0909.4736 (E. Tomasi-Gustafsson et al.)

Compilation and analysis of charge asymmetry measurements from electron
and positron scattering on nucleon and nuclei    [PDF]

E. Tomasi-Gustafsson, M. Osipenko, E. A. Kuraev, Yu. Bystritsky

World data on the lepton-charge asymmetry in the elastic and inelastic lepton scattering off the proton and nuclei are compiled and discussed. After reviewing the published results, we compare the elastic data to a model calculation of the two-photon exchange mechanism. We show that the existing data do not provide any evidence for the two-photon contribution. At significance level 0.05 the data allow to exclude the two-photon exchange as an explanation for the difference between Rosenbluth and polarization measurements of proton electromagnetic form factors.

View original: http://arxiv.org/abs/0909.4736