Photoproduction of electron-positron pairs on the proton in the resonance region - art. no. 015205

Production of lepton pairs in the gamma p-->e(-)e(+)p reaction is studied a t photon energies up to 1 GeV. We show that even if lepton charge is not me asured there are extensive kinematical regimes where the nuclear process do minates over the Bethe-Heitler contribution. The decomposition is performed of the unpolarized cross section for virtual Compton scattering in terms o f response functions. These are expressed in terms of a polarization densit y matrix of the virtual photon and are shown to be sensitive to the propert ies of baryon resonances in the first and the second resonance regions. In the analysis a unitary K-matrix model is used, based on an effective Lagran gian including nucleon, mesons, and baryon resonances with masses up to 1.7 GeV. Results of the model are compared with data for real-photon Compton s cattering and predictions are given for observables in photoproduction of l epton pairs.