamma p scattering, we evaluate the impact parameter distribution of pp collisions with a hard parton-parton process as a function of p_T of the produced parton (jet). We find that the average pp impact parameters in such events depend very weakly on p_T in the range 2 < p_T < few 100 GeV, while they are much smaller than those in minimum-bias inelastic collisions. The impact parameters in turn govern the observable transverse multiplicity in such events (in the direction perpendicular to the trigger particle or jet). Measuring the transverse multiplicity as a function of p_T thus provides an effective tool for determining the minimum p_T for which a given trigger particle originates from a hard parton-parton process.
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.
Time and polarization dependent double scattering calculations of lidar returns from water clouds
NASA Technical Reports Server (NTRS)
Garner, R. C.
1992-01-01
We describe and present results of a double scattering lidar model which we use to calculate lidar returns from water clouds. The model is used in conjunction with the Phillips Laboratory's (Geophysics Directorate) low altitude Nd:YAG lidar system to determine microphysical properties of water clouds. The model determines the Stokes parameters of the backscattered lidar radiation, from media composed of spherical particles, as a function of time. The Stokes parameters of the radiation of the lidar return are determined, at each time, by considering all radiation which has traveled the same path length from transmitter to receiver while making two successive single scatters. Each single scatter is considered a Mie scatter. We have also developed a Mie scattering program for use with the double scattering model. Each single scatter takes into account the polarization of the incident and scattered radiation. Inputs to the double scattering mode include the receiver area and field of view, the receiver integration time, the extinction coefficient as a function of distance into the cloud, the particle size distribution (assumed independent of position), and the complex index of refraction of the spherical particles.
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)
Koirala, Suman Bandhu
The EG1-DVCS experiment with CLAS at Jefferson Lab collected semi-inclusive pion electro-production data on longitudinally polarized solid state NH3 and ND3 targets with longitudinally polarized electrons of approximately 6 GeV energy. Data on all three pion channels, pi +, pi-- and pi0, were collected simultaneously. The charged pions were identified by their time-of-flight information whereas the neutral pions were reconstructed from the invariant mass of two photons. The experiment covered a wide kinematic range: 1 GeV 2 ≤ Q2 ≤ 3.2 GeV2, 0.12 ≤ xB ≤ 0.48, 0.0 GeV ≤ Ph⊥ ≤ 1.0 GeV and 0.3 ≤ z ≤ 0.7. The beam single (ALU), target single (AUL) and beam-target double ( ALL) spin azimuthal asymmetries in semi-inclusive deep-inelastic scattering (SIDIS) off the proton and the deuteron extracted from the data are presented. The results of the azimuthal asymmetries for the proton are presented as a function of two variables: (xB, Ph⊥), (z, P h⊥) and (xB, z). Due to limited statistics, the azimuthal asymmetries for the deuteron are presented as a function of a single variable for the variables xB, z and Ph ⊥. Some theoretical and phenomenological predictions as well as earlier published results are compared with the results from this analysis. All the results are plotted and suitably tabulated for further analysis. The SIDIS azimuthal asymmetries are convolutions of fragmentation functions and transverse momentum dependent parton distribution functions (TMDs). The TMDs describe transverse momenta and spins of quarks and gluons inside nucleons. They open a window on the contribution of the orbital angular momentum of the quarks and gluons to the total spin of the nucleons. The results presented in this work are sensitive to these leading twist TMDs: f 1, g1, h⊥ 1L, and h⊥ 1. The significant precision of the results from this analysis will highly constrain the extractions of the associated TMDs which will substantially contribute towards further
Modeling Nucleon Generalized Parton Distributions
Radyushkin, Anatoly V.
2013-05-01
We discuss building models for nucleon generalized parton distributions (GPDs) H and E that are based on the formalism of double distributions (DDs). We found that the usual "DD+D-term" construction should be amended by an extra term, xiE^1_+ (x,xi) built from the alpha/Beta moment of the DD e(Beta,alpha) that generates GPD E(x,xi). Unlike the D-term, this function has support in the whole -1< x<1 region, and in general does not vanish at the border points |x|=xi.
On the Accuracy of Double Scattering Approximation for Atmospheric Polarization Computations
NASA Technical Reports Server (NTRS)
Korkin, Sergey V.; Lyapustin, Alexei I.; Marshak, Alexander L.
2011-01-01
Interpretation of multi-angle spectro-polarimetric data in remote sensing of atmospheric aerosols require fast and accurate methods of solving the vector radiative transfer equation (VRTE). The single and double scattering approximations could provide an analytical framework for the inversion algorithms and are relatively fast, however accuracy assessments of these approximations for the aerosol atmospheres in the atmospheric window channels have been missing. This paper provides such analysis for a vertically homogeneous aerosol atmosphere with weak and strong asymmetry of scattering. In both cases, the double scattering approximation gives a high accuracy result (relative error approximately 0.2%) only for the low optical path - 10(sup -2) As the error rapidly grows with optical thickness, a full VRTE solution is required for the practical remote sensing analysis. It is shown that the scattering anisotropy is not important at low optical thicknesses neither for reflected nor for transmitted polarization components of radiation.
Evolution and models for skewed parton distribution
Musatov, I.C.; Radyushkin, A.V.
1999-05-17
The authors discuss the structure of the ''forward visible'' (FW) parts of double and skewed distributions related to usual distributions through reduction relations. They use factorized models for double distributions (DDs) {tilde f}(x,{alpha}) in which one factor coincides with the usual (forward) parton distribution and another specifies the profile characterizing the spread of the longitudinal momentum transfer. The model DDs are used to construct skewed parton distributions (SPDs). For small skewedness, the FW parts of SPDs H ({tilde x},{xi}) can be obtained by averaging forward parton densities f({tilde x}-{xi}{alpha}) with the weight {rho}({alpha}) coinciding with the profile function of the double distribution {tilde f}(x, {alpha}) at small x. They show that if the x{sup n} moments {tilde f}{sub n}({alpha}) of DDs have the asymptotic (1-{alpha}{sup 2}){sup n+1} profile, then the {alpha}-profile of {tilde f}(x,{alpha}) for small x is completely determined by small-x behavior of the usual parton distribution. They demonstrate that, for small {xi}, the model with asymptotic profiles for {tilde f}{sub n}({alpha}) is equivalent to that proposed recently by Shuvaev et al., in which the Gegenbauer moments of SPDs do not depend on {xi}. They perform a numerical investigation of the evolution patterns of SPDs and give interpretation of the results of these studies within the formalism of double distributions.
The MESA polarimetry chain and the status of its double scattering polarimeter
Aulenbacher, K.; Bartolomé, P. Aguar; Molitor, M.; Tioukine, V.
2013-11-07
We plan to have two independent polarimetry systems at MESA based on totally different physical processes. A first one tries to minimize the systematic uncertainties in double polarized Mo/ller scattering, which is to be achieved by stored hydrogen atoms in an atomic trap (Hydro-Mo/ller-Polarimeter). The other one relies on the equality of polarizing and analyzing power which allows to measure the effective analyzing power of a polarimeter with very high accuracy. Since the status of Hydro-Mo/ller is presented in a separate paper we concentrate on the double scattering polarimeter in this article.
Double electron ionization in Compton scattering of high energy photons by helium atoms
Amusia, M.Y.; Mikhailov, A.I.
1995-08-01
The cross section for double-electron ionization of two-electron atoms and ions in Compton scattering of high energy photons is calculated. It is demonstrated that its dependence on the incoming photon frequency is the same as that for single-electron ionization. The ratio of {open_quotes}double-to-single{close_quotes} ionization in Compton scattering was found to be energy independent and almost identical with the corresponding value for photoionization. For the He atom it is 1.68%. This surprising result deserves experimental verification.
The MESA polarimetry chain and the status of its double scattering polarimeter
NASA Astrophysics Data System (ADS)
Aulenbacher, K.; Bartolomé, P. Aguar; Molitor, M.; Tioukine, V.
2013-11-01
We plan to have two independent polarimetry systems at MESA based on totally different physical processes. A first one tries to minimize the systematic uncertainties in double polarized Mo/ller scattering, which is to be achieved by stored hydrogen atoms in an atomic trap (Hydro-Mo/ller-Polarimeter). The other one relies on the equality of polarizing and analyzing power which allows to measure the effective analyzing power of a polarimeter with very high accuracy. Since the status of Hydro-Mo/ller is presented in a separate paper we concentrate on the double scattering polarimeter in this article.
Chu, Yizhuo; Wang, Dongxing; Zhu, Wenqi; Crozier, Kenneth B
2011-08-01
The strong coupling between localized surface plasmons and surface plasmon polaritons in a double resonance surface enhanced Raman scattering (SERS) substrate is described by a classical coupled oscillator model. The effects of the particle density, the particle size and the SiO2 spacer thickness on the coupling strength are experimentally investigated. We demonstrate that by tuning the geometrical parameters of the double resonance substrate, we can readily control the resonance frequencies and tailor the SERS enhancement spectrum. PMID:21934853
Utilization of Double Scanning in Ultrasonic Testing to Improve the Quality of the Scatterer Images
NASA Astrophysics Data System (ADS)
Bazulin, E. G.
2001-11-01
Derivation of a formula for double scanning, when a radiator and a receiver move independently along parallel straight lines, is presented. Advantages of this technique are discussed in comparison with the method of projection in the spectral space, which is also used for a coherent reconstruction of a scatterer image. The efficiency of the double scanning technique in suppressing the phantom images produced by transformed and rescattered pulses is demonstrated in a numerical experiment.
NASA Astrophysics Data System (ADS)
Hong, Sang-Hoon; Wdowinski, Shimon
2012-01-01
Common vegetation scattering theories indicate that short wavelength Synthetic Aperture Radar (SAR) observations (X- and C-band) measure mainly vegetation canopies as the short-wavelength radar signal interacts mostly with upper sections of the vegetation. Furthermore, these theories also suggest that SAR cross- polarization (cross-pol) observations reflect only volume scattering. Consequently most SAR decomposition techniques assume that the cross-pol signal represents solely volume scattering. However, short-wavelength and cross-pol observations from the Everglades wetlands, south Florida, suggest that a significant portion of the SAR signal scatters from the surface and not only from the upper sections of the vegetation. The indication for surface scattering in wetland environment is derived from phase observable processed using interferometric techniques. The interferometric SAR (InSAR) observations reveal coherent phase signal in all polarizations and all wavelengths, reflecting water level changes beneath the vegetation. This coherent phase signal cannot be explained by neither volume scattering nor radar signal interaction with the upper sections of the vegetations, because canopies and branches are frequently move by wind. The only way that such coherent signal can be maintained and represents surface water level changes is when a multiple bounce from the vegetation and surface occurs. The simplest multi-bounce scattering mechanism that generate cross-pol signal occurs by rotated dihedrals. Thus, we use the rotated dihedral mechanism to explain the InSAR wetland observations and to revise the current vegetation scattering theories to accounts also for double bounce component in cross-pol observations.
Parton Propagation and Fragmentation in QCD Matter
Alberto Accardi, Francois Arleo, William Brooks, David D'Enterria, Valeria Muccifora
2009-12-01
We review recent progress in the study of parton propagation, interaction and fragmentation in both cold and hot strongly interacting matter. Experimental highlights on high-energy hadron production in deep inelastic lepton-nucleus scattering, proton-nucleus and heavy-ion collisions, as well as Drell-Yan processes in hadron-nucleus collisions are presented. The existing theoretical frameworks for describing the in-medium interaction of energetic partons and the space-time evolution of their fragmentation into hadrons are discussed and confronted to experimental data. We conclude with a list of theoretical and experimental open issues, and a brief description of future relevant experiments and facilities.
Khosravi, H.; Daneshfar, N.; Bahari, A.
2010-05-15
The cross section of two alternating concentric double silica-gold nanoshell (DSGNS) is obtained as a function of wavelength. Numerical calculations show that two alternating concentric DSGNSs display two separated scattering peaks that the intensity and position of the scattering peaks depend on two gold shells thicknesses and silica layer thickness between them. By varying thicknesses of the layers of the gold shells, two alternating concentric DSGNS can be designed with the scattering peak from the visible to infrared regions of the spectrum.
Double scattering of light from Biophotonic Nanostructures with short-range order
Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Prum, Richard O.; Mochrie, Simon G.J.; Dufresne, Eric R.; Cao, Hui
2010-07-28
We investigate the physical mechanism for color production by isotropic nanostructures with short-range order in bird feather barbs. While the primary peak in optical scattering spectra results from constructive interference of singly-scattered light, many species exhibit secondary peaks with distinct characteristic. Our experimental and numerical studies show that these secondary peaks result from double scattering of light by the correlated structures. Without an analog in periodic or random structures, such a phenomenon is unique for short-range ordered structures, and has been widely used by nature for non-iridescent structural coloration.
Multiple parton interaction studies at DØ
Lincoln, D.
2016-04-01
Here, we present the results of studies of multiparton interactions done by the DØ collaboration using the Fermilab Tevatron at a center of mass energy of 1.96 TeV. We also present three analyses, involving three distinct final signatures: (a) a photon with at least 3 jets ( γ + 3jets), (b) a photon with a bottom or charm quark tagged jet and at least 2 other jets ( γ + b/c + 2jets), and (c) two J/ ψ mesons. The fraction of photon + jet events initiated by double parton scattering is about 20%, while the fraction for events inmore » which two J/ ψ mesons were produced is 30 ± 10. While the two measurements are statistically compatible, the difference might indicate differences in the quark and gluon distribution within a nucleon. Finally, this speculation originates from the fact that photon + jet events are created by collisions with quarks in the initial states, while J/ ψ events are produced preferentially by a gluonic initial state.« less
Studies of Transverse Momentum Distributions of Partons
NASA Astrophysics Data System (ADS)
Avagyan, Harut
2014-03-01
The detailed understanding of the orbital structure of partonic distributions, encoded in Transverse Momentum Dependent (TMD) parton distributions, has been widely recognized as key objective of the JLab 12 GeV upgrade, the polarised pp program at RHIC, and a driving force behind the construction of the Electron Ion Collider. Several proposals have been already approved by the JLab PAC to study TMDs using different spin-azimuthal asymmetries at JLab12 and were awarded the highest physics rating. Although the interest in TMDs has grown enormously we are still in need of fresh theoretical and phenomenological ideas. One of the main challenges still remaining is the extraction of actual 3D parton distribution functions from hard scattering processes in nucleons and nuclei. In this talk, we present an overview of the latest developments and future studies of the TMDs.
Double-logarithmic asymptotics of quark scattering amplitudes with flavor exchange
Kirschner, R.; Lipatov, L.N.
1982-09-01
We propose simple equations in terms of the definite-signature partial waves of the quark scattering and annihilation amplitudes with quark-quark and quark-antiquark states in the exchange channel. We discuss the singularities in the complex angular momentum plane generated by the double-logarithmic contributions and point out their relation to the particle Regge trajectories.
Parton Distributions Working Group
de Barbaro, L.; Keller, S. A.; Kuhlmann, S.; Schellman, H.; Tung, W.-K.
2000-07-20
This report summarizes the activities of the Parton Distributions Working Group of the QCD and Weak Boson Physics workshop held in preparation for Run II at the Fermilab Tevatron. The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, the authors introduce a Manifesto that describes an optimal method for reporting data.
Double-confocal resonator for X-ray generation via intracavity Thomson scattering
Xie, M.
1995-12-31
There has been a growing interest in developing compact X-ray sources through Thomson scattering of a laser beam by a relativistic electron beam. For higher X-ray flux it is desirable to have the scattering to occur inside an optical resonator where the laser power is higher. In this paper I propose a double-confocal resonator design optimized for head-on Thomson scattering inside an FEL oscillator and analyze its performance taking into account the diffraction and FEL gain. A double confocal resonator is equivalent to two confocal resonators in series. Such a resonator has several advantages: it couples electron beam through and X-ray out of the cavity with holes on cavity mirrors, thus allowing the system to be compact; it supports the FEL mode with minimal diffraction loss through the holes; it provides a laser focus in the forward direction for a better mode overlap with the electron beam; and it provides a focus at the same location in the backward direction for higher Thomson scattering efficiency; in addition, the mode size at the focal point and hence the Rayleigh range can be adjusted simply through intracavity apertures; furthermore, it gives a large mode size at the mirrors to reduce power loading. Simulations as well as analytical results will be presented. Also other configurations of intracavity Thomson scattering where the double-confocal resonator could be useful will be discussed.
Generalized parton distributions of the pion
Broniowski, Wojciech; Arriola, Enrique Ruiz; Golec-Biernat, Krzysztof
2008-08-31
Generalized Parton Distributions of the pion are evaluated in chiral quark models with the help of double distributions. As a result the polynomiality conditions are automatically satisfied. In addition, positivity constraints, proper normalization and support, sum rules, and soft pion theorems are fulfilled. We obtain explicit expressions holding at the low-energy quark-model scale, which exhibit no factorization in the t-dependence. The crucial QCD evolution of the quark-model distributions is carried out up to experimental or lattice scales. The obtained results for the Parton Distribution Function and the Parton Distribution Amplitude describe the available experimental and lattice data, confirming that the quark-model scale is low, around 320 MeV.
NASA Astrophysics Data System (ADS)
Mason, D. C.; Giustarini, L.; Garcia-Pintado, J.; Cloke, H. L.
2014-05-01
Flooding is a particular hazard in urban areas worldwide due to the increased risks to life and property in these regions. Synthetic Aperture Radar (SAR) sensors are often used to image flooding because of their all-weather day-night capability, and now possess sufficient resolution to image urban flooding. The flood extents extracted from the images may be used for flood relief management and improved urban flood inundation modelling. A difficulty with using SAR for urban flood detection is that, due to its side-looking nature, substantial areas of urban ground surface may not be visible to the SAR due to radar layover and shadow caused by buildings and taller vegetation. This paper investigates whether urban flooding can be detected in layover regions (where flooding may not normally be apparent) using double scattering between the (possibly flooded) ground surface and the walls of adjacent buildings. The method estimates double scattering strengths using a SAR image in conjunction with a high resolution LiDAR (Light Detection and Ranging) height map of the urban area. A SAR simulator is applied to the LiDAR data to generate maps of layover and shadow, and estimate the positions of double scattering curves in the SAR image. Observations of double scattering strengths were compared to the predictions from an electromagnetic scattering model, for both the case of a single image containing flooding, and a change detection case in which the flooded image was compared to an un-flooded image of the same area acquired with the same radar parameters. The method proved successful in detecting double scattering due to flooding in the single-image case, for which flooded double scattering curves were detected with 100% classification accuracy (albeit using a small sample set) and un-flooded curves with 91% classification accuracy. The same measures of success were achieved using change detection between flooded and un-flooded images. Depending on the particular flooding
Studies of transverse momentum dependent parton distributions and Bessel weighting
Aghasyan, M.; Avakian, H.; De Sanctis, E.; Gamberg, L.; Mirazita, M.; Musch, B.; Prokudin, A.; Rossi, P.
2015-03-01
In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/Q2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.
Studies of transverse momentum dependent parton distributions and Bessel weighting
Aghasyan, M.; Avakian, H.; De Sanctis, E.; Gamberg, L.; Mirazita, M.; Musch, B.; Prokudin, A.; Rossi, P.
2015-03-01
In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Montemore » Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/Q2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.« less
Studies of transverse momentum dependent parton distributions and Bessel weighting
NASA Astrophysics Data System (ADS)
Aghasyan, M.; Avakian, H.; De Sanctis, E.; Gamberg, L.; Mirazita, M.; Musch, B.; Prokudin, A.; Rossi, P.
2015-03-01
In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/ Q 2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.
Global analysis of nuclear parton distributions
NASA Astrophysics Data System (ADS)
de Florian, Daniel; Sassot, Rodolfo; Zurita, Pia; Stratmann, Marco
2012-04-01
We present a new global QCD analysis of nuclear parton distribution functions and their uncertainties. In addition to the most commonly analyzed data sets for the deep-inelastic scattering of charged leptons off nuclei and Drell-Yan dilepton production, we include also measurements for neutrino-nucleus scattering and inclusive pion production in deuteron-gold collisions. The analysis is performed at next-to-leading order accuracy in perturbative QCD in a general mass variable flavor number scheme, adopting a current set of free nucleon parton distribution functions, defined accordingly, as reference. The emerging picture is one of consistency, where universal nuclear modification factors for each parton flavor reproduce the main features of all data without any significant tension among the different sets. We use the Hessian method to estimate the uncertainties of the obtained nuclear modification factors and examine critically their range of validity in view of the sparse kinematic coverage of the present data. We briefly present several applications of our nuclear parton densities in hard nuclear reactions at BNL-RHIC, CERN-LHC, and a future electron-ion collider.
Observation and studies of double $J/\\psi$ production at the Tevatron
Abazov, Victor Mukhamedovich; et al.
2014-12-08
We present the observation of doubly-produced $J/\\psi$ mesons with the D0 detector at Fermilab in $p\\bar{p}$ collisions at $\\sqrt{s}=1.96$ TeV. The production cross section for both singly and doubly-produced $J/\\psi$ mesons is measured using a sample with an integrated luminosity of 8.1fb$^{-1}$. For the first time, the double $J/\\psi$ production cross section is separated into contributions due to single and double parton scatterings. Using these measurements, we determine the effective cross section $\\sigma_{eff}$, a parameter characterizing an effective spatial area of the parton-parton interactions and related to the parton spatial density inside the nucleon.
NASA Astrophysics Data System (ADS)
Mason, David; Giustarini, Laura; Garcia-Pintado, Javier; Cloke, Hannah
2014-05-01
Flooding is a particular hazard in urban areas worldwide due to the increased risks to life and property in these regions. SAR sensors are often used to image flooding because of their all-weather day-night capability, and now possess sufficient resolution to image urban flooding. The flood extents extracted from the images may be used for flood relief management and improved urban flood inundation modelling. A difficulty with using SAR for urban flood detection is that, due to its side-looking nature, substantial areas of urban ground surface may not be visible to the SAR due to radar layover and shadow caused by buildings and taller vegetation. While most flooding along roads perpendicular to the satellite direction of travel may be detected successfully, a good deal of the flooding along roads parallel to it will remain unseen. Considering the latter, an area of flooded road in front of the wall of a building on the farther side of a road from the satellite track may be allocated to the same range bin as the wall, causing layover which generally results in a strong return, and a possible misclassification of flooded ground as un-flooded. This paper investigates whether urban flooding can be detected in layover regions using double scattering [1]. If the road in a layover region is flooded, backscatter due to the double scattering from sensor to road to wall to sensor (or vice versa) should be stronger than if the road is not flooded. The method estimates double scattering strengths using a SAR image in conjunction with a high resolution LiDAR height map of the urban area. A SAR simulator is applied to the LiDAR data to generate maps of layover and shadow, and estimate the positions of double scattering curves in the SAR image. Observations of double scattering strengths were compared to the predictions from an electromagnetic scattering model, for both the case of a single image containing flooding, and a change detection case in which the flooded image was
Prospects For Measurements Of Generalized Parton Distributions At COMPASS
Neyret, Damien
2007-06-13
The concept of Generalized Parton Distributions extends classical parton distributions by giving a '3-dimensional' view of the nucleons, allowing to study correlations between the parton longitudinal momentum and its transverse position in the nucleon. Measurements of such generalized distributions can be done with the COMPASS experiment, in particular using Deeply Virtual Compton Scattering events. They require to modify the set-up of COMPASS by introducing a recoil proton detector, an additional electromagnetic calorimeter and a new liquid hydrogen target. These upgrades are presently under study, and the first data taking could take place in 2010.
Bolognini, Gabriele; Bononi, Alberto
2009-04-27
We present a theoretical study of the performance of distributed Raman amplifiers with higher order pumping schemes, focusing in particular on double Rayleigh scattering (DRS) noise. Results show an unexpected significant DRS noise reduction for pumping order higher than third, allowing for an overall performance improvement of carefully designed distributed amplifiers, ensuring a large optical signal-to-noise ratio improvement together with reduced DRS-induced penalties.
Single and double inclusive forward jet production at the LHC at √{ s} = 7 and 13 TeV
NASA Astrophysics Data System (ADS)
Bury, Marcin; Deak, Michal; Kutak, Krzysztof; Sapeta, Sebastian
2016-09-01
We provide a description of the transverse momentum spectrum of single inclusive forward jets produced at the LHC, at the center-of-mass energies of 7 and 13 TeV, using the high energy factorization (HEF) framework. We subsequently study double inclusive forward jet production and, in particular, we calculate contributions to azimuthal angle distributions coming from double parton scattering. We also compare our results for double inclusive jet production to those obtained with the PYTHIA Monte Carlo generator. This comparison confirms that the HEF resummation acts like an initial state parton shower. It also points towards the need to include final state radiation effects in the HEF formalism.
Double-scattering/reflection in a single nanoparticle for intensified ultrasound imaging.
Zhang, Kun; Chen, Hangrong; Guo, Xiasheng; Zhang, Dong; Zheng, Yuanyi; Zheng, Hairong; Shi, Jianlin
2015-03-05
Ultrasound contrast agents (UCAs) designed by the conventional composition-based strategy, often suffer from relatively low ultrasound utilization efficiency. In this report, a structure-based design concept of double-scattering/reflection in a single nanoparticle for enhancing ultrasound imaging has been proposed. To exemplify this concept, a rattle-type mesoporous silica nanostructure (MSN) with two contributing interfaces has been employed as the ideal model. Contributed by double-scattering/reflection interfaces, the rattle-type MSN, as expected, performs much better in in vitro and in vivo ultrasound imaging than the other two nanostructures (solid and hollow) containing only one scattering/reflection interface. More convincingly, related acoustic measurements and simulation calculations also confirm this design concept. Noticeably, the rattle-type MSN has also been demonstrated capable of improving intracellular ultrasound molecular imaging. As a universal method, the structure-design concept can extend to guide the design of new generation UCAs with many other compositions and similar structures (e.g., heterogeneous rattle-type, double-shelled).
Double-scattering/reflection in a Single Nanoparticle for Intensified Ultrasound Imaging
Zhang, Kun; Chen, Hangrong; Guo, Xiasheng; Zhang, Dong; Zheng, Yuanyi; Zheng, Hairong; Shi, Jianlin
2015-01-01
Ultrasound contrast agents (UCAs) designed by the conventional composition-based strategy, often suffer from relatively low ultrasound utilization efficiency. In this report, a structure-based design concept of double-scattering/reflection in a single nanoparticle for enhancing ultrasound imaging has been proposed. To exemplify this concept, a rattle-type mesoporous silica nanostructure (MSN) with two contributing interfaces has been employed as the ideal model. Contributed by double-scattering/reflection interfaces, the rattle-type MSN, as expected, performs much better in in vitro and in vivo ultrasound imaging than the other two nanostructures (solid and hollow) containing only one scattering/reflection interface. More convincingly, related acoustic measurements and simulation calculations also confirm this design concept. Noticeably, the rattle-type MSN has also been demonstrated capable of improving intracellular ultrasound molecular imaging. As a universal method, the structure-design concept can extend to guide the design of new generation UCAs with many other compositions and similar structures (e.g., heterogeneous rattle-type, double-shelled). PMID:25739832
Access to generalized parton distributions at COMPASS
Nowak, Wolf-Dieter
2015-04-10
A brief experimentalist's introduction to Generalized Parton Distributions (GPDs) is given. Recent COMPASS results are shown on transverse target-spin asymmetries in hard exclusive ρ{sup 0} production and their interpretation in terms of a phenomenological model as indication for chiral-odd, transverse GPDs is discussed. For deeply virtual Compton scattering, it is briefly outlined how to access GPDs and projections are shown for future COMPASS measurements.
Huang, J.; Allada, K.; Dutta, C.; Katich, J.; Qian, X.; Wang, Y.; Zhang, Y.; Aniol, K.; Annand, J. R. M.; Averett, T.; et al
2012-01-01
We report the first measurement of the double-spin asymmetry ALT for charged pion electroproduction in semi-inclusive deep inelastic electron scattering on a transversely polarized 3He target. The kinematics focused on the valence quark region, 0.16 < x < 0.35 with 1.4 < Q2 < 2.7 GeV2. The corresponding neutron ALT asymmetries were extracted from the measured 3He asymmetries and proton/3He cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function g1Tq and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for π- production on 3Hemore » and the neutron, while our π+ asymmetries are consistent with zero.« less
Modeling the Pion Generalized Parton Distribution
NASA Astrophysics Data System (ADS)
Mezrag, C.
2016-02-01
We compute the pion Generalized Parton Distribution (GPD) in a valence dressed quarks approach. We model the Mellin moments of the GPD using Ansätze for Green functions inspired by the numerical solutions of the Dyson-Schwinger Equations (DSE) and the Bethe-Salpeter Equation (BSE). Then, the GPD is reconstructed from its Mellin moment using the Double Distribution (DD) formalism. The agreement with available experimental data is very good.
Evolution and models for skewed parton distributions
Musatov, I. V.; Radyushkin, A. V.
2000-04-01
We discuss the structure of the ''forward visible'' (FV) parts of double and skewed distributions related to the usual distributions through reduction relations. We use factorized models for double distributions (DD's) f(tilde sign)(x,{alpha}) in which one factor coincides with the usual (forward) parton distribution and another specifies the profile characterizing the spread of the longitudinal momentum transfer. The model DD's are used to construct skewed parton distributions (SPD's). For small skewedness, the FV parts of SPD's H(x(tilde sign),{xi}) can be obtained by averaging forward parton densities f(x(tilde sign)-{xi}{alpha}) with the weight {rho}({alpha}) coinciding with the profile function of the double distribution f(tilde sign)(x,{alpha}) at small x. We show that if the x{sup n} moments f(tilde sign){sub n}({alpha}) of DD's have the asymptotic (1-{alpha}{sup 2}){sup n+1} profile, then the {alpha} profile of f(tilde sign)(x,{alpha}) for small x is completely determined by the small-x behavior of the usual parton distribution. We demonstrate that, for small {xi}, the model with asymptotic profiles for f(tilde sign){sub n}({alpha}) is equivalent to that proposed recently by Shuvaev et al., in which the Gegenbauer moments of SPD's do not depend on {xi}. We perform a numerical investigation of the evolution patterns of SPD's and give an interpretation of the results of these studies within the formalism of double distributions. (c) 2000 The American Physical Society.
NASA Astrophysics Data System (ADS)
Nefedov, M. A.; Saleev, V. A.
2015-11-01
The hadroproduction of prompt isolated photon pairs at high energies is studied in the framework of the parton Reggeization approach. The real part of the NLO corrections is computed (the NLO⋆ approximation), and the procedure for the subtraction of double counting between real parton emissions in the hard-scattering matrix element and unintegrated parton distribution function is constructed for the amplitudes with Reggeized quarks in the initial state. The matrix element of the important next-to-next-to-leading-order subprocess R R →γ γ with full dependence on the transverse momenta of the initial-state Reggeized gluons is obtained. We compare obtained numerical results with diphoton spectra measured at the Tevatron and the LHC and find a good agreement of our predictions with experimental data at the high values of diphoton transverse momentum, pT, and especially at the pT larger than the diphoton invariant mass, M . In this multi-Regge kinematics region, the NLO correction is strongly suppressed, demonstrating the self-consistency of the parton Reggeization approach.
Observation of satellite peaks and dips in the scattering of light in a double-pass geometry.
Méndez, E R; Chaikina, E I; Escamilla, H M
1999-06-01
We report the experimental observation of enhanced backscattering and satellite peaks and dips in light scattered by a system that involves double passage of waves through a random-phase screen and a birefringent crystal.
Partonic Transverse Momentum Distributions
Rossi, Patrizia
2010-08-04
In recent years parton distributions have been generalized to account also for transverse degrees of freedom and new sets of more general distributions, Transverse Momentum Dependent (TMD) parton distributions and fragmentation functions were introduced. Different experiments worldwide (HERMES, COMPASS, CLAS, JLab-Hall A) have measurements of TMDs in semi-inclusive DIS processes as one of their main focuses of research. TMD studies are also an important part of the present and future Drell-Yan experiments at RICH and JPARC and GSI, respectively, Studies of TMDs are also one of the main driving forces of the Jefferson Lab (JLab) 12 GeV upgrade project. Progress in phenomenology and theory is flourishing as well. In this talk an overview of the latest developments in studies of TMDs will be given and newly released results, ongoing activities, as well as planned near term and future measurements will be discussed.
Are partons confined tachyons?
Noyes, H.P.
1996-03-01
The author notes that if hadrons are gravitationally stabilized ``black holes``, as discrete physics suggests, it is possible that partons, and in particular quarks, could be modeled as tachyons, i.e. particles having v{sup 2} > c{sup 2}, without conflict with the observational fact that neither quarks nor tachyons have appeared as ``free particles``. Some consequences of this model are explored.
FAST NEUTRON SOURCE DETECTION AT LONG DISTANCES USING DOUBLE SCATTER SPECTROMETRY.
FORMAN,L.VANIER,P.WELSH,K.
2003-08-03
Fast neutrons can be detected with relatively high efficiency, >15%, using two planes of hydrogenous scintillator detectors where a scatter in the first plane creates a start pulse and scatter in the second plane is separated by time-of-flight. Indeed, the neutron spectrum of the source can be determined as the sum of energy deposited by pulse height in the first added to the energy of the second found by time-of-flight to the second detector. Gamma rays can also create a double scatter by Compton interaction in the first with detection in the second, but these events occur in a single time window because the scattered photons all travel at the speed of light. Thus, gamma ray events can be separated from neutrons by the time-of-flight differences. We have studied this detection system with a Cf-252 source using Bicron 501A organic scintillators and report on the ability to efficiently detect fast neutrons with high neutron/gamma detection ratios. We have further studied cosmic-ray neutron background detection response that is the dominant background in long range detection. We have found that most of the neutrons are excluded from the time-of-flight window because they are either too high in energy, >10 keV, or too low, < 10 keV. Moreover, if the detection planes are position-sensitive, the angular direction of the source can be determined by the ratio of the energy of scattered protons in the first detector relative to the position and energy of the scattered neutron detected in the second. This ability to locate the source in theta is useful, but more importantly increases the signal to noise relative to cosmic-ray produced neutrons that are relatively isotropic. This technique may be used in large arrays to detect neutrons at ranges up to 0.5 kilometer.
Enhanced Raman scattering assisted by ultrahigh order modes of the double metal cladding waveguide
Xu, Tian; Huang, Liming; Jin, Yonglong; Fang, Jinghuai E-mail: fjhuai@ntu.edu.cn; Yin, Cheng E-mail: fjhuai@ntu.edu.cn; Huang, Meizhen
2014-10-20
Distinguished from the usual strategy to enhance the Raman scattering such as creating hot spots in the surface-enhanced Raman scattering, this paper takes a quite different approach based on the double metal cladding waveguide. The target analyte is located in the guiding layer of sub-millimeter scale, where several ultrahigh order modes with high intensity are simultaneously excited via a focused laser beam. The experimental setup is simple, and both simulation and experimental results confirm the enhancement mechanism of these oscillating modes. Other appealing features include the large detection area and the ability to excite guided modes via both polarizations. This scheme can be applied to large molecules detection and readily integrated with other Raman enhancement techniques.
Double-Polarized pd Scattering and Test of Time-reversal Invariance
NASA Astrophysics Data System (ADS)
Uzikov, Yuriy
2016-02-01
The integrated proton-deuteron cross section σ˜ for the case of transversal polarization ppy of the proton and tensor polarization Pxz of the deuteron provides a null test signal for time-reversal invariance violating but P-parity conserving effects. The corresponding experiment is planned at COSY to measure the observable σ˜. Here we consider in general case the status of the null-test observable in pd scattering, calculate σ˜ within the Glauber theory of the double-polarized pd scattering at 100 - 1000 MeV and study the contribution of the deuteron S- and D-waves for several type of the T-odd NN interactions.
Double Folding Potential of Different Interaction Models for 16O + 12C Elastic Scattering
NASA Astrophysics Data System (ADS)
Hamada, Sh.; Bondok, I.; Abdelmoatmed, M.
2016-08-01
The elastic scattering angular distributions for 16O + 12C nuclear system have been analyzed using double folding potential of different interaction models: CDM3Y1, CDM3Y6, DDM3Y1 and BDM3Y1. We have extracted the renormalization factor N r for the different concerned interaction models. Potential created by BDM3Y1 model of interaction has the shallowest depth which reflects the necessity to use higher renormalization factor. The experimental angular distributions for 16O + 12C nuclear system in the energy range 115.9-230 MeV exhibited unmistakable refractive features and rainbow phenomenon.
Multi-wavelength generation based on cascaded Raman scattering and self-frequency-doubling in KTA
NASA Astrophysics Data System (ADS)
Zhong, K.; Li, J. S.; Xu, D. G.; Ding, X.; Zhou, R.; Wen, W. Q.; Li, Z. Y.; Xu, X. Y.; Wang, P.; Yao, J. Q.
2010-04-01
A multi-wavelength laser is developed based on cascaded stimulated Raman scattering (SRS) and self-frequency-doubling in an x-cut KTA crystal pumped by an A-O Q-switched Nd:YAG laser. The generation of 1178 nm from cascaded SRS of 234 and 671 cm-1 Raman modes is observed. The six wavelengths, including the fundamental 1064 nm, four Stokes waves at 1091, 1120, 1146, 1178 nm, and the second harmonic generation (SHG) of 1146 nm, are tens to hundreds of millwatts for each at 10 kHz, corresponding to a total conversion efficiency of 8.72%.
Diffuse magnetic neutron scattering in the highly frustrated double perovskite Ba2YRuO6
Nilsen, Gøran. J.; Thompson, Corey M.; Ehlers, Georg; Marjerrison, Casey A.; Greedan, John E.
2015-02-23
Here we investigated diffuse magnetic scattering in the highly frustrated double perovskite Ba2YRuO6 using polarized neutrons. Consistent with previous reports, the material shows two apparent transitions at 47 and 36 K to an eventual type I face-centered-cubic magnetic ground state. The (100) magnetic reflection shows different behavior from the five other observed reflections upon heating from 1.8 K, with the former broadening well beyond the resolution limit near 36 K. Closer examination of the latter group reveals a small, but clear, increase in peak widths between 36 and 47 K, indicating that this regime is dominated by short-range spin correlations.more » Diffuse magnetic scattering persists above 47 K near the position of (100) to at least 200 K, consistent with strong frustration. Reverse Monte Carlo (RMC) modeling of the diffuse scattering from 45 to 200 K finds that the spin-spin correlations between nearest and next-nearest neighbors are antiferromagnetic and ferromagnetic, respectively, at temperatures near the upper ordering temperature, but both become antiferromagnetic and of similar magnitude above 100 K. The significance of this unusual crossover is discussed in light of the super-superexchange interactions between nearest and next-nearest neighbors in this material and the demands of type I order. The dimensionality of the correlations is addressed by reconstructing the scattering in the (hk0) plane using the RMC spin configurations. This indicates that one-dimensional spin correlations dominate at temperatures close to the first transition. In addition, a comparison between mean-field calculations and (hk0) scattering implies that further neighbor couplings play a significant role in the selection of the ground state. Finally, the results and interpretation are compared with those recently published for monoclinic Sr2YRuO6, and similarities and differences are emphasized.« less
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.
Pisano, S.; Biselli, A.; Niccolai, S.; Seder, E.; Guidal, M.; Mirazita, M.; Adhikari, K. P.; Adikaram, D.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Bosted, P.; Briscoe, B.; Brock, J.; Brooks, W. K.; Burkert, V. D.; Carlin, C.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Compton, N.; Contalbrigo, M.; Cortes, O.; Crabb, D. G.; Crede, V.; D' Angelo, A.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fersch, R.; Filippi, A.; Fleming, J. A.; Fradi, A.; Garillon, B.; Garcon, M.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guo, L.; Hafidi, K.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S. M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jenkins, D.; Jiang, X.; Jo, H. S.; Joo, K.; Joosten, S.; Keith, C. D.; Keller, D.; Kim, A.; Kim, W.; Klein, F. J.; Kubarovsky, V.; Kuhn, S. E.; Lenisa, P.; Livingston, K.; Lu, H. Y.; MacCormick, M.; MacGregor, Ian J. D.; Mayer, M.; McKinnon, B.; Meekins, D. G.; Meyer, C. A.; Mokeev, V.; Montgomery, R. A.; Moody, C. I.; Munoz Camacho, C.; Nadel-Turonski, P.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Phelps, W.; Phillips, J. J.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatie, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Skorodumina, I.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Tian, Ye; Tkachenko, S.; Turisini, M.; Ungaro, M.; Voutier, E.; Walford, N. K.; Watts, D. P.; Wei, X.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.
2015-03-19
Single-beam, single-target, and double-spin asymmetries for hard exclusive photon production on the proton e→p→e'p'γ are presented. The data were taken at Jefferson Lab using the CLAS detector and a longitudinally polarized ^{14}NH_{3} target. The three asymmetries were measured in 165 4-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. The kinematic dependences of the obtained asymmetries are discussed and compared to the predictions of models of Generalized Parton Distributions. As a result, the measurement of three DVCS spin observables at the same kinematic points allows a quasi-model-independent extraction of the imaginary parts of the H and H~ Compton Form Factors, which give insight into the electric and axial charge distributions of valence quarks in the proton.
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.
Global QCD Analysis of Polarized Parton Densities
Stratmann, Marco
2009-08-04
We focus on some highlights of a recent, first global Quantum Chromodynamics (QCD) analysis of the helicity parton distributions of the nucleon, mainly the evidence for a rather small gluon polarization over a limited region of momentum fraction and for interesting flavor patterns in the polarized sea. It is examined how the various sets of data obtained in inclusive and semi-inclusive deep inelastic scattering and polarized proton-proton collisions help to constrain different aspects of the quark, antiquark, and gluon helicity distributions. Uncertainty estimates are performed using both the robust Lagrange multiplier technique and the standard Hessian approach.
PARTON SATURATION, PRODUCTION, AND EQUILIBRATION IN HIGH ENERGY NUCLEAR COLLISIONS
VENUGOPALAN,R.
1999-03-20
Deeply inelastic scattering of electrons off nuclei can determine whether parton distributions saturate at HERA energies. If so, this phenomenon will also tell us a great deal about how particles are produced, and whether they equilibrate, in high energy nuclear collisions.
Large area double scattering telescope for balloon-borne studies of neutrons and gamma rays
NASA Technical Reports Server (NTRS)
Zych, A. D.; Herzo, D.; Koga, R.; Millard, W. A.; Moon, S.; Ryan, J.; Wilson, R.; White, R. S.; Dayton, B.
1975-01-01
A large area double scattering telescope for balloon-borne research is described. It measures the flux, energy and direction of 2-100 MeV neutrons and 0.5-30 MeV gamma rays. These measurements are made using time-of-flight and pulse height analysis techniques with two large tanks of mineral oil liquid scintillator. Results from Monte Carlo calculations of the efficiency, energy resolution and angular resolution are presented and the electronics implementation for the processing of 80 photomultiplier tubes signals will be discussed. The detector weighs 800 kg with a large part of this weight being the liquid scintillator (320 kg). It will be flown at 3 mbars for flight durations up to 40 hours. The first flight is planned for Spring, 1975.
Scattering equations, twistor-string formulas and double-soft limits in four dimensions
NASA Astrophysics Data System (ADS)
He, Song; Liu, Zhengwen; Wu, Jun-Bao
2016-07-01
We study scattering equations and formulas for tree amplitudes of various theories in four dimensions, in terms of spinor helicity variables and on-shell superspace for supersymmetric theories. As originally obtained in Witten's twistor string theory and other twistor-string models, the equations can take either polynomial or rational forms, and we clarify the simple relation between them. We present new, four-dimensional formulas for all tree amplitudes in the non-linear sigma model, a special Galileon theory and the maximally supersymmetric completion of the Dirac-Born-Infeld theory. Furthermore, we apply the formulas to study various double-soft theorems in these theories, including the emissions of a pair of soft photons, fermions and scalars for super-amplitudes in super-DBI theory.
Chen, Peili; Liu, Shaopu; Liu, Zhongfang; Hu, Xiaoli
2011-01-01
The interaction between palladium(II)-aminophylline and fluorescein sodium was investigated by resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectrum. In pH 4.4 Britton-Robinson (BR) buffer medium, aminophylline (Ami) reacted with palladium(II) to form chelate cation([Pd(Ami)]2+), which further reacted with fluorescein sodium (FS) to form ternary mixed ligand complex [Pd(Ami)(FS)2]. As a result, resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering spectrum (FDS) were enhanced. The maximum scattering wavelengths of [Pd(Ami)(FS)2] were located at 300 nm (RRS), 650 nm (SOS) and 304 nm (FDS). The scattering intensities were proportional to the Ami concentration in a certain range and the detection limits were 7.3 ng mL(-1) (RRS), 32.9 ng mL(-1) (SOS) and 79.1 ng mL(-1) (FDS), respectively. Based on it, the new simple, rapid, and sensitive scattering methods have been proposed to determine Ami in urine and serum samples. Moreover, the formation mechanism of [Pd(Ami)(FS)2] and the reasons for enhancement of RRS were fully discussed. PMID:21163688
A Gravitational Double-scattering Mechanism for Generating High-velocity Objects during Halo Mergers
NASA Astrophysics Data System (ADS)
Samsing, Johan
2015-02-01
We present a dynamical model that describes how halo particles can receive a significant energy kick from the merger between their own host halo and a target halo. This could provide a possible explanation for some high-velocity objects, including extended systems like globular clusters (GCs). In the model we especially introduce a double-scattering mechanism, where a halo particle receives a significant part of its total energy kick by first undergoing a gravitational deflection by the target halo and subsequently by its original host halo. This generates an energy kick that is due to the relative velocity between the halos during the deflections. We derive analytically the total kick energy of the particle, which is composed of energy from the double-scattering mechanism and tidal fields, as a function of its position in its original host halo just before merger. In the case of a 1:10 merger, we find that the presented mechanisms can easily generate particles with a velocity approximately two times the virial velocity of the target halo. This motivates us to suggest that the high velocity of the recently discovered GC HVGC-1 can be explained by a head-on halo merger. Finally, we illustrate the orbital evolution of high-velocity particles outside the virial sphere of the target halo by solving the equation of motion in an expanding universe. We find a sweet spot around a scale factor of 0.3-0.5 for ejecting particles into large orbits, which can easily reach beyond approximately five virial radii.
