Nucleon form factors at threshold

Budker Institute of Nuclear Physics, Novosibirsk, Russia

^* e-mail: A.I.Milstein@inp.nsk.su
^** This work is supported in part by the Russian Science Foundation (project 14-50-00580)

Published online: 18 October 2019

Abstract

The pp¯invariant mass spectra in the processes e⁺e⁻→ pp¯, e⁺e⁻→ nn¯, J/ψ → pp¯ω, J/ψ → pp¯ρ, and J/ψ → pp¯γ close to the pp¯is discussed. The optical potentials for NN¯pair in the superposition of S and D waves (due to tensor forces) at spin unity of the pair, as well as for NN¯pair in the S wave at spin zero of the pair, are proposed. The parameters of the potentials are obtained by fitting the cross sections of NN¯scattering together with the pp¯invariant mass spectra in e⁺e⁻→ pp¯annihilation and J/ψ decays. Good agreement with the available experimental data is achieved. Using our potential and the Green’s function approach we also describe the cross section of e⁺ e⁻→ 6π and the η^’π⁺ π⁻ invariant mass spectrum in the decay J/ψ → γη^’π⁺π⁻ in the energy region near the NN¯threshold.