The Nuclear Effect Induced by Additional Parton Evolution and Recombination in Nuclear Environment

Abstract

The relationship between the parton transverse momentum and longitudinal momentum, which is obtained by analysing the hadron tensor in the deep inelastic scattering (DIS) process, indicates that the transverse size of partons in a nucleon is sensitively affected by the effective nucleon mass. The change in this transverse size gives rise to an Additional Parton Evolution (APE) in the nuclear environment refer to the normal QCD parton evolution thus resulting in new parton distributions. The self-consistent integral equations for these new parton distributions are given. Having undergone the normal QCD evolution and the additional evolution in the nuclear environment, the partons with the small x participate in recombination and contribute to the nuclear shadowing effect. The reasonably good descriptions of the nuclear effect of structure functions, nuclear Drell-Yan ratios and nuclear gluon distributions are presented. A quantitative comparison between the APE model and the Q^2-rescaling model is made.