A GRAVITATIONAL DOUBLE-SCATTERING MECHANISM FOR GENERATING HIGH-VELOCITY OBJECTS DURING HALO MERGERS
Samsing, Johan
2015-02-01
We present a dynamical model that describes how halo particles can receive a significant energy kick from the merger between their own host halo and a target halo. This could provide a possible explanation for some high-velocity objects, including extended systems like globular clusters (GCs). In the model we especially introduce a double-scattering mechanism, where a halo particle receives a significant part of its total energy kick by first undergoing a gravitational deflection by the target halo and subsequently by its original host halo. This generates an energy kick that is due to the relative velocity between the halos during the deflections. We derive analytically the total kick energy of the particle, which is composed of energy from the double-scattering mechanism and tidal fields, as a function of its position in its original host halo just before merger. In the case of a 1:10 merger, we find that the presented mechanisms can easily generate particles with a velocity approximately two times the virial velocity of the target halo. This motivates us to suggest that the high velocity of the recently discovered GC HVGC-1 can be explained by a head-on halo merger. Finally, we illustrate the orbital evolution of high-velocity particles outside the virial sphere of the target halo by solving the equation of motion in an expanding universe. We find a sweet spot around a scale factor of 0.3-0.5 for ejecting particles into large orbits, which can easily reach beyond approximately five virial radii.
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).
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.
Optical vector analysis based on double-sideband modulation and stimulated Brillouin scattering.
Qing, Ting; Li, Shupeng; Xue, Min; Pan, Shilong
2016-08-01
A high-resolution and high-accuracy optical vector analysis based on optical double-sideband modulation and stimulated Brillouin scattering is proposed and experimentally demonstrated. Different from the conventional OVA based on optical single-sideband modulation, in which the measurement range is limited by the bandwidth of the microwave and optoelectronic components, and the measurement accuracy is restricted by the high-order sidebands, the proposed technique measures the magnitude and phase responses by making use of both ±1st-order sidebands without spectrum response aliasing. As a result, the measurement range is doubled, and the high-order, sideband-induced errors only appear at specific frequencies that are predictable and removable. A proof-of-concept experiment is carried out. The transmission response of a fiber Bragg grating, in a range of 80 GHz, is measured with a resolution of less than 667 kHz by using 40 GHz microwave components. PMID:27472646
Towards a model of pion generalized parton distributions from Dyson-Schwinger equations
Moutarde, H.
2015-04-10
We compute the pion quark Generalized Parton Distribution H{sup q} and Double Distributions F{sup q} and G{sup q} in a coupled Bethe-Salpeter and Dyson-Schwinger approach. We use simple algebraic expressions inspired by the numerical resolution of Dyson-Schwinger and Bethe-Salpeter equations. We explicitly check the support and polynomiality properties, and the behavior under charge conjugation or time invariance of our model. We derive analytic expressions for the pion Double Distributions and Generalized Parton Distribution at vanishing pion momentum transfer at a low scale. Our model compares very well to experimental pion form factor or parton distribution function data.
Generalized parton distributions: Status and perspectives
Weiss, Christian
2009-01-01
We summarize recent developments in understanding the concept of generalized parton distributions (GPDs), its relation to nucleon structure, and its application to high-Q^2 electroproduction processes. Following a brief review of QCD factorization and transverse nucleon structure, we discuss (a) new theoretical methods for the analysis of deeply-virtual Compton scattering (t-channel-based GPD parametrizations, dispersion relations); (b) the phenomenology of hard exclusive meson production (experimental tests of dominance of small-size configurations, model-independent comparative studies); (c) the role of GPDs in small-x physics and pp scattering (QCD dipole model, central exclusive diffraction). We emphasize the usefulness of the transverse spatial (or impact parameter) representation for both understanding the reaction mechanism in hard exclusive processes and visualizing the physical content of the GPDs.
Strongly interacting parton matter equilibration
Ozvenchuk, V.; Linnyk, O.; Bratkovskaya, E.; Gorenstein, M.; Cassing, W.
2012-07-15
We study the kinetic and chemical equilibration in 'infinite' parton matter within the Parton-Hadron-String Dynamics transport approach. The 'infinite' matter is simulated within a cubic box with periodic boundary conditions initialized at different energy densities. Particle abundances, kinetic energy distributions, and the detailed balance of the off-shell quarks and gluons in the strongly-interacting quarkgluon plasma are addressed and discussed.
Off-forward parton distribution
Ji, X.
1998-12-01
Recent developments in studying off-forward parton distributions are discussed. In this talk, the author discusses the recent developments in studying the off-forward parton distributions (OFPD`s). He has written a topical review article on the subject, which will soon be published in Journal of Physics G. The interested audience can consult that article for details. His talk consists of three parts: definition of the new distributions, their physical significance, and experimental measurements.
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.
A triple axis double crystal multiple reflection camera for ultra small angle X-ray scattering
NASA Astrophysics Data System (ADS)
Lambard, Jacques; Lesieur, Pierre; Zemb, Thomas
1992-06-01
To extend the domain of small angle X-ray scattering requires multiple reflection crystals to collimate the beam. A double crystal, triple axis X-ray camera using multiple reflection channel cut crystals is described. Procedures for measuring the desmeared scattering cross-section on absolute scale are described as well as the measurement from several typical samples : fibrils of collagen, 0.3 μm diameter silica spheres, 0.16 μm diameter interacting latex spheres, porous lignite coal, liquid crystals in a surfactant-water system, colloidal crystal of 0.32 μm diameter silica spheres. L'extension du domaine de diffusion des rayons-X vers les petits angles demande l'emploi de cristaux à réflexions multiples pour collimater le faisceau. Nous décrivons une caméra à rayons-X à trois axes où les réflexions multiples sont réalisées dans deux cristaux à gorge. Nous donnons ensuite les procédures de déconvolution pour obtenir la section efficace de diffusion en échelle absolue, ainsi que les résultats des mesures effectuées avec plusieurs échantillons typiques : fibres de collagène, sphères de silice de 0,3 μm de diamètre, sphères de latex de 0,16 μm de diamètre en interaction, charbon lignite poreux, cristaux liquides formés dans un système eau-tensioactif, solution colloïdale de sphères de silice de 0,32 μm de diamètre.
Tuning Interior Nanogaps of Double-shelled Au/Ag Nanoboxes for Surface-Enhanced Raman Scattering
Zhang, Weiqing; Rahmani, Mohsen; Niu, Wenxin; Ravaine, Serge; Hong, Minghui; Lu, Xianmao
2015-01-01
Double-shelled Au/Ag hollow nanoboxes with precisely controlled interior nanogaps (1 to 16 nm) were synthesized for gap-tunable surface-enhanced Raman scattering (SERS). The double-shelled nanoboxes were prepared via a two-step galvanic replacement reaction approach using Ag nanocubes as the templates, while 4-aminothiolphenol (4-ATP) as SERS probe molecules were loaded between the two shells. More than 10-fold enhancement of SERS is observed from the double-shelled nanoboxes than Ag nanocubes. In addition, the SERS of the double-shelled nanoboxes increase significantly with the decrease of gap size, consistent with the theoretical prediction that smaller gap size induces larger localized electromagnetic enhancement. PMID:25670352
Tuning interior nanogaps of double-shelled Au/Ag nanoboxes for surface-enhanced Raman scattering.
Zhang, Weiqing; Rahmani, Mohsen; Niu, Wenxin; Ravaine, Serge; Hong, Minghui; Lu, Xianmao
2015-02-11
Double-shelled Au/Ag hollow nanoboxes with precisely controlled interior nanogaps (1 to 16 nm) were synthesized for gap-tunable surface-enhanced Raman scattering (SERS). The double-shelled nanoboxes were prepared via a two-step galvanic replacement reaction approach using Ag nanocubes as the templates, while 4-aminothiolphenol (4-ATP) as SERS probe molecules were loaded between the two shells. More than 10-fold enhancement of SERS is observed from the double-shelled nanoboxes than Ag nanocubes. In addition, the SERS of the double-shelled nanoboxes increase significantly with the decrease of gap size, consistent with the theoretical prediction that smaller gap size induces larger localized electromagnetic enhancement.
Boukhalfa, Sofiane; Gordon, Daniel; He, Lilin; Melnichenko, Yuri B; Nitta, Naoki; Magasinski, Alexandre; Yushin, Gleb
2014-03-25
Experimental studies showed the impact of the electrolyte solvents on both the ion transport and the specific capacitance of microporous carbons. However, the related structure-property relationships remain largely unclear and the reported results are inconsistent. The details of the interactions of the charged carbon pore walls with electrolyte ions and solvent molecules at a subnanometer scale are still largely unknown. Here for the first time we utilize in situ small angle neutron scattering (SANS) to reveal the electroadsorption of organic electrolyte ions in carbon pores of different sizes. A 1 M solution of tetraethylammonium tetrafluoroborate (TEATFB) salt in deuterated acetonitrile (d-AN) was used in an activated carbon with the pore size distribution similar to that of the carbons used in commercial double layer capacitors. In spite of the incomplete wetting of the smallest carbon pores by the d-AN, we observed enhanced ion sorption in subnanometer pores under the applied potential. Such results suggest the visible impact of electrowetting phenomena counterbalancing the high energy of the carbon/electrolyte interface in small pores. This behavior may explain the characteristic butterfly wing shape of the cyclic voltammetry curve that demonstrates higher specific capacitance at higher applied potentials, when the smallest pores become more accessible to electrolyte. Our study outlines a general methodology for studying various organic salts-solvent-carbon combinations.
Illuminating the 1/x Moment of Parton Distribution Functions
Brodsky, Stanley J.; Llanes-Estrada, Felipe J.; Szczepaniak, Adam P.; /Indiana U.
2007-10-15
The Weisberger relation, an exact statement of the parton model, elegantly relates a high-energy physics observable, the 1/x moment of parton distribution functions, to a nonperturbative low-energy observable: the dependence of the nucleon mass on the value of the quark mass or its corresponding quark condensate. We show that contemporary fits to nucleon structure functions fail to determine this 1/x moment; however, deeply virtual Compton scattering can be described in terms of a novel F1/x(t) form factor which illuminates this physics. An analysis of exclusive photon-induced processes in terms of the parton-nucleon scattering amplitude with Regge behavior reveals a failure of the high Q2 factorization of exclusive processes at low t in terms of the Generalized Parton-Distribution Functions which has been widely believed to hold in the past. We emphasize the need for more data for the DVCS process at large t in future or upgraded facilities.
Advanced light-scattering materials: Double-textured ZnO:B films grown by LP-MOCVD
NASA Astrophysics Data System (ADS)
Addonizio, M. L.; Spadoni, A.; Antonaia, A.
2013-12-01
Double-textured ZnO:B layers with enhanced optical scattering in both short and long wavelength regions have been successfully fabricated using MOCVD technique through a three step process. Growth of double-textured structures has been induced by wet etching on polycrystalline ZnO surface. Our double-layer structure consists of a first ZnO:B layer wet etched and subsequently used as substrate for a second ZnO:B layer deposition. Polycrystalline ZnO:B layers were etched by utilizing diluted solutions of fluoridic acid (HF), chloridric acid (HCl) and phosphoric acid (H3PO4) and their effect on surface morphology modification was systematically investigated. The morphology of the second deposited ZnO layer strongly depended on the surface properties of the etched ZnO first layer. Growth of cauliflower-like texture was induced by protrusions presence on the HCl etched surface. Optimized double-layer structure shows a cauliflower-like double texture with higher RMS roughness and increased spectral haze values in both short and long wavelength regions, compared to conventional pyramidal-like single texture. Furthermore, this highly scattering structure preserves excellent optical and electrical properties.
Charge symmetry at the partonic level
Londergan, J. T.; Peng, J. C.; Thomas, A. W.
2010-07-01
This review article discusses the experimental and theoretical status of partonic charge symmetry. It is shown how the partonic content of various structure functions gets redefined when the assumption of charge symmetry is relaxed. We review various theoretical and phenomenological models for charge symmetry violation in parton distribution functions. We summarize the current experimental upper limits on charge symmetry violation in parton distributions. A series of experiments are presented, which might reveal partonic charge symmetry violation, or alternatively might lower the current upper limits on parton charge symmetry violation.
Experimental studies of Generalized Parton Distributions
NASA Astrophysics Data System (ADS)
Niccolai, Silvia
2015-12-01
Generalized Parton Distributions (GPDs) are nowadays the object of an intense effort of research, in the perspective of understanding nucleon structure. They describe the correlations between the longitudinal momentum and the transverse spatial position of the partons inside the nucleon and they can give access to the contribution of the orbital momentum of the quarks to the nucleon spin. Deeply Virtual Compton scattering (DVCS), the electroproduction on the nucleon, at the quark level, of a real photon, is the process more directly interpretable in terms of GPDs of the nucleon. Depending on the target nucleon (proton or neutron) and on the DVCS observable extracted (cross-sections, target- or beam-spin asymmetries, etc.), different sensitivity to the various GPDs for each quark flavor can be exploited. This article is focused on recent promising results, obtained at Jefferson Lab, on cross-sections and asymmetries for DVCS, and their link to GPDs. These data open the way to a “tomographic” representation of the structure of the nucleon, allowing the extraction of transverse-space densities of the quarks at fixed longitudinal momentum. The extensive experimental program to measure GPDs at Jefferson Lab with the 12 GeV-upgraded electron accelerator and the complementary detectors that will be housed in three experimental Halls (A, B and C), will also be presented.
General Helicity Formalism for Polarized Semi-Inclusive Deep Inelastic Scattering
Anselmino, M; Boglione, M; D’Alesio, U; Melis, S; Murgia, F; Nocera, E R; Prokudin, A
2011-06-01
We study polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes, within the QCD parton model and a factorization scheme, taking into account all transverse motions, of partons inside the initial proton and of hadrons inside the fragmenting partons. We use the helicity formalism. The elementary interactions are computed at LO with non collinear exact kinematics, which introduces phases in the expressions of their helicity amplitudes. Several Transverse Momentum Dependent (TMD) distribution and fragmentation functions appear and contribute to the cross sections and to spin asymmetries. Our results agree with those obtained with different formalisms, showing the consistency of our approach. The full expression for single and double spin asymmetries is derived. Simplified, explicit analytical expressions, convenient for phenomenological studies, are obtained assuming a factorized Gaussian dependence on intrinsic momenta for the TMDs.
Medium Effects in Parton Distributions
William Detmold, Huey-Wen Lin
2011-12-01
A defining experiment of high-energy physics in the 1980s was that of the EMC collaboration where it was first observed that parton distributions in nuclei are non-trivially related to those in the proton. This result implies that the presence of the nuclear medium plays an important role and an understanding of this from QCD has been an important goal ever since Here we investigate analogous, but technically simpler, effects in QCD and examine how the lowest moment of the pion parton distribution is modified by the presence of a Bose-condensed gas of pions or kaons.
Nuclear modifications of Parton Distribution Functions
NASA Astrophysics Data System (ADS)
Adeluyi, Adeola Adeleke
-called shadowing region. We also investigate the effects of nuclear modifications on observed quantities in ultrarelativistic nucleus-nucleus collisions. Specifically, we consider deuteron-gold collisions and observables which are directly impacted by modifications, such as pseudorapidity asymmetry and nuclear modification factors. A good description of the shadowing region is afforded by Gribov Theory. Gribov related the shadowing correction to the differential diffractive hadron-nucleon cross section. We generalize Gribov theory to include both the real part of the diffractive scattering amplitude and higher order multiple scattering necessary for heavy nuclei. The diffractive dissociation inputs are taken from experiments. We calculate observables in deuteron-gold collisions. Utilizing the factorization theorem, we use the existing parameterizations of nuclear PDFs and fragmentation functions in a pQCD-improved parton model to calculate nuclear modification factors and pseudorapidity asymmetries. The nuclear modification factor is essentially the ratio of the deuteron-gold cross section to that of the proton-proton cross section scaled by the number of binary collisions. The pseudorapidity asymmetry is the ratio of the cross section in the negative rapidity region relative to that in the equivalent positive rapidity region. Both quantities are sensitive to the effects of nuclear modifications on PDFs. Results are compared to experimental data from the BRAHMS and STAR collaborations.
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.
New model for nucleon generalized parton distributions
Radyushkin, Anatoly V.
2014-01-01
We describe a new type of models for nucleon generalized parton distributions (GPDs) H and E. They are heavily based on the fact nucleon GPDs require to use two forms of double distribution (DD) representations. The outcome of the new treatment is that the usual DD+D-term construction should be amended by an extra term, {xi} E{sub +}{sup 1} (x,{xi}) which has the DD structure {alpha}/{beta} e({beta},{alpha}, with e({beta},{alpha}) being the DD that generates GPD E(x,{xi}). We found that this function, unlike the D-term, has support in the whole -1 <= x <= 1 region. Furthermore, it does not vanish at the border points |x|={xi}.
NASA Astrophysics Data System (ADS)
Krishna Podagatlapalli, G.; Hamad, Syed; Tewari, Surya P.; Sreedhar, S.; Prasad, Muvva D.; Venugopal Rao, S.
2013-02-01
We have fabricated stable silver nanoparticles (NPs) and nanostructures (NSs) effectively through double ablation of bulk silver substrate immersed in double distilled water using ˜2 ps laser pulses. The effects of multiple/double/single ablation on silver substrates via surface morphology studies along with average size distribution of Ag NPs were investigated. Prepared Ag NPs in solution exhibited yellow color with an absorption peak near 410 nm, assigned to localized surface Plasmon resonance of nano-sized silver. Depending on the ablation parameters average sizes observed were ˜13 nm/˜17 nm in multiple/double ablation case and ˜7 nm in single ablation case. High resolution transmission electron microscope studies highlighted that most of the Ag NPs were spherical and polycrystalline in nature. Surface morphology of the substrates was characterized by field emission scanning electron microscope and atomic force microscope. A different scenario was observed in the double ablation case compared to single/multiple ablation case. Double ablation resulted in dome like NSs on the substrate with dimensions of few hundreds of nanometers while single ablation did not. Nonlinear optical (NLO) properties of Ag NPs were investigated using Z-scan technique with ˜2 ps pulses and corresponding NLO coefficients were obtained. Surface enhanced Raman scattering (SERS) studies on multiple/double ablated Ag substrates with adsorbed Rhodamine 6G molecules were carried out using excitation wavelengths of 532 nm, 785 nm, and three orders of enhancement in Raman signal intensity was observed. Furthermore, influence of laser fluence on the fabrication of SERS active Ag substrates with double ablation was also investigated. In this case, Raman spectra of adsorbed Research Department eXplosive (RDX) molecules on ablated surfaces were recorded for 532 nm and 785 nm excitation. Enhancements up to 460 were observed from substrates fabricated at fluences of 12 J/cm2, 16 J/cm2 with
Gaining analytic control of parton showers
Tackmann, Frank; Bauer, Christian W.; Tackmann, Frank J.
2007-05-14
Parton showers are widely used to generate fully exclusive final states needed to compare theoretical models to experimental observations. While, in general, parton showers give a good description of the experimental data, the precise functional form of the probability distribution underlying the event generation is generally not known. The reason is that realistic parton showers are required to conserve four-momentum at each vertex. In this paper we investigate in detail how four-momentum conservation is enforced in a standard parton shower and why this destroysthe analytic control of the probability distribution. We show how to modify a parton shower algorithm such that it conserves four-momentum at each vertex, but for which the full analytic form of the probability distribution is known. We then comment how this analytic control can be used to match matrix element calculations with parton showers, and to estimate effects of power corrections and other uncertainties in parton showers.
Zhang, Ning; Li, Xin; Jiang, Lan; Shi, Xuesong; Li, Cong; Lu, Yongfeng
2013-09-15
This Letter presents a simple, efficient approach for high surface-enhanced Raman scattering by one-step controllable fabrication of hierarchical structures (nanoparticles+subwavelength ripples) on silicon substrates in silver nitrate solutions using femtosecond double pulses based on nanoscale electron dynamics control. As the delays of the double pulses increase from 0 fs to 1 ps, the hierarchical structures can be controlled with (1) nanoparticles--the number of nanoparticles in the range of 40-100 nm reaches the maximum at 800 fs and (2) ripples--the subwavelength ripples become intermittent with decreased ablation depths. The redistributed nanoparticles and the modified ripple structures contribute to the maximum enhancement factor of 2.2×10(8) (measured by 10(-6) M rhodamine 6G solution) at the pulse delay of 800 fs.
NASA Astrophysics Data System (ADS)
Zhang, Jian-Xiang; Moortgat, Philip A.; Aker, Pamela M.
1996-11-01
Experimental confirmation that morphology-dependent stimulated Raman scattering can be used as an optical imaging technique is given. The water structure variations present at a charged water/air interface have been mapped. The measured structure variations track precisely that given by the Gouy-Chapman theory. We present, to our knowledge, the first experimental investigations of water solvent response in the diffuse part of the electric double layer. Imaging experiments on droplets charged to both positive and negative values have enabled us to determine the neutral water/air interface potential.
Zhang, J.; Moortgat, P.A.; Aker, P.M.
1996-11-01
Experimental confirmation that morphology-dependent stimulated Raman scattering can be used as an optical imaging technique is given. The water structure variations present at a charged water/air interface have been mapped. The measured structure variations track precisely that given by the Gouy{endash}Chapman theory. We present, to our knowledge, the first experimental investigations of water solvent response in the diffuse part of the electric double layer. Imaging experiments on droplets charged to both positive and negative values have enabled us to determine the neutral water/air interface potential. {copyright} {ital 1996 American Institute of Physics.}
Double-hadron leptoproduction in the nuclear medium.
Airapetian, A; Akopov, N; Akopov, Z; Amarian, M; Andrus, A; Aschenauer, E C; Augustyniak, W; Avakian, R; Avetissian, A; Avetissian, E; Bailey, P; Belostotski, S; Bianchi, N; Blok, H P; Böttcher, H; Borissov, A; Borysenko, A; Brüll, A; Bryzgalov, V; Capiluppi, M; Capitani, G P; Ciullo, G; Contalbrigo, M; Dalpiaz, P F; Deconinck, W; De Leo, R; Demey, M; De Nardo, L; De Sanctis, E; Devitsin, E; Diefenthaler, M; Di Nezza, P; Dreschler, J; Düren, M; Ehrenfried, M; Elalaoui-Moulay, A; Elbakian, G; Ellinghaus, F; Elschenbroich, U; Fabbri, R; Fantoni, A; Felawka, L; Frullani, S; Funel, A; Gapienko, G; Gapienko, V; Garibaldi, F; Garrow, K; Gavrilov, G; Gharibyan, V; Giordano, F; Grebeniouk, O; Gregor, I M; Griffioen, K; Guler, H; Hadjidakis, C; Hartig, M; Hasch, D; Hasegawa, T; Hesselink, W H; Hillenbrand, A; Hoek, M; Holler, Y; Hommez, B; Hristova, I; Iarygin, G; Ivanilov, A; Izotov, A; Jackson, H E; Jgoun, A; Kaiser, R; Keri, T; Kinney, E; Kisselev, A; Kobayashi, T; Kopytin, M; Korotkov, V; Kozlov, V; Krauss, B; Kravchenko, P; Krivokhijine, V G; Lagamba, L; Lapikás, L; Lenisa, P; Liebing, P; Linden-Levy, L A; Lorenzon, W; Lu, J; Lu, S; Ma, B-Q; Maiheu, B; Makins, N C R; Mao, Y; Marianski, B; Marukyan, H; Masoli, F; Mexner, V; Meyners, N; Michler, T; Mikloukho, O; Miller, C A; Miyachi, Y; Muccifora, V; Murray, M; Nagaitsev, A; Nappi, E; Naryshkin, Y; Negodaev, M; Nowak, W-D; Ohsuga, H; Osborne, A; Perez-Benito, R; Pickert, N; Raithel, M; Reggiani, D; Reimer, P E; Reischl, A; Roelon, A R; Riedl, C; Rith, K; Rosner, G; Rostomyan, A; Rubacek, L; Rubin, J; Ryckbosch, D; Salomatin, Y; Sanjiev, I; Savin, I; Schäfer, A; Schnell, G; Schüler, K P; Seele, J; Seidl, R; Seitz, B; Shearer, C; Shibata, T-A; Shutov, V; Sinram, K; Stancari, M; Statera, M; Steffens, E; Steijger, J J M; Stenzel, H; Stewart, J; Stinzing, F; Streit, J; Tait, P; Tanaka, H; Taroian, S; Tchuiko, B; Terkulov, A; Trzcinski, A; Tytgat, M; Vandenbroucke, A; van der Nat, P B; van der Steenhoven, G; van Haarlem, Y; Veretennikov, D; Vikhrov, V; Vogel, C; Wang, S; Ye, Y; Ye, Z; Yen, S; Zihlmann, B; Zupranski, P
2006-04-28
The first measurements of double-hadron production in deep-inelastic scattering within the nuclear medium were made with the HERMES spectrometer at DESY HERA using a 27.6 GeV positron beam. By comparing data for deuterium, nitrogen, krypton, and xenon nuclei, the influence of the nuclear medium on the ratio of double-hadron to single-hadron yields was investigated. Nuclear effects on the additional hadron are clearly observed, but with little or no difference among nitrogen, krypton, or xenon, and with smaller magnitude than effects seen on previously measured single-hadron multiplicities. The data are compared with models based on partonic energy loss or prehadronic scattering and with a model based on a purely absorptive treatment of the final-state interactions. Thus, the double-hadron ratio provides an additional tool for studying modifications of hadronization in nuclear matter. PMID:16712217
Nuclear Parton Distributions with the LHeC
NASA Astrophysics Data System (ADS)
Klein, Max
2016-03-01
Nuclear parton distributions are far from being known today because of an infant experimental base. Based on design studies of the LHeC and using new simulations, of the inclusive neutral and charged current cross section measurements and of the strange, charm and beauty densities in nuclei, it is demonstrated how that energy frontier electron-ion collider would unfold the complete set of nuclear PDFs in a hugely extended kinematic range of deep inelastic scattering, extending in Bjorken x down to values near to 10-6 in the perturbative domain. Together with a very precise and complete set of proton PDFs, the LHeC nPDFs will thoroughly change the theoretical understanding of parton dynamics and structure inside hadrons.
Generalized parton distributions of the pion in chiral quark models and their QCD evolution
Broniowski, Wojciech; Ruiz Arriola, Enrique; Golec-Biernat, Krzysztof
2008-02-01
We evaluate generalized parton distributions of the pion in two chiral quark models: the spectral quark model and the Nambu-Jona-Lasinio model with a Pauli-Villars regularization. We proceed by the evaluation of double distributions through the use of a manifestly covariant calculation based on the {alpha} representation of propagators. As a result polynomiality is incorporated automatically and calculations become simple. In addition, positivity and normalization constraints, sum rules, and soft-pion theorems are fulfilled. We obtain explicit formulas, holding at the low-energy quark-model scale. The expressions exhibit no factorization in the t-dependence. The QCD evolution of those parton distributions is carried out to experimentally or lattice accessible scales. We argue for the need of evolution by comparing the parton distribution function and the parton distribution amplitude of the pion to the available experimental and lattice data, and confirm that the quark-model scale is low, about 320 MeV.
Working Group I: Parton distributions: Summary report for the HERA LHC Workshop Proceedings
Dittmar, M.; Forte, S.; Glazov, A.; Moch, S.; Alekhin, S.; Altarelli, G.; Andersen, Jeppe R.; Ball, R.D.; Blumlein, J.; Bottcher, H.; Carli, T.; Ciafaloni, M.; Colferai, D.; Cooper-Sarkar, A.; Corcella, G.; Del Debbio, L.; Dissertori, G.; Feltesse, J.; Guffanti, A.; Gwenlan, C.; Huston, J.; /Zurich, ETH /DESY, Zeuthen /Serpukhov, IHEP /CERN /Rome III U. /INFN, Rome3 /Cambridge U. /Edinburgh U. /Florence U. /INFN, Florence /Oxford U. /DSM, DAPNIA, Saclay /Michigan State U. /Uppsala U. /Barcelona U., ECM /Podgorica U. /Turin U. /INFN, Turin /Harish-Chandra Res. Inst. /Fermilab /Hamburg U., Inst. Theor. Phys. II
2005-11-01
We provide an assessment of the impact of parton distributions on the determination of LHC processes, and of the accuracy with which parton distributions (PDFs) can be extracted from data, in particular from current and forthcoming HERA experiments. We give an overview of reference LHC processes and their associated PDF uncertainties, and study in detail W and Z production at the LHC.We discuss the precision which may be obtained from the analysis of existing HERA data, tests of consistency of HERA data from different experiments, and the combination of these data. We determine further improvements on PDFs which may be obtained from future HERA data (including measurements of F{sub L}), and from combining present and future HERA data with present and future hadron collider data. We review the current status of knowledge of higher (NNLO) QCD corrections to perturbative evolution and deep-inelastic scattering, and provide reference results for their impact on parton evolution, and we briefly examine non-perturbative models for parton distributions. We discuss the state-of-the art in global parton fits, we assess the impact on them of various kinds of data and of theoretical corrections, by providing benchmarks of Alekhin and MRST parton distributions and a CTEQ analysis of parton fit stability, and we briefly presents proposals for alternative approaches to parton fitting. We summarize the status of large and small x resummation, by providing estimates of the impact of large x resummation on parton fits, and a comparison of different approaches to small x resummation, for which we also discuss numerical techniques.
NASA Astrophysics Data System (ADS)
Tian, Fengling; Huang, Wei; Yang, Jidong; Li, Qin
In pH 3.25-3.35 Britton-Robinson (BR) buffer solution, albendazole (ABZ) could react with eosin Y (EY) to form a 1:1 ion-association complex, which not only results in the quenching of fluorescence, but also resulted in the great enhancement of resonance Rayleigh scattering (RRS) and frequency doubling scattering (FDS). Furthermore, a new RRS spectrum will appear, and the maximum RRS wavelength was located at about 356 nm. The detection limit for ABZ were 21.51 ng mL-1 for the fluorophotometry, 6.93 ng mL-1 for the RRS method and 12.89 ng mL-1 for the FDS method. Among them, the RRS method had the highest sensitivity. The experimental conditions were optimized and effects of coexisting substances were evaluated. Meanwhile, the influences of coexisting substances were tested. The methods have been successfully applied to the determination of ABZ in capsules and human urine samples. The composition and structure of the ion-association complex and the reaction mechanism were discussed.
New mechanisms for double charmed meson production at the LHCb
NASA Astrophysics Data System (ADS)
Maciuła, Rafał; Saleev, Vladimir A.; Shipilova, Alexandra V.; Szczurek, Antoni
2016-07-01
We discuss production of D0D0 (and Dbar0Dbar0) pairs related to the LHCb Collaboration results for √{ s} = 7 TeV in proton-proton scattering. We consider double-parton scattering (DPS) mechanisms of double c c bar production and subsequent cc →D0D0 hadronization as well as double g and mixed gc c bar production with gg →D0D0 and gc →D0D0 hadronization calculated with the help of the scale-dependent hadronization functions of Kniehl et al. Single-parton scattering (SPS) mechanism of digluon production is also taken into account. We compare our results with several correlation observables in azimuthal angle φD0D0 between D0 mesons or in dimeson invariant mass MD0D0. The inclusion of new mechanisms with g →D0 fragmentation leads to larger cross sections, than when including only DPS mechanism cc →D0D0 with standard scale-independent fragmentation functions. Some consequences of the presence of the new mechanisms are discussed. In particular a larger σeff is needed to describe the LHCb data. There is a signature that σeff may depend on transverse momentum of c quarks and/or c bar antiquarks.
Fleyer, Michael; Heerschap, Seth; Cranch, Geoffrey A; Horowitz, Moshe
2016-03-15
We study, theoretically and experimentally, intensity noise induced by double Rayleigh scattering in long optical fibers. The results of the theoretical model are compared to experimental results performed with a high-coherence-length laser with a frequency noise spectrum that is dominated by 1/fν noise. Excellent quantitative agreement between theoretical and experimental RF spectra were obtained for frequencies as low as 10 Hz and for fiber lengths between 4 and 45 km. Strong low-frequency intensity noise that is induced by 1/fν frequency noise of the laser may limit the performance of interferometric fiber optic sensors that require high-coherence-length lasers. The intensity noise due to double Rayleigh backscattering can be suppressed by reducing the coherence length of the laser. Therefore, the intensity noise has a complex and non-monotonic dependence on the 1/fν frequency noise amplitude of the laser. Stimulated Brillouin scattering will add a significant noise for input powers greater than about 7 mW for a 30 km length fiber.
Projective symmetry of partons in Kitaev's honeycomb model
NASA Astrophysics Data System (ADS)
Mellado, Paula
2015-03-01
Low-energy states of quantum spin liquids are thought to involve partons living in a gauge-field background. We study the spectrum of Majorana fermions of Kitaev's honeycomb model on spherical clusters. The gauge field endows the partons with half-integer orbital angular momenta. As a consequence, the multiplicities reflect not the point-group symmetries of the cluster, but rather its projective symmetries, operations combining physical and gauge transformations. The projective symmetry group of the ground state is the double cover of the point group. We acknowledge Fondecyt under Grant No. 11121397, Conicyt under Grant No. 79112004, and the Simons Foundation (P.M.); the Max Planck Society and the Alexander von Humboldt Foundation (O.P.); and the US DOE Grant No. DE-FG02-08ER46544 (O.T.).
Parton branching in the color mutation model
NASA Astrophysics Data System (ADS)
Hwa, Rudolph C.; Wu, Yuanfang
1999-11-01
The soft production problem in hadronic collisions as described in the eikonal color mutation branching model is improved in the way that the initial parton distribution is treated. Furry branching of the partons is considered as a means of describing the nonperturbative process of parton reproduction in the soft interaction. The values of all the moments,
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.
Double-critical-point phenomena in three-component liquid mixtures: Light-scattering investigations
NASA Astrophysics Data System (ADS)
Prafulla, B. V.; Narayanan, T.; Kumar, A.
1992-12-01
Measurements of osmotic compressibility (near the lower consolute point, TL) in two reentrant liquid mixtures [3-methylpyridine (MP)+water (W)+heavy water (HW) and MP+W+NaCl] are presented. The closest approach to the double critical point (DCP) was marked by a sample of loop size (ΔT)=250 mK. Analyzing the data by means of the conventional field variable t[=\\|(Tc-T)/Tc\\|] yielded an exact doubling of the critical exponent (CE) γ for a ΔT=250 mK. The approach to double criticality (for intermediate ΔT) is described by a crossover of the CE from the doubled to its single limit as t-->0. Recourse to a more appropriate field variable, tUL[=\\|(TU-T)(TL-T)/TUTL\\|], restores the Ising value of γ(=1.24) for any ΔT. The salt-doped mixtures permitted us to observe a doubling of the extended scaling exponent (Δ) and also to scrutinize the ionic critical phenomena. The range of simple scaling in MP+W+HW was found to be extremely large. Switching to a modified variable t'UL[=\\|(TU-T)(TL-T)/T2\\|] led to a remarkable enhancement in the weight of the extended scaling term in both the mixtures-in apparent disagreement with the earlier findings that reported a widening of the asymptotic region. Non-phase-separating samples of MP+W+HW showed the expected saturating divergence preceded by a region of doubled γ as TD (DCP temperature) was neared. Most of the facets of our investigations can be comprehended in terms of the geometrical picture of phase transitions as well as the Landau-Ginzburg theory as applied to the reentrant phase transitions.
NASA Astrophysics Data System (ADS)
Schoenbeck, N. L.; Dowd, A. S.; Fonck, R. J.; Schlossberg, D. J.; Winz, G. R.
2012-10-01
A novel Thomson scattering system has been deployed on the Pegasus Toroidal Experiment. It provides a relatively low-cost, simplified design. Scattering is achieved using a 7 ns, 2 J frequency doubled Nd:YAG laser operating at 532 nm. The laser focuses to ˜3 mm diameter within the plasma via a 7 m beam-line. The beam-line contains cameras as beam finders and remotely adjustable mirrors for shot-to-shot alignment. A custom multi-element lens collects scattered photons from 15 cm < Rmaj< 85 cm with 1.2 cm radial resolution. Eight fiber optic bundles provide 8 spatial points for sampling the laser or background light. Each set of 8 channels is measured in a single spectrometer that utilizes a high efficiency (˜80%) volume phase holographic grating and a high quantum efficiency (> 40%) image intensified CCD (ICCD) camera. Three spectrometers provide a total of 24 channels. Two interchangeable gratings exist to cover low (Te = 10--100 eV) and high (Te = 0.10--1 keV) electron temperature regimes on Pegasus. The spectrometer is optimized for ne from mid-10^18 to mid-10^19 m-3. The signal-to-noise expected is ˜0.5 of an equivalent system using Nd:YAG at 1064 nm and avalanche photodiode detectors.
KOVCHEGOV,Y.V.
2000-04-25
The authors derive an equation determining the small-x evolution of the F{sub 2} structure function of a large nucleus which resumes a cascade of gluons in the leading logarithmic approximation using Mueller's color dipole model. In the traditional language it corresponds to resummation of the pomeron fan diagrams, originally conjectured in the GLR equation. The authors show that the solution of the equation describes the physics of structure functions at high partonic densities, thus allowing them to gain some understanding of the most interesting and challenging phenomena in small-x physics--saturation.
NASA Astrophysics Data System (ADS)
Thakkar, Disha; Gevriya, Bhavesh; Mashru, R. C.
2014-03-01
Linezolid reacted with palladium to form 1:1 binary cationic chelate which further reacted with eosin dye to form 1:1 ternary ion association complex at pH 4 of Walpole's acetate buffer in the presence of methyl cellulose. As a result not only absorption spectra were changed but Resonance Rayleigh Scattering (RRS), Second-order Scattering (SOS) and Frequency Doubling Scattering (FDS) intensities were greatly enhanced. The analytical wavelengths of RRS, SOS and FDS (λex/λem) of ternary complex were located at 538 nm/538 nm, 240 nm/480 nm and 660 nm/330 nm, respectively. The linearity range for RRS, SOS and FDS methods were 0.01-0.5 μg mL-1, 0.1-2 μg mL-1 and 0.2-1.8 μg mL-1, respectively. The sensitivity order of three methods was as RRS > SOS > FDS. Accuracy of all methods were determined by recovery studies and showed recovery between 98% and 102%. Intraday and inter day precision were checked for all methods and %RSD was found to be less than 2 for all methods. The effects of foreign substances were tested on RRS method and it showed the method had good selectivity. For optimization of process parameter, Taguchi orthogonal array design L8(24) was used and ANOVA was adopted to determine the statistically significant control factors that affect the scattering intensities of methods. The reaction mechanism, composition of ternary ion association complex and reasons for scattering intensity enhancement was discussed in this work.
Huang, Danhong; Lyo, S.K.
1999-08-09
The effect of higher-order corrections to the Born approximation is studied for the previously obtained giant conductance enhancement in tunnel-coupled double quantum wires in a parallel magnetic field. The relative correction is found to be significant and depends on various effects such as the magnetic field, electron and impurity densities, impurity positions, symmetric and asymmetric doping profiles, and center barrier thickness.
The parton distribution function library
Plothow-Besch, H.
1995-07-01
This article describes an integrated package of Parton Density Functions called PDFLIB which has been added to the CERN Program Library Pool W999 and is labelled as W5051. In this package all the different sets of parton density functions of the Nucleon, Pion and the Photon which are available today have been put together. All these sets have been combined in a consistent way such that they all have similar calling sequences and no external data files have to be read in anymore. A default set has been prepared, although those preferring their own set or wanting to test a new one may do so within the package. The package also offers a program to calculate the strong coupling constant {alpha}, to first or second order. The correct {Lambda}{sub QCD} associated to the selected set of structure functions and the number of allowed flavours with respect to the given Q{sup 2} is automatically used in the calculation. The selection of sets, the program parameters as well as the possibilities to modify the defaults and to control errors occurred during execution are described.
Jet correlations from unintegrated parton distributions
Hautmann, F.; Jung, H.
2008-10-13
Transverse-momentum dependent parton distributions can be introduced gauge-invariantly in QCD from high-energy factorization. We discuss Monte Carlo applications of these distributions to parton showers and jet physics, with a view to the implications for the Monte Carlo description of complex hadronic final states with multiple hard scales at the LHC.
Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting
NASA Astrophysics Data System (ADS)
Gamberg, Leonard
2015-04-01
We present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. Advantages of employing Bessel weighting are that transverse momentum weighted asymmetries provide a means to disentangle the convolutions in the cross section in a model independent way. The resulting compact expressions immediately connect to work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions. As a test case, we apply the procedure to studies of the double longitudinal spin asymmetry in SIDIS using a dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations. Bessel weighting provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs. Work is supported by the U.S. Department of Energy under Contract No. DE-FG02-07ER41460.
Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting
NASA Astrophysics Data System (ADS)
Gamberg, Leonard
2015-10-01
We present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. Advantages of employing Bessel weighting are that transverse momentum weighted asymmetries provide a means to disentangle the convolutions in the cross section in a model independent way. The resulting compact expressions immediately connect to work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions. As a test case, we apply the procedure to studies of the double longitudinal spin asymmetry in SIDIS using a dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations. Bessel weighting provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs. Work is supported by the U.S. Department of Energy under Contract No. DE-FG02-07ER41460.
Raman scattering of a photon with frequency doubling by a channelled positron
Kalashnikov, N P; Krokhin, O N
2014-12-31
We have analysed the possibility of appearance of anti-Stokes lines in the spectrum of Raman scattering of a photon by a 'quasi-bound' charged particle in the regime of planar (axial) channelling. It is shown that radiation may emerge at the frequency, which is a combination of the incident photon frequency ω{sub 0} and transition frequency ω{sub i} in the transverse quantised motion of a channelled particle: ω = ω{sub 0} ± 2γ{sup 2}ω{sub i}, where γ is the relativistic (Lorentz) factor of a channelled particle. (nonlinear optical phenomena)
First JAM results on the determination of polarized parton distributions
Accardi, Alberto; Jimenez-Delgado, Pedro; Melnitchouk, Wally
2014-01-01
The Jefferson Lab Angular Momentum (JAM) Collaboration is a new initiative to study the angular momentum dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions at intermediate and large x from world data on polarized deep-inelastic scattering are presented. Different aspects of global QCD analysis are discussed, including the effects of nuclear structure of deuterium and {sup 3}He targets, target mass corrections and higher twist contributions to the g{sub 1} and g{sub 2} structure functions.
Transverse Momentum-Dependent Parton Distributions From Lattice QCD
Michael Engelhardt, Bernhard Musch, Philipp Haegler, Andreas Schaefer
2012-12-01
Starting from a definition of transverse momentum-dependent parton distributions for semi-inclusive deep inelastic scattering and the Drell-Yan process, given in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection, a scheme to determine such observables in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are presented, focusing in particular on their dependence on the staple extent and the Collins-Soper evolution parameter.
First JAM results on the determination of polarized parton distributions
Jimenez-Delgado, Pedro
2013-04-01
The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed to the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering will be presented and compared with previous determinations from other groups. Different aspects of global QCD analysis will be discussed, including effects due to nuclear structure, higher twist, and target-mass corrections, as well as the impact of different data selections.
Transverse Momentum-Dependent Parton Distributions from Lattice QCD
NASA Astrophysics Data System (ADS)
Engelhardt, M.; Musch, B.; Hägler, P.; Negele, J.; Schäfer, A.
Starting from a definition of transverse momentum-dependent parton distributions for semi-inclusive deep inelastic scattering and the Drell-Yan process, given in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection, a scheme to determine such observables in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are presented, focusing in particular on their dependence on the staple extent and the Collins-Soper evolution parameter.
Chiral dynamics and partonic structure at large transverse distances
Strikman, M.; Weiss, C.
2009-12-30
In this paper, we study large-distance contributions to the nucleon’s parton densities in the transverse coordinate (impact parameter) representation based on generalized parton distributions (GPDs). Chiral dynamics generates a distinct component of the partonic structure, located at momentum fractions x≲M_{π}/M_{N} and transverse distances b~1/M_{π}. We calculate this component using phenomenological pion exchange with a physical lower limit in b (the transverse “core” radius estimated from the nucleon’s axial form factor, R_{core}=0.55 fm) and demonstrate its universal character. This formulation preserves the basic picture of the “pion cloud” model of the nucleon’s sea quark distributions, while restricting its application to the region actually governed by chiral dynamics. It is found that (a) the large-distance component accounts for only ~1/3 of the measured antiquark flavor asymmetry d¯-u¯ at x~0.1; (b) the strange sea quarks s and s¯ are significantly more localized than the light antiquark sea; (c) the nucleon’s singlet quark size for x<0.1 is larger than its gluonic size, (b^{2})_{q+q¯}>(b^{2})_{g}, as suggested by the t-slopes of deeply-virtual Compton scattering and exclusive J/ψ production measured at HERA and FNAL. We show that our approach reproduces the general N_{c}-scaling of parton densities in QCD, thanks to the degeneracy of N and Δ intermediate states in the large-N_{c} limit. Finally, we also comment on the role of pionic configurations at large longitudinal distances and the limits of their applicability at small x.
Research of the system response of neutron double scatter imaging for MLEM reconstruction
NASA Astrophysics Data System (ADS)
Zhang, M.; Peng, B. D.; Sheng, L.; Li, K. N.; Zhang, X. P.; Li, Y.; Li, B. K.; Yuan, Y.; Wang, P. W.; Zhang, X. D.; Li, C. H.
2015-03-01
A Maximum Likelihood image reconstruction technique has been applied to neutron scatter imaging. The response function of the imaging system can be obtained by Monte Carlo simulation, which is very time-consuming if the number of image pixels and particles is large. In this work, to improve time efficiency, an analytical approach based on the probability of neutron interaction and transport in the detector is developed to calculate the system response function. The response function was applied to calculate the relative efficiency of the neutron scatter imaging system as a function of the incident neutron energy. The calculated results agreed with simulations by the MCNP5 software. Then the maximum likelihood expectation maximization (MLEM) reconstruction method with the system response function was used to reconstruct data simulated by Monte Carlo method. The results showed that there was good consistency between the reconstruction position and true position. Compared with back-projection reconstruction, the improvement in image quality was obvious, and the locations could be discerned easily for multiple radiation point sources.
Inelastic neutron scattering studies of Ge-76 and Se-76: relevance to neutrinoless double-beta decay
Crider, Ben; Peters, Erin; Ross, T.J.; McEllistrem, M; Prados-Estevez, F.; Allmond, James M; Vanhoy, J.R.; Yates, S.W.
2015-01-01
Inelastic neutron scattering measurements were performed at the University of Kentucky Accelerator Laboratory on enriched Ge-76 and Se-76 scattering samples. From measurements at incident neutron energies from 2.0 to 4.0 MeV, many new levels were identified and characterized in each nucleus; level lifetimes, transition probabilities, multipole mixing ratios, and other properties were determined. In addition, gamma-ray cross sections for the Ge-76(n,n'gamma) reaction were measured at neutron energies up to 5.0 MeV, with the goal of determining the cross sections of gamma rays in 2040-keV region, which corresponds to the region of interest in the neutrinoless double beta decay of Ge-76. Gamma rays from the three strongest branches from the 3952-keV level were observed, but the previously reported 2041-keV gamma ray was not. Population cross sections across the range of incident neutron energies were determined for the 3952-keV level, resulting in a cross section of similar to 0.1 mb for the 2041-keV branch using the previously determined branching ratios. Beyond this, the data from these experiments indicate that previously unreported gamma rays from levels in Ge-76 can be found in the 2039-keV region.
