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Measurements of vector boson production in lead-lead and proton-lead collisions with the ATLAS detector

NUCLEAR PHYSICS A 2014年 931卷 724-728页

作者： Grabowska-Bold, Iwona AGH Univ Sci & Technol PL-30059 Krakow Poland

Photons and weak bosons do not interact strongly and, thus, their production yields provide direct tests of scaling with a number of binary nucleon nucleon collisions in the heavy-ion environment. In addition, they should be sensitive to the nuclear modification of porton distribution functions (nPDF). Proton-lead collisions also provide an excellent opportunity to test nPDF in a less dense environment than lead lead via looking at forward backward production of weak bosons. The ATLAS detector has proven to be an excellent apparatus in measurements involving photons, electrons and muons, the latter being products of weak boson decays, in the high occupancy environment produced in heavy-ion collisions. The experiment has recorded 30 nb(-1) of proton lead data and 140 mu b(-1) of lead lead data, both of which have similar integrated partonic luminosities. We present the prompt photon, Z and W boson yields as a function of centrality, and also differentially in transverse momentum and rapidity, in lead lead and proton lead collisions from the ATLAS experiment. For W-+/- bosons, a lepton charge asymmetry has also been studied, which may also shed light on nPDF. (C) 2014 CERN. Published by Elsevier B.V. All rights reserved.

关键词： Lead-lead and proton-lead collisions Electroweak bosons parton distribution functions Lepton charge asymmetry

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Delineating the Polarized and Unpolarized parton Structure of the Nucleon

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International Journal of Modern Physics: Conference Series 2015年第37期ijmpcs卷

作者： Pedro Jimenez-Delgado Thomas Jefferson National Accelerator Facility 12000 Jefferson Avenue Suite 1 Newport News VA 23606 USA

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.

关键词： Perturbative quantum chromodynamics parton distribution functions polarized scattering

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Nucleon spin structure at very high x

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PHYSICS LETTERS B 2013年第1-3期727卷 249-254页

作者： Roberts, Craig D. Holt, Roy J. Schmidt, Sebastian M. Argonne Natl Lab Div Phys Argonne IL 60439 USA Forschungszentrum Julich Inst Adv Simulat D-52425 Julich Germany JARA D-52425 Julich Germany

Dyson-Schwinger equation treatments of the strong interaction show that the presence and importance of nonpointlike diquark correlations within the nucleon are a natural consequence of dynamical chiral symmetry breaking. Using this foundation, we deduce a collection of simple formulae, expressed in terms of diquark appearance and mixing probabilities, from which one may compute ratios of longitudinal-spin-dependent u- and d-quark parton distribution functions on the domain x similar or equal to 1. A comparison with predictions from other approaches plus a consideration of extant and planned experiments shows that the measurement of nucleon longitudinal spin asymmetries on x similar or equal to 1 can add considerably to our capacity for discriminating between contemporary pictures of nucleon structure. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Continuum strong QCD Diquark correlations Dynamical chiral symmetry breaking Dyson-Schwinger equations Nucleon longitudinal spin asymmetries parton distribution functions Valence quarks at very high x

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DETERMINATION OF CHARM QUARK MASS AND α_s(M_Z) FROM HERA DATA

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MODERN PHYSICS LETTERS A 2013年第26期28卷

作者： Cooper-Sarkar, Amanda Univ Oxford Dept Phys Oxford OX1 3RH England

Charm production data from HERA may he used to determine the charm quark and jet production data from HERA may be used to determine alpha(s)(M-Z). Recent results are summarised.

关键词： Quantum chromodynamics QCD strong coupling constant running coupling constant parton distribution functions PDFs Deep Inelastic Scattering (DIS) HERA flavour charm heavy quark mass flavour-number schemes variable flavour number scheme fixed flavour number scheme

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A Mathematica interface to NNPDFs

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Nuclear Physics B - Proceedings Supplements 2013年 234卷 54-57页

作者： Hartland, Nathan P. Nocera, Emanuele R. Tait Institute School of Physics and Astronomy University of Edinburgh EH9 3JZ United Kingdom Dipartimento di Fisica Università di Milano INFN Sezione di Milano I-20133 Milano Via Celoria 16 Italy

We present a Mathematica interface for handling the parton distribution functions of the NNDPF Collaboration, available from the NNPDF hepforge website http://***/. As a case study we briefly summarise the first PDF set which includes all relevant LHC data, NNPDF2.3, and demonstrate the use of our new Mathematica interface. © 2012 Elsevier B.V.

关键词： Mathematica NNPDF parton distribution functions

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Symmetry breaking effect on determination of polarized and unpolarized parton distributions

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Nuclear Physics B - Proceedings Supplements 2013年 234卷 66-69页

作者： Arbabifar, F. Khorramian, Ali N. Khanpour, H. Atashbar Tehrani, S. Physics Department Semnan University Semnan Iran School of Particles and Accelerators IPM (Institute for Studies in Theoretical Physics and Mathematics) Tehran P.O. Box 19395-5531 Iran

We perform a new extraction for unpolarized and polarized parton distribution functions considering a flavor decompositions for sea quarks and applying very recent deep inelastic scattering (DIS) and semi inclusive deep inelastic scattering (SIDIS) data in the fixed flavor number scheme (FFNS) framework. In the new symmetry breaking scenario the light quark and antiquark densities are extracted separately and new parametrization forms are determined for them. The heavy flavors contribution, including charm and bottom quarks, are also taken to be account for unpolarized distributions. © 2012 Elsevier B.V.

