Absence of shadowing in Drell-Yan production at finite transverse momentum exchange

Abstract

Within a perturbative scalar QED model recently considered by Brodsky et al., we study how leading-twist Coulomb rescatterings affect the Drell-Yan cross section at small x = x_{target}, and compare to the case of deep inelastic scattering at small x_{B}. We show that in the range where the transverse momentum transferred to the target is large compared to its minimal value $\sim \text{morder}x$, Coulomb rescatterings affect the DIS cross section but not the Drell-Yan production rate. This illustrates that the leading-twist parton distribution functions become non-universal when cross sections which are differential in target-related particles are considered.

Comments: 22 pages, latex, feynmf