Forward production of high mass muon pairs in pion-nucleon interactions

The production of muon pairs in negative pion nucleon interactions has been studied at a center-of-mass energy of 12.2 GeV. About 4000 events have been collected over a broad range of longitudinal momentum and invariant mass. A comparison with the Drell-Yan Model has been made, confirming the factorization hypothesis. The results favor a non-vanishing value of the pion structure function at the kinematic limit of large longitudinal momentum. Other departures from the standard parton-QCD model are found in this region. The angular distribution of the muon pair becomes characteristic of longitudinal virtual photon polarization, and the transverse momentum of the pair is found to decrease. 39 refs., 70 figs., 21 tabs