Dilepton production by protons on nuclei and the partonic origin of depletion at small momentum fraction.

Abstract

We discuss and extend our previous predictions of dilepton depletion at small target parton momentum fraction in proton-nucleus collisions. These predictions were based on an analysis of the partonic origin of the European Muon Collaboration effect in deep-inelastic scattering (DIS) in a treatment of nuclei allowing multiquark clusters to be formed. With this input, we calculate the ratio of dimuons produced on nuclei to those produced on free nucleons. We obtain excellent agreement with data from a recent experiment, emphasizing that all input information came from our previous DIS analysis. Our calculations predict that beyond the range of presently measured data, there will be considerable dependence on the momentum carried by the annihilating parton in the incident proton.