Constraints on the Proton's Gluon Density from Lepton-Pair Production
  Massive lepton-pair production, the Drell-Yan process, should be a good source of independent constraints on the gluon density, free from the experimental and theoretical complications of photon isolation that beset studies of prompt photon production. We provide predictions for the spin-averaged and spin-dependent differential cross sections as a function of transverse momentum $Q_T$. 
E. L. Berger (Argonne) and M. Klasen (Hamburg)