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arXiv · 1901.09379

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

V. V. Bytev·E. Tomasi-Gustafsson
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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.

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V. V. Bytev, E. Tomasi-Gustafsson. 2019-01-27. Updated analysis of recent results on electron and positron elastic scattering on proton. https://doi.org/10.1103/physrevc.99.025205

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