Lepton helicity distributions in the polarized Drell-Yan process

The lepton helicity distributions in the polarized Drell-Yan process at BNL RHIC energy are investigated. For events with a relatively low invariant mass of a lepton pair in which the weak interaction is negligible, only a measurement of lepton helicity can prove the antisymmetric part of the hadronic tensor. Therefore it might be interesting to consider the helicity distributions of leptons to obtain more information on the structure of the nucleon from the polarized Drell-Yan process. We estimate the QCD corrections at the O(alpha(s)) level to the hadronic tensor including both intermediate gamma and Z bosons. We present numerical analyses for different invariant masses and show that the u ((u) over bar) and d ((d) over bar) quarks give different and characteristic contributions to the lepton helicity distributions. We also estimate the lepton helicity asymmetry for the various proton spin configurations.