Freiburg 1998 – wissenschaftliches Programm
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T: Teilchenphysik
T 606: Strukturfkt. IV / Nukleonenspin II
T 606.1: Vortrag
Donnerstag, 26. März 1998, 08:30–08:45, HS F
The role of NLO corrections for the determination of the d-ū asymmetry from pp and pd Drell-Yan production — •W. Schäfer1, N. N. Nikolaev1,2, and J. Speth1 — 1Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich — 2L. D. Landau Institute, Moscow, Russia
The so-called K-factor which parameterizes NLO corrections to Drell-Yan production is known to be large, K∼ 2. Furthermore, the annihilation and QCD Compton diagrams exhibit quite a different beam and target dependence. We discuss how this beam and target dependence of the K-factor can affect the comparison of the pp and pd Drell-Yan processes in terms of the asymmetric d and ū distributions in the proton. We analyze in detail which kind of conspiracy of the gluon and sea distributions in the proton provides an approximate constancy of the K-factor and offer simple expansion for different components of the K-factor in terms of the valence, glue and sea distribution functions. We compare the predictions for the K-factor from different recent parameterizations for the parton distribution functions (CTEQ,MRS,GRV). We focus on the large-x region relevant to extraction of the large-x sea parton desbities from the recent Drell-Yan data from the E866 FNAL experiment. We comment on the impact of QCD Compton diagrams on the interpretation of the recent experimental data from the E866 experiment on pp and pd Drell-Yan in terms of the d-ū asymmetry in the proton.