Bound States and Perturbative QCD Effects in Lepton Pair Production

In this paper we compare the bound state or constituent interchange model and perturbative QCD contributions to lepton pair production. We improve the CIM model with explicit one-gluon exchange calculations of bound state effects and use a general gauge invariant amplitude. We also use off mass shell kinematics to provide finite results at zero momentum transfer. Recent lepton pair data in transverse momentum Ql is fit predominantly with the CIM contribution, with consistent normalization to other CIM processes. The emergence of the QCD contribution at larger Ql and higher energy is also studied. (Submitted to Phys. Rev.) * Supported in part by the National Science Foundation and the Department of Energy under contract no. EY-76-C-03-0515. -2