Study of the electromagnetic form factors of the nucleons in the timelike region

Abstract

Abstract The electromagnetic form factors GE and GM of the proton and neutron in the timelike region are extracted in a study of the processes e+e− → $$ \overline{p}p $$ p ¯ p and e+e− → $$ \overline{n}n $$ n ¯ n . The reaction amplitude is evaluated within the distorted wave Born approximation, with the interaction of the antinucleon-nucleon $$ \left(\overline{N}N\right) $$ N ¯ N pair taken into account. The latter is constructed within SU(3) chiral effective field theory up to next-to-leading order. An excellent description of the e+e− → $$ \overline{N}N $$ N ¯ N data in the energy region from the $$ \overline{N}N $$ N ¯ N threshold up to center-of-mass energies Ecm = 2.2 GeV is achieved. Results for the electromagnetic form factors GE, GM, GE/GM, and the subtracted effective form factors, Gosc, are provided. These can be helpful for further studies of the properties of the nucleons.