NASA Astrophysics Data System (ADS)
Tan, Xuanping; Yang, Jidong; Li, Qin; Yang, Qiong; Shen, Yizhong
2016-05-01
Four simple and accurate spectrophotometric methods were proposed for the simultaneous determination of three β-adrenergic blockade, e.g. atenolol, metoprolol and propranolol. The methods were based on the reaction of the three drugs with erythrosine B (EB) in a Britton-Robinson buffer solution at pH 4.6. EB could combine with the drugs to form three ion-association complexes, which resulted in the resonance Rayleigh scattering (RRS) intensity that is enhanced significantly with new RRS peaks that appeared at 337 nm and 370 nm, respectively. In addition, the fluorescence intensity of EB was also quenched. The enhanced scattering intensities of the two peaks and the fluorescence quenched intensity of EB were proportional to the concentrations of the drugs, respectively. What is more, the RRS intensity overlapped with the double-wavelength of 337 nm and 370 nm (so short for DW-RRS) was also proportional to the drugs concentrations. So, a new method with highly sensitive for simultaneous determination of three bisoprolol drugs was established. Finally, the optimum reaction conditions, influencing factors and spectral enhanced mechanism were investigated. The new DW-RRS method has been applied to simultaneously detect the three β-blockers in fresh serum with satisfactory results.
Double Resonant Raman Scattering and Valley Coherence Generation in Monolayer WSe2
NASA Astrophysics Data System (ADS)
Wang, G.; Glazov, M. M.; Robert, C.; Amand, T.; Marie, X.; Urbaszek, B.
2015-09-01
The electronic states at the direct band gap of monolayer transition metal dichalcogenides such as WSe2 at the K+ and K- valleys are related by time reversal and may be viewed as pseudospins. The corresponding optical interband transitions are governed by robust excitons. Excitation with linearly polarized light yields the coherent superposition of exciton pseudospin states, referred to as coherent valley states. Here, we uncover how and why valley coherence can be generated efficiently. In double resonant Raman spectroscopy, we show that the optically generated 2 s exciton state differs from the 1 s state by exactly the energy of the combination of several prominent phonons. Superimposed on the exciton photoluminescence (PL), we observe the double resonant Raman signal. This spectrally narrow peak shifts with the excitation laser energy as incoming photons match the 2 s and outgoing photons the 1 s exciton transition. The multiphonon resonance has important consequences: following linearly polarized excitation of the 2 s exciton, a superposition of valley states is efficiently transferred from the 2 s to 1 s state. This explains the high degree of valley coherence measured for the 1 s exciton PL.
Crider, B. P.; Peters, E. E.; Allmond, J. M.; McEllistrem, M. T.; Prados-Estévez, F. M.; Ross, T. J.; Vanhoy, J. R.; Yates, S. W.
2015-09-11
The experimental signature in searches for the neutrinoless double- decay of 76Ge is a peak near 2039 keV in the spectrum. Given the low probability of the process, it is important that the background in this region be well understood. Moreover, inelastic scattering reactions with neutrons from muon-induced interactions and ( ,n) reactions in the surrounding materials or in the detector can provide contributions to the background. We also measured the production cross sections for rays from the 76Ge(n,n ) reaction in the 2039-keV region at incident neutron energies up to 4.9 MeV. In addition to determining that the crossmore » sections of a previously known 2040.7-keV ray from the 3952-keV level in 76 Ge are rather small, we find that a larger contribution arises from a 2037.5-keV ray which is attributed to a newly identified level at 3147 keV in 76Ge. Finally, a third contribution is also possible from another new level at 3577 keV. These results indicate that the 2039-keV region in 76Ge neutrinoless double- decay searches is more complex than was previously thought.« less
NASA Astrophysics Data System (ADS)
McKinzie, Matthew Gordon
1995-01-01
Angular distributions for the reactions ^{27}Al, ^{28 }Si(pi^{+/- },pi^{+/-} ) at T_pi = 180 MeV and an excitation function at theta_ {rm lab.} = 5^{ rm o} for the reaction ^{27}Al(pi^{+}, pi^{-})^{27}P were measured using the Energetic Pion Channel and Spectrometer at the Clinton P. Anderson Meson Physics Facility in Los Alamos, New Mexico. Angular distributions for the reaction ^{27}Al(n,p)^ {27}Mg were measured at T_ {rm N} = 198 MeV using the Medium Resolution Spectrometer at Canada's Tri-University Meson Facility in Vancouver, British Columbia. Multipole matrix elements were extracted in a macroscopic manner from the pion inelastic angular distributions using the distorted-wave impulse approximation and collective -model transition densities. Microscopic calculations of these extracted matrix elements and of the pion angular distributions were examined. Double charge exchange (DCX) excitation functions to the ^{27}P ground state and an excited state were measured at nine incident pion energies from T_pi = 100 to 293.4 MeV. The systematics of DCX excitation functions to low-lying states is reviewed in light of these data. Microscopic calculations of DCX for and near A = 27 are investigated. Double giant resonances in ^{27}P were observed at the three highest energies. The (n,p) charge exchange angular distributions were obtained for theta_{rm lab.} = 0^circ, 4^circ, 8^ circ, 12^circ, 18^circ and 24^ circ. The Gamow-Teller strength distribution was measured and compared to a microscopic calculation. The constant of proportionality between reduced transition probability and cross section (the unit cross section) was generalized and examined for configuration dependence. Data for higher spin-multipole isovector excitations are presented, including low-lying spin-isospin E2 strength and negative -parity giant resonances.
NASA Technical Reports Server (NTRS)
Gao, R. S.; Dutta, C. M.; Lane, N. F.; Smith, K. A.; Stebbings, R. F.; Kimura, M.
1992-01-01
Measurements and calculations of differential cross sections for direct scattering, single-charge transfer, and double-charge transfer in collisions of 1.5-, 2.0-, 6.0-, and 10.0-keV (He-3)2+ with an He-4 target are reported. The measurements cover laboratory scattering angles below 1.5 deg with an angular resolution of about 0.03 deg. A quantum-mechanical molecular-state representation is employed in the calculations; in the case of single-charge transfer a two-state close-coupling calculation is carried out taking into account electron-translation effects. The theoretical calculations agree well with the experimental results for direct scattering and double-charge transfer. The present calculation identifies the origins of oscillatory structures observed in the differential cross sections.
Constraints on spin-dependent parton distributions at large x from global QCD analysis
NASA Astrophysics Data System (ADS)
Jimenez-Delgado, P.; Avakian, H.; Melnitchouk, W.
2014-11-01
We investigate the behavior of spin-dependent parton distribution functions (PDFs) at large parton momentum fractions x in the context of global QCD analysis. We explore the constraints from existing deep-inelastic scattering data, and from theoretical expectations for the leading x → 1 behavior based on hard gluon exchange in perturbative QCD. Systematic uncertainties from the dependence of the PDFs on the choice of parametrization are studied by considering functional forms motivated by orbital angular momentum arguments. Finally, we quantify the reduction in the PDF uncertainties that may be expected from future high-x data from Jefferson Lab at 12 GeV.
NASA Astrophysics Data System (ADS)
Tojo, H.; Yamada, I.; Yasuhara, R.; Ejiri, A.; Hiratsuka, J.; Togashi, H.; Yatsuka, E.; Hatae, T.; Funaba, H.; Hayashi, H.; Takase, Y.; Itami, K.
2016-09-01
This paper evaluates the accuracy of electron temperature measurements and relative transmissivities of double-pass Thomson scattering diagnostics. The electron temperature (Te) is obtained from the ratio of signals from a double-pass scattering system, then relative transmissivities are calculated from the measured Te and intensity of the signals. How accurate the values are depends on the electron temperature (Te) and scattering angle (θ), and therefore the accuracy of the values was evaluated experimentally using the Large Helical Device (LHD) and the Tokyo spherical tokamak-2 (TST-2). Analyzing the data from the TST-2 indicates that a high Te and a large scattering angle (θ) yield accurate values. Indeed, the errors for scattering angle θ = 135° are approximately half of those for θ = 115°. The method of determining the Te in a wide Te range spanning over two orders of magnitude (0.01-1.5 keV) was validated using the experimental results of the LHD and TST-2. A simple method to provide relative transmissivities, which include inputs from collection optics, vacuum window, optical fibers, and polychromators, is also presented. The relative errors were less than approximately 10%. Numerical simulations also indicate that the Te measurements are valid under harsh radiation conditions. This method to obtain Te can be considered for the design of Thomson scattering systems where there is high-performance plasma that generates harsh radiation environments.
An O([alpha][sub s]) Monte Carlo for W production with parton showering
Baer, H.A.
1991-01-01
We construct an event generator for p[bar p][yields]W[sup +]X[yields]e[sup +][nu]X including complete O([alpha][sub s]) corrections, and interface with initial and final state parton showers. Problems with negative weights and with double counting higher order parton radiation are averted. We present results for W+n-jet production, and compare with results from complete tree-level calculations, and shower calculations off of the lowest order 2[yields]2 sub-process. We also compute the [sub qT](W) distribution, and compare with data.
An O({alpha}{sub s}) Monte Carlo for W production with parton showering
Baer, H.A.
1991-12-31
We construct an event generator for p{bar p}{yields}W{sup +}X{yields}e{sup +}{nu}X including complete O({alpha}{sub s}) corrections, and interface with initial and final state parton showers. Problems with negative weights and with double counting higher order parton radiation are averted. We present results for W+n-jet production, and compare with results from complete tree-level calculations, and shower calculations off of the lowest order 2{yields}2 sub-process. We also compute the {sub qT}(W) distribution, and compare with data.
NASA Astrophysics Data System (ADS)
Crider, Benjamin P.
While neutrino oscillations indicate that neutrino flavors mix and that neutrinos have mass, they do not supply information on the absolute mass scale of the three flavors of neutrinos. Currently, the only viable way to determine this mass scale is through the observation of the theoretically predicted process of neutrinoless double-beta decay (0nubetabeta). This yet-to-be-observed decay process is speculated to occur in a handful of nuclei and has predicted half-lives greater than 1025 years. Observation of 0nubetabeta is the goal of several large-scale, multinational efforts and consists of detecting a sharp peak in the summed energies at the Q-value of the reaction. An exceptional candidate for the observation of 0nubetabeta is 76Ge, which offers an excellent combination of capabilities and sensitivities, and two such collaborations, MAJORANA and GERDA, propose tonne-scale experiments that have already begun initial phases using a fraction of the material. The absolute scale of the neutrino masses hinges on a matrix element, which depends on the ground-state wave functions for both the parent (76Ge) and daughter (76Se) nuclei in the 0nubetabeta decay and can only be calculated from nuclear structure models. Efforts to provide information on the applicability of these models have been undertaken at the University of Kentucky Accelerator Laboratory using gamma-ray spectroscopy following inelastic scattering reactions with monoenergetic, accelerator-produced fast neutrons. Information on new energy levels and transitions, spin and parity assignments, lifetimes, multipole mixing ratios, and transition probabilities have been determined for 76Se, the daughter of 76Ge 0nubetabeta, up to 3.0 MeV. Additionally, inaccuracies in the accepted level schemes have been addressed. Observation of 0nubetabeta requires precise knowledge of potential contributors to background within the region of interest, i.e., approximately 2039 keV for 76Ge. In addition to backgrounds
Unraveling hadron structure with generalized parton distributions
Andrei Belitsky; Anatoly Radyushkin
2004-10-01
The recently introduced generalized parton distributions have emerged as a universal tool to describe hadrons in terms of quark and gluonic degrees of freedom. They combine the features of form factors, parton densities and distribution amplitudes - the functions used for a long time in studies of hadronic structure. Generalized parton distributions are analogous to the phase-space Wigner quasi-probability function of non-relativistic quantum mechanics which encodes full information on a quantum-mechanical system. We give an extensive review of main achievements in the development of this formalism. We discuss physical interpretation and basic properties of generalized parton distributions, their modeling and QCD evolution in the leading and next-to-leading orders. We describe how these functions enter a wide class of exclusive reactions, such as electro- and photo-production of photons, lepton pairs, or mesons.
Pre-equilibrium parton dynamics: Proceedings
Wang, Xin-Nian
1993-12-31
This report contains papers on the following topics: parton production and evolution; QCD transport theory; interference in the medium; QCD and phase transition; and future heavy ion experiments. This papers have been indexed separately elsewhere on the data base.
QCD-aware partonic jet clustering for truth-jet flavour labelling
NASA Astrophysics Data System (ADS)
Buckley, Andy; Pollard, Chris
2016-02-01
We present an algorithm for deriving partonic flavour labels to be applied to truth particle jets in Monte Carlo event simulations. The inputs to this approach are final pre-hadronisation partons, to remove dependence on unphysical details such as the order of matrix element calculation and shower generator frame recoil treatment. These are clustered using standard jet algorithms, modified to restrict the allowed pseudojet combinations to those in which tracked flavour labels are consistent with QCD and QED Feynman rules. The resulting algorithm is shown to be portable between the major families of shower generators, and largely insensitive to many possible systematic variations: it hence offers significant advantages over existing ad hoc labelling schemes. However, it is shown that contamination from multi-parton scattering simulations can disrupt the labelling results. Suggestions are made for further extension to incorporate more detailed QCD splitting function kinematics, robustness improvements, and potential uses for truth-level physics object definitions and tagging.
Soft factor subtraction and transverse momentum dependent parton distributions on the lattice
NASA Astrophysics Data System (ADS)
Ji, Xiangdong; Sun, Peng; Xiong, Xiaonu; Yuan, Feng
2015-04-01
We study the transverse momentum dependent (TMD) parton distributions in the newly proposed quasiparton distribution function framework in Euclidean space. In this framework, the parton distributions can be extracted from lattice observables in a systematic expansion of 1 /Pz where Pz is the hadron momentum. A soft factor subtraction is found to be essential to make the TMDs calculable on the lattice. We show that the quasi-TMDs with the associated soft factor subtraction can be applied in hard QCD scattering processes such as Drell-Yan lepton pair production in hadronic collisions. This allows future lattice calculations to provide information on the nonperturbative inputs and energy evolutions for the TMDs. Extension to the generalized parton distributions and quantum phase space Wigner distributions will lead to a complete nucleon tomography on the lattice.
The midpoint between dipole and parton showers
Höche, Stefan; Prestel, Stefan
2015-09-28
We present a new parton-shower algorithm. Borrowing from the basic ideas of dipole cascades, the evolution variable is judiciously chosen as the transverse momentum in the soft limit. This leads to a very simple analytic structure of the evolution. A weighting algorithm is implemented that allows one to consistently treat potentially negative values of the splitting functions and the parton distributions. Thus, we provide two independent, publicly available implementations for the two event generators PYTHIA and SHERPA.
Transverse-momentum-dependent parton distributions (TMDs)
NASA Astrophysics Data System (ADS)
Bacchetta, Alessandro
2011-10-01
Transverse-momentum-dependent parton distributions (TMDs) provide three-dimensional images of the partonic structure of the nucleon in momentum space. We made impressive progress in understanding TMDs, both from the theoretical and experimental point of view. This brief overview on TMDs is divided in two parts: in the first, an essential list of achievements is presented. In the second, a selection of open questions is discussed.
NASA Astrophysics Data System (ADS)
Patrick, Cheryl Elizabeth
Next-generation neutrino oscillation experiments, such as DUNE and Hyper-Kamiokande, hope to measure charge-parity (CP) violation in the lepton sector. In order to do this, they must dramatically reduce their current levels of uncertainty, particularly those due to neutrino-nucleus interaction models. As CP violation is a measure of the difference between the oscillation properties of neutrinos and antineutrinos, data about how the less-studied antineutrinos interact is especially valuable. We present the MINERvA experiment's first double-differential scattering cross sections for antineutrinos on scintillator, in the few-GeV range relevant to experiments such as DUNE and NOvA. We also present total antineutrino-scintillator quasi-elastic cross sections as a function of energy, which we compare to measurements from previous experiments. As well as being useful to help reduce oscillation experiments' uncertainty, our data can also be used to study the prevalence of various correlation and final-state interaction effects within the nucleus. We compare to models produced by different model generators, and are able to draw first conclusions about the predictions of these models.
Jordanova, Vania Koleva; Tu, Weichao; Chen, Yue; Morley, Steven Karl; Panaitescu, Alin -Daniel; Reeves, Geoffrey D.; Kletzing, Craig A.
2016-09-01
Here, mechanisms for electron injection, trapping, and loss in the near-Earth space environment are investigated during the October 2012 “double-dip” storm using our magnetically self-consistent ring current model (RAM-SCB). Pitch angle and energy scattering are included for the first time in RAM-SCB using L and magnetic local time (MLT) dependent event-specific chorus wave models inferred from NOAA POES and Van Allen Probes EMFISIS observations. The dynamics of the source (~10s keV) and seed (~100s keV) populations of the radiation belts simulated with RAM-SCB is compared with Van Allen Probes MagEIS observations in the morning sector and with measurements from NOAA-15more » satellite in the predawn and afternoon MLT sectors. We find that although the low-energy (E < 100 keV) electron fluxes are in good agreement with observations, increasing significantly by magnetospheric convection during both SYM-H dips while decreasing during the intermediate recovery phase, the injection of high-energy electrons is underestimated by this mechanism throughout the storm. Local acceleration by chorus waves intensifies the electron fluxes at E ≥ 50 keV considerably and RAM-SCB simulations overestimate the observed trapped fluxes by more than an order of magnitude; the simulated with RAM-SCB precipitating fluxes are weaker and their temporal and spatial evolution agree well with POES/MEPED data.« less
Pérez-Andújar, Angélica; Newhauser, Wayne D; DeLuca, Paul M
2014-01-01
In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient. PMID:19147903
NASA Astrophysics Data System (ADS)
Herziger, Felix; Vierck, Asmus; Laudenbach, Jan; Maultzsch, Janina
2015-12-01
We present a theoretical model to describe the double-resonant scattering process in arbitrary carbon nanotubes (CNTs). We use this approach to investigate the defect-induced D mode in CNTs and unravel the dependence of the D -mode frequency on the CNT diameter and on the energy of the resonant optical transition. Our approach is based on the symmetry of the hexagonal lattice and geometric considerations; hence the method is independent of the exact model that is chosen to describe the electronic band structure or the phonon dispersion. We finally clarify the diameter dependence of this Raman mode that has been under discussion in the past and demonstrate that, depending on the experimental conditions, in general two different dependencies can be measured. We also prove that CNTs with an arbitrary chiral index can exhibit a D mode in their Raman spectrum, in contrast to previous symmetry-based arguments. Furthermore, we give a direct quantification of the curvature-induced phonon frequency corrections of the D mode in CNTs with respect to graphite.
Patrick, Cheryl
2016-01-01
Next-generation neutrino oscillation experiments, such as DUNE and Hyper-Kamiokande, hope to measure charge-parity (CP) violation in the lepton sector. In order to do this, they must dramatically reduce their current levels of uncertainty, particularly those due to neutrino-nucleus interaction models. As CP violation is a measure of the difference between the oscillation properties of neutrinos and antineutrinos, data about how the less-studied antineutrinos interact is especially valuable. We present the MINERvA experiment's first double-differential scattering cross sections for antineutrinos on scintillator, in the few-GeV range relevant to experiments such as DUNE and NOvA. We also present total antineutrino-scintillator quasi-elastic cross sections as a function of energy, which we compare to measurements from previous experiments. As well as being useful to help reduce oscillation experiments' uncertainty, our data can also be used to study the prevalence of various cor relation and final-state interaction effects within the nucleus. We compare to models produced by different model generators, and are able to draw first conclusions about the predictions of these models.
NASA Astrophysics Data System (ADS)
Jordanova, V.
2015-12-01
The mechanisms for particle injection in the near-Earth space environment and their subsequent trapping or loss have been studied for many years, however, their theoretical evaluation and implementation in numerical models remain challenging. We address these outstanding questions using our RAM-SCB model that couples the kinetic ring current-atmosphere interactions model with an Euler potential-based three-dimensional plasma equilibrium code. We simulate wave-particle interactions on a global scale using L and MLT-dependent event-specific wave models and investigate the fast dropout of the radiation belts during the October 2012 "double-dip" storm event. The calculated cold plasma densities with a coupled time-dependent 2-D plasmasphere model show good agreement with in situ EMFISIS observations along the Van Allen Probes' orbits. The simulated with RAM-SCB precipitating electron fluxes are compared with measurements of electron precipitation by multiple NOAA satellites during the investigated storm event. The combined effects from radial transport and scattering by plasma waves on ring current and radiation belt dynamics are evaluated.
Implementing the LPM effect in a parton cascade model
NASA Astrophysics Data System (ADS)
Coleman-Smith, C. E.; Bass, S. A.; Srivastava, D. K.
2011-07-01
Parton Cascade Models (PCM [K. Geiger, B. Muller, Nucl. Phys. B369 (1992) 600-654; S. A. Bass, B. Muller, D. K. Srivastava, Phys. Lett. B551 (2003) 277-283; Z. Xu and C. Greiner, Phys. Rev. C 76, 024911 (2007); D. Molnar and M. Gyulassy, Phys. Rev. C 62, 054907 (2000)]), which describe the full time-evolution of a system of quarks and gluons using pQCD interactions are ideally suited for the description of jet production, including the emission, evolution and energy-loss of the full parton shower in a hot and dense QCD medium. The Landau-Pomeranchuk-Migdal (LPM) effect [L. D. Landau, I. J. Pomeranchuk, Dolk. Akad. Nauk. SSSR 92 (92); A. B. Migdal, Phys. Rev. 103 (6) (1956) 1811-1820], the quantum interference of parton wave functions due to repeated scatterings against the background medium, is likely the dominant in-medium effect affecting jet suppression. We have implemented a probabilistic implementation of the LPM effect [K. Zapp, J. Stachel, U. A. Wiedemann, Phys. Rev. Lett. 103 (2009) 152302] within the PCM which can be validated against previously derived analytical calculations by Baier et al (BDMPS-Z) [R. Baier, Y. L. Dokshitzer, A. H. Mueller, S. Peigne, D. Schiff, Nucl. Phys. B478 (1996) 577-597; R. Baier, Y. L. Dokshitzer, S. Peigne, D. Schiff, Phys. Lett. B345 (1995) 277-286; R. Baier, Y. L. Dokshitzer, A. H. Mueller, S. Peigne, D. Schiff, Nucl. Phys. B483 (1997) 291-320; B. Zakharov, JETP Lett. 63 (1996) 952-957; B. Zakharov, JETP Lett. 65 (1997) 615-620]. Presented at the 6th International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2010).
NASA Astrophysics Data System (ADS)
Jawalkar, Sucheta Shrikant
Measurements in the late 1980s at CERN revealed that quark spins account for a small fraction of the proton's spin. This so-called spin crisis spurred a number of new experiments to identify the proton's silent spin contributors, namely, the spin of the gluons, which hold the quarks together, and the orbital angular momentum of both quarks and gluons. One such experiment was eg1-dvcs at the Thomas Jefferson National Accelerator Facility in Newport News, Va., which ran in 2009 and collected approximately 19 billion electron triggers for hydrogen. I will present new measurements of the single and double-spin asymmetries ALU, AUL and ALL for pi+, pi - and pi0, measured as a function of Bjorken xB, squared momentum transfer Q2, hadron energy fraction z, and hadron transverse momentum Ph ⊥. These asymmetries, which are convolutions of transverse-momentum-dependent parton distributions and fragmentation functions, correlate with the transverse momentum, and therefore with the orbital motion, of the struck quark.
Deeply virtual Compton scattering on longitudinally polarized protons and neutrons at CLAS
Silvia Niccolai
2012-04-01
This paper focuses on a measurement of deeply virtual Compton scattering (DVCS) performed at Jefferson Lab using a nearly-6-GeV polarized electron beam, two longitudinally polarized (via DNP) solid targets of protons (NH{sub 3}) and deuterons (ND{sub 3}) and the CEBAF Large Acceptance Spectrometer. Here, preliminary results for target-spin asymmetries and double (beam-target) asymmetries for proton DVCS, as well as a very preliminary extraction of beam-spin asymmetry for neutron DVCS, are presented and linked to Generalized Parton Distributions.
Constraints on parton distribution from CDF
Bodek, A.; CDF Collaboration
1995-10-01
The asymmetry in W{sup -} - W{sup +} production in p{bar p} collisions and Drell-Yan data place tight constraints on parton distributions functions. The W asymmetry data constrain the slope of the quark distribution ratio d(x)/u(x) in the x range 0.007-0.27. The published W asymmetry results from the CDF 1992.3 data ({approx} 20 pb{sup -1}) greatly reduce the systematic error originating from the choice of PDF`s in the W mass measurement at CDF. These published results have also been included in the CTEQ3, MRSA, and GRV94 parton distribution fits. These modern parton distribution functions axe still in good agreement with the new 1993-94 CDF data({approx} 108 pb{sup -1} combined). Preliminary results from CDF for the Drell-Yan cross section in the mass range 11-350 GeV/c{sup 2} are discussed.
Endpoint behavior of high-energy scattering cross sections
Chay, Junegone; Kim, Chul
2010-11-01
In high-energy processes near the endpoint, there emerge new contributions associated with spectator interactions. Away from the endpoint region, these new contributions are suppressed compared to the leading contribution, but the leading contribution becomes suppressed as we approach the endpoint and the new contributions become comparable. We present how the new contributions scale as we reach the endpoint and show that they are comparable to the suppressed leading contributions in deep inelastic scattering by employing a power-counting analysis. The hadronic tensor in deep inelastic scattering is shown to factorize including the spectator interactions, and it can be expressed in terms of the light cone distribution amplitudes of initial hadrons. We also consider the contribution of the spectator contributions in Drell-Yan processes. Here the spectator interactions are suppressed compared to double parton annihilation according to the power counting.
Measurement of parton shower observables with OPAL
NASA Astrophysics Data System (ADS)
Fischer, N.; Gieseke, S.; Kluth, S.; Plätzer, S.; Skands, P.
2016-07-01
A study of QCD coherence is presented based on a sample of about 397,000 e+e- hadronic annihilation events collected at √s = 91 GeV with the OPAL detector at LEP. The study is based on four recently proposed observables that are sensitive to coherence effects in the perturbative regime. The measurement of these observables is presented, along with a comparison with the predictions of different parton shower models. The models include both conventional parton shower models and dipole antenna models. Different ordering variables are used to investigate their influence on the predictions.
Lappi, T.; Venugopalan, R.; Mantysaari, H.
2015-02-25
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multi-parton Fock states in the nuclear wavefunctions. In particular, the saturation scale that characterizes this multi-parton dynamics is significantly larger in central events relative to minimum bias events. As an application, we examine the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model.
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.
Transverse momentum-dependent parton distribution functions in lattice QCD
Engelhardt, Michael G.; Musch, Bernhard U.; Haegler, Philipp G.; Negele, John W.; Schaefer, Andreas
2013-08-01
A fundamental structural property of the nucleon is the distribution of quark momenta, both parallel as well as perpendicular to its propagation. Experimentally, this information is accessible via selected processes such as semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process (DY), which can be parametrized in terms of transversemomentum-dependent parton distributions (TMDs). On the other hand, these distribution functions can be extracted from nucleon matrix elements of a certain class of bilocal quark operators in which the quarks are connected by a staple-shaped Wilson line serving to incorporate initial state (DY) or final state (SIDIS) interactions. A scheme for evaluating such matrix elements within lattice QCD is developed. This requires casting the calculation in a particular Lorentz frame, which is facilitated by a parametrization of the matrix elements in terms of invariant amplitudes. Exploratory results are presented for the time-reversal odd Sivers and Boer-Mulders transverse momentum shifts.
Transverse momentum-dependent parton distribution functions from lattice QCD
Michael Engelhardt, Philipp Haegler, Bernhard Musch, John Negele, Andreas Schaefer
2012-12-01
Transverse momentum-dependent parton distributions (TMDs) relevant for semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process can be defined in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection. Starting from such a definition, a scheme to determine TMDs in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are obtained using ensembles at the pion masses 369MeV and 518MeV, focusing in particular on the dependence of these shifts on the staple extent and a Collins-Soper-type evolution parameter quantifying proximity of the staples to the light cone.
Iterative Monte Carlo analysis of spin-dependent parton distributions
NASA Astrophysics Data System (ADS)
Sato, Nobuo; Melnitchouk, W.; Kuhn, S. E.; Ethier, J. J.; Accardi, A.; Jefferson Lab Angular Momentum Collaboration
2016-04-01
We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The analysis is performed using a new iterative Monte Carlo fitting technique which generates stable fits to polarized parton distribution functions (PDFs) with statistically rigorous uncertainties. Inclusion of the Jefferson Lab data leads to a reduction in the PDF errors for the valence and sea quarks, as well as in the gluon polarization uncertainty at x ≳0.1 . The study also provides the first determination of the flavor-separated twist-3 PDFs and the d2 moment of the nucleon within a global PDF analysis.
Studies of partonic transverse momentum and spin structure of the nucleon
NASA Astrophysics Data System (ADS)
Contalbrigo, M.
2014-06-01
The investigation of the partonic degrees of freedom beyond collinear approximation (3D description) has been gained increasing interest in the last decade. The Thomas Jefferson National Laboratory, after the CEBAF upgrade to 12 GeV, will become the most complete facility for the investigation of the hadron structure in the valence region by scattering of polarized electron off various polarized nucleon targets. A compendium of the planned experiments is here presented.
Statistical approach of parton distributions: a closer look at the high-xregion
Soffer, Jacques
2011-09-21
We recall the physical features of the parton distributions in the quantum statistical approach of the nucleon, which allows to describe simultaneously, unpolarized and polarized Deep Inelastic Scattering data. Some predictionsfrom a next-to-leading order QCD analysis are compared to recent experimental results and we stress the importance of some tests in the high-x region, to confirm the validity of this approach.
Fragmentation of parton jets at small x
Kirschner, R.
1985-08-01
The parton fragmentation function is calculated in the region of small x in the doubly logarithmic approximation of QCD. For this, the method of separating the softest particle, which has hitherto been applied only in the Regge kinematic region, is developed. Simple arguments based on unitarity and gauge invariance are used to derive the well known condition of ordering of the emission angles.
Progress in the dynamical parton distributions
Jimenez-Delgado, Pedro
2012-06-01
The present status of the (JR) dynamical parton distribution functions is reported. Different theoretical improvements, including the determination of the strange sea input distribution, the treatment of correlated errors and the inclusion of alternative data sets, are discussed. Highlights in the ongoing developments as well as (very) preliminary results in the determination of the strong coupling constant are presented.
Parton Distributions and Spin-Orbital Correlations
Yuan, Feng
2007-09-24
In this talk, I summarize a recent study showing that the large-x parton distributions contain important information on the quark orbital angular momentum of nucleon. This contribution could explain the conflict between the experimental data and the theory predictions for the polarized quark distributions. Future experiments at JLab shall provide further test for our predictions.
PARTON DISTRIBUTIONS AND SPIN-ORBITAL CORRELATIONS.
FENG,Y.
2007-05-21
In this talk, the author summarizes a recent study showing that the large-x parton distributions contain important information on the quark orbital angular momentum of nucleon. This contribution could explain the conflict between the experimental data and the theory predictions for the polarized quark distributions. Future experiments at JLAB shall provide further test for our predictions.
QCD parton model at collider energies
Ellis, R.K.
1984-09-01
Using the example of vector boson production, the application of the QCD improved parton model at collider energies is reviewed. The reliability of the extrapolation to SSC energies is assessed. Predictions at ..sqrt..S = 0.54 TeV are compared with data. 21 references.
Systematic Improvement of QCD Parton Showers
Winter, Jan; Hoeche, Stefan; Hoeth, Hendrik; Krauss, Frank; Schonherr, Marek; Zapp, Korinna; Schumann, Steffen; Siegert, Frank; /Freiburg U.
2012-05-17
In this contribution, we will give a brief overview of the progress that has been achieved in the field of combining matrix elements and parton showers. We exemplify this by focusing on the case of electron-positron collisions and by reporting on recent developments as accomplished within the SHERPA event generation framework.
Deeply Virtual Exclusive Processes and Generalized Parton Distributions
,
2011-06-01
The goal of the comprehensive program in Deeply Virtual Exclusive Scattering at Jefferson Laboratory is to create transverse spatial images of quarks and gluons as a function of their longitudinal momentum fraction in the proton, the neutron, and in nuclei. These functions are the Generalized Parton Distributions (GPDs) of the target nucleus. Cross section measurements of the Deeply Virtual Compton Scattering (DVCS) reaction ep {yields} ep{gamma} in Hall A support the QCD factorization of the scattering amplitude for Q^2 {>=} 2 GeV^2. Quasi-free neutron-DVCS measurements on the Deuteron indicate sensitivity to the quark angular momentum sum rule. Fully exclusive H(e, e'p{gamma} ) measurements have been made in a wide kinematic range in CLAS with polarized beam, and with both unpolarized and longitudinally polarized targets. Existing models are qualitatively consistent with the JLab data, but there is a clear need for less constrained models. Deeply virtual vector meson production is studied in CLAS. The 12 GeV upgrade will be essential for for these channels. The {rho} and {omega} channels reactions offer the prospect of flavor sensitivity to the quark GPDs, while the {phi}-production channel is dominated by the gluon distribution.
Deeply virtual Compton scattering off nuclei
Voutier, Eric
2009-01-01
Deeply virtual Compton scattering (DVCS) is the golden exclusive channel for the study of the partonic structure of hadrons, within the universal framework of generalized parton distributions (GPDs). This paper presents the aim and general ideas of the DVCS experimental program off nuclei at the Jefferson Laboratory. The benefits of the study of the coherent and incoherent channels to the understanding of the EMC (European Muon Collaboration) effect are discussed, along with the case of nuclear targets to access neutron GPDs.
Global parton distributions with nuclear and finite-Q^2 corrections
Owens, J. F.; Accardi, Alberto; Melnitchouk, Wally
2013-05-01
We present three new sets of parton distribution functions (PDFs) determined by global fits to a wide variety of data for hard scattering processes. The analysis includes target mass and higher twist corrections needed for the description of deep inelastic scattering data at large x and low Q^2, and nuclear corrections for deuterium targets. The PDF sets correspond to three different models for the nuclear effects, and provide a more realistic uncertainty range for the d quark PDF, in particular, compared with previous fits. We describe the PDF error sets for each choice of the nuclear corrections, and provide a user interface for utilizing the distributions.
Calculating scattering amplitudes efficiently
Dixon, L.
1996-01-01
We review techniques for more efficient computation of perturbative scattering amplitudes in gauge theory, in particular tree and one- loop multi-parton amplitudes in QCD. We emphasize the advantages of (1) using color and helicity information to decompose amplitudes into smaller gauge-invariant pieces, and (2) exploiting the analytic properties of these pieces, namely their cuts and poles. Other useful tools include recursion relations, special gauges and supersymmetric rearrangements. 46 refs., 11 figs.
Generalized parton distributions and exclusive processes
Guzey, Vadim
2013-10-01
In last fifteen years, GPDs have emerged as a powerful tool to reveal such aspects of the QCD structure of the nucleon as: - 3D parton correlations and distributions; - spin content of the nucleon. Further advances in the field of GPDs and hard exclusive processes rely on: - developments in theory and new methods in phenomenology such as new flexible parameterizations, neural networks, global QCD fits - new high-precision data covering unexplored kinematics: JLab at 6 and 12 GeV, Hermes with recoil detector, Compass, EIC. This slide-show presents: Nucleon structure in QCD, particularly hard processes, factorization and parton distributions; and a brief overview of GPD phenomenology, including basic properties of GPDs, GPDs and QCD structure of the nucleon, and constraining GPDs from experiments.
Parton Distributions in the Impact Parameter Space
Matthias Burkardt
2009-08-01
Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark is transversely polarized. In combination with the final state interactions, this transverse deformation provides a natural mechanism for naive-T odd transverse single-spin asymmetries in semi-inclusive DIS. The deformation can also be related to the transverse force acting on the active quark in polarized DIS at higher twist.
NASA Astrophysics Data System (ADS)
Zhu, L.; Zhao, Y. L.; Lin, X. P.; Gu, X. Q.; Qiang, Y. H.
2014-01-01
Dye-sensitized solar cells (DSSCs) are fabricated based on double-layered films of TiO2 nanospheres and TiO2 nanorod arrays (NRAs). TiO2 nanospheres, including TiO2 hollow spheres (HSs) and TiO2 solid spheres (SSs), were served as light-scattering layers on TiO2 NRAs as composite photoanodes. The as-prepared TiO2 NRAs, TiO2 HSs and TiO2 SSs have been characterized by field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The photoelectric properties of DSSCs were investigated by UV-vis reflectance spectra, current-voltage curves and electrochemical impedance spectroscopy. Owing to the synergic effects of the TiO2 HSs (SSs) and NRAs, including large specific surface area of HSs (SSs) as light-scattering layer for effective dye adsorption and harvesting light and rapid electron transport in one dimensional TiO2 NRAs, the optimal energy conversion efficiency of DSSCs with as-prepared double-layered films as nanocomposite photoanode (5.40%) were far higher than the ones using single-layered NRAs films (1.56%).
Impact of hadronic and nuclear corrections on global analysis of spin-dependent parton distributions
Jimenez-Delgado, Pedro; Accardi, Alberto; Melnitchouk, Wally
2014-02-01
We present the first results of a new global next-to-leading order analysis of spin-dependent parton distribution functions from the most recent world data on inclusive polarized deep-inelastic scattering, focusing in particular on the large-x and low-Q^2 regions. By directly fitting polarization asymmetries we eliminate biases introduced by using polarized structure function data extracted under nonuniform assumptions for the unpolarized structure functions. For analysis of the large-x data we implement nuclear smearing corrections for deuterium and 3He nuclei, and systematically include target mass and higher twist corrections to the g_1 and g_2 structure functions at low Q^2. We also explore the effects of Q^2 and W^2 cuts in the data sets, and the potential impact of future data on the behavior of the spin-dependent parton distributions at large x.
Guzey, Vadim; Goeke, Klaus; Siddikov, Marat
2009-01-01
We generalize the leading twist theory of nuclear shadowing and calculate quark and gluon generalized parton distributions (GPDs) of spinless nuclei. We predict very large nuclear shadowing for nuclear GPDs. In the limit of the purely transverse momentum transfer, our nuclear GPDs become impact parameter dependent nuclear parton distributions (PDFs). Nuclear shadowing induces non-trivial correlations between the impact parameter $b$ and the light-cone fraction $x$. We make predictions for the deeply virtual Compton scattering (DVCS) amplitude and the DVCS cross section on $^{208}$Pb at high energies. We calculate the cross section of the Bethe-Heitler (BH) process and address the issue of the extraction of the DVCS signal from the $e A \\to e \\gamma A$ cross section. We find that the $e A \\to e \\gamma A$ differential cross section is dominated by DVCS at the momentum transfer $t$ near the minima of the nuclear form factor. We also find that nuclear shadowing leads
Novel phenomenology of parton distributions from the Drell-Yan process
NASA Astrophysics Data System (ADS)
Peng, Jen-Chieh; Qiu, Jian-Wei
2014-05-01
The Drell-Yan massive lepton-pair production in hadronic collisions provides a unique tool complementary to the Deep-Inelastic Scattering for probing the partonic substructures in hadrons. We review key concepts, approximations, and progress for QCD factorization of the Drell-Yan process in terms of collinear or transverse momentum dependent (TMD) parton distribution functions. We present experimental results from recent fixed-target Drell-Yan as well as W and Z boson production at colliders, focusing on the topics of flavor structure of the nucleon sea as well as the extraction of novel Sivers and Boer-Mulders functions via single transverse spin asymmetries and azimuthal lepton angular distribution of the Drell-Yan process. Prospects for future Drell-Yan experiments are also presented.
New parton structure functions and minijets in the two-component dual parton model
Bopp, F.W.; Pertermann, D. ); Engel, R. ); Ranft, J. )
1994-04-01
We use new fits to parton structure functions, including structure functions with Lipatov behavior at small [ital x] values and discuss the minijet component in the two-component dual parton model with a supercritical Pomeron as demanded by the fits to cross-section data. We find that a consistent model can only be formulated with a [ital p][sub [perpendicular]hr] cutoff for the minijets increasing with energy. The implications for particle production in hadronic collisions at TeV energies are discussed.
The Polarized TMDs in the covariant parton model approach
A.V. Efremov, P. Schweitzer, O.V. Teryaev, P. Zavada
2011-05-01
We derive relations between polarized transverse momentum dependent distribution functions (TMDs) and the usual parton distribution functions (PDFs) in the 3D covariant parton model, which follow from Lorentz invariance and the assumption of a rotationally symmetric distribution of parton momenta in the nucleon rest frame. Using the known PDF $g_{1}^{q}(x)$ as input we predict the $x$- and $\\mathbf{p}_{T}$-dependence of all polarized twist-2 naively time-reversal even (T-even) TMDs.
Schorstein, Kai; Popescu, Alexandru; Göbel, Marco; Walther, Thomas
2008-01-01
Temperature profiles of the ocean are of interest for weather forecasts, climate studies and oceanography in general. Currently, mostly in situ techniques such as fixed buoys or bathythermographs deliver oceanic temperature profiles. A LIDAR method based on Brillouin scattering is an attractive alternative for remote sensing of such water temperature profiles. It makes it possible to deliver cost-effective on-line data covering an extended region of the ocean. The temperature measurement is based on spontaneous Brillouin scattering in water. In this contribution, we present the first water temperature measurements using a Yb:doped pulsed fiber amplifier. The fiber amplifier is a custom designed device which can be operated in a vibrational environment while emitting narrow bandwidth laser pulses. The device shows promising performance and demonstrates the feasibility of this approach. Furthermore, the current status of the receiver is briefly discussed; it is based on an excited state Faraday anomalous dispersion optical filter.
A.V. Efremov, P. Schweitzer, O.V. Teryaev, P. Zavada
2011-03-01
We derive relations between transverse momentum dependent distribution functions (TMDs) and the usual parton distribution functions (PDFs) in the 3D covariant parton model, which follow from Lorentz invariance and the assumption of a rotationally symmetric distribution of parton momenta in the nucleon rest frame. Using the known PDFs f_1(x) and g_1(x) as input we predict the x- and pT-dependence of all twist-2 T-even TMDs.
Tao, Liang; McCurdy, Bill; Rescigno, Tom
2010-06-10
Our previously developed finite-element/ discrete variable representation in prolate spheroidal coordinates is extended to two-electron systems with a study of double ionization of H$_2$ with fixed-nuclei. Particular attention is paid to the development of fast and accurate methods for treating the electron-electron interaction. The use of exterior complex scaling in the implementation offers a simple way of enforcing Coulomb boundary conditions for the electronic double continuum. While the angular distributions calculated in this study are found to be completely consistent with our earlier treatments that employed single-center expansions in spherical coordinates, we find that the magnitude of the integrated cross sections are sensitive to small changes in the initial-state wave function. The present formulation offers significant advantages with respect to convergence and efficiency and opens the way to calculations on more complicated diatomic targets.
J.W. Negele; R.C. Brower; P. Dreher; R. Edwards; G. Fleming; Ph. Hagler; U.M. Heller; Th. Lippert; A.V.Pochinsky; D.B. Renner; D. Richards; K. Schilling; W. Schroers
2004-04-01
This talk presents recent calculations in full QCD of the lowest three moments of generalized parton distributions and the insight they provide into the behavior of nucleon electromagnetic form factors, the origin of the nucleon spin, and the transverse structure of the nucleon. In addition, new exploratory calculations in the chiral regime of full QCD are discussed.
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).
First moments of nucleon generalized parton distributions
Wang, P.; Thomas, A. W.
2010-06-01
We extrapolate the first moments of the generalized parton distributions using heavy baryon chiral perturbation theory. The calculation is based on the one loop level with the finite range regularization. The description of the lattice data is satisfactory, and the extrapolated moments at physical pion mass are consistent with the results obtained with dimensional regularization, although the extrapolation in the momentum transfer to t=0 does show sensitivity to form factor effects, which lie outside the realm of chiral perturbation theory. We discuss the significance of the results in the light of modern experiments as well as QCD inspired models.
Adamczyk, L.
2015-08-26
We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, ALL, in polarized pp collisions at center-of-mass energy √s = 200 GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. Lastly, the measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x > 0.05 .
Adamczyk, L.
2015-08-26
We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, A_{LL}, in polarized pp collisions at center-of-mass energy √s = 200 GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. Lastly, the measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x > 0.05 .
NASA Technical Reports Server (NTRS)
Lawandy, Nabil M.
1987-01-01
The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for three different sets of relaxation rates. These rates correspond to: (1) Far Infrared (FIR) Raman lasers in the diabatic collision regime without consideration of coupled population decay in a closed system, (2) Raman FIR lasers in the diabatic collision regime with coupled population conserving decay, and (3) IR Raman gain in cesium vapor. The model is further expanded to include Doppler broadening and used to predict the peak gain as a function of detuning for a frequency doubled Alexandrite laser-pumped cesium vapor gain cell.
Nucleon Generalized Parton Distributions from Full Lattice QCD
Robert Edwards; Philipp Haegler; David Richards; John Negele; Konstantinos Orginos; Wolfram Schroers; Jonathan Bratt; Andrew Pochinsky; Michael Engelhardt; George Fleming; Bernhard Musch; Dru Renner
2007-07-03
We present a comprehensive study of the lowest moments of nucleon generalized parton distributions in N_f=2+1 lattice QCD using domain wall valence quarks and improved staggered sea quarks. Our investigation includes helicity dependent and independent generalized parton distributions for pion masses as low as 350 MeV and volumes as large as (3.5 fm)^3.
The parton orbital angular momentum: Status and prospects
NASA Astrophysics Data System (ADS)
Liu, Keh-Fei; Lorcé, Cédric
2016-06-01
Theoretical progress on the formulation and classification of the quark and gluon orbital angular momenta (OAM) is reviewed. Their relation to parton distributions and open questions and puzzles are discussed. We give a status report on the lattice calculation of the parton kinetic and canonical OAM and point out several strategies to calculate the quark and gluon canonical OAM on the lattice.
Allegood, M.S.; Baba, J.S.
