In an experiment at the VEPP-2000 {e^ + }{e^ - } collider, the processes {e^ + }{e^ - } n n and {e^ + }{e^ - } p p were studied. The cross section of the {e^ + }{e^ - } p p process and the ratio | {{{{G₄}} / {{{{G{₄}} {{G₌}}}}. -0em} {{G₌}}}} | of electric and magnetic formfactors of proton and neutron were measured near the nucleon threshold with the SND detector. The preliminary value of the | {{{{G₄}} / {{{{G{₄}} {{G₌}}}}. -0em} {{G₌}}}} | ratio for the neutron is consistent with unity, while for the proton this value varies in the range of 1. 2 to 1. 8.
Achasov et al. (Mon,) studied this question.