Dilepton decays of nucleon resonances and dilepton production cross sections in proton-proton collisions

Abstract

Relativistic, kinematically complete phenomenological expressions for the dilepton decay rates of nucleon resonances with arbitrary spin and parity are derived in terms of the magnetic, electric, and Coulomb transition form factors. The dilepton decay rates of the nucleon resonances with masses below 2 GeV are estimated using the extended vector meson dominance (eVMD) model for the transition form factors. The model provides an unified description of the photo- and electroproduction data and of the vector meson and dilepton decays of the nucleon resonances. The constraints on the transition form factors from the quark counting rules are taken into account explicitly. The remaining parameters of the model are fixed by fitting the available photo- and electroproduction data and using results of the multichannel partial-wave analysis of the $\pi N$ scattering. The results are used to describe dilepton spectra measured at BEVALAC in proton-proton collisions.