2008-01-01
Light interaction with biological tissue can be described using three parameters: the scattering and absorption coeffi cients (μs and μa), as well as the anisotropy (g) which describes the directional dependence of the scattered photons. Accurately determining these optical properties for different tissue types at specifi c wavelengths simultaneously would be benefi cial for a variety of different biomedical applications. The goal of this project was to take a user defi ned g-value and determine the remaining two parameters for a specifi ed wavelength range. A fully automated computer program and process was developed to collect data for all wavelengths in a timely and accurate manner. LabVIEW® was used to write programs to automate raw intensity data collection from a spectrometer equipped integrating sphere, conversion of the data into a format for analysis via Scott Prahl’s Inverse Adding-Doubling (IAD) C code execution, and fi nally computation of the optical properties based on the output from the IAD code. To allow data to be passed effi ciently between LabVIEW® and C code program modules, the two were combined into a single program (OPT 3.1). OPT 3.1 was tested using tissue mimicking phantoms. Determination of the absorption and scattering coeffi cients showed excellent agreement with theory for wavelengths where the user inputted single g-value was suffi ciently precise. Future improvements entail providing for multi-wavelength g-value entry to extend the accuracy of results to encompass the complete multispectral range. Ultimately, the data collection process and algorithms developed through this effort will be used to examine actual biological tissues for the purpose of building and refi ning models for light-tissue interactions.
Hu, Zhaosheng; Liu, Zhe; Li, Lin; Quan, Baogang; Li, Yunlong; Li, Junjie; Gu, Changzhi
2014-10-15
Fabricating perfect plasmonic nanostructures has been a major challenge in surface enhanced Raman scattering (SERS) research. Here, a double-layer stacked Au/Al2O3@Au nanosphere structures is designed on the silicon wafer to bring high density, high intensity "hot spots" effect. A simply reproducible high-throughput approach is shown to fabricate feasibly this plasmonic nanostructures by rapid thermal annealing (RTA) and atomic layer deposition process (ALD). The double-layer stacked Au nanospheres construct a three-dimensional plasmonic nanostructure with tunable nanospacing and high-density nanojunctions between adjacent Au nanospheres by ultrathin Al2O3 isolation layer, producing highly strong plasmonic coupling so that the electromagnetic near-field is greatly enhanced to obtain a highly uniform increase of SERS with an enhancement factor (EF) of over 10(7). Both heterogeneous nanosphere group (Au/Al2O@Ag) and pyramid-shaped arrays structure substrate can help to increase the SERS signals further, with a EF of nearly 10(9). These wafer-scale, high density homo/hetero-metal-nanosphere arrays with tunable nanojunction between adjacent shell-isolated nanospheres have significant implications for ultrasensitive Raman detection, molecular electronics, and nanophotonics.
Zenaiev, O.; Geiser, A.; Lipka, K.; Blumlein, J.; Cooper-Sarkar, A.; Garzelli, M. -V.; Guzzi, M.; Kuprash, O.; Moch, S. -O.; Nadolsky, P.; et al
2015-08-01
The impact of recent measurements of heavy-flavour production in deep inelastic ep scattering and in pp collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions x of the proton momentum, down to x~5×10-6. This kinematic range is currently not covered by othermore » experimental data in perturbative QCD fits.« less
Zenaiev, O.; Geiser, A.; Lipka, K.; Blumlein, J.; Cooper-Sarkar, A.; Garzelli, M. -V.; Guzzi, M.; Kuprash, O.; Moch, S. -O.; Nadolsky, P.; Placakyte, R.; Rabbertz, K.; Schienbein, I.; Starovoitov, P.
2015-08-01
The impact of recent measurements of heavy-flavour production in deep inelastic ep scattering and in pp collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions x of the proton momentum, down to x~5×10^{-6}. This kinematic range is currently not covered by other experimental data in perturbative QCD fits.
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.
Studies of Multi-Parton Interactions in Photon+Jets Events at D0
Bandurin, Dmitry; /Florida State U.
2011-09-01
We consider sample of inclusive {gamma} + 3 jet events collected by the D0 experiment. The double parton fraction (f{sub DP}) and effective cross section {sigma}{sub eff}, a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p{sub T}) jet transverse momentum p{sub T}{sup jet2} within the 15 {le} p{sub T}{sup jet2} {le} 30 GeV range. Also we measured cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p{sub T}) of the {gamma} + leading jet system and p{sub T} of the other jet for {gamma} + 2 jet, or p{sub T} sum of the two other jets for {gamma} + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators.
Parton Charge Symmetry Violation: Electromagnetic Effects and W Production Asymmetries
J.T. Londergan; D.P. Murdock; A.W. Thomas
2006-04-14
Recent phenomenological work has examined two different ways of including charge symmetry violation in parton distribution functions. First, a global phenomenological fit to high energy data has included charge symmetry breaking terms, leading to limits on the magnitude of parton charge symmetry breaking. In a second approach, two groups have included the coupling of partons to photons in the QCD evolution equations. One possible experiment that could search for isospin violation in parton distributions is a measurement of the asymmetry in W production at a collider. In this work we include both of the postulated sources of parton charge symmetry violation. We show that, given charge symmetry violation of a magnitude consistent with existing high energy data, the expected W production asymmetries would be quite small, generally less than one percent.
Double-doorway model for pion-nucleon elastic scattering in the [ital S][sub 11] channel
McLeod, R.J. ); Ernst, D.J. )
1994-02-01
Resonance energy pion-nucleon elastic scattering in the [ital S][sub 11] channel is modeled by assuming that the pion plus nucleon couple to two resonances, the resonances couple to inleastic channels, but there is no direct coupling of the pion-nucleon channel to the inelastic channels. The model is solved by matrix [ital N]/[ital D] methods. The coupling of the inelastic channels to the elastic channel is taken directly from data. Using form factors from the constituent quark model, we find the model is able to reproduce the experimentally determined pion-nucleon phases in the [ital S][sub 11] channel over the resonance region and that the resonance part of the amplitude is negligible at low energies.
The Generalized Parton Distribution program in Hall A at Jefferson Lab
Camacho, C. Munoz
2008-10-13
Recent results on the Generalized Parton Distribution (GPD) program at Jefferson Lab (JLab) will be presented. The emphasis will be in the Hall A program aiming at measuring Q{sup 2}--dependences of different terms of the Deeply Virtual Compton Scattering (DVCS) cross section. This is a fundamental step before one can extract GPD information from JLab DVCS data. Neutral pion production will also be discussed and results from the CLAS collaboration will be shown. Finally, the upcoming program in Hall A, using both a 6 GeV beam ({approx_equal}2010) and a 11 GeV beam ({approx_equal}2015) will be described.
Dynamical next-to-next-to-leading order parton distributions
Jimenez-Delgado, P.; Reya, E.
2009-04-01
Utilizing recent deep inelastic scattering measurements ({sigma}{sub r},F{sub 2,3,L}) and data on hadronic dilepton production we determine at next-to-next-to-leading order (NNLO) (3-loop) of QCD the dynamical parton distributions of the nucleon generated radiatively from valencelike positive input distributions at an optimally chosen low resolution scale (Q{sub 0}{sup 2}<1 GeV{sup 2}). These are compared with 'standard' NNLO distributions generated from positive input distributions at some fixed and higher resolution scale (Q{sub 0}{sup 2}>1 GeV{sup 2}). Although the NNLO corrections imply in both approaches an improved value of {chi}{sup 2}, typically {chi}{sub NNLO}{sup 2}{approx_equal}0.9{chi}{sub NLO}{sup 2}, present deep inelastic scattering data are still not sufficiently accurate to distinguish between NLO results and the minute NNLO effects of a few percent, despite the fact that the dynamical NNLO uncertainties are somewhat smaller than the NLO ones and both are, as expected, smaller than those of their standard counterparts. The dynamical predictions for F{sub L}(x,Q{sup 2}) become perturbatively stable already at Q{sup 2}=2-3 GeV{sup 2} where precision measurements could even delineate NNLO effects in the very small-x region. This is in contrast to the common standard approach but NNLO/NLO differences are here less distinguishable due to the larger 1{sigma} uncertainty bands. Within the dynamical approach we obtain {alpha}{sub s}(M{sub Z}{sup 2})=0.1124{+-}0.0020, whereas the somewhat less constrained standard fit gives {alpha}{sub s}(M{sub Z}{sup 2})=0.1158{+-}0.0035.
Timelike Compton Scattering at Jlab
Paremuzyan, Rafayel G.
2014-01-01
It is demonstrated, that with exclusive final state, data from electron scattering experiments that are recorded with loose trigger requirements can be used to analyze photoproduction reactions. A preliminary results on Timelike Compton Scattering using the electroproduction data from the CLAS detector at Jefferson Lab are presented. In particular, using final state (pe{sup -}e{sup +}) photoproduction of vector mesons and timelike photon is studied. Angular asymmetries in Timelike Compton Scattering region is compared with model predictions in the framework of Generalized Parton Distribution.
Pion valence-quark parton distribution function
NASA Astrophysics Data System (ADS)
Chang, Lei; Thomas, Anthony W.
2015-10-01
Within the Dyson-Schwinger equation formulation of QCD, a rainbow ladder truncation is used to calculate the pion valence-quark distribution function (PDF). The gap equation is renormalized at a typical hadronic scale, of order 0.5 GeV, which is also set as the default initial scale for the pion PDF. We implement a corrected leading-order expression for the PDF which ensures that the valence-quarks carry all of the pion's light-front momentum at the initial scale. The scaling behavior of the pion PDF at a typical partonic scale of order 5.2 GeV is found to be (1 - x) ν, with ν ≃ 1.6, as x approaches one.
Polarization of partons in the proton
Kobayakawa, K.; Morii, T. ); Tanaka, S. ); Yamanishi, T. )
1992-10-01
The spin-dependent distribution functions of quarks and gluons in a proton are studied so as to explain the European Muon Collaboration {ital g}{sub 1}{sup {ital p}}({ital x}) data by introducing a new model, in which characteristics of both the static quark and the quark-parton model are taken into account. The {ital x} dependence of {ital g}{sub 1}{sup {ital p}}({ital x}) is reproduced well. It is shown that polarized gluons through the anomaly play a significant role and the resultant sum of quark spin is 0.375. Furthermore, {ital g}{sub 1}{sup {ital n}}({ital x}) as well as {ital g}{sub 1}{sup {ital p}}({ital x}) is predicted for future experiments.
Evolution effects on parton energy loss with detailed balance
Cheng Luan; Wang Enke
2010-07-15
The initial conditions in the chemically nonequilibrated medium and Bjorken expanding medium at Relativistic Heavy Ion Collider (RHIC) are determined. With a set of rate equations describing the chemical equilibration of quarks and gluons based on perturbative QCD, we investigate the consequence for parton evolution at RHIC. With considering parton evolution, it is shown that the Debye screening mass and the inverse mean free-path of gluons reduce with increasing proper time in the QGP medium. The parton evolution affects the parton energy loss with detailed balance, both parton energy loss from stimulated emission in the chemically nonequilibrated expanding medium and in Bjorken expanding medium are linear dependent on the propagating distance rather than square dependent in the static medium. The energy absorption cannot be neglected at intermediate jet energies and small propagating distance of the energetic parton in contrast with that it is important only at intermediate jet energy in the static medium. This will increase the energy and propagating distance dependence of the parton energy loss and will affect the shape of suppression of moderately high P{sub T} hadron spectra.
Slopsema, R. L. Flampouri, S.; Yeung, D.; Li, Z.; Lin, L.; McDonough, J. E.; Palta, J.
2014-09-15
Purpose: The purpose of this investigation is to determine if a single set of beam data, described by a minimal set of equations and fitting variables, can be used to commission different installations of a proton double-scattering system in a commercial pencil-beam dose calculation algorithm. Methods: The beam model parameters required to commission the pencil-beam dose calculation algorithm (virtual and effective SAD, effective source size, and pristine-peak energy spread) are determined for a commercial double-scattering system. These parameters are measured in a first room and parameterized as function of proton energy and nozzle settings by fitting four analytical equations to the measured data. The combination of these equations and fitting values constitutes the golden beam data (GBD). To determine the variation in dose delivery between installations, the same dosimetric properties are measured in two additional rooms at the same facility, as well as in a single room at another facility. The difference between the room-specific measurements and the GBD is evaluated against tolerances that guarantee the 3D dose distribution in each of the rooms matches the GBD-based dose distribution within clinically reasonable limits. The pencil-beam treatment-planning algorithm is commissioned with the GBD. The three-dimensional dose distribution in water is evaluated in the four treatment rooms and compared to the treatment-planning calculated dose distribution. Results: The virtual and effective SAD measurements fall between 226 and 257 cm. The effective source size varies between 2.4 and 6.2 cm for the large-field options, and 1.0 and 2.0 cm for the small-field options. The pristine-peak energy spread decreases from 1.05% at the lowest range to 0.6% at the highest. The virtual SAD as well as the effective source size can be accurately described by a linear relationship as function of the inverse of the residual energy. An additional linear correction term as function of
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.
Parity violation in deep inelastic scattering
Souder, P.
1994-04-01
AA beam of polarized electrons at CEBAF with an energy of 8 GeV or more will be useful for performing precision measurements of parity violation in deep inelastic scattering. Possible applications include precision tests of the Standard Model, model-independent measurements of parton distribution functions, and studies of quark correlations.
Field-theoretical description of deep inelastic scattering
Geyer, B.; Robaschik, D.; Wieczorek, E.
1980-01-01
The most important theoretical notions concerning deep inelastic scattering are reviewed. Topics discussed are the model-independent approach, which is based on the general principles of quantum field theory, the application of quantum chromodynamics to deep inelastic scattering, approaches based on the quark--parton model, the light cone algebra, and conformal invariance, and also investigations in the framework of perturbation theory.
NASA Astrophysics Data System (ADS)
Zhu, Yang-Zhu; Yi, Shi-He; He, Lin; Tian, Li-Feng; Zhou, Yong-Wei
2013-01-01
In a Mach 3.8 wind tunnel, both instantaneous and time-averaged flow structures of different scales around a blunt double-cone with or without supersonic film cooling were visualized via nano-tracer planar laser scattering (NPLS), which has a high spatiotemporal resolution. Three experimental cases with different injection mass flux rates were carried out. Many typical flow structures were clearly shown, such as shock waves, expansion fans, shear layers, mixing layers, and turbulent boundary layers. The analysis of two NPLS images with an interval of 5 μs revealed the temporal evolution characteristics of flow structures. With matched pressures, the laminar length of the mixing layer was longer than that in the case with a larger mass flux rate, but the full covered region was shorter. Structures like K—H (Kelvin—Helmholtz) vortices were clearly seen in both flows. Without injection, the flow was similar to the supersonic flow over a backward-facing step, and the structures were relatively simpler, and there was a longer laminar region. Large scale structures such as hairpin vortices were visualized. In addition, the results were compared in part with the schlieren images captured by others under similar conditions.
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.
Delineating parton distributions and the strong coupling
Jimenez-Delgado, P.; Reya, E.
2014-04-29
In this study, global fits for precision determinations of parton distributions, together with the highly correlated strong coupling α_{s}, are presented up to next-to-next-to- leading order (NNLO) of QCD utilizing most world data (charm and jet production data are used where theoretically possible), except Tevatron gauge boson production data and LHC data which are left for genuine predictions. This is done within the 'dynamical' (valencelike input at Q_{0}^{2} = 0.8 GeV^{2} ) and 'standard' (input at Q_{0}^{2} = 2 GeV^{2}) approach. The stability and reliability of the results are ensured by including nonperturbative higher-twist terms, nuclear corrections as well as target mass corrections, and by applying various (Q^{2}, W^{2}) cuts on available data. In addition, the Q_{0}^{2} dependence of the results is studied in detail. Predictions are given, in particular for LHC, on gauge and Higgs boson as well as for top-quark pair production. At NNLO the dynamical approach results in α_{s}(M_{Z}^{2}) = 0.1136 ± 0.0004, whereas the somewhat less constrained standard fit gives α_{s}(M_{Z}^{2}) = 0.1162 ± 0.0006.
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.
Recent progress on nuclear parton distribution functions
NASA Astrophysics Data System (ADS)
Hirai, M.; Kumano, S.; Saito, K.
2011-09-01
We report current status of global analyses on nuclear parton distribution functions (NPDFs). The optimum NPDFs are determined by analyzing high-energy nuclear reaction data. Due to limited experimental measurements, antiquark modifications have large uncertainties at x > 0.2 and gluon modifications cannot be determined. A nuclear modification difference between u and d quark distributions could be an origin of the long-standing NuTeV sin2θw anomaly. There is also an issue of nuclear modification differences between the structure functions of charged-lepton and neutrino reactions. Next, nuclear clustering effects are discussed in structure functions F2A as a possible explanation for an anomalous result in the 9Be nucleus at the Thomas Jefferson National Accelerator Facility (JLab). Last, tensor-polarized quark and antiquark distribution functions are extracted from HERMES data on the polarized structure function b1 of the deuteron, and they could be used for testing theoretical models and for proposing future experiments, for example, the one at JLab. Such measurements could open a new field of spin physics in spin-one hadrons.
Delineating parton distributions and the strong coupling
Jimenez-Delgado, P.; Reya, E.
2014-04-29
In this study, global fits for precision determinations of parton distributions, together with the highly correlated strong coupling αs, are presented up to next-to-next-to- leading order (NNLO) of QCD utilizing most world data (charm and jet production data are used where theoretically possible), except Tevatron gauge boson production data and LHC data which are left for genuine predictions. This is done within the 'dynamical' (valencelike input at Q02 = 0.8 GeV2 ) and 'standard' (input at Q02 = 2 GeV2) approach. The stability and reliability of the results are ensured by including nonperturbative higher-twist terms, nuclear corrections as well asmore » target mass corrections, and by applying various (Q2, W2) cuts on available data. In addition, the Q02 dependence of the results is studied in detail. Predictions are given, in particular for LHC, on gauge and Higgs boson as well as for top-quark pair production. At NNLO the dynamical approach results in αs(MZ2) = 0.1136 ± 0.0004, whereas the somewhat less constrained standard fit gives αs(MZ2) = 0.1162 ± 0.0006.« less
Patel, Sunita; Blose, Joshua M; Sokoloski, Joshua E; Pollack, Lois; Bevilacqua, Philip C
2012-11-20
The interferon-inducible, double-stranded (ds) RNA-activated protein kinase (PKR) contains a dsRNA-binding domain (dsRBD) and plays key roles in viral pathogenesis and innate immunity. Activation of PKR is typically mediated by long dsRNA, and regulation of PKR is disfavored by most RNA imperfections, including bulges and internal loops. Herein, we combine isothermal titration calorimetry (ITC), electrophoretic mobility shift assays, and small-angle X-ray scattering (SAXS) to dissect the thermodynamic basis for the specificity of the dsRBD termed "p20" for various RNAs and to detect any RNA conformational changes induced upon protein binding. We monitor binding of p20 to chimeric duplexes containing terminal RNA-DNA hybrid segments and a central dsRNA segment, which was either unbulged ("perfect") or bulged. The ITC data reveal strong binding of p20 to the perfect duplex (K(d) ~ 30 nM) and weaker binding to the bulged duplex (K(d) ~ 2-5 μM). SAXS reconstructions and p(r) distance distribution functions further uncover that p20 induces no significant conformational change in perfect dsRNA but largely straightens bulged dsRNA. Together, these observations support the dsRBD's ability to tightly bind to only A-form RNA and suggest that in a noninfected cell, PKR may be buffered via weak interactions with various bulged and looped RNAs, which it may straighten. This work suggests that PKR-regulating RNAs with complex secondary and tertiary structures likely mimic dsRNA and/or engage portions of PKR outside of the dsRBD.
NASA Astrophysics Data System (ADS)
Dremin, I. M.
2013-01-01
Colliding high-energy hadrons either produce new particles or scatter elastically with their quantum numbers conserved and no other particles produced. We consider the latter case here. Although inelastic processes dominate at high energies, elastic scattering contributes considerably (18-25%) to the total cross section. Its share first decreases and then increases at higher energies. Small-angle scattering prevails at all energies. Some characteristic features can be seen that provide information on the geometrical structure of the colliding particles and the relevant dynamical mechanisms. The steep Gaussian peak at small angles is followed by the exponential (Orear) regime with some shoulders and dips, and then by a power-law decrease. Results from various theoretical approaches are compared with experimental data. Phenomenological models claiming to describe this process are reviewed. The unitarity condition predicts an exponential fall for the differential cross section with an additional substructure to occur exactly between the low momentum transfer diffraction cone and a power-law, hard parton scattering regime under high momentum transfer. Data on the interference of the Coulomb and nuclear parts of amplitudes at extremely small angles provide the value of the real part of the forward scattering amplitude. The real part of the elastic scattering amplitude and the contribution of inelastic processes to the imaginary part of this amplitude (the so-called overlap function) are also discussed. Problems related to the scaling behavior of the differential cross section are considered. The power-law regime at highest momentum transfer is briefly described.
Huang, J.; Allada, K.; Dutta, C.; Katich, J.; Qian, X.; Wang, Y.; Zhang, Y.; Aniol, K.; Annand, J. R. M.; Averett, T.; Benmokhtar, F.; Bertozzi, W.; Bradshaw, P. C.; Bosted, P.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, C.; Chen, J. -P.; Chen, W.; Chirapatpimol, K.; Chudakov, E.; Cisbani, E.; Cornejo, J. C.; Cusanno, F.; Dalton, M. M.; Deconinck, W.; de Jager, C. W.; De Leo, R.; Deng, X.; Deur, A.; Ding, H.; Dolph, P. A. M.; Dutta, D.; El Fassi, L.; Frullani, S.; Gao, H.; Garibaldi, F.; Gaskell, D.; Gilad, S.; Gilman, R.; Glamazdin, O.; Golge, S.; Guo, L.; Hamilton, D.; Hansen, O.; Higinbotham, D. W.; Holmstrom, T.; Huang, M.; Ibrahim, H. F.; Iodice, M.; Jiang, X.; Jin, G.; Jones, M. K.; Kelleher, A.; Kim, W.; Kolarkar, A.; Korsch, W.; LeRose, J. J.; Li, X.; Li, Y.; Lindgren, R.; Liyanage, N.; Long, E.; Lu, H. -J.; Margaziotis, D. J.; Markowitz, P.; Marrone, S.; McNulty, D.; Meziani, Z. -E.; Michaels, R.; Moffit, B.; Muñoz Camacho, C.; Nanda, S.; Narayan, A.; Nelyubin, V.; Norum, B.; Oh, Y.; Osipenko, M.; Parno, D.; Peng, J. C.; Phillips, S. K.; Posik, M.; Puckett, A. J. R.; Qiang, Y.; Rakhman, A.; Ransome, R. D.; Riordan, S.; Saha, A.; Sawatzky, B.; Schulte, E.; Shahinyan, A.; Shabestari, M. H.; Širca, S.; Stepanyan, S.; Subedi, R.; Sulkosky, V.; Tang, L. -G.; Tobias, A.; Urciuoli, G. M.; Vilardi, I.; Wang, K.; Wojtsekhowski, B.; Yan, X.; Yao, H.; Ye, Y.; Ye, Z.; Yuan, L.; Zhan, X.; Zhang, Y. -W.; Zhao, B.; Zheng, X.; Zhu, L.; Zhu, X.; Zong, X.
2012-01-01
We report the first measurement of the double-spin asymmetry A_{LT} for charged pion electroproduction in semi-inclusive deep inelastic electron scattering on a transversely polarized ^{3}He target. The kinematics focused on the valence quark region, 0.16 < x < 0.35 with 1.4 < Q^{2} < 2.7 GeV^{2}. The corresponding neutron A_{LT} asymmetries were extracted from the measured ^{3}He asymmetries and proton/^{3}He cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function g_{1T}^{q} and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for π^{-} production on ^{3}He and the neutron, while our π^{+} asymmetries are consistent with zero.
Event generator tunes obtained from underlying event and multiparton scattering measurements
NASA Astrophysics Data System (ADS)
Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Brondolin, E.; Dragicevic, M.; Erö, J.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hartl, C.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Knünz, V.; König, A.; Krammer, M.; Krätschmer, I.; Liko, D.; Matsushita, T.; Mikulec, I.; Rabady, D.; Rahbaran, B.; Rohringer, H.; Schieck, J.; Schöfbeck, R.; Strauss, J.; Treberer-Treberspurg, W.; Waltenberger, W.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Alderweireldt, S.; Cornelis, T.; de Wolf, E. A.; Janssen, X.; Knutsson, A.; Lauwers, J.; Luyckx, S.; van de Klundert, M.; van Haevermaet, H.; van Mechelen, P.; van Remortel, N.; van Spilbeeck, A.; Abu Zeid, S.; Blekman, F.; D'Hondt, J.; Daci, N.; de Bruyn, I.; Deroover, K.; Heracleous, N.; Keaveney, J.; Lowette, S.; Moreels, L.; Olbrechts, A.; Python, Q.; Strom, D.; Tavernier, S.; van Doninck, W.; van Mulders, P.; van Onsem, G. P.; van Parijs, I.; Barria, P.; Brun, H.; Caillol, C.; Clerbaux, B.; de Lentdecker, G.; Fasanella, G.; Favart, L.; Grebenyuk, A.; Karapostoli, G.; Lenzi, T.; Léonard, A.; Maerschalk, T.; Marinov, A.; Perniè, L.; Randle-Conde, A.; Seva, T.; Vander Velde, C.; Yonamine, R.; Vanlaer, P.; Yonamine, R.; Zenoni, F.; Zhang, F.; Adler, V.; Beernaert, K.; Benucci, L.; Cimmino, A.; Crucy, S.; Dobur, D.; Fagot, A.; Garcia, G.; Gul, M.; McCartin, J.; Ocampo Rios, A. A.; Poyraz, D.; Ryckbosch, D.; Salva, S.; Sigamani, M.; Tytgat, M.; van Driessche, W.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Beluffi, C.; Bondu, O.; Brochet, S.; Bruno, G.; Caudron, A.; Ceard, L.; da Silveira, G. G.; Delaere, C.; Favart, D.; Forthomme, L.; Giammanco, A.; Hollar, J.; Jafari, A.; Jez, P.; Komm, M.; Lemaitre, V.; Mertens, A.; Musich, M.; Nuttens, C.; Perrini, L.; Pin, A.; Piotrzkowski, K.; Popov, A.; Quertenmont, L.; Selvaggi, M.; Vidal Marono, M.; Beliy, N.; Hammad, G. H.; Júnior, W. L. Aldá; Alves, F. L.; Alves, G. A.; Brito, L.; Correa Martins Junior, M.; Hamer, M.; Hensel, C.; Moraes, A.; Pol, M. E.; Rebello Teles, P.; Belchior Batista Das Chagas, E.; Carvalho, W.; Chinellato, J.; Custódio, A.; da Costa, E. M.; de Jesus Damiao, D.; de Oliveira Martins, C.; Fonseca de Souza, S.; Huertas Guativa, L. M.; Malbouisson, H.; Matos Figueiredo, D.; Mora Herrera, C.; Mundim, L.; Nogima, H.; Prado da Silva, W. L.; Santoro, A.; Sznajder, A.; Tonelli Manganote, E. J.; Vilela Pereira, A.; Ahuja, S.; Bernardes, C. A.; de Souza Santos, A.; Dogra, S.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Mercadante, P. G.; Moon, C. S.; Novaes, S. F.; Padula, Sandra S.; Romero Abad, D.; Ruiz Vargas, J. C.; Aleksandrov, A.; Hadjiiska, R.; Iaydjiev, P.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Vutova, M.; Dimitrov, A.; Glushkov, I.; Litov, L.; Pavlov, B.; Petkov, P.; Ahmad, M.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Chen, M.; Cheng, T.; Du, R.; Jiang, C. H.; Plestina, R.; Romeo, F.; Shaheen, S. M.; Spiezia, A.; Tao, J.; Wang, C.; Wang, Z.; Zhang, H.; Asawatangtrakuldee, C.; Ban, Y.; Li, Q.; Liu, S.; Mao, Y.; Qian, S. J.; Wang, D.; Xu, Z.; Avila, C.; Cabrera, A.; Chaparro Sierra, L. F.; Florez, C.; Gomez, J. P.; Gomez Moreno, B.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Puljak, I.; Ribeiro Cipriano, P. M.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Kadija, K.; Luetic, J.; Micanovic, S.; Sudic, L.; Attikis, A.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Rykaczewski, H.; Bodlak, M.; Finger, M.; Finger, M.; Abdelalim, A. A.; Awad, A.; Mahrous, A.; Mohammed, Y.; Radi, A.; Calpas, B.; Kadastik, M.; Murumaa, M.; Raidal, M.; Tiko, A.; Veelken, C.; Eerola, P.; Pekkanen, J.; Voutilainen, M.; Härkönen, J.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Peltola, T.; Tuominen, E.; Tuominiemi, J.; Tuovinen, E.; Wendland, L.; Talvitie, J.; Tuuva, T.; Besancon, M.; Couderc, F.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Favaro, C.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Machet, M.; Malcles, J.; Rander, J.; Rosowsky, A.; Titov, M.; Zghiche, A.; Antropov, I.; Baffioni, S.; Beaudette, F.; Busson, P.; Cadamuro, L.; Chapon, E.; Charlot, C.; Dahms, T.; Davignon, O.; Filipovic, N.; Granier de Cassagnac, R.; Jo, M.; Lisniak, S.; Mastrolorenzo, L.; Miné, P.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Ortona, G.; Paganini, P.; Pigard, P.; Regnard, S.; Salerno, R.; Sauvan, J. B.; Sirois, Y.; Strebler, T.; Yilmaz, Y.; Zabi, A.; Agram, J.-L.; Andrea, J.; Aubin, A.; Bloch, D.; Brom, J.-M.; Buttignol, M.; Chabert, E. C.; Chanon, N.; Collard, C.; Conte, E.; Coubez, X.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Goetzmann, C.; Le Bihan, A.-C.; Merlin, J. A.; Skovpen, K.; van Hove, P.; Gadrat, S.; Beauceron, S.; Bernet, C.; Boudoul, G.; Bouvier, E.; Carrillo Montoya, C. A.; Chierici, R.; Contardo, D.; Courbon, B.; Depasse, P.; El Mamouni, H.; Fan, J.; Fay, J.; Gascon, S.; Gouzevitch, M.; Ille, B.; Lagarde, F.; Laktineh, I. B.; Lethuillier, M.; Mirabito, L.; Pequegnot, A. L.; Perries, S.; Ruiz Alvarez, J. D.; Sabes, D.; Sgandurra, L.; Sordini, V.; Vander Donckt, M.; Verdier, P.; Viret, S.; Toriashvili, T.; Lomidze, D.; Autermann, C.; Beranek, S.; Edelhoff, M.; Feld, L.; Heister, A.; Kiesel, M. K.; Klein, K.; Lipinski, M.; Ostapchuk, A.; Preuten, M.; Raupach, F.; Schael, S.; Schulte, J. F.; Verlage, T.; Weber, H.; Wittmer, B.; Zhukov, V.; Ata, M.; Brodski, M.; Dietz-Laursonn, E.; Duchardt, D.; Endres, M.; Erdmann, M.; Erdweg, S.; Esch, T.; Fischer, R.; Güth, A.; Hebbeker, T.; Heidemann, C.; Hoepfner, K.; Knutzen, S.; Kreuzer, P.; Merschmeyer, M.; Meyer, A.; Millet, P.; Olschewski, M.; Padeken, K.; Papacz, P.; Pook, T.; Radziej, M.; Reithler, H.; Rieger, M.; Scheuch, F.; Sonnenschein, L.; Teyssier, D.; Thüer, S.; Cherepanov, V.; Erdogan, Y.; Flügge, G.; Geenen, H.; Geisler, M.; Hoehle, F.; Kargoll, B.; Kress, T.; Kuessel, Y.; Künsken, A.; Lingemann, J.; Nehrkorn, A.; Nowack, A.; Nugent, I. M.; Pistone, C.; Pooth, O.; Stahl, A.; Aldaya Martin, M.; Asin, I.; Bartosik, N.; Behnke, O.; Behrens, U.; Bell, A. J.; Borras, K.; Burgmeier, A.; Campbell, A.; Choudhury, S.; Costanza, F.; Diez Pardos, C.; Dolinska, G.; Dooling, S.; Dorland, T.; Eckerlin, G.; Eckstein, D.; Eichhorn, T.; Flucke, G.; Gallo, E.; Garcia, J. Garay; Geiser, A.; Gizhko, A.; Gunnellini, P.; Hauk, J.; Hempel, M.; Jung, H.; Kalogeropoulos, A.; Karacheban, O.; Kasemann, M.; Katsas, P.; Kieseler, J.; Kleinwort, C.; Korol, I.; Lange, W.; Leonard, J.; Lipka, K.; Lobanov, A.; Lohmann, W.; Mankel, R.; Marfin, I.; Melzer-Pellmann, I.-A.; Meyer, A. B.; Mittag, G.; Mnich, J.; Mussgiller, A.; Naumann-Emme, S.; Nayak, A.; Ntomari, E.; Perrey, H.; Pitzl, D.; Placakyte, R.; Raspereza, A.; Roland, B.; Sahin, M. Ö.; Saxena, P.; Schoerner-Sadenius, T.; Schröder, M.; Seitz, C.; Spannagel, S.; Trippkewitz, K. D.; Walsh, R.; Wissing, C.; Blobel, V.; Centis Vignali, M.; Draeger, A. R.; Erfle, J.; Garutti, E.; Goebel, K.; Gonzalez, D.; Görner, M.; Haller, J.; Hoffmann, M.; Höing, R. S.; Junkes, A.; Klanner, R.; Kogler, R.; Kovalchuk, N.; Lapsien, T.; Lenz, T.; Marchesini, I.; Marconi, D.; Meyer, M.; Nowatschin, D.; Ott, J.; Pantaleo, F.; Peiffer, T.; Perieanu, A.; Pietsch, N.; Poehlsen, J.; Rathjens, D.; Sander, C.; Scharf, C.; Schettler, H.; Schleper, P.; Schlieckau, E.; Schmidt, A.; Schwandt, J.; Sola, V.; Stadie, H.; Steinbrück, G.; Tholen, H.; Troendle, D.; Usai, E.; Vanelderen, L.; Vanhoefer, A.; Vormwald, B.; Barth, C.; Baus, C.; Berger, J.; Böser, C.; Butz, E.; Chwalek, T.; Colombo, F.; de Boer, W.; Descroix, A.; Dierlamm, A.; Fink, S.; Frensch, F.; Friese, R.; Giffels, M.; Gilbert, A.; Haitz, D.; Hartmann, F.; Heindl, S. M.; Husemann, U.; Katkov, I.; Kornmayer, A.; Lobelle Pardo, P.; Maier, B.; Mildner, H.; Mozer, M. U.; Müller, T.; Müller, Th.; Plagge, M.; Quast, G.; Rabbertz, K.; Röcker, S.; Roscher, F.; Sieber, G.; Simonis, H. J.; Stober, F. 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T.; Derdzinski, M.; Holzner, A.; Kelley, R.; Klein, D.; Letts, J.; MacNeill, I.; Olivito, D.; Padhi, S.; Pieri, M.; Sani, M.; Sharma, V.; Simon, S.; Tadel, M.; Tu, Y.; Vartak, A.; Wasserbaech, S.; Welke, C.; Würthwein, F.; Yagil, A.; Zevi Della Porta, G.; Bradmiller-Feld, J.; Campagnari, C.; Dishaw, A.; Dutta, V.; Flowers, K.; Franco Sevilla, M.; Geffert, P.; George, C.; Golf, F.; Gouskos, L.; Gran, J.; Incandela, J.; McColl, N.; Mullin, S. D.; Mullin, S. D.; Richman, J.; Stuart, D.; Suarez, I.; West, C.; Yoo, J.; Anderson, D.; Apresyan, A.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Mott, A.; Newman, H. B.; Pena, C.; Pierini, M.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Andrews, M. B.; Azzolini, V.; Calamba, A.; Carlson, B.; Ferguson, T.; Paulini, M.; Russ, J.; Sun, M.; Vogel, H.; Vorobiev, I.; Cumalat, J. P.; Ford, W. T.; Gaz, A.; Jensen, F.; Johnson, A.; Krohn, M.; Mulholland, T.; Nauenberg, U.; Stenson, K.; Wagner, S. R.; Alexander, J.; Chatterjee, A.; Chaves, J.; Chu, J.; Dittmer, S.; Eggert, N.; Mirman, N.; Nicolas Kaufman, G.; Patterson, J. R.; Rinkevicius, A.; Ryd, A.; Skinnari, L.; Soffi, L.; Sun, W.; Tan, S. M.; Teo, W. D.; Thom, J.; Thompson, J.; Tucker, J.; Weng, Y.; Wittich, P.; Abdullin, S.; Albrow, M.; Apollinari, G.; Banerjee, S.; Bauerdick, L. A. T.; Beretvas, A.; Berryhill, J.; Bhat, P. C.; Bolla, G.; Burkett, K.; Butler, J. N.; Cheung, H. W. K.; Chlebana, F.; Cihangir, S.; Elvira, V. D.; Fisk, I.; Freeman, J.; Gottschalk, E.; Gray, L.; Green, D.; Grünendahl, S.; Gutsche, O.; Hanlon, J.; Hare, D.; Harris, R. M.; Hasegawa, S.; Hirschauer, J.; Hu, Z.; Jayatilaka, B.; Jindariani, S.; Johnson, M.; Joshi, U.; Jung, A. W.; Klima, B.; Kreis, B.; Lammel, S.; Linacre, J.; Lincoln, D.; Lipton, R.; Liu, T.; Lopes de Sá, R.; Lykken, J.; Maeshima, K.; Marraffino, J. M.; Martinez Outschoorn, V. I.; Maruyama, S.; Mason, D.; McBride, P.; Merkel, P.; Mishra, K.; Mrenna, S.; Nahn, S.; Newman-Holmes, C.; O'Dell, V.; Pedro, K.; Prokofyev, O.; Rakness, G.; Sexton-Kennedy, E.; Soha, A.; Spalding, W. J.; Spiegel, L.; Strobbe, N.; Taylor, L.; Tkaczyk, S.; Tran, N. V.; Uplegger, L.; Vaandering, E. W.; Vernieri, C.; Verzocchi, M.; Vidal, R.; Weber, H. A.; Whitbeck, A.; Acosta, D.; Avery, P.; Bortignon, P.; Bourilkov, D.; Carnes, A.; Carver, M.; Curry, D.; Das, S.; Field, R. D.; Furic, I. K.; Gleyzer, S. V.; Hugon, J.; Konigsberg, J.; Korytov, A.; Kotov, K.; Low, J. F.; Ma, P.; Matchev, K.; Mei, H.; Milenovic, P.; Mitselmakher, G.; Rank, D.; Rossin, R.; Shchutska, L.; Snowball, M.; Sperka, D.; Terentyev, N.; Thomas, L.; Wang, J.; Wang, S.; Yelton, J.; Hewamanage, S.; Linn, S.; Markowitz, P.; Martinez, G.; Rodriguez, J. L.; Adams, J. R.; Ackert, A.; Adams, T.; Askew, A.; Bein, S.; Bochenek, J.; Diamond, B.; Haas, J.; Hagopian, S.; Hagopian, V.; Johnson, K. F.; Khatiwada, A.; Prosper, H.; Weinberg, M.; Baarmand, M. M.; Bhopatkar, V.; Colafranceschi, S.; Hohlmann, M.; Kalakhety, H.; Noonan, D.; Roy, T.; Yumiceva, F.; Adams, M. R.; Apanasevich, L.; Berry, D.; Betts, R. R.; Bucinskaite, I.; Cavanaugh, R.; Evdokimov, O.; Gauthier, L.; Gerber, C. E.; Hofman, D. J.; Kurt, P.; O'Brien, C.; Sandoval Gonzalez, L. D.; Silkworth, C.; Turner, P.; Varelas, N.; Wu, Z.; Zakaria, M.; Bilki, B.; Clarida, W.; Dilsiz, K.; Durgut, S.; Gandrajula, R. P.; Haytmyradov, M.; Khristenko, V.; Merlo, J.-P.; Mermerkaya, H.; Mestvirishvili, A.; Moeller, A.; Nachtman, J.; Ogul, H.; Onel, Y.; Ozok, F.; Penzo, A.; Snyder, C.; Tiras, E.; Wetzel, J.; Yi, K.; Anderson, I.; Anderson, I.; Barnett, B. A.; Blumenfeld, B.; Eminizer, N.; Fehling, D.; Feng, L.; Gritsan, A. V.; Maksimovic, P.; Martin, C.; Osherson, M.; Roskes, J.; Sady, A.; Sarica, U.; Swartz, M.; Xiao, M.; Xin, Y.; You, C.; Xiao, M.; Baringer, P.; Bean, A.; Benelli, G.; Bruner, C.; Kenny, R. P.; Majumder, D.; Majumder, D.; Malek, M.; Murray, M.; Sanders, S.; Stringer, R.; Wang, Q.; Ivanov, A.; Kaadze, K.; Khalil, S.; Makouski, M.; Maravin, Y.; Mohammadi, A.; Saini, L. K.; Skhirtladze, N.; Toda, S.; Lange, D.; Rebassoo, F.; Wright, D.; Anelli, C.; Baden, A.; Baron, O.; Belloni, A.; Calvert, B.; Eno, S. C.; Ferraioli, C.; Gomez, J. A.; Hadley, N. J.; Jabeen, S.; Jabeen, S.; Kellogg, R. G.; Kolberg, T.; Kunkle, J.; Lu, Y.; Mignerey, A. C.; Shin, Y. H.; Skuja, A.; Tonjes, M. B.; Tonwar, S. C.; Apyan, A.; Barbieri, R.; Baty, A.; Bierwagen, K.; Brandt, S.; Bierwagen, K.; Busza, W.; Cali, I. A.; Demiragli, Z.; Di Matteo, L.; Gomez Ceballos, G.; Goncharov, M.; Gulhan, D.; Iiyama, Y.; Innocenti, G. M.; Klute, M.; Kovalskyi, D.; Lai, Y. S.; Lee, Y.-J.; Levin, A.; Luckey, P. D.; Marini, A. C.; McGinn, C.; Mironov, C.; Narayanan, S.; Niu, X.; Paus, C.; Ralph, D.; Roland, C.; Roland, G.; Salfeld-Nebgen, J.; Stephans, G. S. F.; Sumorok, K.; Varma, M.; Velicanu, D.; Veverka, J.; Wang, J.; Wang, T. W.; Wyslouch, B.; Yang, M.; Zhukova, V.; Dahmes, B.; Evans, A.; Finkel, A.; Gude, A.; Hansen, P.; Kalafut, S.; Kao, S. C.; Klapoetke, K.; Kubota, Y.; Lesko, Z.; Mans, J.; Nourbakhsh, S.; Ruckstuhl, N.; Rusack, R.; Tambe, N.; Turkewitz, J.; Acosta, J. G.; Oliveros, S.; Avdeeva, E.; Bloom, K.; Bose, S.; Claes, D. R.; Dominguez, A.; Fangmeier, C.; Gonzalez Suarez, R.; Kamalieddin, R.; Keller, J.; Knowlton, D.; Kravchenko, I.; Meier, F.; Monroy, J.; Ratnikov, F.; Siado, J. E.; Snow, G. R.; Alyari, M.; Dolen, J.; George, J.; Godshalk, A.; Harrington, C.; Iashvili, I.; Kaisen, J.; Kharchilava, A.; Kumar, A.; Rappoccio, S.; Roozbahani, B.; Alverson, G.; Barberis, E.; Baumgartel, D.; Chasco, M.; Hortiangtham, A.; Massironi, A.; Morse, D. M.; Nash, D.; Orimoto, T.; Teixeira de Lima, R.; Trocino, D.; Wang, R.-J.; Wood, D.; Zhang, J.; Hahn, K. A.; Kubik, A.; Mucia, N.; Odell, N.; Pollack, B.; Pozdnyakov, A.; Schmitt, M.; Stoynev, S.; Sung, K.; Trovato, M.; Velasco, M.; Brinkerhoff, A.; Dev, N.; Hildreth, M.; Jessop, C.; Karmgard, D. J.; Kellams, N.; Lannon, K.; Marinelli, N.; Meng, F.; Mueller, C.; Musienko, Y.; Planer, M.; Reinsvold, A.; Ruchti, R.; Smith, G.; Taroni, S.; Valls, N.; Wayne, M.; Wolf, M.; Woodard, A.; Antonelli, L.; Brinson, J.; Bylsma, B.; Durkin, L. S.; Flowers, S.; Hart, A.; Hill, C.; Hughes, R.; Ji, W.; Ling, T. Y.; Liu, B.; Luo, W.; Puigh, D.; Rodenburg, M.; Winer, B. L.; Wulsin, H. W.; Driga, O.; Elmer, P.; Hardenbrook, J.; Hebda, P.; Koay, S. A.; Lujan, P.; Marlow, D.; Medvedeva, T.; Mooney, M.; Olsen, J.; Palmer, C.; Piroué, P.; Saka, H.; Stickland, D.; Tully, C.; Zuranski, A.; Malik, S.; Barnes, V. E.; Benedetti, D.; Bortoletto, D.; Gutay, L.; Jha, M. K.; Jones, M.; Jung, K.; Miller, D. H.; Neumeister, N.; Primavera, F.; Radburn-Smith, B. C.; Shi, X.; Shipsey, I.; Silvers, D.; Sun, J.; Svyatkovskiy, A.; Wang, F.; Xie, W.; Xu, L.; Parashar, N.; Stupak, J.; Adair, A.; Akgun, B.; Chen, Z.; Ecklund, K. M.; Geurts, F. J. M.; Guilbaud, M.; Li, W.; Michlin, B.; Northup, M.; Padley, B. P.; Redjimi, R.; Roberts, J.; Rorie, J.; Tu, Z.; Zabel, J.; Betchart, B.; Bodek, A.; de Barbaro, P.; Demina, R.; Eshaq, Y.; Ferbel, T.; Galanti, M.; Galanti, M.; Garcia-Bellido, A.; Han, J.; Harel, A.; Hindrichs, O.; Hindrichs, O.; Khukhunaishvili, A.; Petrillo, G.; Tan, P.; Verzetti, M.; Arora, S.; Barker, A.; Chou, J. P.; Contreras-Campana, C.; Contreras-Campana, E.; Ferencek, D.; Gershtein, Y.; Gray, R.; Halkiadakis, E.; Hidas, D.; Hughes, E.; Kaplan, S.; Kunnawalkam Elayavalli, R.; Lath, A.; Nash, K.; Panwalkar, S.; Park, M.; Salur, S.; Schnetzer, S.; Sheffield, D.; Somalwar, S.; Stone, R.; Thomas, S.; Thomassen, P.; Walker, M.; Foerster, M.; Riley, G.; Rose, K.; Spanier, S.; York, A.; Bouhali, O.; Castaneda Hernandez, A.; Celik, A.; Dalchenko, M.; de Mattia, M.; Delgado, A.; Dildick, S.; Dildick, S.; Eusebi, R.; Gilmore, J.; Huang, T.; Kamon, T.; Krutelyov, V.; Krutelyov, V.; Mueller, R.; Osipenkov, I.; Pakhotin, Y.; Patel, R.; Patel, R.; Perloff, A.; Rose, A.; Safonov, A.; Tatarinov, A.; Ulmer, K. A.; Akchurin, N.; Cowden, C.; Damgov, J.; Dragoiu, C.; Dudero, P. R.; Faulkner, J.; Kunori, S.; Lamichhane, K.; Lee, S. W.; Libeiro, T.; Undleeb, S.; Volobouev, I.; Appelt, E.; Delannoy, A. G.; Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Mao, Y.; Melo, A.; Ni, H.; Sheldon, P.; Snook, B.; Tuo, S.; Velkovska, J.; Xu, Q.; Arenton, M. W.; Cox, B.; Francis, B.; Goodell, J.; Hirosky, R.; Ledovskoy, A.; Li, H.; Lin, C.; Neu, C.; Sinthuprasith, T.; Sun, X.; Wang, Y.; Wolfe, E.; Wood, J.; Xia, F.; Clarke, C.; Harr, R.; Karchin, P. E.; Kottachchi Kankanamge Don, C.; Lamichhane, P.; Sturdy, J.; Belknap, D. A.; Carlsmith, D.; Cepeda, M.; Dasu, S.; Dodd, L.; Duric, S.; Gomber, B.; Grothe, M.; Hall-Wilton, R.; Herndon, M.; Hervé, A.; Klabbers, P.; Lanaro, A.; Levine, A.; Long, K.; Loveless, R.; Mohapatra, A.; Ojalvo, I.; Perry, T.; Pierro, G. A.; Polese, G.; Ruggles, T.; Sarangi, T.; Savin, A.; Sharma, A.; Smith, N.; Smith, W. H.; Taylor, D.; Woods, N.
