$N\bar{N}$ production in $e^{+}e^{-}$ annihilation near the threshold revisited

Abstract

Production of pp and nn pairs in e + e − annihilation near the threshold of the process is discussed with account for the new experimental data appeared recently. Since a significant part of these new data was obtained at energies noticeably exceeding the threshold, we also take into account the form factor describing the amplitude of N N pair production at small distances. The effective optical potential, which describes a sharp dependence of the N N production cross sections near the threshold, consists of the central potential for S and D waves and the tensor potential. These potentials differ for the states with isospin I = 0 and I = 1 of N N pair. The optical potential describes well N N scattering phases, the cross sections of pp and nn production in e + e − annihilation near the threshold, the electromagnetic form factors GE and GM for protons and neutrons, as well as the cross sections of the processes e + e − → 6π and e + e − → K + K − π + π − .