Massive Lepton Pair Production — the Drell-Yan Process — with Nuclear Targets

Abstract

The Drell-Yan process, hA → (μμ^-)X, in which a massive lepton-pair is produced inclusively from a nuclear target, offers the possibility for gaining unique insight into the A dependence of the quark and antiquark densities of nuclei, q^A(x,Q²) and q^-A(x,Q²). Measurements are crucial for testing whether the A dependence of deep-inelastic structure functions, known as the EMC effect, is a universal, process independent property of parton densities. Precise experiments with pion and nucleon beams on nuclear targets would extend knowledge of the A dependence of quark and antiquark densities of nuclei into important intervals of the fractional longitudinal momentum variable x which are not accessible easily in deep inelastic scattering. Models constructed to interpret the EMC effect are used to obtain predictions for the A dependence of massive lepton pair production. For tests of quantum chromodynamics, isolating nuclear dependence is necessary before definite conclusions can be drawn on the behavior of the pion structure function and on the magnitude and kinematic variation of predicted higher order terms (K factor). I indicate the sensitive regions of phase space and the increased level of experimental precision which is needed if a contribution is to be made to isolating the A dependence of quark and antiquark densities from the Drell-Yan process.