2016-03-01
New sets of parameters ("tunes") for the underlying-event (UE) modelling of the pythia8, pythia6 and herwig++ Monte Carlo event generators are constructed using different parton distribution functions. Combined fits to CMS UE proton-proton ({p}{p}) data at sqrt{s} = 7 text {TeV} and to UE proton-antiproton ({p}overline{p} ) data from the CDF experiment at lower sqrt{s}, are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton-proton collisions at 13 text {TeV}. In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons are presented of the UE tunes to "minimum bias" (MB) events, multijet, and Drell-Yan (q overline{q} rightarrow Z/ γ ^* rightarrow lepton-antilepton+jets) observables at 7 and 8 text {TeV}, as well as predictions for MB and UE observables at 13 text {TeV}.
Polarized 3 parton production in inclusive DIS at small x
NASA Astrophysics Data System (ADS)
Ayala, Alejandro; Hentschinski, Martin; Jalilian-Marian, Jamal; Tejeda-Yeomans, Maria Elena
2016-10-01
Azimuthal angular correlations between produced hadrons/jets in high energy collisions are a sensitive probe of the dynamics of QCD at small x. Here we derive the triple differential cross section for inclusive production of 3 polarized partons in DIS at small x. The target proton or nucleus is described using the Color Glass Condensate (CGC) formalism. The resulting expressions are used to study azimuthal angular correlations between produced partons in order to probe the gluon structure of the target hadron or nucleus. Our analytic expressions can also be used to calculate the real part of the Next to Leading Order (NLO) corrections to di-hadron production in DIS by integrating out one of the three final state partons.
VBFNLO: A parton level Monte Carlo for processes with electroweak bosons
NASA Astrophysics Data System (ADS)
Arnold, K.; Bähr, M.; Bozzi, G.; Campanario, F.; Englert, C.; Figy, T.; Greiner, N.; Hackstein, C.; Hankele, V.; Jäger, B.; Klämke, G.; Kubocz, M.; Oleari, C.; Plätzer, S.; Prestel, S.; Worek, M.; Zeppenfeld, D.
2009-09-01
VBFNLO is a fully flexible parton level Monte Carlo program for the simulation of vector boson fusion, double and triple vector boson production in hadronic collisions at next-to-leading order in the strong coupling constant. VBFNLO includes Higgs and vector boson decays with full spin correlations and all off-shell effects. In addition, VBFNLO implements CP-even and CP-odd Higgs boson via gluon fusion, associated with two jets, at the leading-order one-loop level with the full top- and bottom-quark mass dependence in a generic two-Higgs-doublet model. A variety of effects arising from beyond the Standard Model physics are implemented for selected processes. This includes anomalous couplings of Higgs and vector bosons and a Warped Higgsless extra dimension model. The program offers the possibility to generate Les Houches Accord event files for all processes available at leading order. Program summaryProgram title:VBFNLO Catalogue identifier: AEDO_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDO_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL version 2 No. of lines in distributed program, including test data, etc.: 339 218 No. of bytes in distributed program, including test data, etc.: 2 620 847 Distribution format: tar.gz Programming language: Fortran, parts in C++ Computer: All Operating system: Linux, should also work on other systems Classification: 11.1, 11.2 External routines: Optionally Les Houches Accord PDF Interface library and the GNU Scientific library Nature of problem: To resolve the large scale dependence inherent in leading order calculations and to quantify the cross section error induced by uncertainties in the determination of parton distribution functions, it is necessary to include NLO corrections. Moreover, whenever stringent cuts are required on decay products and/or identified jets the question arises whether the scale dependence and a k-factor, defined
Delineating the polarized and unpolarized partonic structure of the nucleon
Jimenez-Delgado, Pedro
2015-03-01
Our latest results on the extraction of parton distribution functions of the nucleon are reported. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are given, including a careful treatment of hadronic and nuclear corrections, as well as results on the impact of present and future data in our understanding of the spin of the nucleon.
Delineating the polarized and unpolarized partonic structure of the nucleon
Jimenez-Delgado, Pedro
2015-03-01
Reports on our latest extractions of parton distribution functions of the nucleon are given. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of the nucleon.
Transverse momentum dependent (TMD) parton distribution functions: Status and prospects*
Angeles-Martinez, R.; Bacchetta, A.; Balitsky, Ian I.; Boer, D.; Boglione, M.; Boussarie, R.; Ceccopieri, F. A.; Cherednikov, I. O.; Connor, P.; Echevarria, M. G.; et al
2015-01-01
In this study, we review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum qT spectra of Higgs and vector bosons for low qT, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present the application of a new tool, TMDLIB, to parton density fits and parameterizations.
The role of the input scale in parton distribution analyses
Pedro Jimenez-Delgado
2012-08-01
A first systematic study of the effects of the choice of the input scale in global determinations of parton distributions and QCD parameters is presented. It is shown that, although in principle the results should not depend on these choices, in practice a relevant dependence develops as a consequence of what is called procedural bias. This uncertainty should be considered in addition to other theoretical and experimental errors, and a practical procedure for its estimation is proposed. Possible sources of mistakes in the determination of QCD parameter from parton distribution analysis are pointed out.
New limits on intrinsic charm in the nucleon from global analysis of parton distributions.
Jimenez-Delgado, P; Hobbs, T J; Londergan, J T; Melnitchouk, W
2015-02-27
We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q^{2}≳1 GeV^{2} and W^{2}≳3.5 GeV^{2}, including fixed-target proton and deuteron cross sections at lower energies that were excluded in previous global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with ⟨x⟩_{IC} at most 0.5% (corresponding to an IC normalization of ∼1%) at the 4σ level for Δχ^{2}=1. We also critically assess the impact of older EMC measurements of F_{2}^{c} at large x, which favor a nonzero IC, but with very large χ^{2} values. PMID:25768757
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.
Charge-exchange reactions from the standpoint of the parton model
NASA Astrophysics Data System (ADS)
Nekrasov, M. L.
2015-11-01
Using simple arguments, we show that charge-exchange reactions at high energies go through the hard scattering of fast quarks. On this basis we describe π-p→ M0n and K-p→ M0Λ, M0=π0,η,η', in a combined approach which defines hard contributions in the parton model and soft ones in Regge phenomenology. The disappearance of a dip according to recent GAMS- 4π data in the differential cross-section K-p→ηΛ at \\vert t\\vert≈ 0.4-0.5 (GeV/c)2 at transition to relatively high momenta, is explained as a manifestation of a mode change of summation of hard contributions from coherent to incoherent. Other manifestations of the mentioned mode change are discussed. Constraints on the η- η{^' mixing and gluonium admixture in η{^' are obtained.
New Limits on Intrinsic Charm in the Nucleon from Global Analysis of Parton Distributions
NASA Astrophysics Data System (ADS)
Jimenez-Delgado, P.; Hobbs, T. J.; Londergan, J. T.; Melnitchouk, W.
2015-02-01
We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q2≳1 GeV2 and W2≳3.5 GeV2 , including fixed-target proton and deuteron cross sections at lower energies that were excluded in previous global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with ⟨x ⟩IC at most 0.5% (corresponding to an IC normalization of ˜1 % ) at the 4 σ level for Δ χ2=1 . We also critically assess the impact of older EMC measurements of F2c at large x , which favor a nonzero IC, but with very large χ2 values.
New limits on intrinsic charm in the nucleon from global analysis of parton distributions
Jimenez-Delgado, P.; Hobbs, T. J.; Londergan, J. T.; Melnitchouk, W.
2015-02-27
We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q2 ≥ 1 GeV2 and W2 ≥ 3.5 GeV2, including fixed-target proton and deuteron deep cross sections at lower energies that were excluded in previously global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with (x)IC at most 0.5% (corresponding to an IC normalization of ~1%) at the 4σ level for ΔX2 = 1.more » We also assess the impact of older EMC measurements of Fc2c at large x, which favor a nonzero IC, but with very large X2 values.« less
A dynamical picture of hadron-hadron collisions with the string-parton model
Dean, D.J. Vanderbilt Univ., Nashville, TN . Dept. of Physics and Astronomy); Umar, A.S. . Dept. of Physics and Astronomy); Wu, J.S.; Strayer, M.R. )
1991-01-01
We introduce a dynamical model for the description of hadron-hadron collisions at relativistic energies. The model is based on classical Nambu-Goto strings. The string motion is performed in unrestricted four-dimensional space-time. The string endpoints are interpreted as partons which carry energy and momentum. We study e{sup +}e{sup {minus}}, e -- p, and p -- p collisions at various center of mass energies. The three basic features of our model are as follows. An ensemble of strings with different endpoint dynamics is used to approximately reproduce the valence quark structure functions. We introduce an adiabatic hadronization mechanism for string breakup via q{bar q} pair production. The interaction between strings is formulated in terms of a quark-quark scattering amplitude and exchange. This model will be used to describe relativistic heavy-ion collisions in future work. 28 refs., 3 figs., 1 tab.
Iterative Monte Carlo analysis of spin-dependent parton distributions
Sato, Nobuo; Melnitchouk, Wally; Kuhn, Sebastian E.; Ethier, Jacob J.; Accardi, Alberto
2016-04-05
We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The analysis is performed using a new iterative Monte Carlo fitting technique which generates stable fits to polarized parton distribution functions (PDFs) with statistically rigorous uncertainties. Inclusion of the Jefferson Lab data leads to a reduction in the PDF errors for the valence and sea quarks, as well as in the gluon polarization uncertainty at x ≳ 0.1. Furthermore, the study also provides the first determination of the flavor-separated twist-3 PDFsmore » and the d2 moment of the nucleon within a global PDF analysis.« less
Impact of CLAS and COMPASS data on polarized parton densities and higher twist
Leader, Elliot; Sidorov, Aleksander V.; Stamenov, Dimiter B.
2007-04-01
We have reanalyzed the world data on inclusive polarized deep inelastic scattering (DIS) including the very precise CLAS proton and deuteron data, as well as the latest COMPASS data on the asymmetry A{sub 1}{sup d}, and have studied the impact of these data on polarized parton densities and higher twist effects. We demonstrate that the low Q{sup 2} CLAS data improve essentially our knowledge of higher twist corrections to the spin structure function g{sub 1}, while the large Q{sup 2} COMPASS data influence mainly the strange quark density. In our new analysis we find that a negative polarized gluon density, or one that changes sign as a function of x, cannot be ruled out on the basis of the present DIS data.
nCTEQ15: Global analysis of nuclear parton distributions with uncertainties in the CTEQ framework
NASA Astrophysics Data System (ADS)
Kovařík, K.; Kusina, A.; Ježo, T.; Clark, D. B.; Keppel, C.; Lyonnet, F.; Morfín, J. G.; Olness, F. I.; Owens, J. F.; Schienbein, I.; Yu, J. Y.
2016-04-01
We present the new nCTEQ15 set of nuclear parton distribution functions (PDFs) with uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear dependence using data on nuclei all the way up to 208Pb. The uncertainties are determined using the Hessian method with an optimal rescaling of the eigenvectors to accurately represent the uncertainties for the chosen tolerance criteria. In addition to the deep inelastic scattering and Drell-Yan processes, we also include inclusive pion production data from the Relativistic Heavy Ion Collider to help constrain the nuclear gluon PDF. Furthermore, we investigate the correlation of the data sets with specific nuclear PDF flavor components and asses the impact of individual experiments. We also provide comparisons of the nCTEQ15 set with recent fits from other groups.
nCTEQ15 - Global analysis of nuclear parton distributions with uncertainties in the CTEQ framework
Kovarik, K.; Kusina, A.; Jezo, T.; Clark, D. B.; Keppel, C.; Lyonnet, F.; Morfin, J. G.; Olness, F. I.; Owens, J. F.; Schienbein, I.; et al
2016-04-28
We present the new nCTEQ15 set of nuclear parton distribution functions with uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear dependence using data on nuclei all the way up to 208Pb. The uncertainties are determined using the Hessian method with an optimal rescaling of the eigenvectors to accurately represent the uncertainties for the chosen tolerance criteria. In addition to the Deep Inelastic Scattering (DIS) and Drell-Yan (DY) processes, we also include inclusive pion production data from RHIC to help constrain the nuclear gluon PDF. Here, we investigate the correlation of the data sets with specific nPDFmore » flavor components, and asses the impact of individual experiments. We also provide comparisons of the nCTEQ15 set with recent fits from other groups.« less
Lattice QCD Studies of Transverse Momentum-Dependent Parton Distribution Functions
NASA Astrophysics Data System (ADS)
Engelhardt, M.; Musch, B.; Hägler, P.; Negele, J.; Schäfer, A.
2015-09-01
Transverse momentum-dependent parton distributions (TMDs) relevant for semi-inclusive deep inelastic scattering and the Drell-Yan process can be defined in terms of matrix elements of a quark bilocal operator containing a staple-shaped gauge link. Such a definition opens the possibility of evaluating TMDs within lattice QCD. By parametrizing the aforementioned matrix elements in terms of invariant amplitudes, the problem can be cast in a Lorentz frame suited for the lattice calculation. Results for selected TMD observables are presented, including a particular focus on their dependence on a Collins-Soper-type evolution parameter, which quantifies proximity of the staple-shaped gauge links to the light cone.
New approach to parton shower Monte Carlo event generators for precision QCD theory: HERWIRI1.0(31)
Joseph, S.; Ward, B. F. L.; Majhi, S.; Yost, S. A.
2010-04-01
By implementing the new IR-improved Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-Callan-Symanzik (DGLAP-CS) kernels recently developed by one of us in the HERWIG6.5 environment we generate a new Monte Carlo (MC), HERWIRI1.0(31), for hadron-hadron scattering at high energies. We use MC data to illustrate the comparison between the parton shower generated by the standard DGLAP-CS kernels and that generated by the new IR-improved DGLAP-CS kernels. The interface to MC-NLO, MC-NLO/HERWIRI, is illustrated. Comparisons with FNAL data and some discussion of possible implications for LHC phenomenology are also presented.
Li, Gen; Lee, Martin A.
2015-09-01
The effects of scatter-dominated interplanetary transport on the spectral properties of the differential fluence of large gradual solar energetic particle (SEP) events are investigated analytically. The model assumes for simplicity radial constant solar wind and radial magnetic field. The radial diffusion coefficient is calculated with quasilinear theory by assuming a spectrum of Alfvén waves propagating parallel to the magnetic field. Cross-field transport is neglected. The model takes into consideration several essential features of gradual event transport: nearly isotropic ion distributions, adiabatic deceleration in a divergent solar wind, and particle radial scattering mean free paths increasing with energy. Assuming an impulsive and spherically symmetric injection of SEPs with a power-law spectrum near the Sun, the predicted differential fluence spectrum exhibits at 1 AU three distinctive power laws for different energy domains. The model naturally reproduces the spectral features of the double power-law proton differential fluence spectra that tend to be observed in extremely large SEP events. We select nine western ground-level events (GLEs) out of the 16 GLEs during Solar Cycle 23 and fit the observed double power-law spectra to the analytical predictions. The compression ratio of the accelerating shock wave, the power-law index of the ambient wave intensity, and the proton radial scattering mean free path are determined for the nine GLEs. The derived parameters are generally in agreement with the characteristic values expected for large gradual SEP events.
Intrinsic transverse momentum and parton correlations from dynamical chiral symmetry breaking
Peter Schweitzer, Mark Strikman, Christian Weiss
2013-01-01
scattering processes. Under certain conditions the nonperturbative parton correlations predicted here could be observed in particle correlations between the current and target fragmentation regions of deep-inelastic scattering.
Parton shower evolution in a 3D hydrodynamical medium
Renk, Thorsten
2008-09-15
We present a Monte Carlo simulation of the perturbative quantum chromodynamics shower developing after a hard process embedded in a heavy-ion collision. The main assumption is that the cascade of branching partons traverses a medium that (consistent with standard radiative energy loss pictures) is characterized by a local transport coefficient q-circumflex that measures the virtuality per unit length transferred to a parton that propagates in this medium. This increase in parton virtuality alters the development of the shower and in essence leads to extra induced radiation and hence a softening of the momentum distribution in the shower. After hadronization, this leads to the concept of a medium-modified fragmentation function. On the level of observables, this is manifest as the suppression of high-transverse-momentum (P{sub T}) hadron spectra. We simulate the soft medium created in heavy-ion collisions by a 3D hydrodynamical evolution and average the medium-modified fragmentation function over this evolution to compare with data on single inclusive hadron suppression and extract the q-circumflex that characterizes the medium. Finally, we discuss possible uncertainties of the model formulation and argue that the data in a soft momentum show evidence of qualitatively different physics that presumably cannot be described by a medium-modified parton shower.
Recent progress in the statistical approach of parton distributions
Soffer, Jacques
2011-07-15
We recall the physical features of the parton distributions in the quantum statistical approach of the nucleon. Some predictions from a next-to-leading order QCD analysis are compared to recent experimental results. We also consider their extension to include their transverse momentum dependence.
Global parton distributions for the LHC Run II
NASA Astrophysics Data System (ADS)
Ball, R. D.
2016-07-01
We review the next generation global PDF sets: NNPDF3.0, MMHT14 and CT14. We describe the global datasets, particularly the new data from LHC Run I, the developments in QCD theory and PDF methodology, recent improvements in their combination and delivery, and future prospects for parton determination at Run II.
Parton-Hadron-String Dynamics at relativistic collider energies
NASA Astrophysics Data System (ADS)
Bratkovskaya, E. L.; Cassing, W.; Konchakovski, V. P.; Linnyk, O.
2011-04-01
The novel Parton-Hadron-String Dynamics (PHSD) transport approach is applied to nucleus-nucleus collisions at RHIC energies with respect to differential hadronic spectra in comparison to available data. The PHSD approach is based on a dynamical quasiparticle model for partons (DQPM) matched to reproduce recent lattice-QCD results from the Wuppertal-Budapest group in thermodynamic equilibrium. The transition from partonic to hadronic degrees of freedom is described by covariant transition rates for the fusion of quark-antiquark pairs or three quarks (antiquarks), respectively, obeying flavor current-conservation, color neutrality as well as energy-momentum conservation. Our dynamical studies for heavy-ion collisions at relativistic collider energies are compared to earlier results from the Hadron-String Dynamics (HSD) approach - incorporating no explicit dynamical partonic phase - as well as to experimental data from the STAR, PHENIX, BRAHMS and PHOBOS Collaborations for Au + Au collisions at the top RHIC energy of √{s}=200 GeV. We find a reasonable reproduction of hadron rapidity distributions and transverse mass spectra and also a fair description of the elliptic flow of charged hadrons as a function of the centrality of the reaction and the transverse momentum p. Furthermore, an approximate quark-number scaling of the elliptic flow v of hadrons is observed in the PHSD results, too.
Evolution of minimum-bias parton fragmentation in nuclear collisions
Trainor, Thomas A.
2009-10-15
Minimum-bias fragment distributions (FDs) are calculated by folding a power-law parton energy spectrum with parametrized fragmentation functions (FFs) derived from e{sup +}-e{sup -} and p-p collisions. Substantial differences between measured e{sup +}-e{sup -} and p-p FFs suggest that FF 'universality' may not be a valid assumption. The common parton spectrum is constrained by comparison with a p-p p{sub t} spectrum hard component. Changes in FFs due to parton 'energy loss' or 'medium modification' are modeled by altering FF parametrizations consistent with rescaling QCD splitting functions. In-vacuum and in-medium FDs are compared with spectrum hard components from 200-GeV Au-Au collisions for several centralities. The reference for all nuclear collisions is the FD derived from in-vacuum e{sup +}-e{sup -} FFs. The hard component for p-p and peripheral Au-Au collisions is found to be strongly suppressed for smaller fragment momenta, consistent with the FD derived from in-vacuum p-p FFs. At a particular centrality the Au-Au hard component transitions to enhancement at smaller momenta and suppression at larger momenta, consistent with FDs derived from in-medium e{sup +}-e{sup -} FFs. Fragmentation systematics suggest that QCD color connections change dramatically in more-central A-A collisions. Observed parton and hadron spectrum systematics are inconsistent with saturation-scale arguments used to support assumptions of parton thermalization.
Toward a QCD analysis of jet rates in deep-inelastic Muon-Proton scattering
Salgado, C.W.; E665 Collaboration
1993-08-01
Measurements of multi-jet production rates in deep-inelastic Muon-Proton scattering at Fermilab-E665 are presented. Jet rates defined by the JADE clustering algorithm are compared to perturbative Quantum chromodynamics (PQCD) and different Monte Carlo model predictions. The applicability of the jet-parton duality hypothesis is studied. We obtain hadronic jet rates which are approximately a factor of two higher than PQCD predictions at the parton level. Possible causes for this discrepancy are discussed.
Measurements of transverse momentum in semi-inclusive deep-inelastic scattering at CLAS
K.A. Griffioen
2012-12-01
With mounting experimental evidence that only a small fraction of the proton's spin comes from the spins of its quarks and gluons, the quest for orbital angular momentum has begun. The parton distributions relevant to this depend on transverse quark momenta. Recent CLAS semi-inclusive deep-inelastic scattering measurements probe these new transverse-momentum-dependent parton distributions using longitudinally polarized beams and targets and detecting {pi}{sup +},{pi}{sup -} and {pi}{sup 0} in the final state.
NASA Astrophysics Data System (ADS)
Zhu, Jian; Li, Jian-jun; Zhao, Jun-wu
2014-09-01
The tunable scattering cross section of oxide layer-coated Al nanoshell has been computationally studied as a function of wavelength. The calculation results show that the two resonance light scattering (RLS) peaks of Al nanoshell have higher frequency and greater intensity than that of Au and Ag nanoshell. Both of the two scattering peaks, which are corresponding to anti-symmetric and symmetric plasmon coupling, take place in the ultraviolet range. And the anti-symmetric scattering peak could be tuned down to the deep-ultraviolet wavelength below 200 nm. By increasing radius and dielectric constant of the inner core, or decreasing the thickness of the oxide layer, the anti-symmetric scattering peak with short wavelength could be enhanced and has greater intensity than that of symmetric scattering peak with long wavelength, which is different from that of Au and Ag nanoshells. Obtaining intense RLS peaks from Al nanoshell at deep-ultraviolet region presents a potential for the application of ultra-sensitive biosensing, ultraviolet material characterization, and ultraviolet nanoscale imaging.
APACIC++ 2.0. A PArton Cascade In C++
NASA Astrophysics Data System (ADS)
Krauss, F.; Schälicke, A.; Soff, G.
2006-06-01
The new version of the parton shower module APACIC++ for the SHERPA event generator framework is presented. It incorporates some features, that are specific for the consistent merging with multi-particle matrix elements at tree-level. This publication also includes some example results and a short description of the upgraded class structure of APACIC++, version 2.0. Program summaryTitle of program:APACIC++, version 2.0 Catalogue identifier:ADNE_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADNE_v2_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Catalogue identifier of previous version: ADNE Authors of previous version: R. Kuhn, F. Krauss, B. Iványi, G. Soff Journal reference of previous version: Comput. Phys. Commun. 134 (2001) 223 Licensing provisions: none Operating system under which the program has been tested: Linux, Unix, Darwin Programming language: C++ No. of lines in distributed program, including test data, etc.: 78 352 No. of bytes in distributed program, including test data, etc.: 2 561 276 External routines/libraries used: The makeinstall requires the autotools package Distribution format: tar gzip file Nature of the physical problem: Modern collider-based experiments in particle physics are characterized by increasing energies that are released and, thus, by a growing number of particles that are produced. The large numbers of involved particles renders it impossible to derive fully analytical predictions for a detailed description of the final state. In addition, the transformation of the partons of perturbative quantum field theory into the experimentally observable hadrons is until now not understood on a quantitative level. These obstacles prevent a direct comparison of analytical predictions with experimental data, and simulation tools need to be employed to bridge this gap. Method of solution: The event generator SHERPA with a new version of the parton shower module APACIC++ is able to
Deeply Virtual Compton Scattering with CLAS
F.X. Girod
2007-12-17
The beam spin asymmetries of the reaction ep -> epg in the Bjorken regime were measured over a wide kinematical domain using the CLAS detector and a new lead-tungstate calorimeter. Through the interference of the Bethe-Heitler process with Deeply Virtual Compton Scattering, those asymmetries provide constraints for the nucleon Generalized Parton Distributions models. The observed shapes are in agreement with twist-2 dominance predictions.
Deep and shallow inelastic scattering
Ray, Heather
2015-05-15
In this session we focused on the higher energy deep and shallow inelastic particle interactions, DIS and SIS. DIS interactions occur when the energy of the incident particle beam is so large that the beam is able to penetrate the nucleons inside of the target nuclei. These interactions occur at the smallest level possible, that of the quark-gluon, or parton, level. SIS interactions occur in an intermediate energy range, just below the energy required for DIS interactions. The DIS cross section formula contains structure functions that describe our understanding of the underlying parton structure of nature. The full description of DIS interactions requires three structure functions: two may be measured in charged lepton or neutrino scattering, but one can only be extracted from neutrino DIS data. There are reasons to expect that the impact of nuclear effects could be different for neutrinos engaging in the DIS interaction, vs those felt by leptons. In fact, fits by the nCTEQ collaboration have found that the neutrino-Fe structure functions appear to differ from those extracted from lepton scattering data [1]. To better understand the global picture of DIS and SIS, we chose a three-pronged attack that examined recent experimental results, data fits, and latest theory predictions. Experimental results from neutrino and lepton scattering, as well as collider experiments, were presented.
Nilsen, Gøran. J.; Thompson, Corey M.; Ehlers, Georg; Marjerrison, Casey A.; Greedan, John E.
2015-02-23
Here we investigated diffuse magnetic scattering in the highly frustrated double perovskite Ba_{2}YRuO_{6} using polarized neutrons. Consistent with previous reports, the material shows two apparent transitions at 47 and 36 K to an eventual type I face-centered-cubic magnetic ground state. The (100) magnetic reflection shows different behavior from the five other observed reflections upon heating from 1.8 K, with the former broadening well beyond the resolution limit near 36 K. Closer examination of the latter group reveals a small, but clear, increase in peak widths between 36 and 47 K, indicating that this regime is dominated by short-range spin correlations. Diffuse magnetic scattering persists above 47 K near the position of (100) to at least 200 K, consistent with strong frustration. Reverse Monte Carlo (RMC) modeling of the diffuse scattering from 45 to 200 K finds that the spin-spin correlations between nearest and next-nearest neighbors are antiferromagnetic and ferromagnetic, respectively, at temperatures near the upper ordering temperature, but both become antiferromagnetic and of similar magnitude above 100 K. The significance of this unusual crossover is discussed in light of the super-superexchange interactions between nearest and next-nearest neighbors in this material and the demands of type I order. The dimensionality of the correlations is addressed by reconstructing the scattering in the (hk0) plane using the RMC spin configurations. This indicates that one-dimensional spin correlations dominate at temperatures close to the first transition. In addition, a comparison between mean-field calculations and (hk0) scattering implies that further neighbor couplings play a significant role in the selection of the ground state. Finally, the results and interpretation are compared with those recently published for monoclinic Sr_{2}YRuO_{6}, and similarities and differences are emphasized.
Parton transverse momentum and orbital angular momentum distributions
NASA Astrophysics Data System (ADS)
Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael; Liuti, Simonetta
2016-08-01
The quark orbital angular momentum component of proton spin, Lq, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on partonic intrinsic transverse momentum. Connecting the definitions provides the key for correlating direct experimental determinations of Lq and evaluations through lattice QCD calculations. The direct observation of quark orbital angular momentum does not require transverse spin polarization but can occur using longitudinally polarized targets.
HEAVY QUARKS AT RHIC FROM PARTON TRANSPORT THEORY.
MOLNAR, D.
2006-05-15
There are several indications that an opaque partonic medium is created in energetic Au+Au collisions ({radical}s{sub NN} {approx} GeV/nucleon) at the Relativistic Heavy Ion Collider (RHIC). At the extreme densities of {approx} 10-100 times normal nuclear density reached even heavy-flavor hadrons are affected significantly. Heavy-quark observables are presented from the parton transport model MPC, focusing on the nuclear suppression pattern, azimuthal anisotropy (''elliptic flow''), and azimuthal correlations. Comparison with Au + Au data at top RHIC energy {radical}s{sub NN} = 200 GeV indicates significant heavy quark rescattering, corresponding roughly five times higher opacities than estimates based on leading-order perturbative QCD. We propose measurements of charm-anticharm, e.g., D-meson azimuthal correlations as a sensitive, independent probe to corroborate these findings.
Small-x parton content of the photon
NASA Astrophysics Data System (ADS)
Forshaw, J. R.; Harriman, P. N.
1992-11-01
The parton content of the photon is examined systematically. In the low-Q2 region (Q2<1 GeV2) we assume the photon behaves largely according to the vector-meson-dominance (VMD) hypothesis, while for higher Q2 we supplement the VMD with a purely perturbative pointlike component and QCD corrections. Special care is taken in the region of small x: we work in the leading-logarithm approximation (LLA) in 1/x at low Q2 and in the LLA in Q2 for Q2>4 GeV2. We include small-x shadowing effects in the VMD sector and show that they need not be considered in the pointlike sector where the parton content is much less.
Transverse momentum dependent (TMD) parton distribution functions: Status and prospects*
Angeles-Martinez, R.; Bacchetta, A.; Balitsky, Ian I.; Boer, D.; Boglione, M.; Boussarie, R.; Ceccopieri, F. A.; Cherednikov, I. O.; Connor, P.; Echevarria, M. G.; Ferrera, G.; Grados Luyando, J.; Hautmann, F.; Jung, H.; Kasemets, T.; Kutak, K.; Lansberg, J. P.; Lykasov, G.; Madrigal Martinez, J. D.; Mulders, P. J.; Nocera, E. R.; Petreska, E.; Pisano, C.; Placakyte, R.; Radescu, V.; Radici, M.; Schnell, G.; Signori, A.; Szymanowski, L.; Taheri Monfared, S.; Van der Veken, F. F.; van Haevermaet, H. J.; Van Mechelen, P.; Vladimirov, A. A.; Wallon, S.
2015-01-01
In this study, we review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum q_{T} spectra of Higgs and vector bosons for low q_{T}, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present the application of a new tool, TMD_{LIB}, to parton density fits and parameterizations.
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.
Parton interpretation of the nucleon spin-dependent structure functions
Mankiewicz, L. ); Ryzak, Z. )
1991-02-01
We discuss the interpretation of the nucleon's polarized structure function {ital g}{sub 2}({ital x}). If the target state is represented by its Fock decomposition on the light cone, the operator-product expansion allows us to demonstrate that moments of {ital g}{sub 2}({ital x}) are related to overlap integrals between wave functions of opposite longitudinal polarizations. In the light-cone formalism such wave functions are related by the kinematical operator {ital scrY}, or light-cone parity. As a consequence, it can be shown that moments of {ital g}{sub 2} give information about the same parton wave function, or probability amplitude to find a certain parton configuration in the target which defines {ital g}{sub 1}({ital x}) or {ital F}{sub 2}({ital x}). Specific formulas are given, and possible applications to the phenomenology of the nucleon structure in QCD are discussed.
Moments of nucleon spin-dependent generalized parton distributions
Wolfram Schroers; Richard Brower; Patrick Dreher; Robert Edwards; George Fleming; P. Hagler; Urs Heller; Thomas Lippert; John Negele; Andrew Pochinsky; Dru Renner; David Richards; Klaus Schilling
2004-03-01
We present a lattice measurement of the first two moments of the spin-dependent GPD H-tilde(x,xi,t). From these we obtain the axial coupling constant and the second moment of the spin-dependent forward parton distribution. The measurements are done in full QCD using Wilson fermions. In addition, we also present results from a first exploratory study of full QCD using Asqtad sea and domain-wall valence fermions.
Leading Twist Parton Distribution Amplitudes in Heavy Vector Mesons
NASA Astrophysics Data System (ADS)
Gao, Fei; Ding, Minghui; Chang, Lei; Liu, Yu-Xin; Roberts, Craig D.
2016-03-01
We employed QCD's Dyson-Schwinger equations (DSEs) for heavy quarks and obtained the leading twist parton distribution amplitudes (PDAs) in heavy vector mesons J/Ψ and ϒ. We found that all of the amplitudes are narrower than the asymptotic form, while they deviate from δ function. This indicates that the interaction between the two continent quarks are still important in the mesons consisted of charm and bottom quarks.
Deeply Pseudoscalar Meson Electroproduction with CLAS and Generalized Parton Distributions
Guidal, Michel; Kubarovsky, Valery P.
2015-06-01
We discuss the recent data of exclusive $\\pi^0$ (and $\\pi^+$) electroproduction on the proton obtained by the CLAS collaboration at Jefferson Lab. It is observed that the cross sections, which have been decomposed in $\\sigma_T+\\epsilon\\sigma_L$, $\\sigma_{TT}$ and $\\sigma_{LT}$ structure functions, are dominated by transverse amplitude contributions. The data can be interpreted in the Generalized Parton Distribution formalism provided that one includes helicity-flip transversity GPDs.
NASA Astrophysics Data System (ADS)
Mkrtchyan, Arthur; Albayrak, Ibrahim; Horn, Tanja; Nadel-Turonski, Pawel
2015-04-01
Deeply Virtual Comtpon Scattering (DVCS) is deemed the simplest and cleanest way to access the Generalized Parton Distributions (GPDs) of the nucleon. The DVCS process interferes with the Bethe-Heitler process allowing one to access the DVCS amplitudes. The imaginary part of the Compton amplitude is now relatively well understood, primarily through measurements of DVCS. However, much less is known about the real part of the amplitude. Time-like Compton Scattering (TCS) is the inverse process of DVCS and provides a new and promising way for probing the real part of the amplitude, and so constraining GPDs. Comparing data from Time-like Compton Scattering and the space-like DVCS process will also allow for testing the universality of GPDs. First studies of TCS using real tagged and quasi-real untagged photons were carried out at Jefferson Lab 6 GeV. In this talk, preliminary results on asymmetries and extraction of the real part of the CFF using photoproduction data and a comparison to electroproduction data will be presented. We will also discuss future plans for dilepton production at Jefferson Lab 12 GeV. Supported in part by NSF Grant PHY-1306227.
NASA Astrophysics Data System (ADS)
Zhang, Le; Hou, De-Fu; Qin, Guang-You
2016-08-01
We study the production of jet-bremsstrahlung photons through scattering with the constituents of dense nuclear matter within the framework of deep-inelastic scattering off a large nucleus. Applying a gradient expansion up to the second order for the exchanged three-dimensional momentum between jet and medium, we derive the single-photon bremsstrahlung spectrum with the inclusion of contributions from the transverse broadening as well as the longitudinal drag and diffusion of the hard parton's momentum. We also compare the medium-induced photon radiation spectra for single scattering and from the resummation of multiple scatterings. It is found that the coupling between different scatterings can give an additional contribution to medium-induced photon radiation, while for small momentum exchange the leading contribution from the drag and diffusions to the photon emission spectra remain the same for single and multiple scatterings.
Quantum Chromodynamics and Deep Inelastic Scattering
NASA Astrophysics Data System (ADS)
Ellis, R. Keith
2016-10-01
This article first describes the parton model which was the precursor of the QCD description of hard scattering processes. After the discovery of QCD and asymptotic freedom, the first successful applications were to Deep Inelastic lepton-hadron scattering. The subsequent application of QCD to processes with two initial state hadrons required the understanding and proof of factorization. To take the fledgling theory and turn it into the robust calculational engine it has become today, required a number of technical and conceptual developments which will be described. Prospects for higher loop calculations are also reviewed.
Timelike Compton Scattering - A First Look (CLAS)
Pawel Nadel-Turonski
2009-12-01
A major goal of the 12 GeV upgrade at Jefferson Lab is to map out the Generalized Parton Distributions (GPDs) in the valence region. This is primarily done through Deeply Virtual Compton Scattering (DVCS), which provides the simplest and cleanest way of accessing the GPDs. However, the “inverse” process, Timelike Compton Scattering (TCS), can provide an important complement, in particular formeasuring the real part of the amplitude and understanding corrections at finite Q2. The first measurements of TCS have recently been carried out in Hall B at Jefferson Lab, using both tagged and untagged photon beams.
Roy, Gilles; Roy, Nathalie
2008-03-20
A multiple-field-of-view (MFOV) lidar is used to characterize size and optical depth of low concentration of bioaerosol clouds. The concept relies on the measurement of the forward scattered light by using the background aerosols at various distances at the back of a subvisible cloud. It also relies on the subtraction of the background aerosol forward scattering contribution and on the partial attenuation of the first-order backscattering. The validity of the concept developed to retrieve the effective diameter and the optical depth of low concentration bioaerosol clouds with good precision is demonstrated using simulation results and experimental MFOV lidar measurements. Calculations are also done to show that the method presented can be extended to small optical depth cloud retrieval.
Wee partons in large nuclei: From virtual dream to hard reality
Venugopalan, R.
1995-06-01
We construct a weak coupling, many body theory to compute parton distributions in large nuclei for x {much_lt} A{sup {minus} 1/3}. The wee partons are highly coherent, non-Abelian Weizsaecker-Williams fields. Radiative corrections to the classical results axe discussed. The parton distributions for a single nucleus provide the initial conditions for the dynamical evolution of matter formed in ultrarelativistic nuclear collisions.
PHANTOM: A Monte Carlo event generator for six parton final states at high energy colliders
NASA Astrophysics Data System (ADS)
Ballestrero, Alessandro; Belhouari, Aissa; Bevilacqua, Giuseppe; Kashkan, Vladimir; Maina, Ezio
2009-03-01
PHANTOM is a tree level Monte Carlo for six parton final states at proton-proton, proton-antiproton and electron-positron colliders at O(αEM6) and O(αEM4αS2) including possible interferences between the two sets of diagrams. This comprehends all purely electroweak contributions as well as all contributions with one virtual or two external gluons. It can generate unweighted events for any set of processes and it is interfaced to parton shower and hadronization packages via the latest Les Houches Accord protocol. It can be used to analyze the physics of boson-boson scattering, Higgs boson production in boson-boson fusion, tt¯ and three boson production. Program summaryProgram title:PHANTOM (V. 1.0) Catalogue identifier: AECE_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECE_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.: 175 787 No. of bytes in distributed program, including test data, etc.: 965 898 Distribution format: tar.gz Programming language: Fortran 77 Computer: Any with a UNIX, LINUX compatible Fortran compiler Operating system: UNIX, LINUX RAM: 500 MB Classification: 11.1 External routines: LHAPDF (Les Houches Accord PDF Interface, http://projects.hepforge.org/lhapdf/), CIRCE (beamstrahlung for ee ILC collider). Nature of problem: Six fermion final state processes have become important with the increase of collider energies and are essential for the study of top, Higgs and electroweak symmetry breaking physics at high energy colliders. Since thousands of Feynman diagrams contribute in a single process and events corresponding to hundreds of different final states need to be generated, a fast and stable calculation is needed. Solution method:PHANTOM is a tree level Monte Carlo for six parton final states at proton-proton, proton-antiproton and
Deeply Virtual Compton Scattering off 4He
NASA Astrophysics Data System (ADS)
Joosten, Sylvester; CLAS Collaboration
2015-10-01
The European Muon Collaboration (EMC) observed the first signs of a modification of the partonic structure of the nucleon when present in a nuclear medium. The precise nature of these effects, as well as their underlying cause, is yet to be determined. The generalized parton distribution (GPD) framework provides a powerful tool to study the partonic structure of nucleons inside a nucleus. Hard exclusive leptoproduction of a real photon off a nucleon, deeply virtual Compton scattering (DVCS), is presently considered the cleanest experimental access to the GPDs, through the Compton form factors (CFFs). This is especially the case for scattering off the spin-zero helium nucleus, where only a single CFF contributes to the process. The real and imaginary parts of this CFF can be constrained through the beam-spin asymmetry (BSA). We will present the first measurements of the DVCS process off 4He using the CEBAF 6 GeV polarized electron beam and the CLAS detector at JLab. The CLAS detector was supplemented with an inner electromagnetic calorimeter for photons produced at small angles, as well as a radial time projection chamber (RTPC) to detect low-energy recoil nuclei. This setup allowed for a clean measurement of the BSA in both the coherent and incoherent channels.
Roy, Nathalie; Roy, Gilles
2008-08-10
Diffractive target plates are used to emulate aerosols of known size and concentration. These target plates are used to validate and determine the sensitivity of a multiple-field-of-view lidar signal inversion technique based on double-scattering measurement to retrieve the particle size and the concentration of small optical depth clouds. We estimate that nighttime and daytime quantification (size and concentration) is possible for optical depths as low as 0.005 and 0.016, respectively. The recovery technique limiting factors are the shot noise, the laser features, the optical lens quality, the background illumination level, the background aerosol fluctuations, and the noise introduced by the lidar detector, a gated intensified camera (camera G-ICCD).
Imaging the proton via hard exclusive production in diffractive pp scattering
Charles Hyde; Leonid Frankfurt; Mark Strikman; Christian Weiss
2007-05-21
We discuss the prospects for probing Generalized Parton Distributions (GPDs) via exclusive production of a high-mass system (H = heavy quarkonium, di-photon, di-jet, Higgs boson) in diffractive pp scattering, pp -> p + H + p. In such processes the interplay of hard and soft interactions gives rise to a diffraction pattern in the final-state proton transverse momenta, which is sensitive to the transverse spatial distribution of partons in the colliding protons. We comment on the plans for diffractive pp measurements at RHIC and LHC. Such studies could complement future measurements of GPDs in hard exclusive ep scattering (JLab, COMPASS, EIC).
Lawandy, N.M.
1987-01-01
The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for three different sets of relaxation rates. These rates correspond to: (1) Far Infrared (FIR) Raman lasers in the diabatic collision regime without consideration of coupled population decay in a closed system, (2) Raman FIR lasers in the diabatic collision regime with coupled population conserving decay, and (3) IR Raman gain in cesium vapor. The model is further expanded to include Doppler broadening and used to predict the peak gain as a function of detuning for a frequency doubled Alexandrite laser-pumped cesium vapor gain cell.
Experimental overview of Generalized Parton Distribution results from HERMES
Zihlmann, B.
2009-08-04
Over the course of more than a decade the HERMES experiment has accumulated a wealth of data with electron and positron beams on various gaseous targets from Hydrogen up to Xenon. In addition, the beams and targets can be polarized. This data set is viewed in the context of Generalized Parton Distributions, a theoretical formalism with an explicit three dimensional view of the structure of the nucleon. It provides a link between experimental observables and the total angular momentum of the quarks in the nucleon.
Generalized Parton distributions with CLAS and CLAS12
S. Niccolai
2012-04-01
Recent promising results obtained with the Jefferson Lab CLAS detector on deeply virtual exclusive processes and their link to the Generalized Parton Distributions, along with the experimental program to study GPDs at the 12-GeV upgraded JLab using the CLAS12 detector, are discussed here. With its wide acceptance, high luminosity, good resolution and particle identification capabilities, as well as large Q2 and xB coverage (1 GeV < Q2 < 10 GeV2, 0.1 < xB < 0.8), CLAS12 will be the ideal facility to pursue the research on the 3-dimensional structure of the nucleon in the valence region.
Parton-hadron matter in- and out-off equilibrium
NASA Astrophysics Data System (ADS)
Bratkovskaya, E. L.; Ozvenchuk, V.; Cassing, W.; Konchakovski, V. P.; Linnyk, O.
2013-08-01
We study the shear and bulk viscosities of partonic and hadronic matter - as well as the electric conductivity - as functions of temperature T within the Parton-Hadron-String Dynamics (PHSD) off-shell transport approach. Dynamical hadronic and partonic systems in equilibrium are studied by the PHSD simulations in a finite box with periodic boundary conditions. The ratio of the shear viscosity to entropy density η(T)/s(T) from PHSD shows a minimum (with a value of about 0.1) close to the critical temperature Tc, while it approaches the perturbative QCD (pQCD) limit at higher temperatures in line with lattice QCD results. For T < Tc, i.e. in the hadronic phase, the ratio η/s rises fast with decreasing temperature due to a lower interaction rate of the hadronic system and a significantly smaller number of degrees-of-freedom. The bulk viscosity ζ(T) - evaluated in the relaxation time approach - is found to strongly depend on the effects of mean fields (or potentials) in the partonic phase. We find a significant rise of the ratio ζ(T)/s(T) in the vicinity of the critical temperature Tc, when consistently including the scalar mean-field from PHSD, which is also in agreement with that from lQCD calculations. Furthermore, we present the results for the ratio (η + 3ζ/4)/s, which is found to depend non-trivially on temperature and to generally agree with the lQCD calculations as well. Within the PHSD calculations, the strong maximum of ζ(T)/η(T) close to Tc has to be attributed to mean-fields (or potential) effects that in PHSD are encoded in the temperature dependence of the quasiparticle masses, which is related to the infrared enhancement of the resummed (effective) coupling g(T). We also find that the dimensionless ratio of the electric conductivity over temperature σ0/T rises above Tc approximately linearly with T up to T = 2.5Tc, but approaches a constant above 5Tc, as expected qualitatively from perturbative QCD (pQCD).