关键词： parton distribution functions Symmetry breaking

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Proton Structure Measurements from HERA to LHC

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Nuclear Physics B - Proceedings Supplements 2013年 234卷 62-65页

作者： Chekelian, Vladimir MPI for Physics Munich Germany

The inclusive ep neutral and charged current deep-inelastic scattering cross sections are measured in the H1 and ZEUS experiments at HERA, with an electron beam energy of 27.6 GeV and a nominal proton beam energy of 920 GeV and reduced proton beam energies of 575 and 460 GeV. The data span six orders of magnitude in negative four-momentum-transfer squared, Q², and in Bjorken x. These data are used to determine the proton structure functions and to perform analyses in the QCD framework. The parton distribution functions of the proton, determined in QCD fits, are used for cross section calculations of various processes and for comparisons to data at the LHC. © 2012 Elsevier B.V.

关键词： DIS HERA Neutral and charged currents parton distribution functions QCD Structure functions

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Collective Perspective on Advances in Dyson–Schwinger Equation QCD

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Communications in Theoretical Physics 2012年第7期58卷 79-134页

作者： Adnan Bashir Ian C.Clet Bruno El-Bennich Craig D.Roberts Peter C.Tandy Instituto de Física y Matemticas Universidad Michoacana de San Nicols de Hidalgo Edificio C-3Ciudad UniversitariaMoreliaMichoacn 58040Mxico Physics Division Argonne National Laboratory ArgonneIllinois 60439USA Center for Nuclear Research Department of PhysicsKent State UniversityKent OH 44242USA CSSM and CoEPP School of Chemistry and Physics University of AdelaideAdelaide SA 5005Australia Laboratorio de Física Teórica e Computao Científica Universidade Cruzeiro do Sul01506-000 So PauloSPBrazil Instituto de Física Torica Universidade Estadual Paulista01140-070 So PauloSPBrazil Department of Physics Center for High Energy Physics and State Key Laboratory of Nuclear Physics and TechnologyPeking University Institut für Kernphysik Forschungszentrum JülichD-52425 JülichGermany Department of Physics Illinois Institute of TechnologyChicagoIllinois 60616-3793USA

We survey contemporary studies of hadrons and strongly interacting quarks using QCD's Dyson-Schwinger equations, addressing the following aspects: confinement and dynamical chiral symmetry breaking; the hadron spectrum; hadron elastic and transition form factors, from small-to large-Q2; parton distribution functions; the physics of hadrons containing one or more heavy quarks; and properties of the quark gluon plasma.

关键词： confinement dynamical chiral symmetry breaking Dyson-Schwinger equations hadron spectrum hadron elastic and transition form factors heavy mesons in-hadron condensates parton distribution functions quark gluon plasma UA（1）-problem

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Reweighting and unweighting of parton distributions and the LHC W lepton asymmetry data

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NUCLEAR PHYSICS B 2012年第3期855卷 608-638页

作者： Ball, Richard D. Begone, Valerio Cerutti, Francesco Del Debbio, Luigi Forte, Stefano Guffanti, Alberto Hartland, Nathan P. Latorre, Jose I. Rojo, Juan Ubiali, Maria Univ Edinburgh Tait Inst JCMB KB Edinburgh EH9 3JZ Midlothian Scotland Univ Freiburg Inst Phys D-79104 Freiburg Germany Univ Barcelona Dept Estructura & Constituents Mat E-08028 Barcelona Spain Univ Milan Dipartimento Fis I-20133 Milan Italy Niels Bohr Inst Niels Bohr Int Acad DK-2100 Copenhagen Denmark Niels Bohr Inst Discovery Ctr DK-2100 Copenhagen Denmark Rhein Westfal TH Aachen Inst Theoret Teilchenphys & Kosmol D-52056 Aachen Germany Ist Nazl Fis Nucl Sez Milano I-20133 Milan Italy

We develop in more detail our reweighting method for incorporating new datasets in parton fits based on a Monte Carlo representation of PDFs. After revisiting the derivation of the reweighting formula, we show how to construct an unweighted PDF replica set which is statistically equivalent to a given reweighted set. We then use reweighting followed by unweighting to test the consistency of the method, specifically by verifying that results do not depend on the order in which new data are included in the fit via reweighting. We apply the reweighting method to study the impact of LHC W lepton asymmetry data on the NNPDF2.1 set. We show how these data reduce the PDF uncertainties of light quarks in the medium and small x region, providing the first solid constraints on PDFs from LHC data. (C) 2011 Elsevier B.V. All rights reserved.

关键词： parton distribution functions W lepton asymmetry data

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Q²-DEPENDENCE OF THE STATISTICAL parton distributionS IN THE VALON APPROACH

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INTERNATIONAL JOURNAL OF MODERN PHYSICS A 2012年第16期27卷 1250083-1-1250083-22页

作者： Sohaily, S. Yazdanpanah, M. M. Mirjalili, A. Shahid Bahonar Kerman Univ Dept Phys Kerman Iran Yazd Univ Dept Phys Yazd 89195741 Iran

We employ the statistical approach to obtain the nucleon parton distributions. Statistical distributions are considered as well for partons in the valon model in which a nucleon is assumed to be a state of three valence quark clusters (valon). Analytic expressions of the x-dependent of parton distribution functions (PDFs) in the valon model are obtained statistically in the whole x region [0, 1] in terms of the statistical parameters such as temperature, chemical potential and accessible volume. Since PDFs are obtained by taking the required sum rules including Gottfried sum rule at different energy scales, the Q(2)-dependence of these parameters can be obtained. Therefore the parton distributions as a function of Q(2) will be resulted. To make the calculations more precise, we extend our results to contain three flavors rather than two light u and d quarks.

关键词： parton distribution functions valon model statistical approach

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