Lepton Asymmetry in Polarized Drell-Yan

Abstract

The lepton helicity distributions in the polarized Drell-Yan process at RHIC energy are investigated. In the absence of the weak interaction, only the 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 nucleon from the polarized Drell-Yan process. We estimate the QCD corrections at ${\cal O} (\alpha_s)$ level to the hadronic tensor including both intermediate $\gamma$ and $Z$ bosons. We report the numerical analyses on the $Z$ pole and show that the $u (\bar{u})$ and $d (\bar{d})$ quarks give different and characteristic contributions to the lepton helicity distributions. We also estimate the lepton helicity asymmetry for the various proton's spin configurations.