QCD coherence effects in high energy reactions with nuclei

Abstract

In this work, coherence effects in deep inelastic scattering (DIS) and in the Drell-Yan (DY) process off nuclei are investigated, in particular nuclear shadowing. The target rest frame and the color dipole formulation are employed. Multiple scatterings are treated in Glauber-Gribov theory, which is modified to include the nuclear form factor to all orders. Based on the mean coherence length, which is defined in this work, it is estimated that gluon shadowing is negligible at x_{Bj}>0.01. Parameter free calculations are compared to NMC and E665 data for DIS and to E772 data for DY. In both cases, good agreement is found. It is however not possible to reproduce the effect observed by HERMES. For dileptons in proton-nucleus collisions at RHIC energies, considerable shadowing for the whole x_F range is predicted. The influence of the nucleus on the DY transverse momentum distribution is also studied. Furthermore, a new parametrization of the dipole cross section is presented.