Pion and kaon valence-quark parton distribution functions
Nguyen, Trang; Bashir, Adnan; Roberts, Craig D.; Tandy, Peter C.
2011-06-15
A rainbow-ladder truncation of QCD's Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to {pi}-N Drell-Yan data for the pion's u-quark distribution and to Drell-Yan data for the ratio u{sub K}(x)/u{sub {pi}}(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
Pion and kaon valence-quark parton distribution functions.
Nguyen, T.; Bashir, A.; Roberts, C. D.; Tandy, P. C.
2011-06-16
A rainbow-ladder truncation of QCD's Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to {pi}-N Drell-Yan data for the pion's u-quark distribution and to Drell-Yan data for the ratio u{sub K}(x)/u{sub {pi}}(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
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).
Multiparticle production in a two-component dual parton model
Aurenche, P. ); Bopp, F.W. ); Capella, A. ); Kwiecinski, J. ); Maire, M. ); Ranft, J.; Tran Thanh Van, J. )
1992-01-01
The dual parton model (DPM) describes soft and semihard multiparticle production. The version of the DPM presented in this paper includes soft and hard mechanisms as well as diffractive processes. The model is formulated as a Monte Carlo event generator. We calculate in this model, in the energy range of the hadron colliders, rapidity distributions and the rise of the rapidity plateau with the collision energy, transverse-momentum distributions and the rise of average transverse momenta with the collision energy, multiplicity distributions in different pseudorapidity regions, and transverse-energy distributions. For most of these quantities we find a reasonable agreement with experimental data.
An emergent world of gauge force and partons
NASA Astrophysics Data System (ADS)
Ma, Yao; Weng, Zheng-Yu
2014-09-01
We illustrate how a completely new world of gauge force emerges from a conventional condensed matter system in a rigorous way. A characteristic energy scale (Mott gap) separates such an exotic universe from the ordinary one that we condensed matter physicists are more familiar with at higher energies. The governing physical law is no longer about individual electrons but concerns fractionalized particles, i.e., partons, as the new collective modes resulted from strong correlation among the electrons. Novel phenomena in this low-energy universe are clearly distinguished from Landau's Fermi liquid described by the perturbative quantum many-body theory.
Parton branching model for pp¯ collisions
NASA Astrophysics Data System (ADS)
Chan, A. H.; Chew, C. K.
1990-02-01
A detailed analysis of the behavior of the initial numbers of gluons and quarks in the generalized multiplicity distribution (GMD) is presented. Two special cases of GMD, namely, the negative-binomial distribution and the Furry-Yule distribution, are also discussed in relation to the non-single-diffractive data at 200, 546, and 900 GeV c.m.-system energies and pseudorapidity intervals ηc. The GMD may provide an alternate distribution to understand parton action for future pp¯ collisions at high TeV energies.
Pion and kaon valence-quark parton distribution functions
NASA Astrophysics Data System (ADS)
Nguyen, Trang; Bashir, Adnan; Roberts, Craig D.; Tandy, Peter C.
2011-06-01
A rainbow-ladder truncation of QCD’s Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to π-N Drell-Yan data for the pion’s u-quark distribution and to Drell-Yan data for the ratio uK(x)/uπ(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
NASA Astrophysics Data System (ADS)
Trainor, Thomas A.
2015-03-01
The expression "multiple parton interactions" (MPI) denotes a conjectured QCD mechanism representing contributions from secondary (semi)hard parton scattering to the transverse azimuth region (TR) of jet-triggered p-p collisions. MPI is an object of underlying-event (UE) studies that consider variation of TR nch or pt yields relative to a trigger condition (leading hadron or jet pt). An alternative approach is 2D trigger-associated (TA) correlations on hadron transverse momentum pt or rapidity yt in which all hadrons from all p-p events are included. Based on a two-component (soft+hard) model (TCM) of TA correlations a jet-related TA hard component is isolated. Contributions to the hard component from the triggered dijet and from secondary dijets (MPI) can be distinguished, including their azimuth dependence relative to the trigger direction. Measured e+-e- and p-p¯ fragmentation functions and a minimum-bias jet spectrum from 200 GeV p-p¯ collisions are convoluted to predict the 2D hard component of TA correlations as a function of p-p collision multiplicity. The agreement between QCD predictions and TA correlation data is quantitative, confirming a dijet interpretation for the TCM hard component. The TA azimuth dependence is inconsistent with conventional UE assumptions.
Crider, B. P.; Peters, E. E.; Allmond, J. M.; McEllistrem, M. T.; Prados-Estévez, F. M.; Ross, T. J.; Vanhoy, J. R.; Yates, S. W.
2015-09-11
The experimental signature in searches for the neutrinoless double- decay of ^{76}Ge is a peak near 2039 keV in the spectrum. Given the low probability of the process, it is important that the background in this region be well understood. Moreover, inelastic scattering reactions with neutrons from muon-induced interactions and ( ,n) reactions in the surrounding materials or in the detector can provide contributions to the background. We also measured the production cross sections for rays from the ^{76}Ge(n,n ) reaction in the 2039-keV region at incident neutron energies up to 4.9 MeV. In addition to determining that the cross sections of a previously known 2040.7-keV ray from the 3952-keV level in ^{76} Ge are rather small, we find that a larger contribution arises from a 2037.5-keV ray which is attributed to a newly identified level at 3147 keV in ^{76}Ge. Finally, a third contribution is also possible from another new level at 3577 keV. These results indicate that the 2039-keV region in ^{76}Ge neutrinoless double- decay searches is more complex than was previously thought.
LHAPDF6: parton density access in the LHC precision era
NASA Astrophysics Data System (ADS)
Buckley, Andy; Ferrando, James; Lloyd, Stephen; Nordström, Karl; Page, Ben; Rüfenacht, Martin; Schönherr, Marek; Watt, Graeme
2015-03-01
The Fortran LHAPDF library has been a long-term workhorse in particle physics, providing standardised access to parton density functions for experimental and phenomenological purposes alike, following on from the venerable PDFLIB package. During Run 1 of the LHC, however, several fundamental limitations in LHAPDF's design have became deeply problematic, restricting the usability of the library for important physics-study procedures and providing dangerous avenues by which to silently obtain incorrect results. In this paper we present the LHAPDF 6 library, a ground-up re-engineering of the PDFLIB/LHAPDF paradigm for PDF access which removes all limits on use of concurrent PDF sets, massively reduces static memory requirements, offers improved CPU performance, and fixes fundamental bugs in multi-set access to PDF metadata. The new design, restricted for now to interpolated PDFs, uses centralised numerical routines and a powerful cascading metadata system to decouple software releases from provision of new PDF data and allow completely general parton content. More than 200 PDF sets have been migrated from LHAPDF 5 to the new universal data format, via a stringent quality control procedure. LHAPDF 6 is supported by many Monte Carlo generators and other physics programs, in some cases via a full set of compatibility routines, and is recommended for the demanding PDF access needs of LHC Run 2 and beyond.
A meta-analysis of parton distribution functions
NASA Astrophysics Data System (ADS)
Gao, Jun; Nadolsky, Pavel
2014-07-01
A "meta-analysis" is a method for comparison and combination of nonperturbative parton distribution functions (PDFs) in a nucleon obtained with heterogeneous procedures and assumptions. Each input parton distribution set is converted into a "meta-parametrization" based on a common functional form. By analyzing parameters of the meta-parametrizations from all input PDF ensembles, a combined PDF ensemble can be produced that has a smaller total number of PDF member sets than the original ensembles. The meta-parametrizations simplify the computation of the PDF uncertainty in theoretical predictions and provide an alternative to the 2010 PDF4LHC convention for combination of PDF uncertainties. As a practical example, we construct a META ensemble for computation of QCD observables at the Large Hadron Collider using the next-to-next-to-leading order PDF sets from CTEQ, MSTW, and NNPDF groups as the input. The META ensemble includes a central set that reproduces the average of LHC predictions based on the three input PDF ensembles and Hessian eigenvector sets for computing the combined PDF+α s uncertainty at a common QCD coupling strength of 0.118.
Nonperturbative QCD effects in forward scattering at the LHC
NASA Astrophysics Data System (ADS)
Bahia, C. A. S.; Broilo, M.; Luna, E. G. S.
2015-10-01
We study infrared contributions to semihard parton-parton interactions by considering an effective charge whose finite infrared behavior is constrained by a dynamical mass scale. Using an eikonal QCD-based model in order to connect this semihard parton-level dynamics to the hadron-hadron scattering, we obtain predictions for the proton-proton (p p ) and antiproton-proton (p ¯ p ) total cross sections, σtotp p ,p ¯ p , and the ratios of the real to imaginary part of the forward scattering amplitude, ρp p ,p ¯p. We discuss the theoretical aspects of this formalism and consider the phenomenological implications of a class of energy-dependent form factors in the high-energy behavior of the forward amplitude. We introduce integral dispersion relations specially tailored to relate the real and imaginary parts of eikonals with energy-dependent form factors. Our results, obtained using a group of updated sets of parton distribution functions, are consistent with the recent data from the TOTEM, AUGER, and Telescope Array experiments.
Partonic Equations of State in High-Energy Nuclear Collisions atRHIC
Xu, Nu
2006-10-01
The authors discuss the recent results on equation of state for partonic matter created at RHIC. Issues of partonic collectivity for multi-strange hadrons and J/{psi} from Au + Au collisions at {radical}s{sub NN} = 200 GeV are the focus of this paper.
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.
New limits on intrinsic charm in the nucleon from global analysis of parton distributions
Jimenez-Delgado, P.; Hobbs, T. J.; Londergan, J. T.; Melnitchouk, W.
2015-02-27
We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q^{2} ≥ 1 GeV_{2} and W^{2} ≥ 3.5 GeV^{2}, including fixed-target proton and deuteron deep cross sections at lower energies that were excluded in previously global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with (x)_{IC} at most 0.5% (corresponding to an IC normalization of ~1%) at the 4σ level for Δ_{X2} = 1. We also assess the impact of older EMC measurements of F^{c}_{2}c at large x, which favor a nonzero IC, but with very large X^{2} values.
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.
Lappi, T; Mäntysaari, H; Venugopalan, R
2015-02-27
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multiparton Fock states in the nuclear wave functions. In particular, the saturation scale that characterizes this multiparton dynamics is significantly larger in central events relative to minimum bias events. As an application, we study the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model.
Lappi, T; Mäntysaari, H; Venugopalan, R
2015-02-27
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multiparton Fock states in the nuclear wave functions. In particular, the saturation scale that characterizes this multiparton dynamics is significantly larger in central events relative to minimum bias events. As an application, we study the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model. PMID:25768758
Deep inelastic scattering near the endpoint in soft-collinear effective theory
Chay, Junegone; Kim, Chul
2007-01-01
We apply the soft-collinear effective theory to deep inelastic scattering near the endpoint region. The forward scattering amplitude and the structure functions are shown to factorize as a convolution of the Wilson coefficients, the jet functions, and the parton distribution functions. The behavior of the parton distribution functions near the endpoint region is considered. It turns out that it evolves with the Altarelli-Parisi kernel even in the endpoint region, and the parton distribution function can be factorized further into a collinear part and the soft Wilson line. The factorized form for the structure functions is obtained by the two-step matching, and the radiative corrections or the evolution for each factorized part can be computed in perturbation theory. We present the radiative corrections of each factorized part to leading order in {alpha}{sub s}, including the zero-bin subtraction for the collinear part.
NASA Astrophysics Data System (ADS)
Wodtke, Alec M.
2013-06-01
Atomic and molecular interactions constitute a many-body quantum problem governed fundamentally only by the Coulomb forces between many electrons and nuclei. While simple to state, computers are simply not fast enough to solve this problem by brute force, except for the simplest examples. Combining the Born-Oppenheimer Approximation (BOA) with Density Functional Theory (DFT), however, allows theoretical simulations of extraordinarily complex chemical systems including molecular interactions at solid metal surfaces, the physical basis of surface chemistry. This lecture describes experiments demonstrating the limits of the BOA/DFT approximation as it relates to molecules interacting with solid metal surfaces. One of the most powerful experimental tools at our disposal is a form of double resonance spectroscopy, which allows us to define the quantum state of the molecule both before and after the collision with the surface, providing a complete picture of the resulting energy conversion processes. With such data, we are able to emphasize quantitative measurements that can be directly compared to first principles theories that go beyond the Born-Oppenheimer approximation. One important outcome of this work is the realization that Born-Oppenheimer breakdown can be induced by simple charge transfer reactions that are common in surface chemistry. J. D. White, J. Chen, D. Matsiev, D. J. Auerbach and A. M. Wodtke Nature {433}(7025), 503-505 (2005) Y. H. Huang, C. T. Rettner, D. J. Auerbach and A. M. Wodtke Science {290}(5489), 111-114 (2000) R. Cooper, I. Rahinov, Z. S. Li, D. Matsiev, D. J. Auerbach and A. M. Wodtke Chemical Science {1}(1), 55-61 (2010) J. Larue, T. Schäfer, D. Matsiev, L. Velarde, N. H. Nahler, D. J. Auerbach and A. M. Wodtke PCCP {13}(1), 97-99 (2011).
Nucleon helicity and transversity parton distributions from lattice QCD
NASA Astrophysics Data System (ADS)
Chen, Jiunn-Wei; Cohen, Saul D.; Ji, Xiangdong; Lin, Huey-Wen; Zhang, Jian-Hui
2016-10-01
We present the first lattice-QCD calculation of the isovector polarized parton distribution functions (both helicity and transversity) using the large-momentum effective field theory (LaMET) approach for direct Bjorken-x dependence. We first review the detailed steps of the procedure in the unpolarized case, then generalize to the helicity and transversity cases. We also derive a new mass-correction formulation for all three cases. We then compare the effects of each finite-momentum correction using lattice data calculated at Mπ ≈ 310 MeV. Finally, we discuss the implications of these results for the poorly known antiquark structure and predict the sea-flavor asymmetry in the transversely polarized nucleon.
From Bethe-Salpeter Wave functions to Generalised Parton Distributions
NASA Astrophysics Data System (ADS)
Mezrag, C.; Moutarde, H.; Rodríguez-Quintero, J.
2016-09-01
We review recent works on the modelling of generalised parton distributions within the Dyson-Schwinger formalism. We highlight how covariant computations, using the impulse approximation, allows one to fulfil most of the theoretical constraints of the GPDs. Specific attention is brought to chiral properties and especially the so-called soft pion theorem, and its link with the Axial-Vector Ward-Takahashi identity. The limitation of the impulse approximation are also explained. Beyond impulse approximation computations are reviewed in the forward case. Finally, we stress the advantages of the overlap of lightcone wave functions, and possible ways to construct covariant GPD models within this framework, in a two-body approximation.
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.
Constrained {gamma}Z correction to parity-violating electron scattering
Hall, Nathan Luk; Blunden, Peter Gwithian; Melnitchouk, Wally; Thomas, Anthony W.; Young, Ross D.
2013-11-01
We update the calculation of {gamma}Z interference corrections to the weak charge of the proton. We show how constraints from parton distributions, together with new data on parity-violating electron scattering in the resonance region, significantly reduce the uncertainties on the corrections compared to previous estimates.
Constrained γZ correction to parity-violating electron scattering
Hall, N. L.; Thomas, A. W.; Young, R. D.; Blunden, P. G.; Melnitchouk, W.
2013-11-07
We update the calculation of γZ interference corrections to the weak charge of the proton. We show how constraints from parton distributions, together with new data on parity-violating electron scattering in the resonance region, significantly reduce the uncertainties on the corrections compared to previous estimates.
Jet production in deep inelastic scattering at HERA
Sutton, M. R.
2006-04-11
A number of the most recent results from the wealth of precision HERA data on high transverse energy jet production in deep inelastic scattering are reviewed. These measurements are confronted with predictions from next-to-leading order (NLO) Quantum Chromodynamics and allow the extraction of the strong coupling constant, {alpha}s, and have been used in QCD fits of the parton distribution functions in the proton.
Virtual photon structure functions and the parton content of the electron
Drees, M. ); Godbole, R.M. )
1994-09-01
We point out that in processes involving the parton content of the photon the usual effective photon approximation should be modified. The reason is that the parton content of virtual photons is logarithmically suppressed compared to real photons. We describe this suppression using several simple, physically motivated [ital Ansa]$[ital uml---tze]. Although the parton content of the electron in general no longer factorizes into an electron flux function and a photon structure function, it can still be expressed as a single integral. Numerical examples are given for the [ital e][sup +][ital e][sup [minus
Hard photon production and matrix-element parton-shower merging
Hoeche, Stefan; Schumann, Steffen; Siegert, Frank
2010-02-01
We present a Monte Carlo approach to prompt-photon production, where photons and QCD partons are treated democratically. The photon fragmentation function is modeled by an interleaved QCD+QED parton shower. This known technique is improved by including higher-order real-emission matrix elements. To this end, we extend a recently proposed algorithm for merging matrix elements and truncated parton showers. We exemplify the quality of the Monte Carlo predictions by comparing them to measurements of the photon fragmentation function at LEP and to measurements of prompt photon and diphoton production from the Tevatron experiments.
Deeply Virtual Compton Scattering off the neutron
M. Mazouz; A. Camsonne; C. Munoz Camacho; C. Ferdi; G. Gavalian; E. Kuchina; M. Amarian; K. A. Aniol; M. Beaumel; H. Benaoum; P. Bertin; M. Brossard; J.-P. Chen; E. Chudakov; B. Craver; F. Cusanno; C.W. de Jager; A. Deur; R. Feuerbach; J.-M. Fieschi; S. Frullani; M. Garcon; F. Garibaldi; O. Gayou; R. Gilman; J. Gomez; P. Gueye; P.A.M. Guichon; B. Guillon; O. Hansen; D. Hayes; D. Higinbotham; T. Holmstrom; C.E. Hyde; H. Ibrahim; R. Igarashi; X. Jiang; H.S. Jo; L.J. Kaufman; A. Kelleher; A. Kolarkar; G. Kumbartzki; G. Laveissiere; J.J. LeRose; R. Lindgren; N. Liyanage; H.-J. Lu; D.J. Margaziotis; Z.-E. Meziani; K. McCormick; R. Michaels; B. Michel; B. Moffit; P. Monaghan; S. Nanda; V. Nelyubin; M. Potokar; Y. Qiang; R.D. Ransome; J.-S. Real; B. Reitz; Y. Roblin; J. Roche; F. Sabatie; A. Saha; S. Sirca; K. Slifer; P. Solvignon; R. Subedi; V. Sulkosky; P.E. Ulmer; E. Voutier; K. Wang; L.B. Weinstein; B. Wojtsekhowski; X. Zheng; L. Zhu
2007-12-01
The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D$({\\vec e},e'\\gamma)X$ cross section measured at $Q^2$=1.9 GeV$^2$ and $x_B$=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to $E_q$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.
Deeply Virtual Compton Scattering off the Neutron
Mazouz, M.; Guillon, B.; Real, J.-S.; Voutier, E.
2007-12-14
The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e-vector,e{sup '}{gamma})X cross section measured at Q{sup 2}=1.9 GeV{sup 2} and x{sub B}=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E{sub q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.
Nonstationary interference and scattering from random media
Nazikian, R.
1991-12-01
For the small angle scattering of coherent plane waves from inhomogeneous random media, the three dimensional mean square distribution of random fluctuations may be recovered from the interferometric detection of the nonstationary modulational structure of the scattered field. Modulational properties of coherent waves scattered from random media are related to nonlocal correlations in the double sideband structure of the Fourier transform of the scattering potential. Such correlations may be expressed in terms of a suitability generalized spectral coherence function for analytic fields.
Comparing multiparticle production within a two-component dual parton model with collider data
Hahn, K.; Ranft, J. )
1990-03-01
The dual parton model (DPM) is very successful in describing hadronic multiparticle production. The version of DPM presented includes both soft and hard mechanisms. The hard component is described according to the lowest-order perturbative QCD--parton-model cross section. The model is formulated in the form of a Monte Carlo event generator. Results obtained with this event generator are compared with data on inclusive reactions in the TeV energy range of the CERN and Fermilab hadron colliders.
Evolution of anisotropy of a partonic system from relativistic heavy-ion collisions
Jas, Weronika; Mrowczynski, Stanislaw
2007-10-15
The evolution of anisotropy in momentum and coordinate space of the parton system produced in relativistic heavy-ion collisions is discussed within the free-streaming approximation. The momentum distribution evolves from the prolate shape (elongated along the beam) to the oblate one (squeezed along the beam). At the same time, the eccentricity in coordinate space, which occurs at finite values of impact parameter, decreases. It is argued that the parton system reaches local thermodynamic equilibrium before the momentum distribution becomes oblate.
Hadron mass corrections in semi-inclusive deep-inelastic scattering
Guerrero Teran, Juan Vicente; Ethier, James J.; Accardi, Alberto; Casper, Steven W.; Melnitchouk, Wally
2015-09-24
We found that the spin-dependent cross sections for semi-inclusive lepton-nucleon scattering are derived in the framework of collinear factorization, including the effects of masses of the target and produced hadron at finite Q^{2}. At leading order the cross sections factorize into products of parton distribution and fragmentation functions evaluated in terms of new, mass-dependent scaling variables. Furthermore, the size of the hadron mass corrections is estimated at kinematics relevant for current and future experiments, and the implications for the extraction of parton distributions from semi-inclusive measurements are discussed.
Hadron mass corrections in semi-inclusive deep-inelastic scattering
Guerrero Teran, Juan Vicente; Ethier, James J.; Accardi, Alberto; Casper, Steven W.; Melnitchouk, Wally
2015-09-24
We found that the spin-dependent cross sections for semi-inclusive lepton-nucleon scattering are derived in the framework of collinear factorization, including the effects of masses of the target and produced hadron at finite Q2. At leading order the cross sections factorize into products of parton distribution and fragmentation functions evaluated in terms of new, mass-dependent scaling variables. Furthermore, the size of the hadron mass corrections is estimated at kinematics relevant for current and future experiments, and the implications for the extraction of parton distributions from semi-inclusive measurements are discussed.
Automated parton-shower variations in pythia 8
NASA Astrophysics Data System (ADS)
Mrenna, S.; Skands, P.
2016-10-01
In the era of precision physics measurements at the LHC, efficient and exhaustive estimations of theoretical uncertainties play an increasingly crucial role. In the context of Monte Carlo (MC) event generators, the estimation of such uncertainties traditionally requires independent MC runs for each variation, for a linear increase in total run time. In this work, we report on an automated evaluation of the dominant (renormalization-scale and nonsingular) perturbative uncertainties in the pythia 8 event generator, with only a modest computational overhead. Each generated event is accompanied by a vector of alternative weights (one for each uncertainty variation), with each set separately preserving the total cross section. Explicit scale-compensating terms can be included, reflecting known coefficients of higher-order splitting terms and reducing the effect of the variations. The formalism also allows for the enhancement of rare partonic splittings, such as g →b b ¯ and q →q γ , to obtain weighted samples enriched in these splittings while preserving the correct physical Sudakov factors.
Backward dilepton production in color dipole and parton models
Gay Ducati, Maria Beatriz; Graeve de Oliveira, Emmanuel
2010-03-01
The Drell-Yan dilepton production at backward rapidities is studied in proton-nucleus collisions at Relativistic Heavy Ion Collider and LHC energies by comparing two different approaches: the k{sub T} factorization at next-to-leading order with intrinsic transverse momentum and the same process formulated in the target rest frame, i.e., the color dipole approach. Our results are expressed in terms of the ratio between p(d)-A and p-p collisions as a function of transverse momentum and rapidity. Three nuclear parton distribution functions are used: EKS (Eskola, Kolhinen, and Ruuskanen), EPS08, and EPS09 and, in both approaches, dileptons show sensitivity to nuclear effects, specially regarding the intrinsic transverse momentum. Also, there is room to discriminate between formalisms: the color dipole approach lacks soft effects introduced by the intrinsic k{sub T}. Geometric scaling GBW (Golec-Biernat and Wusthoff) and BUW (Boer, Utermann, and Wessels) color dipole cross section models and also a DHJ (Dumitru, Hayashigaki, and Jalilian-Marian) model, which breaks geometric scaling, are used. No change in the ratio between collisions is observed, showing that this observable is not changed by the particular shape of the color dipole cross section. Furthermore, our k{sub T} factorization results are compared with color glass condensate results at forward rapidities: the results agree at Relativistic Heavy Ion Collider although disagree at LHC, mainly due to the different behavior of target gluon and quark shadowing.
Energy flow along the medium-induced parton cascade
NASA Astrophysics Data System (ADS)
Blaizot, J.-P.; Mehtar-Tani, Y.
2016-05-01
We discuss the dynamics of parton cascades that develop in dense QCD matter, and contrast their properties with those of similar cascades of gluon radiation in vacuum. We argue that such cascades belong to two distinct classes that are characterized respectively by an increasing or a constant (or decreasing) branching rate along the cascade. In the former class, of which the BDMPS, medium-induced, cascade constitutes a typical example, it takes a finite time to transport a finite amount of energy to very soft quanta, while this time is essentially infinite in the latter case, to which the DGLAP cascade belongs. The medium induced cascade is accompanied by a constant flow of energy towards arbitrary soft modes, leading eventually to the accumulation of the initial energy of the leading particle at zero energy. It also exhibits scaling properties akin to wave turbulence. These properties do not show up in the cascade that develops in vacuum. There, the energy accumulates in the spectrum at smaller and smaller energy as the cascade develops, but the energy never flows all the way down to zero energy. Our analysis suggests that the way the energy is shared among the offsprings of a splitting gluon has little impact on the qualitative properties of the cascades, provided the kernel that governs the splittings is not too singular.
Medium Modifications of Hadron Properties and Partonic Processes
Brooks, W. K.; Strauch, S.; Tsushima, K.
2011-06-01
Chiral symmetry is one of the most fundamental symmetries in QCD. It is closely connected to hadron properties in the nuclear medium via the reduction of the quark condensate
Redux on "When is the top quark a parton?"
NASA Astrophysics Data System (ADS)
Dawson, S.; Ismail, A.; Low, Ian
2014-07-01
If a new heavy particle ϕ is produced in association with the top quark in a hadron collider, the production cross section exhibits a collinear singularity of the form log(mϕ/mt), which can be resummed by introducing a top quark parton distribution function (PDF). We reassess the necessity of such resummation in the context of a high-energy pp collider. We find that the introduction of a top PDF typically has a small effect at √S ˜100 TeV due to three factors: (1) αs at the scale μ =mϕ, which is quite small when log(mϕ/mt) is large, (2) the Bjorken x≪1 for mϕ≲10 TeV, and (3) the kinematic region where log(mϕ/mt)≫1 is suppressed by phase space. We consider the example of pp→tH+ at next-to-leading logarithm (NLL) order and show that, in terms of the total cross section, the effect of a top PDF is generically smaller than that of a bottom PDF in the associated production of bϕ. However, in the pT distribution of the charged Higgs, the NLL calculation using a top PDF is crucial to generate the pT distribution for pT≲mt.
From C to Parton Sea: How Supercomputing Reveals Nucleon Structure
NASA Astrophysics Data System (ADS)
Lin, Huey-Wen
2016-03-01
Studying the structure of nucleons is not only important to understanding the strong interactions of quarks and gluons, but also to improving the precision of new-physics searches. Since a broad class of experiments, including the LHC and dark-matter detection, require interactions with nucleons, the mission to probe femtoscale physics is also essential for disentangling Standard-Model contributions from potential new physics. These SM backgrounds require parton distribution functions (PDFs) as inputs. However, after decades of experiments and theoretical efforts, there still remain many unknowns, especially in the sea flavor structure and transversely polarized structure. In a discrete spacetime, we can make a direct numerical calculation of the implications of QCD using sufficiently large supercomputing resources. A nonperturbative approach from first principles, lattice QCD, provides hope to expand our understanding of nucleon structure, especially in regions that are difficult to observe in experiments. In this work, we present a first direct calculation of the Bjorken-x dependence of the PDFs using Large-Momentum Effective Theory (LaMET) and comment on the surprising result revealed for the nucleon sea-flavor asymmetry. The work of HWL is supported in part by the M. Hildred Blewett Fellowship of the American Physical Society, www.aps.org.
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.
Ahlers, H; Müntinga, H; Wenzlawski, A; Krutzik, M; Tackmann, G; Abend, S; Gaaloul, N; Giese, E; Roura, A; Kuhl, R; Lämmerzahl, C; Peters, A; Windpassinger, P; Sengstock, K; Schleich, W P; Ertmer, W; Rasel, E M
2016-04-29
We employ light-induced double Bragg diffraction of delta-kick collimated Bose-Einstein condensates to create three symmetric Mach-Zehnder interferometers. They rely on (i) first-order, (ii) two successive first-order, and (iii) second-order processes which demonstrate the scalability of the corresponding momentum transfer. With respect to devices based on conventional Bragg scattering, these symmetric interferometers double the scale factor and feature a better suppression of noise and systematic uncertainties intrinsic to the diffraction process. Moreover, we utilize these interferometers as tiltmeters for monitoring their inclination with respect to gravity. PMID:27176520
Triple coincidence beam spin asymmetry measurements in Deeply Virtual Compton Scattering
NASA Astrophysics Data System (ADS)
Canan, Mustafa
2011-12-01
The Generalized Parton Distributions (GPDs) provides hitherto the most complete information about the quark structure of hadron. GPDs are accessible through hard-exclusive reactions, among which Deeply Virtual Compton Scattering (DVCS) is the cleanest reaction. A dedicated DVCS experiment on Hydrogen (E00-110) ran in the Hall A at Jefferson Laboratory in Fall 2004. I present here Beam Spin Asymmetry (BSA) results for the ep → epgamma reaction studied in the E00-110 experiment with fully exclusive triple coincidence H(e, e'gammap ) detection. I present a re-calibration of the electromagnetic calorimeter used to detect the high energy photon. This calibration is necessary to account for the effects of pile-up. The results show a 1-sigma disagreement with the double coincidence H(e, e'gamma )p results, I also presents a feasibility study for measurements of neutron GPDs via the 3He ? (e, e'gamma)ppn reaction on a polarized 3He target with JLab at 12 GeV. These measurements offer the prospect of a determination of all four GPDs.
Spin Asymmetry Measurements for Deeply Virtual Compton Scattering on Polarized Protons
NASA Astrophysics Data System (ADS)
Seder, Erin; CLAS Collaboration
2013-10-01
Generalized Parton Distributions (GPDs) have emerged as a universal tool to describe hadrons, particularly nucleons, in terms of their elementary constituents, quarks and gluons. Spin asymmetry measurements in the reaction e --> p --> --> ep γ, such as the proton target spin asymmetry which is directly proportional to the imaginary part of the Deeply Virtual Compton Scattering amplitude, give access to different combinations of GPDs. Combined measurements of proton target spin asymmetry (TSA), electron beam helicity asymmetry (BSA), and electron-proton double spin asymmetry (DSA) at the same kinematic points allows access to GPDs through a semi-model independent extraction of Compton Form Factors (CFFs). Preliminary TSA, BSA, and DSA studies for the reaction e --> p --> --> ep γ and extracted CFFs will be presented from a dedicated experiment at Jefferson Lab using the CEBAF 6 GeV polarized electron beam, a polarized solid state 14 NH3 target, and the CEBAF Large Acceptance Spectrometer (CLAS) equipped with an additional Inner Calorimeter (IC). The accessible kinematic range for these measurements covers 1 < Q2 < 4.5 GeV2, 0.1 < xB < 0.58, and 0.08 < - t < 1.8 GeV2.
The cross section for double Compton scattering
NASA Technical Reports Server (NTRS)
Gould, R. J.
1984-01-01
Employing elementary methods in nonrelativistic quantum electrodynamics, the cross section for gamma sub 0 + e yields e + gamma + gamma is computed for arbitrary energy in the spectrum of the outgoing photons. The final result is given, differential in the energy of one of these photons, for the case where the incident photon is unpolarized and has energy E sub 0 much less than mc-squared, a polarization sum and angular integration being performed for the final-state photons. The cross section has a simple algebraic form resulting from contributions from the sum of squared direct and exchange amplitudes; interference terms from these amplitudes do not contribute to the angular-integrated cross section.
Otto Stern and the double bank shot
NASA Astrophysics Data System (ADS)
Zare, R. N.
1988-06-01
In analogy to a double surface scattering study of Estermann, Frisch and Stern for selecting and detecting the velocity of a beam of particles, it is proposed to use double surface scattering to investigate the collision dynamics of a beam of polarized particles with a known surface. In this proposed experiment, the first surface scattering event prepares a polarized (aligned/oriented) beam of particles, and the second surface scattering event permits the measurement of how the polarized beam interacts with the surface under study.
NASA Astrophysics Data System (ADS)
King, Ben; di Piazza, Antonino; Keitel, Christoph H.
2010-02-01
Double slits provide incoming particles with a choice. Those that survive passage through the slits have chosen from two possible paths, which interfere to distribute them in a wave-like manner. Such wave-particle duality continues to be challenged and investigated in a broad range of disciplines with electrons, neutrons, helium atoms, C60 fullerenes, Bose-Einstein condensates and biological molecules. All variants have hitherto involved material constituents. We present a matterless double-slit scenario in which photons generated from virtual electron-positron pair annihilation in head-on collisions of a probe laser field with two ultra-intense laser beams form a double-slit interference pattern. Such electromagnetic fields are predicted to induce material-like behaviour in vacuum, supporting elastic scattering between photons. Our double-slit scenario presents, on the one hand, a realizable method with which to observe photon-photon scattering and, on the other hand, demonstrates the possibility of both controlling light with light and non-locally investigating features of the quantum vacuum structure.
Bessel-Weighted Asymmetries in Semi Inclusive Deep Inelastic Scattering
D. Boer, L. Gamberg, B.U. Musch, A. Prokudin
2011-10-01
The concept of weighted asymmetries is revisited for semi-inclusive deep inelastic scattering. We consider the cross section in Fourier space, conjugate to the outgoing hadron's transverse momentum, where convolutions of transverse momentum dependent parton distribution functions and fragmentation functions become simple products. Individual asymmetric terms in the cross section can be projected out by means of a generalized set of weights involving Bessel functions. Advantages of employing these Bessel weights are that they suppress (divergent) contributions from high transverse momentum and that soft factors cancel in (Bessel-) weighted asymmetries. Also, the resulting compact expressions immediately connect to previous work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions and to quantities accessible in lattice QCD. Bessel weighted asymmetries are thus model independent observables that augment the description and our understanding of correlations of spin and momentum in nucleon structure.
High energy asymptotics of scattering processes in QCD
Enberg, R.; Golec-Biernat, K.; Munier, S.
2005-10-01
High energy scattering in the QCD parton model was recently shown to be a reaction-diffusion process and, thus, to lie in the universality class of the stochastic Fisher-Kolmogorov-Petrovsky-Piscounov equation. We recall that the latter appears naturally in the context of the parton model. We provide a thorough numerical analysis of the mean-field approximation, given in QCD by the Balitsky-Kovchegov equation. In the framework of a simple stochastic toy model that captures the relevant features of QCD, we discuss and illustrate the universal properties of such stochastic models. We investigate, in particular, the validity of the mean-field approximation and how it is broken by fluctuations. We find that the mean-field approximation is a good approximation in the initial stages of the evolution in rapidity.
The High Energy Asymptotics of Scattering Processes in QCD
Enberg, Rikard; Golec-Biernat, K.; Munier, S.
2005-05-12
High energy scattering in the QCD parton model was recently shown to be a reaction-diffusion process, and thus to lie in the universality class of the stochastic Fisher-Kolmogorov-Petrovsky-Piscounov equation. We recall that the latter appears naturally in the context of the parton model. We provide a thorough numerical analysis of the mean field approximation, given in QCD by the Balitsky-Kovchegov equation. In the framework of a simple stochastic toy model that captures the relevant features of QCD, we discuss and illustrate the universal properties of such stochastic models. We investigate in particular the validity of the mean field approximation and how it is broken by fluctuations. We find that the mean field approximation is a good approximation in the initial stages of the evolution in rapidity.
Nachtmann, O.
2014-11-15
We review ideas on the structure of the QCD vacuum which had served as motivation for the discussion of various non-standard QCD effects in high-energy reactions in articles from 1984 to 1995. These effects include, in particular, transverse-momentum and spin correlations in the Drell–Yan process and soft photon production in hadron–hadron collisions. We discuss the relation of the approach introduced in the above-mentioned articles to the approach, developed later, using transverse-momentum-dependent parton distributions (TDMs). The latter approach is a special case of our more general one which allows for parton entanglement in high-energy reactions. We discuss signatures of parton entanglement in the Drell–Yan reaction. Also for Higgs-boson production in pp collisions via gluon–gluon annihilation effects of entanglement of the two gluons are discussed and are found to be potentially important. These effects can be looked for in the current LHC experiments. In our opinion studying parton-entanglement effects in high-energy reactions is, on the one hand, very worthwhile by itself and, on the other hand, it allows to perform quantitative tests of standard factorisation assumptions. Clearly, the experimental observation of parton-entanglement effects in the Drell–Yan reaction and/or in Higgs-boson production would have a great impact on our understanding how QCD works in high-energy collisions.
Cheltsov, I A
2004-10-31
For a singular double cover of P{sup 3} ramified in a sextic with double line, its birational maps into Fano 3-folds with canonical singularities, elliptic fibrations, and fibrations on surfaces of Kodaira dimension zero are described.
NASA Astrophysics Data System (ADS)
Cheltsov, I. A.
2004-10-01
For a singular double cover of \\mathbb P^3 ramified in a sextic with double line, its birational maps into Fano 3-folds with canonical singularities, elliptic fibrations, and fibrations on surfaces of Kodaira dimension zero are described.
Schuurs, A H B; van Loveren, C
2002-04-01
Double teeth are not really rare, but it is still enigmatic why and how they develop. Based upon the clinical, morphological and anatomical appearance and the number of teeth in mouths with double teeth, the double teeth are labelled as products of 'fusion' and 'clefting', but the criteria to attach such etiological names are lacking. It is assumed that heredity is involved in the development of double teeth. Therefore it is attempted to explain why only one of a homozygotic twin had a double tooth. PMID:11982209
NASA Astrophysics Data System (ADS)
Pasquini, B.; Schweitzer, P.
2014-07-01
At leading twist the transverse momentum dependent parton distributions of the pion consist of two functions, the unpolarized f1,π(x,k⊥2) and the Boer-Mulders function h1,π⊥(x ,k⊥2). We study both functions within a light-front constituent model of the pion, comparing the results with different pion models and the corresponding nucleon distributions from a light-front constituent model. After evolution from the model scale to the relevant experimental scales, the results for the collinear pion valence parton distribution function f1,π(x) are in very good agreement with available parametrizations. Using the light-front constituent model results for the Boer-Mulders functions of the pion and nucleon, we calculate the coefficient ν in the angular distribution of Drell-Yan dileptons produced in pion-nucleus scattering, which is responsible for the violation of the Lam-Tung relation. We find a good agreement with the data, and carefully discuss the range of applicability of our approach.
Double logarithmic asymptotic behavior in quantum chromodynamics
Kirschner, R.
1981-08-01
The double logarithmic contributions to the quark-(anti)quark scattering and annihilation amplitudes are summed to all orders in quantum chromodynamics. The results are a generalization of the calculations of Gorshkov et al. in the case of quantum electrodynamics.
A Higher Order Perturbative Parton Evolution Toolkit (HOPPET)
NASA Astrophysics Data System (ADS)
Salam, G. P.; Rojo, J.
2009-01-01
This document describes a Fortran 95 package for carrying out DGLAP evolution and other common manipulations of parton distribution functions (PDFs). The PDFs are represented on a grid in x-space so as to avoid limitations on the functional form of input distributions. Good speed and accuracy are obtained through the representation of splitting functions in terms of their convolution with a set of piecewise polynomial basis functions, and Runge-Kutta techniques are used for the evolution in Q. Unpolarised evolution is provided to NNLO, including heavy-quark thresholds in the MS¯ scheme, and longitudinally polarised evolution to NLO. The code is structured so as to provide simple access to the objects representing splitting functions and PDFs, making it possible for a user to extend the facilities already provided. A streamlined interface is also available, facilitating use of the evolution part of the code from F77 and C/C++. Program summaryProgram title: HOPPET Catalogue identifier: AEBZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBZ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU Public License No. of lines in distributed program, including test data, etc.: 61 001 No. of bytes in distributed program, including test data, etc.: 270 312 Distribution format: tar.gz Programming language: Fortran 95 Computer: All Operating system: All RAM: ≲10 MB Classification: 11.5 Nature of problem: Solution of the DGLAP evolution equations up to NNLO (NLO) for unpolarised (longitudinally polarised) PDFs, and provision of tools to facilitate manipulation (convolutions, etc.) of PDFs with user-defined coefficient and splitting functions. Solution method: Representation of PDFs on a grid in x, adaptive integration of splitting functions to reduce them to a discretised form, obtaining fast convolutions that are equivalent to integration with an interpolated form of the PDFs; Runge
Abazov, Victor Mukhamedovich; Abbott, Braden Keim; Acharya, Bannanje Sripath; Adams, Mark Raymond; Adams, Todd; Alexeev, Guennadi D.; Alkhazov, Georgiy D.; Alton, Andrew K.; Alverson, George O.; Alves, Gilvan Augusto; Ancu, Lucian Stefan; /Nijmegen U. /Serpukhov, IHEP
2011-01-01
Samples of inclusive {gamma} + 2 jet and {gamma} + 3 jet events collected by the D0 experiment with an integrated luminosity of about 1 fb{sup -1} in p{bar p} collisions at {radical}s = 1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p{sub T}) of the {gamma} + leading jet system (jets are ordered in p{sub T}) and p{sub T} of the other jet for {gamma} + 2 jet, or p{sub T} sum of the two other jets for {gamma} + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the pythia and sherpa Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well described by predictions provided by the pythia MPI models with p{sub T}-ordered showers and by sherpa with the default MPI model. The {gamma} + 2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet p{sub T}.
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.
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.
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.
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.
The heavy quark parton oxymoron: A mini-review of heavy quark production theory in PQCD
Tung, W.-K.
1997-04-20
Conventional perturbative QCD calculations on the production of a heavy quark 'H' consist of two contrasting approaches: the usual QCD parton formalism uses the zero-mass approximation (m{sub H}=0) once above threshold, and treats H just like the other light partons; on the other hand, most recent 'NLO' heavy quark calculations treat m{sub H} as a large parameter and always consider H as a heavy particle, never as a parton, irrespective of the energy scale of the physical process. By their very nature, both these approaches are limited in their regions of applicability. This dichotomy can be resolved in a unified general-mass variable-flavor-number scheme, which retains the m{sub H} dependence at all energies, and which naturally reduces to the two conventional approaches in their respective region of validity. Recent applications to lepto- and hadro-production of heavy quarks are briefly summarized.
Electroweakino pair production at the LHC: NLO SUSY-QCD corrections and parton-shower effects
NASA Astrophysics Data System (ADS)
Baglio, Julien; Jäger, Barbara; Kesenheimer, Matthias
2016-07-01
We present a set of NLO SUSY-QCD calculations for the pair production of neutralinos and charginos at the LHC, and their matching to parton-shower programs in the framework of the POWHEG-BOX program package. The code we have developed provides a SUSY Les Houches Accord interface for setting supersymmetric input parameters. Decays of the neutralinos and charginos and parton-shower effects can be simulated with PYTHIA. To illustrate the capabilities of our program, we present phenomenological results for a representative SUSY parameter point. We find that NLO-QCD corrections increase the production rates for neutralinos and charginos significantly. The impact of parton-shower effects on distributions of the weakinos is small, but non-negligible for jet distributions.
Dynamic color screening in diffractive deep inelastic scattering
NASA Astrophysics Data System (ADS)
Ingelman, Gunnar; Pasechnik, Roman; Werder, Dominik
2016-05-01
We present a novel Monte Carlo implementation of dynamic color screening via multiple exchanges of semisoft gluons as a basic QCD mechanism to understand diffractive electron-proton scattering at the HERA collider. Based on the kinematics of individual events in the standard QCD description of deep inelastic scattering at the parton level, which at low x is dominantly gluon initiated, the probability is evaluated for additional exchanges of softer gluons resulting in an overall color singlet exchange leading to a forward proton and a rapidity gap as the characteristic observables for diffractive scattering. The probability depends on the impact parameter of the soft exchanges and varies with the transverse size of the hard scattering subsystem and is therefore influenced by different QCD effects. We account for matrix elements and parton shower evolution either via conventional DGLAP log Q2 evolution with collinear factorization or CCFM small x evolution with k⊥ factorization and discuss the sensitivity to the gluon density distribution in the proton and the importance of large log x contributions. The overall result is, with only two model parameters which have theoretically motivated values, a satisfactory description of the observed diffractive cross section at HERA obtained in a wide kinematical range.
Coherent radiative parton energy loss beyond the BDMPS-Z limit
NASA Astrophysics Data System (ADS)
Zapp, Korinna Christine; Wiedemann, Urs Achim
2012-06-01
It is widely accepted that a phenomenologically viable theory of jet quenching for heavy ion collisions requires the understanding of medium-induced parton energy loss beyond the limit of eikonal kinematics formulated by Baier-Dokshitzer-Mueller-Peigné-Schiff and Zakharov (BDMPS-Z). Here, we supplement a recently developed exact Monte Carlo implementation of the BDMPS-Z formalism with elementary physical requirements including exact energy-momentum conservation, a refined formulation of jet-medium interactions and a treatment of all parton branchings on the same footing. We document the changes induced by these physical requirements and we describe their kinematic origin.
Studies of Parton Propagation and Hadron Formation in the Space-Time Domain
Brooks, Will; Hakobyan, Hayk
2008-10-13
Over the past decade, new data from HERMES, Jefferson Lab, Fermilab, and RHIC that connect to parton propagation and hadron formation have become available. Semi-inclusive DIS on nuclei, the Drell-Yan reaction, and heavy-ion collisions all bring different kinds of information on parton propagation within a medium, while the most direct information on hadron formation comes from the DIS data. Over the next decade one can hope to begin to understand these data within a unified picture. We briefly survey the most relevant data and the common elements of the physics picture, then highlight the new Jefferson Lab data, and close with a prospective for the future.
nCTEQ15 - Global analysis of nuclear parton distributions with uncertainties
Kusina, A.; Jezo, T.; Clark, D. B.; Keppel, Cynthia; Lyonnet, F.; Morfin, Jorge; Olness, F. I.; Owens, Jeff; Schienbein, I.
