Search

High-pT lepton pair production under the conditions of HERA is studied in order to compare the respective contributions of several different production mechanisms, among them the ?? and the Drell-Yan effects. Various distributions are considered. It is shown that the ?? process systematically and largely dominates. Therefore this type of experiment may allow one to determine the equivalent-photon spectrum of the proton.

Considering the proton either as a three-quark state with its wave function fulfilling QCD sum rules or as a quark-diquark state with wave function parametrizations that are shown to fitGMP, we study the possibility of discriminating between these two competing pictures by comparing their respective predictions for and decays. ForJ/Ψ decay, thep invariantmass distributions derived from either model are found to be of about the same magnitude, but neither of them is able by itself to reproduce present-day data. Differences between the two pictures may eventually show up in the case of Υ(1S) decay, but the predicted counting rates are small. We also consider some other possible production mechanisms for final states.