On radiative corrections to polarization observables in electron-proton scattering

TL;DR

This paper analyzes radiative corrections, especially bremsstrahlung, to polarization observables in elastic electron-proton scattering, showing their significance at various energies and their impact on proton form factor measurements.

Contribution

It provides a model-independent framework for calculating bremsstrahlung corrections, highlighting the importance of proton radiation in polarization transfer experiments.

Findings

Proton radiation correction is non-negligible.

Total correction increases with Q^2 and energy, dominated by TPE.

Bremsstrahlung correction can be around 0.01 at low energies.

Abstract

We consider radiative corrections to polarization observables in elastic electron-proton scattering, in particular, for the polarization transfer measurements of the proton form factor ratio $\mu G_E/G_M$. The corrections are of two types: two-photon exchange (TPE) and bremsstrahlung (BS); in the present work we pay special attention to the latter. Assuming small missing energy or missing mass cut-off, the correction can be represented in a model-independent form, with both electron and proton radiation taken into account. Numerical calculations show that the contribution of the proton radiation is not negligible. Overall, at high $Q^2$ and energies the total correction to $\mu G_E/G_M$ grows, but is dominated by TPE. At low energies both TPE and BS may be significant; the latter amounts to ~ 0.01 for some reasonable cut-off choices.