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Nuclear parton distributions at next to leading order

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Nuclear parton distributions at next to leading order.D.de Florian,R.Sassot ∗†Departamento de F´ısica,Facultad de Ciencias Exactas y Naturales,Universidad de Buenos Aires,Pabell´o n I,Ciudad Universitaria (1428)Buenos Aires,Argentina (Dated:February 1,2008)We perform a next to leading order QCD global analysis of nuclear deep inelastic scattering and Drell-Yan data using the convolution approach to parameterize nuclear parton densities.We find both a significant improvement in the agreement with data compared to previous extractions,and substantial differences in the scale dependence of nuclear effects compared to leading order analyses.PACS numbers:13.60Hb,12.38.Bx,24.85.+p I.INTRODUCTION Ever since the discovery that quark and gluons in bound nucleons show momentum distributions notice-ably different to those measured in free or less bound nucleons [1],two decades ago,the precise determination of nuclear parton densities has awakened growing atten-tion,driving both increasingly precise and comprehen-sive nuclear structure functions measurements [2],and more refined theoretical understanding of the underlying physics.The precise knowledge of nuclear parton distribution functions (nPDF)is not only required for a deeper under-standing of the mechanisms associated to nuclear binding from a QCD improved parton model perspective,but it is also the starting point for the analyses of a wide variety of future and ongoing high energy physics experiments,such as heavy ion collisions at RHIC [3],proton-nucleus collisions to be performed at LHC [4],or neutrino-nucleus interactions in long baseline neutrino experiments [5],for example.Consequently,the accuracy of nPDF is rapidly evolving into a key issue in many areas of particle physics.From the point of view of perturbative QCD,the ex-traction of nPDF can be done in close analogy to what

is done for free nucleons:they are considered as non per-turbative inputs,to be inferred from data,whose rela-tion to the measured observables and energy scale de-pendence are computed order by order in perturbation theory.Although one can not discard larger higher twist power corrections than in the case of free nucleons,or even some sort of nuclear recombination effect,factoriza-tion and universality of nPDF are expected to hold in a very good approximation,over a wide kinematical range in the present experiments.

At variance with nucleon PDF,which driven by the demand of more and more precise predictions,have at-

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