DRELL-YAN PROCESS AND FACTORIZATION IN IMPACT PARAMETER SPACE

The cross section for Drell-Yan pair production in the limit of small x(target) is derived in the rest frame of the target hadron. Our calcu lation is based on the fundamental quantity sigma(rho), the cross sect ion for the scattering of a <q(q)over bar> pair with fixed transverse separation rho off a hadronic target. As in deep inelastic scattering the result can be given in terms of integrals of sigma(rho). This is c onsistent with well-known factorization theorems and also relates high er-twist terms in both processes. An analysis of the angular distribut ion of the produced lepton shows that additional integrals of sigma(rh o) can be obtained in the Drell-Yan process, which are not measurable in inclusive deep inelastic scattering.