Updated analysis of recent results on electron and positron elastic scattering on the proton

Bytev, V.V. (JINR-BLTP, 141980 Dubna, Moscow Region, Russian Federation) ; Tomasi-Gustafsson, E. (DPhN, IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette Cedex, France)

21 February 2019

Abstract: We discuss recent experimental results concerning the cross section ratio of positron over electron elastic scattering on protons, and compare with the predictions of a pre-existent calculation. The deviation from unity of this ratio, i.e., a charge asymmetry different from zero, is the signature of contributions beyond the Born approximation. After reviewing the published results, we compare the elastic data to a calculation which includes the diagram corresponding to two-photon exchange. It turns out that all the data on the cross section ratio, in the limit of their precision, do not show evidence of enhanced two-photon contribution beyond the expected percent level. Our results confirm that experimental evidence for a large contribution of two-photon exchange is not yet found.


Published in: Physical Review C 99 (2019)
Published by: APS
DOI: 10.1103/PhysRevC.99.025205
arXiv: 1901.09379
License: CC-BY-4.0



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