Study of Two-Photon Corrections in the $p\bar{p} --> e+e-$ Process: Hard   Rescattering Mechanism
  We investigate the two-photon corrections to the process $p\bar{p} \to e^+e^-$ at large momentum transfer, aimed to access the time-like nucleon form factors. We estimate the two-photon corrections using a hard rescattering mechanism, which has already been used to calculate the corresponding corrections to elastic electron-proton scattering. Using different nucleon distribution amplitudes, we find that the two-photon corrections to the $p\bar{p} \to e^+e^-$ cross sections in the momentum transfer range 5 - 30 GeV$^2$ is below the 1 % level. 
Julia Guttmann, Nikolai Kivel, Marc Vanderhaeghen
hep-ph