The Impact of NLO-Corrections on the Determination of the   $\bar{u},\bar{d} Content of Nucleons from Drell-Yan Production
  The interpretation of Drell-Yan production in terms of the antiquark densities depends on NLO corrections. Besides the NLO corrections to the familiar annihilation $q\bar{q}\to \gamma^* \to l^+ l^-$, there is a substantial contribution from the QCD Compton subprocesses $gq \to q\gamma^* \to q l^+ l^-$ and $g\bar{q} \to q\gamma^* \to q l^+ l^-$. The beam and target dependence of the two classes of corrections is different. We discuss the impact of this difference on the determination of the $\bar{d}-\bar{u}$ asymmetry in the proton from the comparison of the $pp$ and $pn$ Drell-Yan production. 
W. Schaefer (IKP, FZ-Juelich)