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

A bstract The electromagnetic form factors G E and G M of the proton and neutron in the timelike region are extracted in a study of the processes e + e − → p̄p p ¯ p and e + e − → n̄n n ¯ n . The reaction amplitude is evaluated within the distorted wave Born approximation, with the interaction of the antinucleon-nucleon (N̄N) 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 − → N̄N N ¯ N data in the energy region from the N̄N N ¯ N threshold up to center-of-mass energies E cm = 2.2 GeV is achieved. Results for the electromagnetic form factors G E , G M , G E / G M , and the subtracted effective form factors, G osc , are provided. These can be helpful for further studies of the properties of the nucleons.