Extraction of proton form factors in the timelike region from unpolarized e+ e- ---> p anti-p events

We have performed numerical simulations of the unpolarized e+e-→pp̅ process in kinematic conditions under discussion for a possible upgrade of the existing DAFNE facility. By fitting the cross section angular distribution with a typical Born expression, we can extract information on the ratio |GE/GM| of the proton electromagnetic form factors in the timelike region within a 5%–10% uncertainty. We have explored also non-Born contributions to the cross section by introducing a further component in the angular fit, which is related to two-photon exchange diagrams. We show that these corrections can be identified if larger than 5% of the Born contribution, and if relative phases of the complex form factors do not produce severe cancellations.