Speaker
Oleksandr Koshchii
(George Washington University)
Description
Elastic electron/positron scattering off a nucleus has proved to be an efficient tool to study the
structure of nucleons. Modern cross section and asymmetry measurements at Jlab require radiative corrections to be taken into account. In particular, two-photon exchange (TPE) effects beyond the standard model-independent contributions have to be considered at the current level of precision. Experimentally, the real part of the TPE amplitude can be studied through charge asymmetry measurements in elastic electron/positron scattering on a proton target. Besides that, the imaginary part of the TPE amplitude can be assessed through measurements of normal single spin asymmetries (SSA) (e.g., JLab experiment [1]). Corresponding theoretical
calculations are in the focus of this report.
In my talk, I will present our charge-asymmetry predictions for scattering of unpolarized and massive leptons on the proton target in connection to the MUSE experiment at PSI [2]. These predictions include the contributions coming from hard TPE. I will also discuss our neutron normal SSA calculation at GeV beam energies and compare it with the results of the measurement [1].
[1] Y. W. Zhang et al., PRL 115, 172502 (2015).
[2] R. Gilman et al. (MUSE Collaboration), arXiv:1303.2160.
Primary author
Oleksandr Koshchii
(George Washington University)
Co-author
Andrei Afanasev
(George Washington University)