2015-09-01
We present the first official release of the nCTEQ nuclear parton distribution functions with errors. The main addition to the previous nCTEQ PDFs is the introduction of PDF uncertainties based on the Hessian method. Another important addition is the inclusion of pion production data from RHIC that give us a handle on constraining the gluon PDF. This contribution summarizes our results from arXiv:1509.00792 and concentrates on the comparison with other groups providing nuclear parton distributions.
Examining the Crossover from the Hadronic to Partonic Phase in QCD
Xu Mingmei; Yu Meiling; Liu Lianshou
2008-03-07
A mechanism, consistent with color confinement, for the transition between perturbative and physical vacua during the gradual crossover from the hadronic to partonic phase is proposed. The essence of this mechanism is the appearance and growing up of a kind of grape-shape perturbative vacuum inside the physical one. A percolation model based on simple dynamics for parton delocalization is constructed to exhibit this mechanism. The crossover from hadronic matter to sQGP (strongly coupled quark-gluon plasma) as well as the transition from sQGP to weakly coupled quark-gluon plasma with increasing temperature is successfully described by using this model.
Pion transverse momentum dependent parton distributions in the Nambu and Jona-Lasinio model
NASA Astrophysics Data System (ADS)
Noguera, Santiago; Scopetta, Sergio
2015-11-01
An explicit evaluation of the two pion transverse momentum dependent parton distributions at leading twist is presented, in the framework of the Nambu-Jona Lasinio model with Pauli-Villars regularization. The transverse momentum dependence of the obtained distributions is generated solely by the dynamics of the model. Using these results, the so called generalized Boer-Mulders shift is studied and compared with recent lattice data. The obtained agreement is very encouraging, in particular because no additional parameter has been introduced. A more conclusive comparison would require a precise knowledge of the QCD evolution of the transverse momentum dependent parton distributions under scrutiny.
NASA Astrophysics Data System (ADS)
Ozvenchuk, V.; Linnyk, O.; Gorenstein, M. I.; Bratkovskaya, E. L.; Cassing, W.
2013-06-01
We study the shear and bulk viscosities of partonic and hadronic matter as functions of temperature T within the parton-hadron-string dynamics (PHSD) off-shell transport approach. Dynamical hadronic and partonic systems in equilibrium are studied by the PHSD simulations in a finite box with periodic boundary conditions. The ratio of the shear viscosity to entropy density η(T)/s(T) from PHSD shows a minimum (with a value of about 0.1) close to the critical temperature Tc, while it approaches the perturbative QCD limit at higher temperatures in line with lattice QCD (lQCD) results. For T
Collins, John; Rogers, Ted
2015-04-01
There is considerable controversy about the size and importance of non-perturbative contributions to the evolution of transverse momentum dependent (TMD) parton distribution functions. Standard fits to relatively high-energy Drell-Yan data give evolution that when taken to lower Q is too rapid to be consistent with recent data in semi-inclusive deeply inelastic scattering. Some authors provide very different forms for TMD evolution, even arguing that non-perturbative contributions at large transverse distance bT are not needed or are irrelevant. Here, we systematically analyze the issues, both perturbative and non-perturbative. We make a motivated proposal for the parameterization of the non-perturbative part of the TMD evolution kernel that could give consistency: with the variety of apparently conflicting data, with theoretical perturbative calculations where they are applicable, and with general theoretical non-perturbative constraints on correlation functions at large distances. We propose and use a scheme- and scale-independent function A(bT) that gives a tool to compare and diagnose different proposals for TMD evolution. We also advocate for phenomenological studies of A(bT) as a probe of TMD evolution. The results are important generally for applications of TMD factorization. In particular, they are important to making predictions for proposed polarized Drell- Yan experiments to measure the Sivers function.
Collins, John; Rogers, Ted
2015-04-01
There is considerable controversy about the size and importance of non-perturbative contributions to the evolution of transverse momentum dependent (TMD) parton distribution functions. Standard fits to relatively high-energy Drell-Yan data give evolution that when taken to lower Q is too rapid to be consistent with recent data in semi-inclusive deeply inelastic scattering. Some authors provide very different forms for TMD evolution, even arguing that non-perturbative contributions at large transverse distance bT are not needed or are irrelevant. Here, we systematically analyze the issues, both perturbative and non-perturbative. We make a motivated proposal for the parameterization of the non-perturbative part ofmore » the TMD evolution kernel that could give consistency: with the variety of apparently conflicting data, with theoretical perturbative calculations where they are applicable, and with general theoretical non-perturbative constraints on correlation functions at large distances. We propose and use a scheme- and scale-independent function A(bT) that gives a tool to compare and diagnose different proposals for TMD evolution. We also advocate for phenomenological studies of A(bT) as a probe of TMD evolution. The results are important generally for applications of TMD factorization. In particular, they are important to making predictions for proposed polarized Drell- Yan experiments to measure the Sivers function.« less
Double photoionization of helium with synchrotron x-rays: Proceedings
Not Available
1994-01-01
This report contains papers on the following topics: Overview and comparison of photoionization with charged particle impact; The ratio of double to single ionization of helium: the relationship of photon and bare charged particle impact ionization; Double photoionization of helium at high energies; Compton scattering of photons from electrons bound in light elements; Electron ionization and the Compton effect in double ionization of helium; Elimination of two atomic electrons by a single energy photon; Double photoionization of helium at intermediate energies; Double Photoionization: Gauge Dependence, Coulomb Explosion; Single and Double Ionization by high energy photon impact; The effect of Compton Scattering on the double to single ionization ratio in helium; and Double ionization of He by photoionization and Compton scattering. These papers have been cataloged separately for the database.
Asaturyan, R.; Ent, R.; Mkrtchyan, H.; Navasardyan, T.; Tadevosyan, V.; Adams, G. S.; Ahmidouch, A.; Angelescu, T.; Arrington, J.; Asaturyan, A.; et al
2012-01-01
A large set of cross sections for semi-inclusive electroproduction of charged pions (π±) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared W2 > 4 GeV2 and range in four-momentum transfer squared 2 < Q2 < 4 (GeV/c)2, and cover a range in the Bjorken scaling variable 0.2 < x < 0.6. The fractional energy of the pions spans a range 0.3 < z < 1, with small transverse momenta with respect to the virtual-photon direction, Pt2 < 0.2 (GeV/c)2. The invariant mass that goes undetected, Mx or W',more » is in the nucleon resonance region, W' < 2 GeV. The new data conclusively show the onset of quark-hadron duality in this process, and the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark → pion production mechanisms. The x, z and Pt2 dependences of several ratios (the ratios of favored-unfavored fragmentation functions, charged pion ratios, deuteron-hydrogen and aluminum-deuteron ratios for π+ and π-) have been studied. The ratios are found to be in good agreement with expectations based upon a high-energy quark-parton model description. We find the azimuthal dependences to be small, as compared to exclusive pion electroproduction, and consistent with theoretical expectations based on tree-level factorization in terms of transverse-momentum-dependent parton distribution and fragmentation functions. In the context of a simple model, the initial transverse momenta of d quarks are found to be slightly smaller than for u quarks, while the transverse momentum width of the favored fragmentation function is about the same as for the unfavored one, and both fragmentation widths are larger than the quark widths.« less
NASA Technical Reports Server (NTRS)
Moghaddam, M.; Saatchi, S.
1996-01-01
Several scattering mechanisms contribute to the total radar backscatter cross section measured by the synthetic aperture radar. These are volume scattering, trunk-ground double-bounce scattering, branch-ground double-bounce scattering, and surface scattering. All of these mechanisms are directly related to the dielectric constant of forest components responsible for that mechanism and their moisture.
Making Sense in the City: Dolly Parton, Early Reading and Educational Policy-Making
ERIC Educational Resources Information Center
Hall, Christine; Jones, Susan
2016-01-01
In this paper, we present a case study of a philanthropic literacy initiative, Dolly Parton's Imagination Library, a book-gifting scheme for under 5s, and consider the impact of the scheme on literacy policy in the English city where it was introduced. We bring four lenses to bear on the case study. First, we analyse the operation of the scheme in…
Evolution of the helicity and transversity Transverse-Momentum-Dependent parton distributions
Prokudin, Alexei; Bacchetta, Alessandro
2013-07-01
We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.
Evolution of the helicity and transversity Transverse-Momentum-Dependent parton distributions
Prokudin, Alexey; Bacchetta, Alessandro
2013-10-01
We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.
Drell-Yan Lepton pair production at NNLO QCD with parton showers
Hoeche, Stefan; Li, Ye; Prestel, Stefan
2015-04-13
We present a simple approach to combine NNLO QCD calculations and parton showers, based on the UNLOPS technique. We apply the method to the computation of Drell-Yan lepton-pair production at the Large Hadron Collider. We comment on possible improvements and intrinsic uncertainties.
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.
J. J. Sakurai Prize for Theoretical Particle Physics Talk: Partons, QCD, and Factorization
NASA Astrophysics Data System (ADS)
Soper, Davison
2009-05-01
Many important cross sections in high-energy collisions are analyzed using factorization properties. I review the nature of factorization, how it arose from the parton model, and current issues in its development. This talk will be coordinated with the one by Collins.
Deeply virtual Compton Scattering cross section measured with CLAS
Guegan, Baptistse
2014-09-01
The Generalized Parton Distributions (GPDs) provide a new description of nucleon structure in terms of its elementary constituents, the quarks and the gluons. Including and extending the information provided by the form factors and the parton distribution functions, they describe the correlation between the transverse position and the longitudinal momentum fraction of the partons in the nucleon. Deeply Virtual Compton Scattering (DVCS), the electroproduction of a real photon on a single quark in the nucleon eN --> e'N'g, is the exclusive process most directly interpretable in terms of GPDs. A dedicated experiment to study DVCS with the CLAS detector at Jefferson Lab has been carried out using a 5.9-GeV polarized electron beam and an unpolarized hydrogen target, allowing us to collect DVCS events in the widest kinematic range ever explored in the valence region : 1.0 < Q2 < 4.6 GeV2, 0.1 < xB < 0.58 and 0.09 < -t < 2.0 GeV2. In this paper, we show preliminary results of unpolarized cross sections and of polarized cross section differences for the DVCS channel.
Mathew-Fenn, R.S.; Das, R.; Harbury, P.A.B.
2009-05-26
DNA is thought to behave as a stiff elastic rod with respect to the ubiquitous mechanical deformations inherent to its biology. To test this model at short DNA lengths, we measured the mean and variance of end-to-end length for a series of DNA double helices in solution, using small-angle x-ray scattering interference between gold nanocrystal labels. In the absence of applied tension, DNA is at least one order of magnitude softer than measured by single-molecule stretching experiments. Further, the data rule out the conventional elastic rod model. The variance in end-to-end length follows a quadratic dependence on the number of base pairs rather than the expected linear dependence, indicating that DNA stretching is cooperative over more than two turns of the DNA double helix. Our observations support the idea of long-range allosteric communication through DNA structure.
Jet-parton inelastic interaction beyond eikonal approximation
NASA Astrophysics Data System (ADS)
Abir, Raktim
2013-02-01
Most of the models of jet quenching generally assumes that a jet always travels in a straight eikonal path, which is indeed true for sufficiently hard jet but may not be a good one for moderate and low momentum jet. In this article an attempt has been made to relax part of this approximation for 2→3 processes and found a (15-20)% suppression in the differential cross section for moderately hard jets because of the noneikonal effects. In particular, for the process qq'→qq'g in the centre of momentum frame the scattering with an angle wider than ±0.52π is literally forbidden unlike the process gg→ggg that allows an angular range ±π. This may have consequence on the suppression of hadronic spectra at low transverse momenta.
NASA Astrophysics Data System (ADS)
Karyan, Gevorg
2015-01-01
HERMES experiment at DESY in Hamburg collected a wealth of semi-inclusive deep-inelastic scattering data using the 27.6 GeV lepton beam and pure gaseous, unpolarised hydrogen and deuterium targets. These data can be used in studies of the transverse-momentum dependent effects and can provide a check of existing models for transverse-momentum dependent parton distribution and fragmentation functions.
Quantum chromodynamics and deep-inelastic scattering
Buras, A.J.
1980-08-01
Moments of deep-inelastic structure functions, parton distributions and parton fragmentation functions are discussed in the context of Quantum Chromodynamics with particular emphasis put on higher order corrections. A brief discussion of higher twist contributions is also given.
Deeply Virtual Compton Scattering at JLab Hall A
Eric Voutier
2007-04-16
The deeply virtual Compton scattering reaction has been investigated in the Hall A of the Jefferson Laboratory by measuring longitudinally polarized (e,e'gamma) cross sections, in the valence quark region, for protons and neutrons. In the proton channel, experimental results strongly support the factorization of the cross section at Q2 as low as 2 GeV2, opening the path to systematic measurements of generalized parton distributions (GPDs). In the neutron case, preliminary data show sensitivity to the angular momentum of quarks.
Höche, Stefan; Schönherr, Marek
2012-11-01
We quantify uncertainties in the Monte Carlo simulation of inclusive and dijet final states, which arise from using the MC@NLO technique for matching next-to-leading order parton-level calculations and parton showers. We analyse a large variety of data from early measurements at the LHC. In regions of phase space where Sudakov logarithms dominate over high-energy effects, we observe that the main uncertainty can be ascribed to the free parameters of the parton shower. In complementary regions, the main uncertainty stems from the considerable freedom in the simulation of underlying events.
Quark-Hadron Duality in Electron Scattering
Wally Melnitchouk; Rolf Ent; Cynthia Keppel
2004-08-01
The duality between partonic and hadronic descriptions of physical phenomena is one of the most remarkable features of strong interaction physics. A classic example of this is in electron-nucleon scattering, in which low-energy cross sections, when averaged over appropriate energy intervals, are found to exhibit the scaling behavior expected from perturbative QCD. We present a comprehensive review of data on structure functions in the resonance region, from which the global and local aspects of duality are quantified, including its flavor, spin and nuclear medium dependence. To interpret the experimental findings, we discuss various theoretical approaches which have been developed to understand the microscopic origins of quark-hadron duality in QCD. Examples from other reactions are used to place duality in a broader context, and future experimental and theoretical challenges are identified.
PACIAE 2.1: An updated issue of the parton and hadron cascade model PACIAE 2.0
NASA Astrophysics Data System (ADS)
Sa, Ben-Hao; Zhou, Dai-Mei; Yan, Yu-Liang; Dong, Bao-Guo; Cai, Xu
2013-05-01
the charged particle transverse sphericity is less than unity [8]. Therefore we randomly placed the generated final state hadrons on the circumference of an ellipse with half major axis of pT(1+δp) and a half minor axis of pT(1-δp) instead of a circle. This change is also introduced in the particle/parton production process of hard scattering, multiple interactions, initial- and final-state parton showers, for the nucleus-nucleus collisions [7]. This change is even introduced in the deexcitation of energetic quark (anti-quark) when the phenomenological coalescence model [6] is selected for hadronization. Of course, a new pT should be recalculated by px and py after this change. Then the transverse momentum distribution of the final state hadron may be modified. However, if the deformation parameter δp is less than unity (a small perturbation) the change in transverse momentum distribution may be weak. From ideal hydrodynamic calculations [11] one knows that the integrated elliptic flow parameter is directly proportional to the initial spatial eccentricity of the nuclear overlap zone. Therefore, if the nuclear overlap zone is assumed to be an ellipse with major axis of b=2RA(1+δr) and minor axis of a=2RA(1-δr) for a symmetry nucleus-nucleus collision with nuclear radius of RA, we may assume δp=Cδr where C is an extra model parameter. C=0 corresponds to the original case of px and py put on the circle randomly. In order to calculate δr we first calculate the reaction plane eccentricity [12] ɛ={σ}/{y2-σx2σy2+σx2} according to the participant nucleons spatial distributions inside the nuclear overlap zone [6] in the PACIAE simulation. In the above equation, σx2=x2¯ -x (the same for σy2) and x (x¯) denotes an average of x2 (x) over particles in a single event. The event average reaction plane eccentricity reads <ɛ>=<{σ}/{y2-σx2σy2+σx2}>. On the other hand, the geometric eccentricity [13] of the ellipse-like nuclear overlap zone is ɛg=√{{b2-a2}/{b2
Photon parton distributions in nuclei and the EMC effect
Frankfurt, Leonid; Strikman, Mark
2010-12-01
Photons as well as quarks and gluons are constituents of the infinite momentum frame (IMF) wave function of an energetic particle. They are mostly equivalent photons whose amplitude follows from the Lorentz transformation of the particle rest frame Coulomb field into the IMF and from the conservation of the electromagnetic current. We evaluate in a model independent way the dominant photon contribution \\propto \\alpha_{em}(Z^2/A^{4/3})\\ln(1/R_{A}m_{N}x) to the nuclear structure functions as well as the term \\propto \\alpha_{em}Z/A. In addition we show that the definition of x consistent with the exact kinematics of eA scattering (with exact sum rules) works in the same direction as the nucleus field of equivalent photons. Combined, these effects account for the bulk of the EMC effect for x\\le 0.5 where Fermi motion effects are small. In particular for these x the hadronic mechanism contribution to the EMC effect does not exceed \\sim 3% for all nuclei. Also the A-dependence of the hadronic mechanism of the EMC effect for x > 0.5 is significantly modified.
Coherence effects in scattering order expansion of light by atomic clouds.
Rouabah, Mohamed-Taha; Samoylova, Marina; Bachelard, Romain; Courteille, Philippe W; Kaiser, Robin; Piovella, Nicola
2014-05-01
We interpret cooperative scattering by a collection of cold atoms as a multiple-scattering process. Starting from microscopic equations describing the response of N atoms to a probe light beam, we represent the total scattered field as an infinite series of multiple-scattering events. As an application of the method, we obtain analytical expressions of the coherent intensity in the double-scattering approximation for Gaussian density profiles. In particular, we quantify the contributions of coherent backward and forward scattering.
NASA Astrophysics Data System (ADS)
Adams, M. R.; Arndotïd, S.; Anthony, P. L.; Baker, M. D.; Bartlett, J.; Bhatti, A. A.; Braun, H. M.; Busza, W.; 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.; Jaffe, D. E.; Jancso, G.; Jansen, D. M.; Kaufman, S.; Kennedy, R. D.; Kirk, T.; Kobrak, H. G.; 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.; 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.
1994-01-01
The average squared transverse energy of jets in deep-inelastic muon-nucleon scattering is measured as a function of the momentum transfer squared (Q2), in the range 3
Energy loss in a partonic transport model including bremsstrahlung processes
Fochler, Oliver; Greiner, Carsten; Xu Zhe
2010-08-15
A detailed investigation of the energy loss of gluons that traverse a thermal gluonic medium simulated within the perturbative QCD-based transport model BAMPS (a Boltzmann approach to multiparton scatterings) is presented in the first part of this work. For simplicity the medium response is neglected in these calculations. The energy loss from purely elastic interactions is compared with the case where radiative processes are consistently included based on the matrix element by Gunion and Bertsch. From this comparison, gluon multiplication processes gg{yields}ggg are found to be the dominant source of energy loss within the approach employed here. The consequences for the quenching of gluons with high transverse momentum in fully dynamic simulations of Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC) energy of {radical}(s)=200A GeV are discussed in the second major part of this work. The results for central collisions as discussed in a previous publication are revisited, and first results on the nuclear modification factor R{sub AA} for noncentral Au+Au collisions are presented. They show a decreased quenching compared to central collisions while retaining the same shape. The investigation of the elliptic flow v{sub 2} is extended up to nonthermal transverse momenta of 10 GeV, exhibiting a maximum v{sub 2} at roughly 4 to 5 GeV and a subsequent decrease. Finally the sensitivity of the aforementioned results on the specific implementation of the effective modeling of the Landau-Pomeranchuk-Migdal (LPM) effect via a formation-time-based cutoff is explored.
COLLINEAR SPLITTING, PARTON EVOLUTION AND THE STRANGE-QUARK ASYMMETRY OF THE NUCLEON IN NNLO QCD.
RODRIGO,G.CATANI,S.DE FLORIAN, D.VOGELSANG,W.
2004-04-25
We consider the collinear limit of QCD amplitudes at one-loop order, and their factorization properties directly in color space. These results apply to the multiple collinear limit of an arbitrary number of QCD partons, and are a basic ingredient in many higher-order computations. In particular, we discuss the triple collinear limit and its relation to flavor asymmetries in the QCD evolution of parton densities at three loops. As a phenomenological consequence of this new effect, and of the fact that the nucleon has non-vanishing quark valence densities, we study the perturbative generation of a strange-antistrange asymmetry s(x)-{bar s}(x) in the nucleon's sea.
New parton distributions from large-x and low-Q^{2} data
Alberto Accardi; Christy, M. Eric; Keppel, Cynthia E.; Melnitchouk, Wally; Monaghan, Peter A.; Morfin, Jorge G.; Owens, Joseph F.
2010-02-11
We report results of a new global next-to-leading order fit of parton distribution functions in which cuts on W and Q are relaxed, thereby including more data at high values of x. Effects of target mass corrections (TMCs), higher twist contributions, and nuclear corrections for deuterium data are significant in the large-x region. The leading twist parton distributions are found to be stable to TMC model variations as long as higher twist contributions are also included. Furthermore, the behavior of the d quark as x → 1 is particularly sensitive to the deuterium corrections, and using realistic nuclear smearing models the d-quark distribution at large x is found to be softer than in previous fits performed with more restrictive cuts.
New parton distributions from large-x and low-Q2 data
Alberto Accardi; Christy, M. Eric; Keppel, Cynthia E.; Melnitchouk, Wally; Monaghan, Peter A.; Morfin, Jorge G.; Owens, Joseph F.
2010-02-11
We report results of a new global next-to-leading order fit of parton distribution functions in which cuts on W and Q are relaxed, thereby including more data at high values of x. Effects of target mass corrections (TMCs), higher twist contributions, and nuclear corrections for deuterium data are significant in the large-x region. The leading twist parton distributions are found to be stable to TMC model variations as long as higher twist contributions are also included. Furthermore, the behavior of the d quark as x → 1 is particularly sensitive to the deuterium corrections, and using realistic nuclear smearing modelsmore » the d-quark distribution at large x is found to be softer than in previous fits performed with more restrictive cuts.« less
Off-shell single-top production at NLO matched to parton showers
NASA Astrophysics Data System (ADS)
Frederix, R.; Frixione, S.; Papanastasiou, A. S.; Prestel, S.; Torrielli, P.
2016-06-01
We study the hadroproduction of a W b pair in association with a light jet, focusing on the dominant t-channel contribution and including exactly at the matrix-element level all non-resonant and off-shell effects induced by the finite top-quark width. Our simulations are accurate to the next-to-leading order in QCD, and are matched to the Herwig6 and Pythia8 parton showers through the MC@NLO method. We present phenomenological results relevant to the 8 TeV LHC, and carry out a thorough comparison to the case of on-shell t-channel single-top production. We formulate our approach so that it can be applied to the general case of matrix elements that feature coloured intermediate resonances and are matched to parton showers.
Off-shell single-top production at NLO matched to parton showers
Frederix, R.; Frixione, S.; Papanastasiou, A. S.; Prestel, S.; Torrielli, P.
2016-06-06
We study the hadroproduction of a W b pair in association with a light jet, focusing on the dominant t -channel contribution and including exactly at the matrix-element level all non-resonant and off-shell effects induced by the finite top-quark width. Our simulations are accurate to the next-to-leading order in QCD, and are matched to the Herwig6 and Pythia8 parton showers through the MC@NLO method. We present phenomenological results relevant to the 8 TeV LHC, and carry out a thorough comparison to the case of on-shell t -channel single-top production. Furthermore, we formulate our approach so that it can be appliedmore » to the general case of matrix elements that feature coloured intermediate resonances and are matched to parton showers.« less
Alwall, J.; Hoche, S.; Krauss, F.; Lavesson, N.; Lonnblad, L.; Maltoni, F.; Mangano, M.L.; Moretti, M.; Papadopoulos, C.G.; Piccinini, F.; Schumann, S.; Treccani, M.; Winter, J.; Worek, M.; /SLAC /Durham U., IPPP /Lund U. /Louvain U. /CERN /Ferrara U. /INFN, Ferrara /Athens U. /INFN, Pavia /Dresden, Tech. U. /Karlsruhe U., TP /Silesia U.
2007-06-27
We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all cases, there are important differences.
Nuclear Effects in Neutrino-Nucleus Interactions and the MINERvA Neutrino Nucleus Scattering Program
NASA Astrophysics Data System (ADS)
Morfín, Jorge G.
2011-09-01
Nuclear effects of charged current deep inelastic neutrino-iron scattering have been studied in the frame-work of a χ2 analysis of parton distribution functions (PDFs)1. A set of iron PDFs have been extracted which are then used to compute xBj-dependent and Q2-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. Upon comparing our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for l±-iron scattering we find that, except for very high xBj, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering. The MINERvA neutrino-nucleus scattering experiment at Fermilab, will systematically study neutrino nuclear effects off of He, C, Fe and Pb for a more thorough A-dependent study of nuclear PDFs and these correction factors.
One-Loop Multi-Parton Amplitudes with a Vector Boson for the LHC
Berger, C.F.; Bern, Z.; Dixon, L.J.; Cordero, F.Febres; Forde, D.; Ita, H.; Kosower, D.A.; Maitre, D.; /SLAC
2008-08-11
In this talk, we present the first, numerically stable, results for the one-loop amplitudes needed for computing W; Z + 3 jet cross sections at the LHC to next-to-leading order in the QCD coupling. We implemented these processes in BlackHat, an automated program based on on-shell methods. These methods scale very well with increasing numbers of external partons, and are applicable to a wide variety of problems of phenomenological interest at the LHC.
Engel, R.; Bopp, F.W.; Pertermann, D.; Ranft, J. )
1992-12-01
In the framework of a two-component dual parton model we perform a fit to {ital p{bar p}} total, elastic, inelastic, and single-diffractive cross-section data at collider energies. The fit including diffractive data gives better results using the supercritical soft Pomeron instead of the critical one. Because of the different structure function parametrizations the predictions of cross sections at supercollider energies are subject to large uncertainties.
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.
Multi-parton loop amplitudes and next-to-leading order jet cross-sections
Bern, Z.; Dixon, L.; Kosower, D.A.; Signer, A.
1998-02-01
The authors review recent developments in the calculation of QCD loop amplitudes with several external legs, and their application to next-to-leading order jet production cross-sections. When a number of calculational tools are combined together--helicity, color and supersymmetry decompositions, plus unitarity and factorization properties--it becomes possible to compute multi-parton one-loop QCD amplitudes without ever evaluating analytically standard one-loop Feynman diagrams. One-loop helicity amplitudes are now available for processes with five external partons (ggggg, q{anti q}ggg and q{anti q}q {anti q}{prime} g), and for an intermediate vector boson V {equivalent_to} {gamma}{sup *}, Z, W plus four external partons (V q{anti q} and V q{anti q}q{prime}{anti q}{prime}). Using these amplitudes, numerical programs have been constructed for the next-to-leading order corrections to the processes p{anti p} {yields} 3 jets (ignoring quark contributions so far) and e{sup +}e{sup -} {yields} 4 jets.
Color Effects for Transverse Momentum Dependent Parton Distribution Functions in Hadronic Processes
NASA Astrophysics Data System (ADS)
Buffing, M. G. A.; Mulders, P. J.
2015-09-01
In the Drell-Yan process (DY) a quark and an antiquark, coming from two different protons, produce a colorless virtual photon. In the proton description, we include transverse momentum dependent parton distribution functions (TMD PDFs), which go beyond the ordinary collinear PDFs. As such, we become sensitive to polarization modes of the partons and protons that one cannot probe without accounting for transverse momenta of partons, in particular when one looks at azimuthal asymmetries. Matrix elements used in the description of hadronic processes, such as DY, require the inclusion of gauge links, coming from gluon contributions in the process, which are path-ordered exponentials tracing the color flow. In processes with two hadrons in the initial state the color flow between different parts of the process causes entanglement. We show that in the process of color disentangling each gauge link remains sensitive to this color flow. After disentanglement, we find that particular combinations of TMDs require a different numerical color factor than one might have expected. Such color factors will even play a role for azimuthal asymmetries in the simplest hadronic processes such as the DY process.
Jet production in muon-proton and muon-nuclei scattering at Fermilab-E665
Salgado, C.W.; E665 Collaboration
1993-08-01
Measurements of multi-jet production rates from Muon-Proton Muon- Nuclei scattering at Fermilab-E665 are presented. Jet rates are defined by the JADE clustering algorithm. Rates in Muon-Proton deep-inelastic scattering are compared to perturbative Quantum Chromodynamics (PQCD) and Monte Carlo model predictions. We observe hadronic (2+1)-jet rates which are a factor of two higher than PQCD predictions at the partonic level. Preliminary results from jet production on heavy targets, in the shadowing region, show a suppression of the jet rates as compared to deuterium. The two- forward jet sample present higher suppression as compared to the one-forward jet sample.
Polarized lepton deep-inelastic scattering from few-nucleon targets
NASA Astrophysics Data System (ADS)
Woloshyn, R. M.
1989-06-01
The structure functions for deep-inelastic scattering of polarized leptons from polarized few-nucleon targets (nucleon, 2H, 3He) are calculated in a parton model. Spin-dependent quark distributions constructed along the lines of Carlitz-Kaur model are used. The asymmetry for scattering from polarized 3He is small in magnitude and dominated by the neutron contribution. For 2H, cancellation between proton and neutron contributions leads to a very small asymmetry below x≈0.1. Otherwise the asymmetry is large but dominated by the proton.
Elliptic and triangular flow in p-Pb and peripheral Pb-Pb collisions from parton scatterings
Bzdak, Adam; Ma, Guo-Liang
2014-12-15
Using a multiphase transport model (AMPT) we calculate the elliptic v₂ and triangular v₃ Fourier coefficients of the two-particle azimuthal correlation function in proton-nucleus (p-Pb) and peripheral nucleus-nucleus (Pb-Pb) collisions. Our results for v₃ are in a good agreement with the CMS data collected at the Large Hadron Collider. The v₂ coefficient is very well described in p-Pb collisions and is underestimated for higher transverse momenta in Pb-Pb interactions. The characteristic mass ordering of v₂ in p-Pb is reproduced, whereas for v₃, this effect is not observed. We further predict the pseudorapidity dependence of v₂ and v₃ in p-Pb andmore » observe that both are increasing when going from a proton side to a Pb-nucleus side. Predictions for the higher-order Fourier coefficients, v₄ and v₅, in p-Pb are also presented.« less
Elliptic and triangular flow in p-Pb and peripheral Pb-Pb collisions from parton scatterings
Bzdak, Adam; Ma, Guo-Liang
2014-12-15
Using a multiphase transport model (AMPT) we calculate the elliptic v₂ and triangular v₃ Fourier coefficients of the two-particle azimuthal correlation function in proton-nucleus (p-Pb) and peripheral nucleus-nucleus (Pb-Pb) collisions. Our results for v₃ are in a good agreement with the CMS data collected at the Large Hadron Collider. The v₂ coefficient is very well described in p-Pb collisions and is underestimated for higher transverse momenta in Pb-Pb interactions. The characteristic mass ordering of v₂ in p-Pb is reproduced, whereas for v₃, this effect is not observed. We further predict the pseudorapidity dependence of v₂ and v₃ in p-Pb and observe that both are increasing when going from a proton side to a Pb-nucleus side. Predictions for the higher-order Fourier coefficients, v₄ and v₅, in p-Pb are also presented.
Elliptic and triangular flow in p-Pb and peripheral Pb-Pb collisions from Parton scatterings.
Bzdak, Adam; Ma, Guo-Liang
2014-12-19
Using a multiphase transport model (AMPT) we calculate the elliptic v_{2} and triangular v_{3} Fourier coefficients of the two-particle azimuthal correlation function in proton-nucleus (p-Pb) and peripheral nucleus-nucleus (Pb-Pb) collisions. Our results for v_{3} are in a good agreement with the CMS data collected at the Large Hadron Collider. The v_{2} coefficient is very well described in p-Pb collisions and is underestimated for higher transverse momenta in Pb-Pb interactions. The characteristic mass ordering of v_{2} in p-Pb is reproduced, whereas for v_{3}, this effect is not observed. We further predict the pseudorapidity dependence of v_{2} and v_{3} in p-Pb and observe that both are increasing when going from a proton side to a Pb-nucleus side. Predictions for the higher-order Fourier coefficients, v_{4} and v_{5}, in p-Pb are also presented.
Self Organizing Maps for use in Deep Inelastic Scattering
NASA Astrophysics Data System (ADS)
Askanazi, Evan
2015-04-01
Self Organizing Maps are a type of artificial neural network that has been proven to be particularly useful in solving complex problems in neural biology, engineering, robotics and physics. We are attempting to use the Self Organizing Map to solve problems and probe phenomenological patterns in subatomic physics, specifically in Deep Inelastic Scattering (DIS). In DIS there is a cross section in electron hadron scattering that is dependent on the momentum fraction x of the partons in the hadron and the momentum transfer of the virtual photon exchanged. There is a soft cross part of this cross section that currently can only be found through experimentation; this soft part is comprised of Structure Functions which in turn are comprised of the Parton Distribution Functions (PDFs). We aim to use the Self Organizing Process, or SOP, to take theoretical models of these PDFs and fit it to the previous, known data. The SOP will also be used to probe the behavior of the PDFs in particular at large x values, in order to observe how they congregate. The ability of the SOPto take multidimensional data and convert it into two dimensional output is anticipated to be particularly useful in achieving this aim.
NASA Astrophysics Data System (ADS)
Geiger, Klaus
1997-08-01
VNI is a general-purpose Monte Carlo event generator, which includes the simulation of lepton-lepton, lepton-hadron, lepton-nucleus, hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions. On the basis of renormalization-group improved parton description and quantum-kinetic theory, it uses the real-time evolution of parton cascades in conjunction with a self-consistent hadronization scheme that is governed by the dynamics itself. The causal evolution from a specific initial state (determined by the colliding beam particles) is followed by the time development of the phase-space densities of partons, pre-hadronic parton clusters, and final-state hadrons, in position space, momentum space and color space. The parton evolution is described in terms of a space-time generalization of the familiar momentum-space description of multiple (semi) hard interactions in QCD, involving 2 → 2 parton collisions, 2 → 1 parton fusion processes, and 1 → 2 radiation processes. The formation of color-singlet pre-hadronic clusters and their decays into hadrons, on the other hand, is treated by using a spatial criterion motivated by confinement and a non-perturbative model for hadronization. This article gives a brief review of the physics underlying VNI, which is followed by a detailed description of the program itself. The latter program description emphasizes easy-to-use pragmatism and explains how to use the program (including a simple example), annotates input and control parameters, and discusses output data provided by it.
NASA Technical Reports Server (NTRS)
Williams, Alton C. (Editor); Moorehead, Tauna W. (Editor)
1987-01-01
Topics addressed include: laboratory double layers; ion-acoustic double layers; pumping potential wells; ion phase-space vortices; weak double layers; electric fields and double layers in plasmas; auroral double layers; double layer formation in a plasma; beamed emission from gamma-ray burst source; double layers and extragalactic jets; and electric potential between plasma sheet clouds.
Infrared singularities of scattering amplitudes in perturbative QCD
Becher, Thomas; Neubert, Matthias
2013-11-01
An exact formula is derived for the infrared singularities of dimensionally regularized scattering amplitudes in massless QCD with an arbitrary number of legs, valid at any number of loops. It is based on the conjecture that the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory contains only a single non-trivial color structure, whose coefficient is the cusp anomalous dimension of Wilson loops with light-like segments. Its color-diagonal part is characterized by two anomalous dimensions, which are extracted to three-loop order from known perturbative results for the quark and gluon form factors. This allows us to predict the three-loop coefficients of all 1/epsilon^k poles for an arbitrary n-parton scattering amplitudes, generalizing existing two-loop results.
Theory of high-energy electron scattering by composite targets
Coester, F.
1988-01-01
The emphasis of these expository lectures is on the role of relativistic invariance and the unity of the theory for medium and high energies. Sec. 2 introduces the kinematic notation and provides an elementary derivation of the general cross section. The relevant properties of the Poincare group and the transformation properties of current operators and target states are described in Sec 3. In Sec. 4 representations of target states with kinematic light-front symmetry are briefly discussed. The focus is on two applications. An impulse approximation of inclusive electron nucleus scattering at both medium and high energies. A parton model of the proton applied to deep inelastic scattering of polarized electrons by polarized protons. 19 refs.
Halo phenomena modified by multiple scattering.
NASA Astrophysics Data System (ADS)
Takano, Y.; Kuo-Nan, Liou
1990-05-01
Halo phenomena produced by horizontally oriented plate and column ice crystals are computed. Owing to the effect of multiple scattering, a number of optical features, in addition to the well-known halos and arcs caused by single scattering, can be produced in the sky. These include the parhelia, the anthelion, the uniform and white parhelic circle, and the uniform and white circumzenithal circle in the case of horizontally oriented plates. The anthelion is a result of double scattering that involves horizontally oriented columns that produce the Parry arc. The optical phenomena identified in the present study are compared with those of previous research and discussed.
Asaturyan, R.; Ent, R.; Mkrtchyan, H.; Navasardyan, T.; Tadevosyan, V.; Adams, G. S.; Ahmidouch, A.; Angelescu, T.; Arrington, J.; Asaturyan, A.; Baker, O. K.; Benmouna, N.; Bertoncini, C.; Blok, H. P.; Boeglin, W. U.; Bosted, P. E.; Breuer, H.; Christy, M. E.; Connell, S. H.; Cui, Y.; Dalton, M. M.; Danagoulian, S.; Day, D.; Dunne, J. A.; Dutta, D.; El Khayari, N.; Fenker, H. C.; Frolov, V. V.; Gan, L.; Gaskell, D.; Hafidi, K.; Hinton, W.; Holt, R. J.; Horn, T.; Huber, G. M.; Hungerford, E.; Jiang, X.; Jones, M.; Joo, K.; Kalantarians, N.; Kelly, J. J.; Keppel, C. E.; Kubarovsky, V.; Li, Y.; Liang, Y.; Mack, D.; Malace, S. P.; Markowitz, P.; McGrath, E.; McKee, P.; Meekins, D. G.; Mkrtchyan, A.; Moziak, B.; Niculescu, G.; Niculescu, I.; Opper, A. K.; Ostapenko, T.; Reimer, P. E.; Reinhold, J.; Roche, J.; Rock, S. E.; Schulte, E.; Segbefia, E.; Smith, C.; Smith, G. R.; Stoler, P.; Tang, L.; Ungaro, M.; Uzzle, A.; Vidakovic, S.; Villano, A.; Vulcan, W. F.; Wang, M.; Warren, G.; Wesselmann, F. R.; Wojtsekhowski, B.; Wood, S. A.; Xu, C.; Yuan, L.; Zheng, X.
2012-01-01
A large set of cross sections for semi-inclusive electroproduction of charged pions (π^{±}) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared W^{2} > 4 GeV^{2} and range in four-momentum transfer squared 2 < Q^{2} < 4 (GeV/c)^{2}, and cover a range in the Bjorken scaling variable 0.2 < x < 0.6. The fractional energy of the pions spans a range 0.3 < z < 1, with small transverse momenta with respect to the virtual-photon direction, P_{t}^{2} < 0.2 (GeV/c)^{2}. The invariant mass that goes undetected, M_{x} or W', is in the nucleon resonance region, W' < 2 GeV. The new data conclusively show the onset of quark-hadron duality in this process, and the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark → pion production mechanisms. The x, z and P_{t}^{2} dependences of several ratios (the ratios of favored-unfavored fragmentation functions, charged pion ratios, deuteron-hydrogen and aluminum-deuteron ratios for π^{+} and π^{-}) have been studied. The ratios are found to be in good agreement with expectations based upon a high-energy quark-parton model description. We find the azimuthal dependences to be small, as compared to exclusive pion electroproduction, and consistent with theoretical expectations based on tree-level factorization in terms of transverse-momentum-dependent parton distribution and fragmentation functions. In the context of a simple model, the initial transverse momenta of d quarks are found to be slightly smaller than for u quarks, while the transverse momentum width of the favored fragmentation function is about the same as for the unfavored one, and both fragmentation widths are larger than the quark widths.
Exponential Disks from Stellar Scattering. III. Stochastic Models
NASA Astrophysics Data System (ADS)
Elmegreen, Bruce G.; Struck, Curtis
2016-10-01
Stellar scattering off irregularities in a galaxy disk has been shown to make an exponential radial profile, but no fundamental reason for this has been suggested. Here, we show that exponentials are mathematically expected from random scattering in a disk when there is a slight inward bias in the scattering probability. Such a bias was present in our previous scattering experiments that formed exponential profiles. Double exponentials can arise when the bias varies with radius. This is a fundamental property of scattering and may explain why piece-wise exponential profiles are ubiquitous in galaxies, even after minor mergers and other disruptive events.
NASA Astrophysics Data System (ADS)
Fanelli, C.; Cisbani, E.; Hamilton, D. J.; Salmé, G.; Wojtsekhowski, B.; Ahmidouch, A.; Annand, J. R. M.; Baghdasaryan, H.; Beaufait, J.; Bosted, P.; Brash, E. J.; Butuceanu, C.; Carter, P.; Christy, E.; Chudakov, E.; Danagoulian, S.; Day, D.; Degtyarenko, P.; Ent, R.; Fenker, H.; Fowler, M.; Frlez, E.; Gaskell, D.; Gilman, R.; Horn, T.; Huber, G. M.; de Jager, C. W.; Jensen, E.; Jones, M. K.; Kelleher, A.; Keppel, C.; Khandaker, M.; Kohl, M.; Kumbartzki, G.; Lassiter, S.; Li, Y.; Lindgren, R.; Lovelace, H.; Luo, W.; Mack, D.; Mamyan, V.; Margaziotis, D. J.; Markowitz, P.; Maxwell, J.; Mbianda, G.; Meekins, D.; Meziane, M.; Miller, J.; Mkrtchyan, A.; Mkrtchyan, H.; Mulholland, J.; Nelyubin, V.; Pentchev, L.; Perdrisat, C. F.; Piasetzky, E.; Prok, Y.; Puckett, A. J. R.; Punjabi, V.; Shabestari, M.; Shahinyan, A.; Slifer, K.; Smith, G.; Solvignon, P.; Subedi, R.; Wesselmann, F. R.; Wood, S.; Ye, Z.; Zheng, X.
2015-10-01
Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The wide-angle Compton scattering polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of θcmp=70 ° . The longitudinal transfer KLL, measured to be 0.645 ±0.059 ±0.048 , where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is ˜3 times larger than predicted by the generalized-parton-distribution-based calculations, which indicates a significant unknown contribution to the scattering amplitude.
Aortic arch anomaly; Double arch; Congenital heart defect - double aortic arch; Birth defect heart - double aortic arch ... aorta is a single arch that leaves the heart and moves leftward. In double aortic arch, some ...
Elastic proton-proton scattering at RHIC
Yip, K.
2011-09-03
Here we describe elastic proton+proton (p+p) scattering measurements at RHIC in p+p collisions with a special optics run of {beta}* {approx} 21 m at STAR, at the center-of-mass energy {radical}s = 200 GeV during the last week of the RHIC 2009 run. We present preliminary results of single and double spin asymmetries.
Boughezal, R.; Gehrmann-De Ridder, A.; Ritzmann, M.
2011-02-01
The antenna subtraction formalism allows to calculate QCD corrections to jet observables. Within this formalism, the subtraction terms are constructed using antenna functions describing all unresolved radiation between a pair of hard radiator partons. In this paper, we focus on the subtraction terms for double real radiation contributions to jet observables in hadron-hadron collisions evaluated at NNLO. An essential ingredient to these subtraction terms are the four-parton antenna functions with both radiators in the initial state. We outline the construction of the double real subtraction terms, classify all relevant antenna functions and describe their integration over the relevant antenna phase space. For the initial-initial antenna functions with two quark flavours, we derive the phase space master integrals and obtain the integrated antennae.
Generalized parton distributions from domain wall valence quarks and staggered sea quarks
Renner, Dru; Bratt, Jonathan; Edwards, Robert; Engelhardt, Michael; Fleming, George; Haegler, Philipp; Musch, Bernhard; Negele, John; Orginos, Konstantinos; Pochinsky, Andrew; Richards, David; Schroers, Wolfram
2007-11-01
Moments of the generalized parton distributions of the nucleon, calculated with a mixed action of domain wall valence quarks and asqtad staggered sea quarks, are presented for pion masses extending down to 359 MeV. Results for the moments of the unpolarized, helicity, and transversity distributions are given and compared to the available experimental measurements. Additionally, a selection of the generalized form factors are shown and the implications for the spin decomposition and transverse structure of the nucleon are discussed. Particular emphasis is placed on understanding systematic errors in the lattice calculation and exploring a variety of chiral extrapolations.
Transverse-Momentum Parton Densities:. Gauge Links, Divergences and Soft Factor
NASA Astrophysics Data System (ADS)
Cherednikov, I. O.; Stefanis, N. G.
2011-02-01
We discuss the state-of-the-art of the theory of transverse-momentum dependent parton densities (TMDs), paying special attention to their renormalization properties, the structure of the gauge links in the operator definition, and the role of the soft factor in the factorization formula within the TMD approach to the semi-inclusive processes. We argue that the use of the lightcone axial gauge offers certain advantages for a consistent definition of TMDs as compared to the off-the-light-cone gauges, or covariant gauges with off-the-lightcone gauge links.
Multiple Parton Interactions in ppbar Collisions in D0 Experiment at the Tevatron Collider
Golovanov, Georgy
2016-01-01
The thesis is devoted to the study of processes with multiple parton interactions (MPI) in a ppbar collision collected by D0 detector at the Fermilab Tevatron collider at sqrt(s) = 1.96 TeV. The study includes measurements of MPI event fraction and effective cross section, a process-independent parameter related to the effective interaction region inside the nucleon. The measurements are done using events with a photon and three hadronic jets in the final state. The measured effective cross section is used to estimate background from MPI for WH production at the Tevatron energy
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.
Anomalous coupling, top-mass and parton-shower effects in W + W - production
NASA Astrophysics Data System (ADS)
Bellm, J.; Gieseke, S.; Greiner, N.; Heinrich, G.; Plätzer, S.; Reuschle, C.; von Soden-Fraunhofen, J. F.
