1,129 research outputs found

    EPS09 - Nuclear PDFs and Their Uncertainties at NLO

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    In this talk, we present our recent next-to-leading order (NLO) nuclear parton distribution functions (nPDFs), which we call EPS09. As an extension to earlier NLO analyses, we supplement the deep inelastic scattering and Drell-Yan dilepton data by inclusive midrapidity pion measurements from RHIC in order to reduce the otherwize large freedom in the nuclear gluon densities. Our Hessian-type error analysis leading to a collection of nPDF error sets, is the first of its kind among the nPDF analyses.Comment: 4 pages, 4 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

    The scale dependent nuclear effects in parton distributions for practical applications

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    The scale dependence of the ratios of parton distributions in a proton of a nucleus AA and in the free proton, RiA(x,Q2)=fi/A(x,Q2)/fi(x,Q2)R_i^A(x,Q^2)=f_{i/A}(x,Q^2)/f_i(x,Q^2), is studied within the framework of the lowest order leading-twist DGLAP evolution. By evolving the initial nuclear distributions obtained with the GRV-LO and CTEQ4L sets at a scale Q02Q_0^2, we show that the ratios RiA(x,Q2)R_i^A(x,Q^2) are only moderately sensitive to the choice of a specific modern set of free parton distributions. We propose that to a good first approximation, this parton distribution set-dependence of the nuclear ratios RiA(x,Q2)R_i^A(x,Q^2) can be neglected in practical applications. With this result, we offer a numerical parametrization of RiA(x,Q2)R_i^A(x,Q^2) for all parton flavours ii in any A>2A>2, and at any 106x110^{-6}\le x \le 1 and any Q22.25Q^2\ge 2.25 GeV2^2 for computing cross sections of hard processes in nuclear collisions.Comment: 14 pages, including 4 eps-figure

    A global DGLAP analysis of nuclear PDFs

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    In this talk, we shortly report results from our recent global DGLAP analysis of nuclear parton distributions. This is an extension of our former EKS98-analysis improved with an automated χ2\chi^2 minimization procedure and uncertainty estimates. Although our new analysis show no significant deviation from EKS98, a sign of a significantly stronger gluon shadowing could be seen in the RHIC BRAHMS data.Comment: Talk given at EPS HEP 200

    Constraints for nuclear gluon shadowing from DIS data

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    The Q2Q^2 dependence of the ratios of the cross sections of deep inelastic lepton--nucleus scattering is studied in the framework of leading twist, lowest order perturbative QCD. The logQ2\log Q^2 slope of the ratio F2Sn/F2CF_2^{\rm Sn}/F_2^{\rm C} is computed by using the DGLAP evolution equations, and shown to be sensitive to the nuclear gluon distribution functions. Four different parametrizations for the nuclear effects of parton distributions are studied. We show that the NMC data on the Q2Q^2 dependence of F2Sn/F2CF_2^{\rm Sn}/F_2^{\rm C} rule out the case where nuclear shadowing (suppression) of gluons at x0.01x\sim 0.01 is much larger than the shadowing observed in the ratio F2A/F2DF_2^A/F_2^{\rm D}. We also show that the possible nonlinear correction terms due to gluon fusion in the evolution equations do not change this conclusion. Some consequences for computation of RHIC multiplicities, which probe the region x\gsim0.01, are also discussed.Comment: 11 pages, 3 eps figure

    Estimation of Collision Impact Parameter

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    We demonstrate that the nuclear collision geometry (i.e. impact parameter) can be determined with 1.5 fm accuracy in an event-by-event analysis by measuring the transverse energy flow in the pseudorapidity region 3η53 \le |\eta| \le 5 with a minimal dependence on collision dynamics details at the LHC energy scale. Using the HIJING model we have illustrated our calculation by a simulation of events of nucleus-nucleus interactions at the c.m.s energy from 1 up to 5.5 TeV per nucleon and various type of nuclei.Comment: 6 pages, 3 figure

    ALICE potential for heavy-flavour physics

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    The Large Hadron Collider (LHC), where lead nuclei will collide at the unprecedented c.m.s. energy of 5.5 TeV per nucleon-nucleon pair, will offer new and unique opportunities for the study of the properties of strongly interacting matter at high energy density over extended volumes. We will briefly explain why heavy-flavour particles are well-suited tools for such a study and we will describe how the ALICE experiment is preparing to make use of these tools.Comment: 6 pages, 3 figures, prepared for the Proceedings of "Strange Quark Matter 2007", Levoca, Slovaki

    Constraints for nuclear gluon densities from DIS data

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    The Q2Q^2 dependence of the ratios of nuclear structure functions F2AF_2^A is studied by performing QCD evolution of nuclear parton distribution functions. The log Q2Q^2 slope of these ratios is very sensitive to the nuclear gluon distribution function. Taking different parametrizations, we show that the NMC data on the Q2Q^2 dependence of F2Sn/F2CF_2^{\rm Sn}/F_2^{\rm C} rule out the case where nuclear shadowing (suppression) of gluons at x0.01x\sim 0.01 is much larger than the shadowing observed in the ratio F2A/F2DF_2^A/F_2^{\rm D}. We also take into account modifications to the DGLAP evolution by including gluon fusion terms and see that the effect is small at present energies, and, in any case, a strong gluon shadowing is not favored. The region studied (x0.01x \sim 0.01) is the most relevant for RHIC multiplicities.Comment: 4 pages, 3 postscript figures. Contributed to 37th Rencontres de Moriond on QCD and Hadronic Interactions, Les Arcs, France, 16-23 Mar 200
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