Strong nuclear enhancement in intermediate mass Drell-Yan production

Abstract

We calculate nuclear effect in Drell-Yan massive lepton-pair production in terms of parton multiple scattering in Quantum Chromodynamics (QCD). We present the nuclear modification to inclusive Drell-Yan cross section $d\sigma/dQ^2$ in terms of multiparton correlation functions. By extracting the size of the correlation functions from measured Drell-Yan transverse momentum broadening in nuclear medium, we determine the nuclear modification at $O(\alpha_s/Q^2)$. We find that the nuclear modification strongly enhances the inclusive Drell-Yan cross section in the intermediate mass region (IMR): $1.5 < Q < 2.5$ GeV. We argue that the Drell-Yan process is responsible for the majority of the observed dimuon enhancement in the IMR in the Pb-Pb collisions at CERN SPS.