2016-05-01
We calculate the process ppto {W}+{W}-to {e}+{ν}_e{μ}-{overline{ν}}_{μ } at NLO QCD, including also effective field theory (EFT) operators mediating the ggW + W - interaction, which first occur at dimension eight. We further combine the NLO and EFT matrix elements produced by G oS am with the H erwig7/M atchbox framework, which offers the possibility to study the impact of a parton shower. We assess the effects of the anomalous couplings by comparing them to top-mass effects as well as uncertainties related to variations of the renormalisation, factorisation and hard shower scales.
Matching next-to-leading order predictions to parton showers in supersymmetric QCD
Degrande, Céline; Fuks, Benjamin; Hirschi, Valentin; Proudom, Josselin; Shao, Hua-Sheng
2016-02-03
We present a fully automated framework based on the FeynRules and MadGraph5_aMC@NLO programs that allows for accurate simulations of supersymmetric QCD processes at the LHC. Starting directly from a model Lagrangian that features squark and gluino interactions, event generation is achieved at the next-to-leading order in QCD, matching short-distance events to parton showers and including the subsequent decay of the produced supersymmetric particles. As an application, we study the impact of higher-order corrections in gluino pair-production in a simplified benchmark scenario inspired by current gluino LHC searches.
Hadronic and partonic sources of direct photons in relativistic heavy-ion collisions
NASA Astrophysics Data System (ADS)
Linnyk, O.; Konchakovski, V.; Steinert, T.; Cassing, W.; Bratkovskaya, E. L.
2015-11-01
The direct photon spectra and flow (v2, v3) in heavy-ion collisions at CERN Super Proton Synchrotron, BNL Relativistic Heavy Ion Collider, and CERN Large Hadron Collider energies are investigated within a relativistic transport approach incorporating both hadronic and partonic phases, the parton-hadron-string dynamics (PHSD). In the present work, four extensions are introduced compared to our previous calculations: (i) going beyond the soft-photon approximation (SPA) in the calculation of the bremsstrahlung processes meson +meson →meson +meson +γ , (ii) quantifying the suppression owing to the Landau-Pomeranchuk-Migdal (LPM) coherence effect, (iii) adding the additional channels V +N →N +γ and Δ →N +γ , and (iv) providing PHSD calculations for Pb +Pb collisions at √{sN N}=2.76 TeV . The first issue extends the applicability of the bremsstrahlung calculations to higher photon energies to understand the relevant sources in the region pT=0.5 -1.5 GeV , while the LPM correction turns out to be important for pT<0.4 GeV in the partonic phase. The results suggest that a large elliptic flow v2 of the direct photons signals a significant contribution of photons produced in interactions of secondary mesons and baryons in the late (hadronic) stage of the heavy-ion collision. To further differentiate the origin of the direct photon azimuthal asymmetry (late hadron interactions vs electromagnetic fields in the initial stage), we provide predictions for the photon spectra, elliptic flow, and triangular flow v3(pT) of direct photons at different centralities to be tested by the experimental measurements at the LHC energies. Additionally, we illustrate the magnitude of the photon production in the partonic and hadronic phases as functions of time and local energy density. Finally, the "cocktail" method for an estimation of the background photon elliptic flow, which is widely used in the experimental works, is supported by the calculations within the PHSD transport
Matching next-to-leading order predictions to parton showers in supersymmetric QCD
NASA Astrophysics Data System (ADS)
Degrande, Céline; Fuks, Benjamin; Hirschi, Valentin; Proudom, Josselin; Shao, Hua-Sheng
2016-04-01
We present a fully automated framework based on the FEYNRULES and MADGRAPH5_aMC@NLO programs that allows for accurate simulations of supersymmetric QCD processes at the LHC. Starting directly from a model Lagrangian that features squark and gluino interactions, event generation is achieved at the next-to-leading order in QCD, matching short-distance events to parton showers and including the subsequent decay of the produced supersymmetric particles. As an application, we study the impact of higher-order corrections in gluino pair-production in a simplified benchmark scenario inspired by current gluino LHC searches.
NASA Astrophysics Data System (ADS)
Maltoni, Fabio; Mawatari, Kentarou; Zaro, Marco
2014-01-01
Vector-boson fusion and associated production at the LHC can provide key information on the strength and structure of the Higgs couplings to the Standard Model particles. Using an effective field theory approach, we study the effects of next-to-leading order (NLO) QCD corrections matched to a parton shower on selected observables for various spin-0 hypotheses. We find that inclusion of NLO corrections is needed to reduce the theoretical uncertainties on the total rates as well as to reliably predict the shapes of the distributions. Our results are obtained in a fully automatic way via FeynRules and MadGraph5_aMC@NLO.
Hadron production in deuteron-gold collisions and nuclear parton distributions
Adeluyi, Adeola; Fai, George
2007-11-15
We calculate nuclear modification factors R{sub dAu}, central-to-peripheral ratios, R{sub CP}, and pseudorapidity asymmetries Y{sub Asym} in deuteron-gold collisions at {radical}(s)=200 GeV in the framework of leading-order (LO) perturbative quantum chromodynamics. We use the Eskola-Kolhinen-Salgado (EKS), the Frankfurt-Guzey-Strikman (FGS), and the Hirai-Kumano-Nagai (HKN) nuclear parton distribution functions and the Albino-Kramer-Kniehl (AKK) fragmentation functions in our calculations. Results are compared to experimental data from the BRAHMS and STAR collaborations.
APFEL Web: a web-based application for the graphical visualization of parton distribution functions
NASA Astrophysics Data System (ADS)
Carrazza, Stefano; Ferrara, Alfio; Palazzo, Daniele; Rojo, Juan
2015-05-01
We present APFEL Web, a Web-based application designed to provide a flexible user-friendly tool for the graphical visualization of parton distribution functions. In this note we describe the technical design of the APFEL Web application, motivating the choices and the framework used for the development of this project. We document the basic usage of APFEL Web and show how it can be used to provide useful input for a variety of collider phenomenological studies. Finally we provide some examples showing the output generated by the application.
Hadron production in deuteron-gold collisions and nuclear parton distributions
NASA Astrophysics Data System (ADS)
Adeluyi, Adeola; Fai, George
2007-11-01
We calculate nuclear modification factors RdAu, central-to-peripheral ratios, RCP, and pseudorapidity asymmetries YAsym in deuteron-gold collisions at s=200 GeV in the framework of leading-order (LO) perturbative quantum chromodynamics. We use the Eskola-Kolhinen-Salgado (EKS), the Frankfurt-Guzey-Strikman (FGS), and the Hirai-Kumano-Nagai (HKN) nuclear parton distribution functions and the Albino-Kramer-Kniehl (AKK) fragmentation functions in our calculations. Results are compared to experimental data from the BRAHMS and STAR collaborations.
QCD evolution of naive-time-reversal-odd parton distribution functions
NASA Astrophysics Data System (ADS)
Kang, Zhong-Bo; Qiu, Jian-Wei
2012-07-01
We reexamine the derivation of the leading order QCD evolution equations of twist-3 quark-gluon correlation functions, Tq,F (x , x) and Tq,F (σ) (x , x), which are the first transverse-momentum-moment of the naive-time-reversal-odd parton distribution functions - the Sivers and Boer-Mulders function, respectively. The evolution equations were derived by several groups with apparent differences. We identify the sources that are responsible for the differences, and are able to reconcile the results from various groups.
Double Copies of Fermions as Matter that Interacts Only Gravitationally
NASA Astrophysics Data System (ADS)
de la Cruz, Leonardo; Kniss, Alexander; Weinzierl, Stefan
2016-05-01
Inspired by the recent progress in the field of scattering amplitudes, we discuss hypothetical particles which can be characterized as the double copies of fermions—in the same way gravitons can be viewed as double copies of gauge bosons. As the gravitons, these hypothetical particles interact only through gravitational interactions. We present two equivalent methods for the computation of the relevant scattering amplitudes. The hypothetical particles can be massive and nonrelativistic.
Factorization and non-factorization in diffractive hard scattering
Berera, Arjun
1997-04-20
Factorization, in the sense defined for inclusive hard scattering, is discussed for diffractive hard scattering. A factorization theorem similar to its inclusive counterpart is presented for diffractive DIS. For hadron-hadron diffractive hard scattering, in contrast to its inclusive counterpart, the expected breakdown of factorization is discussed. Cross section estimates are given from a simple field theory model for non-factorizing double-pomeron-exchange (DPE) dijet production with and without account for Sudakov suppression.
New parton distribution functions from a global analysis of quantum chromodynamics
NASA Astrophysics Data System (ADS)
Dulat, Sayipjamal; Hou, Tie-Jiun; Gao, Jun; Guzzi, Marco; Huston, Joey; Nadolsky, Pavel; Pumplin, Jon; Schmidt, Carl; Stump, Daniel; Yuan, C.-P.
2016-02-01
We present new parton distribution functions (PDFs) at next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments and the new D0 charged-lepton rapidity asymmetry data, as well as the use of a more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. For completeness, we also present the CT14 PDFs determined at the LO and the NLO in QCD. Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various αs values and additional sets in general-mass variable flavor number schemes, to deal with heavy partons, with up to three, four, and six active flavors.
Polarised Parton Densities from the Fits to the Deep Inelastic Spin Asymmetries on Nucleons
NASA Astrophysics Data System (ADS)
Bartelski, Jan; Tatur, Stanislaw
2001-07-01
We have updated our next to leading order QCD fit for polarised parton densities [S. Tatur, J. Bartelski, M. Kurzela, Acta Phys. Pol. B31, 647 (2000)] using recent experimental data on the deep inelastic spin asymmetries on nucleons. Our distributions have functional form inspired by the unpolarised ones given by MRST (Martin, Roberts, Stirling and Thorne) fit. In addition to usually used data sample (averaged over variable Q2 for the same value of x variable) we have also considered the points with the same x and different Q2. Our fits to both groups of data give very similar results with substantial antiquark contribution in the measured region of x. In the first case we get rather small (Δ G=0.31) gluon polarisation. For the non averaged data the best fit is obtained when gluon contribution vanishes at Q2=1GeV2. Our new parametrisation of parton densities and additional experimental data taken into account do not change much our previous results.
New parton distribution functions from a global analysis of quantum chromodynamics
Dulat, Sayipjamal; Hou, Tie -Jiun; Gao, Jun; Guzzi, Marco; Nadolsky, Pavel; Pumplin, Jon; Schmidt, Carl; Stump, Daniel; Yuan, C. -P.; Huston, Joey
2016-02-16
Here, we present new parton distribution functions (PDFs) up to next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments and the new D0 charged lepton rapidity asymmetry data, as well as the use of more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. Formore » completeness, we also present the CT14 PDFs determined at the leading order (LO) and the next-to-leading order (NLO) in QCD. Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various αs values and additional sets in general-mass variable flavor number (GM-VFN) schemes, to deal with heavy partons, with up to 3, 4, and 6 active flavors.« less
Thermalization of parton spectra in the colour-flux-tube model
NASA Astrophysics Data System (ADS)
Ryblewski, Radoslaw
2016-09-01
A detailed study of thermalization of the momentum spectra of partons produced via decays of colour flux tubes due to the Schwinger tunnelling mechanism is presented. The collisions between particles are included in the relaxation-time approximation specified by different values of the shear viscosity to entropy density ratio. At first we show that, to a good approximation, the transverse-momentum spectra of the produced partons are exponential, irrespective of the assumed value of the viscosity of the system and the freeze-out time. This thermal-like behaviour may be attributed to specific properties of the Schwinger tunnelling process. In the next step, in order to check the approach of the system towards genuine local equilibrium, we compare the local slope of the model transverse-momentum spectra with the local slope of the fully equilibrated reference spectra characterized by the effective temperature that reproduces the energy density of the system. We find that the viscosity corresponding to the anti-de Sitter/conformal field theory lower bound is necessary for thermalization of the system within about two fermis.
The asymptotic behaviour of parton distributions at small and large x
NASA Astrophysics Data System (ADS)
Ball, Richard D.; Nocera, Emanuele R.; Rojo, Juan
2016-07-01
It has been argued from the earliest days of quantum chromodynamics that at asymptotically small values of x the parton distribution functions (PDFs) of the proton behave as x^α , where the values of α can be deduced from Regge theory, while at asymptotically large values of x the PDFs behave as (1-x)^β , where the values of β can be deduced from the Brodsky-Farrar quark counting rules. We critically examine these claims by extracting the exponents α and β from various global fits of parton distributions, analysing their scale dependence, and comparing their values to the naive expectations. We find that for valence distributions both Regge theory and counting rules are confirmed, at least within uncertainties, while for sea quarks and gluons the results are less conclusive. We also compare results from various PDF fits for the structure function ratio F_2^n/F_2^p at large x, and caution against unrealistic uncertainty estimates due to overconstrained parametrisations.
Thomson scattering at general fusion
NASA Astrophysics Data System (ADS)
Young, W. C.; Parfeniuk, D.
2016-11-01
This paper provides an overview of the Thomson scattering diagnostic in use at General Fusion, including recent upgrades and upcoming plans. The plasma experiment under examination produces temperatures in the 50-500 eV range with density on the order of 1020 m-3. A four spatial point collection optics scheme has been implemented, with plans to expand to six spatial points. Recent changes to the optics of the laser beamline have reduced stray light. The system employs a frequency doubled Nd:YAG laser (532 nm), a grating spectrometer, and a photomultiplier array based detector.
Lacey, Roy A; Wei, R; Ajitanand, N N; Alexander, J M; Gong, X; Jia, J; Mawi, A; Mohapatra, S; Reynolds, D; Salnikov, S; Taranenko, A
2009-10-01
The scaling properties of jet-suppression measurements are compared for nonphotonic electrons (e+/-) and neutral pions (pi(0)) in Au+Au collisions at sqrt[S(NN)]=200 GeV. For a broad range of transverse momenta and collision centralities, the comparison is consistent with jet quenching dominated by radiative energy loss for both heavy and light partons. Less quenching is indicated for heavy quarks via e+/-; this gives an independent estimate of the transport coefficient q that agrees with its magnitude obtained from quenching of light partons via pi(0)'s.
Huston, Joey [Co-Spokesperson; Ownes, Joseph [Co-Spokesperson
The Coordinated Theoretical-Experimental Project on QCD is a multi-institutional collaboration devoted to a broad program of research projects and cooperative enterprises in high-energy physics centered on Quantum Chromodynamics (QCD) and its implications in all areas of the Standard Model and beyond. The Collaboration consists of theorists and experimentalists at 18 universities and 5 national laboratories. More than 65 sets of Parton Distribution Functions are available for public access. Links to many online software tools, information about Parton Distribution Functions, papers, and other resources are also available.
Berger, Edmond L; Gao, Jun; Li, Chong Sheng; Liu, Ze Long; Zhu, Hua Xing
2016-05-27
We present a fully differential next-to-next-to-leading order calculation of charm-quark production in charged-current deep-inelastic scattering, with full charm-quark mass dependence. The next-to-next-to-leading order corrections in perturbative quantum chromodynamics are found to be comparable in size to the next-to-leading order corrections in certain kinematic regions. We compare our predictions with data on dimuon production in (anti)neutrino scattering from a heavy nucleus. Our results can be used to improve the extraction of the parton distribution function of a strange quark in the nucleon.
Berger, Edmond L; Gao, Jun; Li, Chong Sheng; Liu, Ze Long; Zhu, Hua Xing
2016-05-27
We present a fully differential next-to-next-to-leading order calculation of charm-quark production in charged-current deep-inelastic scattering, with full charm-quark mass dependence. The next-to-next-to-leading order corrections in perturbative quantum chromodynamics are found to be comparable in size to the next-to-leading order corrections in certain kinematic regions. We compare our predictions with data on dimuon production in (anti)neutrino scattering from a heavy nucleus. Our results can be used to improve the extraction of the parton distribution function of a strange quark in the nucleon. PMID:27284650
Double-slit experiment in momentum space
NASA Astrophysics Data System (ADS)
Ivanov, I. P.; Seipt, D.; Surzhykov, A.; Fritzsche, S.
2016-08-01
Young's classic double-slit experiment demonstrates the reality of interference when waves and particles travel simultaneously along two different spatial paths. Here, we propose a double-slit experiment in momentum space, realized in the free-space elastic scattering of vortex electrons. We show that this process proceeds along two paths in momentum space, which are well localized and well separated from each other. For such vortex beams, the (plane-wave) amplitudes along the two paths acquire adjustable phase shifts and produce interference fringes in the final angular distribution. We argue that this experiment can be realized with the present-day technology. We show that it gives experimental access to the Coulomb phase, a quantity which plays an important role in all charged particle scattering but which usual scattering experiments are insensitive to.
Survey of background scattering from materials found in small-angle neutron scattering
Barker, J. G.; Mildner, D. F. R.
2015-01-01
Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300–700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a 3He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the 3He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed. PMID:26306088
NASA Astrophysics Data System (ADS)
Stumpf, H.
2003-01-01
Generalized de Broglie-Bargmann-Wigner (BBW) equations are relativistically invariant quantum mechanical many body equations with nontrivial interaction, selfregularization and probability interpretation. Owing to these properties these equations are a suitable means for describing relativistic bound states of fermions. In accordance with de Broglie's fusion theory and modern assumptions about the partonic substructure of elementary fermions, i.e., leptons and quarks, the three-body generalized BBW-equations are investigated. The transformation properties and quantum numbers of the three-parton equations under the relevant group actions are elaborated in detail. Section 3 deals with the action of the isospin group SU(2), a U(1) global gauge group for the fermion number, the hypercharge and charge generators. The resulting quantum numbers of the composite partonic systems can be adapted to those of the phenomenological particles to be described. The space-time transformations and in particular rotations generated by angular momentum operators are considered in Section 4. Based on the compatibility of the BBW-equations and the group theoretical constraints, in Sect. 5 integral equations are formulated in a representation with diagonal energy and total angular momentum variables. The paper provides new insight into the solution space and quantum labels of resulting integral equations for three parton states and prepares the ground for representing leptons and quarks as composite systems.
NASA Astrophysics Data System (ADS)
Hosseinkhani, H.; Modarres, M.
2011-01-01
To overcome the complexity of generalized two hard scale (kt , μ) evolution equation, well known as the Ciafaloni, Catani, Fiorani and Marchesini (CCFM) evolution equations, and calculate the unintegrated parton distribution functions (UPDF), Kimber, Martin and Ryskin (KMR) proposed a procedure based on (i) the inclusion of single-scale (μ) only at the last step of evolution and (ii) the angular ordering constraint (AOC) on the DGLAP terms (the DGLAP collinear approximation), to bring the second scale, kt into the UPDF evolution equations. In this work we intend to use the MSTW2008 (Martin et al.) parton distribution functions (PDF) and try to calculate UPDF for various values of x (the longitudinal fraction of parton momentum), μ (the probe scale) and kt (the parton transverse momentum) to see the general behavior of three-dimensional UPDF at the NLO level up to the LHC working energy scales (μ2). It is shown that there exits some pronounced peaks for the three-dimensional UPDF (fa (x ,kt)) with respect to the two variables x and kt at various energies (μ). These peaks get larger and move to larger values of kt, as the energy (μ) is increased. We hope these peaks could be detected in the LHC experiments at CERN and other laboratories in the less exclusive processes.
Longitudinal-Transverse Separation of Deep-Inelastic Scattering at Low Q² on Nucleons and Nuclei
Tvaskis, Vladas
2004-12-09
Since the early experiments at SLAC, which discovered the nucleon substructure and led to the development of the quark parton model, deep inelastic scattering (DIS) has been the most powerful tool to investigate the partonic substructure of the nucleon. After about 30 years of experiments with electron and muon beams the nucleon structure function F{sub 2}(x,Q{sup 2}) is known with high precision over about four orders of magnitude in x and Q{sup 2}. In the region of Q{sup 2} > 1 (GeV/c){sup 2} the results of the DIS measurements are interpreted in terms of partons (quarks and gluons). The theoretical framework is provided in this case by perturbative Quantum Chromo Dynamics (pQCD), which includes scaling violations, as described by the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) equations. The description starts to fail when Q{sup 2} becomes of the order of 1 (GeV/c){sup 2}, where non-perturbative effects (higher-twist effects), which are still not fully understood, become important (non-pQCD). The sensitivity for order-n twist effects increases with decreasing Q{sup 2}, since they include a factor 1/(Q{sup 2}{sup n}) (n {ge} 1).
Pion scattering and nuclear dynamics
Johnson, M.B.
1988-01-01
A phenomenological optical-model analysis of pion elastic scattering and single- and double-charge-exchange scattering to isobaric-analog states is reviewed. Interpretation of the optical-model parameters is briefly discussed, and several applications and extensions are considered. The applications include the study of various nuclear properties, including neutron deformation and surface-fluctuation contributions to the density. One promising extension for the near future would be to develop a microscopic approach based on powerful momentum-space methods brought to existence over the last decade. In this, the lowest-order optical potential as well as specific higher-order pieces would be worked out in terms of microscopic pion-nucleon and delta-nucleon interactions that can be determined within modern meson-theoretical frameworks. A second extension, of a more phenomenological nature, would use coupled-channel methods and shell-model wave functions to study dynamical nuclear correlations in pion double charge exchange. 35 refs., 11 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Pesic, Peter
2003-10-01
The separateness and connection of individuals is perhaps the central question of human life: What, exactly, is my individuality? To what degree is it unique? To what degree can it be shared, and how? To the many philosophical and literary speculations about these topics over time, modern science has added the curious twist of quantum theory, which requires that the elementary particles of which everything consists have no individuality at all. All aspects of chemistry depend on this lack of individuality, as do many branches of physics. From where, then, does our individuality come? In Seeing Double, Peter Pesic invites readers to explore this intriguing set of questions. He draws on literary and historical examples that open the mind (from Homer to Martin Guerre to Kafka), philosophical analyses that have helped to make our thinking and speech more precise, and scientific work that has enabled us to characterize the phenomena of nature. Though he does not try to be all-inclusive, Pesic presents a broad range of ideas, building toward a specific point of view: that the crux of modern quantum theory is its clash with our ordinary concept of individuality. This represents a departure from the usual understanding of quantum theory. Pesic argues that what is bizarre about quantum theory becomes more intelligible as we reconsider what we mean by individuality and identity in ordinary experience. In turn, quantum identity opens a new perspective on us. Peter Pesic is a Tutor and Musician-in-Residence at St. John's College, Santa Fe, New Mexico. He has a Ph.D. in physics from Stanford University.
Silk, J.; Turner, M.S.
1986-04-01
The Zel'dovich spectrum of adiabatic density perturbations is a generic prediction of inflation. There is increasing evidence that when the spectrum is normalized by observational data on small scales, there is not enough power on large scales to account for the observed large-scale structure in the Universe. Decoupling the spectrum on large and small scales could solve this problem. As a means of decoupling the large and small scales we propose double inflation (i.e., two episodes of inflation). In this scenario the spectrum on large scales is determined by the first episode of inflation and those on small scales by a second episode of inflation. We present three models for such a scenario. By nearly saturating the large angular-scale cosmic microwave anisotropy bound, we can easily account for the observed large-scale structure. We take the perturbations on small scales to be very large, deltarho/rho approx. = 0.1 to 0.01, which results in the production of primordial black holes (PBHs), early formation of structure, reionization of the Universe, and a rich array of astrophysical events. The ..cap omega..-problem is also addressed by our scenario. Allowing the density perturbations produced by the second episode of inflation to be large also lessens the fine-tuning required in the scalar potential and makes reheating much easier. We briefly speculate on the possibility that the second episode of inflation proceeds through the nucleation of bubbles, which today manifest themselves as empty bubbles whose surfaces are covered with galaxies. 37 refs., 1 fig.
Heavy quarkonium production at collider energies: Partonic cross section and polarization
Qiu, Jian -Wei; Kang, Zhong -Bo; Ma, Yan -Qing; Sterman, George
2015-01-27
We calculate the O(α³s) short-distance, QCD collinear-factorized coefficient functions for all partonic channels that include the production of a heavy quark pair at short distances. Thus, this provides the first power correction to the collinear-factorized inclusive hadronic production of heavy quarkonia at large transverse momentum, pT, including the full leading-order perturbative contributions to the production of heavy quark pairs in all color and spin states employed in NRQCD treatments of this process. We discuss the role of the first power correction in the production rates and the polarizations of heavy quarkonia in high-energy hadronic collisions. The consistency of QCD collinearmore » factorization and nonrelativistic QCD factorization applied to heavy quarkonium production is also discussed.« less
Heavy quarkonium production at collider energies: Partonic cross section and polarization
Qiu, Jian -Wei; Kang, Zhong -Bo; Ma, Yan -Qing; Sterman, George
2015-01-27
We calculate the O(α³_{s}) short-distance, QCD collinear-factorized coefficient functions for all partonic channels that include the production of a heavy quark pair at short distances. Thus, this provides the first power correction to the collinear-factorized inclusive hadronic production of heavy quarkonia at large transverse momentum, _{pT}, including the full leading-order perturbative contributions to the production of heavy quark pairs in all color and spin states employed in NRQCD treatments of this process. We discuss the role of the first power correction in the production rates and the polarizations of heavy quarkonia in high-energy hadronic collisions. The consistency of QCD collinear factorization and nonrelativistic QCD factorization applied to heavy quarkonium production is also discussed.
New Angle on the Parton Distribution Functions: Self-Organizing Maps
Honkanen, H.; Liuti, S.
2009-08-04
Neural network (NN) algorithms have been recently applied to construct Parton Distribution Function (PDF) parametrizations, providing an alternative to standard global fitting procedures. Here we explore a novel technique using Self-Organizing Maps (SOMs). SOMs are a class of clustering algorithms based on competitive learning among spatially-ordered neurons. We train our SOMs with stochastically generated PDF samples. On every optimization iteration the PDFs are clustered on the SOM according to a user-defined feature and the most promising candidates are used as a seed for the subsequent iteration using the topology of the map to guide the PDF generating process. Our goal is a fitting procedure that, at variance with the standard neural network approaches, will allow for an increased control of the systematic bias by enabling user interaction in the various stages of the process.
Jo, H S; Girod, F X; Avakian, H; Burkert, V D; Garçon, M; Guidal, M; Kubarovsky, V; Niccolai, S; Stoler, P; Adhikari, K P; Adikaram, D; Amaryan, M J; Anderson, M D; Anefalos Pereira, S; Ball, J; Baltzell, N A; Battaglieri, M; Batourine, V; Bedlinskiy, I; Biselli, A S; Boiarinov, S; Briscoe, W J; Brooks, W K; Carman, D S; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L; Compton, N; Contalbrigo, M; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dupre, R; Alaoui, A El; Fassi, L El; Elouadrhiri, L; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A; Garillon, B; Gevorgyan, N; Ghandilyan, Y; Gilfoyle, G P; Giovanetti, K L; Goetz, J T; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guler, N; Guo, L; Hafidi, K; Hakobyan, H; Harrison, N; Hattawy, M; Hicks, K; Hirlinger Saylor, N; Ho, D; Holtrop, M; Hughes, S M; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Jenkins, D; Joo, K; Joosten, S; Keller, D; Khachatryan, G; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J; Kuhn, S E; Kuleshov, S V; Lenisa, P; Livingston, K; Lu, H Y; MacGregor, I J D; McKinnon, B; Meziani, Z E; Mirazita, M; Mokeev, V; Montgomery, R A; Moutarde, H; Movsisyan, A; Munevar, E; Munoz Camacho, C; Nadel-Turonski, P; Net, L A; Niculescu, G; Osipenko, M; Ostrovidov, A I; Paolone, M; Park, K; Pasyuk, E; Phillips, J J; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Y; Puckett, A J R; Raue, B A; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatié, F; Salgado, C; Schott, D; Schumacher, R A; Seder, E; Simonyan, A; Skorodumina, Iu; Smith, G D; Sokhan, D; Sparveris, N; Stepanyan, S; Strakovsky, I I; Strauch, S; Sytnik, V; Tian, Ye; Tkachenko, S; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K; Watts, D P; Wei, X; Weinstein, L B; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zhao, Z W; Zonta, I
2015-11-20
Unpolarized and beam-polarized fourfold cross sections (d^{4}σ/dQ^{2}dx_{B}dtdϕ) for the ep→e^{'}p^{'}γ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 (Q^{2},x_{B},t) bins over the widest phase space ever explored in the valence-quark region. Several models of generalized parton distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD H, expected to be the dominant contributor to these observables. Through a leading-twist extraction of Compton form factors, these results support the model predictions of a larger nucleon size at lower quark-momentum fraction x_{B}.
Jo, Hyon -Suk
2015-11-17
Unpolarized and beam-polarized four-fold cross sectionsmore » $$\\frac{d^4 \\sigma}{dQ^2 dx_B dt d\\phi}$$ for the $$ep\\to e^\\prime p^\\prime \\gamma$$ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 ($Q^2,x_B,t$) bins over the widest phase space ever explored in the valence-quark region. Several models of Generalized Parton Distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD $H$, expected to be the dominant contributor to these observables. Thus, through a leading-twist extraction of Compton Form Factors, these results reveal a tomographic image of the nucleon.« less
New Angle on the Parton Distribution Functions: Self-Organizing Maps
NASA Astrophysics Data System (ADS)
Honkanen, H.; Liuti, S.
2009-08-01
Neural network (NN) algorithms have been recently applied to construct Parton Distribution Function (PDF) parametrizations, providing an alternative to standard global fitting procedures. Here we explore a novel technique using Self-Organizing Maps (SOMs). SOMs are a class of clustering algorithms based on competitive learning among spatially-ordered neurons. We train our SOMs with stochastically generated PDF samples. On every optimization iteration the PDFs are clustered on the SOM according to a user-defined feature and the most promising candidates are used as a seed for the subsequent iteration using the topology of the map to guide the PDF generating process. Our goal is a fitting procedure that, at variance with the standard neural network approaches, will allow for an increased control of the systematic bias by enabling user interaction in the various stages of the process.
Transverse Momentum Dependent Parton Distribution Functions with Domain Wall Valence Fermions
Bernhard Musch, Robert Edwards, Michael Engelhardt, Philipp Haegler, John Negele, Alexey Prokudin, David Richards, Andreas Schaefer
2011-03-01
Transverse Momentum Dependent Parton Distribution Functions (TMDs) reveal the intrinsic motion of quarks inside the nucleon. They are essential ingredients needed to understand angular asymmetries studied in SIDIS experiments, including current and planned experiments at JLab. Within a class B proposal, we ask for time on the Jefferson Lab computer cluster to extract amplitudes for TMDs from existing lattice QCD gauge configurations and propagators calculated by the USQCD/MILC/LHP collaborations [Aubin 2004, Bratt 2010]. The proposal encompasses more comprehensive studies with a simplified operator [Haegler 2010] along with more realistic and more demanding calculations that promise to give access to time reversal odd TMDs such as the Sivers function. We ask for cluster computer time equivalent to 1.26 million J/Psi core hours, plus disk and tape storage worth 159000 J/Psi core hours.
B-meson production in the Parton Reggeization Approach at Tevatron and the LHC
NASA Astrophysics Data System (ADS)
Karpishkov, A. V.; Nefedov, M. A.; Saleev, V. A.; Shipilova, A. V.
2015-02-01
We study the inclusive hadroproduction of B0, B+ and Bs0 mesons at leading order in the Parton Reggeization Approach using the universal fragmentation functions extracted from the combined e+e- annihilation data from CERN LEP1 and SLAC SLC colliders. We have described B-meson transverse momentum distributions measured in the central region of rapidity by the CDF Collaboration at Fermilab Tevatron and CMS Collaboration at LHC within uncertainties and without free parameters, applying Kimber-Martin-Ryskin unintegrated gluon distribution function in a proton. The forward B-meson production (2.0
Higgs pair production at the LHC with NLO and parton-shower effects
NASA Astrophysics Data System (ADS)
Frederix, R.; Frixione, S.; Hirschi, V.; Maltoni, F.; Mattelaer, O.; Torrielli, P.; Vryonidou, E.; Zaro, M.
2014-05-01
We present predictions for the SM-Higgs-pair production channels of relevance at the LHC: gluon-gluon fusion, VBF, and top-pair, W, Z and single-top associated production. All these results are at the NLO accuracy in QCD, and matched to parton showers by means of the MC@NLO method; hence, they are fully differential. With the exception of the gluon-gluon fusion process, for which a special treatment is needed in order to improve upon the infinite-top-mass limit, our predictions are obtained in a fully automatic way within the publicly available MADGRAPH5_AMC@NLO framework. We show that for all channels in general, and for gluon-gluon fusion and top-pair associated production in particular, NLO corrections reduce the theoretical uncertainties, and are needed in order to arrive at reliable predictions for total rates as well as for distributions.
Jo, Hyon -Suk
2015-11-17
Unpolarized and beam-polarized four-fold cross sections $\\frac{d^4 \\sigma}{dQ^2 dx_B dt d\\phi}$ for the $ep\\to e^\\prime p^\\prime \\gamma$ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 ($Q^2,x_B,t$) bins over the widest phase space ever explored in the valence-quark region. Several models of Generalized Parton Distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD $H$, expected to be the dominant contributor to these observables. Thus, through a leading-twist extraction of Compton Form Factors, these results reveal a tomographic image of the nucleon.
Signal evaluations using singular value decomposition for Thomson scattering diagnostics
Tojo, H. Yatsuka, E.; Hatae, T.; Itami, K.; Yamada, I.; Yasuhara, R.; Funaba, H.; Hayashi, H.
2014-11-15
This paper provides a novel method for evaluating signal intensities in incoherent Thomson scattering diagnostics. A double-pass Thomson scattering system, where a laser passes through the plasma twice, generates two scattering pulses from the plasma. Evaluations of the signal intensities in the spectrometer are sometimes difficult due to noise and stray light. We apply the singular value decomposition method to Thomson scattering data with strong noise components. Results show that the average accuracy of the measured electron temperature (T{sub e}) is superior to that of temperature obtained using a low-pass filter (<20 MHz) or without any filters.
Adams, M.R.; Arndotied, S.; Anthony, P.L.; Baker, M.D.; Bartlett, J.; Bhatti, A.A.; Braun, H.M.; Busza, W.; 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.; Jaffe, D.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.; Roeser, A.; Ryan, J.J.; Salgado, C.W.; Salvarani, A.; Schellman, H.; Schmitt, M.; Schmitz, N.; Schueler, K.P.; Skuja, A.; Snow, G.A.; Soeldner-Rembold, S.; Steinberg, P.H.; Stier, H.E.; Stopa, P.; S
1994-01-24
The average squared transverse energy of jets in deep-inelastic muon-nucleon scattering is measured as a function of the momentum transfer squared ([ital Q][sup 2]), in the range 3[lt][ital Q][sup 2][lt]25 GeV[sup 2]. Perturbative QCD predicts that the average squared parton transverse energy will depend upon the strong coupling constant ([alpha][sub [ital S
Nuclear dependence of structure functions in the shadowing region of deep inelastic scattering
Berger, E.L.; Qiu, Jianwei
1988-07-27
A discussion of nuclear shadowing in deep inelastic lepton scattering is presented. We show that the parton recombination model suggests that shadowing should begin to occur at larger values of Bjorken x as A increases. This expectation as well as that of weak dependence on Q/sup 2/, and the trend of the x dependence of the shadowing phenomenon are consistent with recent data. Shadowing at small x is combined with nuclear bound state effects, responsible for nuclear dependence at larger x, to provide description of the A dependence of the structure function for the entire range of x. 21 refs., 5 figs.
NASA Astrophysics Data System (ADS)
Sokhan, Daria
Measurements of Deeply Virtual Compton Scattering (DVCS) give access to Generalised Parton Distributions (GPDs) which provide a 3D image of the nucleon and carry information on the composition of its spin. Data from both proton and neutron targets is highly desirable for an extraction of all GPDs and to allow their flavour-decomposition. Although a number of measurements have been made on proton targets, data on the neutron is almost non-existent. We present preliminary results in the extraction of beam-spin asymmetry in neutron DVCS from CLAS and the proposed experimental programme with CLAS12 at Jefferson Laboratory.
Longitudinal target-spin asymmetries for deeply virtual Compton scattering
Seder, E.; Biselli, A.; Pisano, S.; Niccolai, S.; Smith, G. D.; Joo, K.; Adhikari, K.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Battaglieri, M.; Bedlinskiy, I.; Bono, J.; Boiarinov, S.; Bosted, P.; Briscoe, W.; Brock, J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Carlin, C.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Crabb, D.; Crede, V.; D’Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dupre, R.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Fradi, A.; Garillon, B.; Garçon, M.; Gevorgyan, N.; Ghandilyan, Y.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Gothe, R. W.; Griffioen, K. A.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hirlinger Saylor, N.; Holtrop, M.; Hughes, S. M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joosten, S.; Keith, C. D.; Keller, D.; Khachatryan, G.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Lenisa, P.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Meekins, D. G.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R.; Moody, C. I.; Moutarde, H.; Movsisyan, A.; Munoz Camacho, C.; Nadel-Turonski, P.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Paolone, M.; Pappalardo, L. L.; Park, K.; Park, S.; Pasyuk, E.; Peng, P.; Phelps, W.; Pogorelko, O.; Price, J. W.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Senderovich, I.; Simonyan, A.; Skorodumina, I.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tang, W.; Tian, Y.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Wei, X.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zonta, I.
2015-01-22
A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6-GeV electron beam, a longitudinally polarized proton target and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for ep → e'p'y events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q^{2}, x_{B}, t and Φ, for 166 four-dimensional bins. In the framework of Generalized Parton Distributions (GPDs), at leading twist the t dependence of these asymmetries provides insight on the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. In conclusion, these results bring important and necessary constraints for the existing parametrizations of chiral-even GPDs.
Longitudinal target-spin asymmetries for deeply virtual Compton scattering
Seder, E.; Biselli, A.; Pisano, S.; Niccolai, S.; Smith, G. D.; Joo, K.; Adhikari, K.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; et al
2015-01-22
A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6-GeV electron beam, a longitudinally polarized proton target and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for ep → e'p'y events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q2, xB, t and Φ, for 166 four-dimensional bins. In the framework of Generalized Parton Distributions (GPDs), at leading twist the t dependence of these asymmetries provides insight on the spatial distribution of the axialmore » charge of the proton, which appears to be concentrated in its center. In conclusion, these results bring important and necessary constraints for the existing parametrizations of chiral-even GPDs.« less
Deeply Virtual Compton Scattering Beam-Spin Asymmetries
F.X. Girod; R.A. Niyazov
2008-01-24
The beam spin asymmetries in the hard exclusive electroproduction of photons on the proton (ep -> epg) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range (x_B from 0.11 to 0.58, Q^2 from 1 to 4.8 GeV^2, -t from 0.09 to 1.8 GeV^2), the azimuthal dependence of the asymmetries is compatible with expectations from leading-twist dominance, A = a*sin(phi)/[1+c*cos(phi)]. This extensive set of data can thus be used to constrain significantly the generalized parton distributions of the nucleon in the valence quark sector.
Scattering approach to quantum transport and many body effects
NASA Astrophysics Data System (ADS)
Pichard, Jean-Louis; Freyn, Axel
2010-12-01
We review a series of works discussing how the scattering approach to quantum transport developed by Landauer and Buttiker for one body elastic scatterers can be extended to the case where electron-electron interactions act inside the scattering region and give rise to many body scattering. Firstly, we give an exact numerical result showing that at zero temperature a many body scatterer behaves as an effective one body scatterer, with an interaction dependent transmission. Secondly, we underline that this effective scatterer depends on the presence of external scatterers put in its vicinity. The implications of this non local scattering are illustrated studying the conductance of a quantum point contact where electrons interact with a scanning gate microscope. Thirdly, using the numerical renormalization group developed by Wilson for the Kondo problem, we study a double dot spinless model with an inter-dot interaction U and inter-dot hopping td, coupled to leads by hopping terms tc. We show that the quantum conductance as a function of td is given by a universal function, independently of the values of U and tc, if one measures td in units of a characteristic scale τ(U,tc). Mapping the double dot system without spin onto a single dot Anderson model with spin and magnetic field, we show that τ(U,tc) = 2TK, where TK is the Kondo temperature of the Anderson model.
Applications of phase conjugate mirror to Thomson scattering diagnostics (invited)
Hatae, T.; Naito, O.; Nakatsuka, M.; Yoshida, H.
2006-10-15
A high performance phase conjugate mirror based on stimulated Brillouin scattering (SBS-PCM) has been applied to the Thomson scattering system in the JT-60U tokamak for the first time in order to improve the measurement performance. A SBS-PCM realized a high reflectivity of 95% at a high input power of 145 W (2.9 J, 50 Hz). Using the SBS-PCM, two methods have been developed to increase the intensity of scattered light. For the first method, we have developed a new optical design to provide a double-pass scattering method with the SBS-PCM. A laser beam passing through the plasma is reflected by the SBS-PCM. The reflected beam passes the plasma again along the same path by means of the phase conjugation of the optically nonlinear stimulated Brillouin scattering process. The double-pass Thomson scattering method using the SBS-PCM has demonstrated an increase of the scattered light by a factor of 1.6 compared with the single-pass scattering method in JT-60U. A multipass Thomson scattering method in which the laser beam can be confined between a couple of SBS-PCMs is also proposed. It is estimated that the multipass scattering method generates the scattered light more than several times as large as that of the single-pass scattering method. For the second method, a high-average-power yttrium aluminum garnet (Nd:YAG) laser system has been developed using the SBS-PCM. The SBS-PCM effectively compensated thermal degradation at two amplifier lines, and the average power was increased by a factor of >8 from 45 W (1.5 J, 30 Hz) to 373 W (7.46 J, 50 Hz). A Nd:YAG laser (5 J, 100 Hz) for the edge Thomson scattering in International Thermonuclear Experimental Reactor (ITER) has been designed based on the result.
The double copy: Bremsstrahlung and accelerating black holes
NASA Astrophysics Data System (ADS)
Luna, Andrés; Monteiro, Ricardo; Nicholso, Isobel; O'Connell, Donal; White, Chris D.
2016-06-01
Advances in our understanding of perturbation theory suggest the existence of a correspondence between classical general relativity and Yang-Mills theory. A concrete example of this correspondence, which is known as the double copy, was recently intro-duced for the case of stationary Kerr-Schild spacetimes. Building on this foundation, we examine the simple time-dependent case of an accelerating, radiating point source. The gravitational solution, which generalises the Schwarzschild solution, includes a non-trivial stress-energy tensor. This stress-energy tensor corresponds to a gauge theoretic current in the double copy. We interpret both of these sources as representing the radiative part of the field. Furthermore, in the simple example of Bremsstrahlung, we determine a scattering amplitude describing the radiation, maintaining the double copy throughout. Our results provide the strongest evidence yet that the classical double copy is directly related to the BCJ double copy for scattering amplitudes.
NASA Technical Reports Server (NTRS)
Ricks, Douglas W.
1993-01-01
There are a number of sources of scattering in binary optics: etch depth errors, line edge errors, quantization errors, roughness, and the binary approximation to the ideal surface. These sources of scattering can be systematic (deterministic) or random. In this paper, scattering formulas for both systematic and random errors are derived using Fourier optics. These formulas can be used to explain the results of scattering measurements and computer simulations.
Approximations for photoelectron scattering
NASA Astrophysics Data System (ADS)
Fritzsche, V.
1989-04-01
The errors of several approximations in the theoretical approach of photoelectron scattering are systematically studied, in tungsten, for electron energies ranging from 10 to 1000 eV. The large inaccuracies of the plane-wave approximation (PWA) are substantially reduced by means of effective scattering amplitudes in the modified small-scattering-centre approximation (MSSCA). The reduced angular momentum expansion (RAME) is so accurate that it allows reliable calculations of multiple-scattering contributions for all the energies considered.
Scattering in optical materials
Musikant, S.
1983-01-01
Topics discussed include internal scattering and surface scattering, environmental effects, and various applications. Papers are presented on scattering in ZnSe laser windows, the far-infrared reflectance spectra of optical black coatings, the effects of standard optical shop practices on scattering, and the damage susceptibility of ring laser gyro class optics. Attention is also given to the infrared laser stimulated desorption of pyridine from silver surfaces, to electrically conductive black optical paint, to light scattering from an interface bubble, and to the role of diagnostic testing in identifying and resolving dimensional stability problems in electroplated laser mirrors.
Microscopic optical potentials for He4 scattering
NASA Astrophysics Data System (ADS)
Egashira, Kei; Minomo, Kosho; Toyokawa, Masakazu; Matsumoto, Takuma; Yahiro, Masanobu
2014-06-01
We present a reliable double-folding (DF) model for He4-nucleus scattering, using the Melbourne g-matrix nucleon-nucleon interaction that explains nucleon-nucleus scattering with no adjustable parameter. In the DF model, only the target density is taken as the local density in the Melbourne g matrix. For He4 elastic scattering from Ni58 and Pb208 targets in a wide range of incident energies from 20 to 200 MeV/nucleon, the DF model with the target-density approximation (TDA) yields much better agreement with the experimental data than the usual DF model with the frozen-density approximation in which the sum of projectile and target densities is taken as the local density. We also discuss the relation between the DF model with the TDA and the conventional folding model in which the nucleon-nucleus potential is folded with the He4 density.
Probing spin flip scattering in ballistic nanosystems
Zeng, Z. M.; Feng, J. F.; Wang, Y.; Han, Prof. X. F.; Zhan, W. S.; Zhang, Xiaoguang; Zhang, Z.
2006-01-01
Because spin-flip scattering length is longer than the electron mean-free-path in a metal, past studies of spin-flip scattering are limited to the diffusive regime. Spin accumulation in the nanometer sized spacer layer of a magnetic double barrier tunnel junction allows the study of spin flip scattering near ballistic limit. We extract the spin-flip conductance $G_s$ of the spacer layer from magnetoresistance measurements. A linear temperature dependence of $G_s$ is found. The bias voltage dependence shows a quantum well resonance which explains the sharp reduction of the magnetoresistance. At 4.2K $G_s$ yields the mean-free-path (70nm) and the spin-flip length ($1.0$-$2.6\\mu$m).
NASA Astrophysics Data System (ADS)
Chang, Wen-Chen
2016-02-01
The observation of the violation of Lam-Tung relation in the πN Drell-Yan process triggered many theoretical speculations. The TMD Boer-Mulders functions characterizing the correlation of transverse momentum and transverse spin for partons in unpolarized hadrons could nicely account for the violation. The COMPASS experiment at CERN will measure the angular distributions of dimuons from the unpolarized Drell-Yan process over a wide kinematic region and study the beam particle dependence. Significant statistics is expected from a successful run in 2015 which will bring further understanding of the origin of the violation of Lam-Tung relation and of the partonic transverse spin structure of the nucleon.