Theoretical calculations for precision polarimetry based on Mott scattering

TL;DR

This paper provides a detailed theoretical analysis of the Sherman function in Mott scattering electron polarimeters, focusing on radiative corrections and their impact on measurement accuracy at typical experimental energies and angles.

Contribution

It offers a comprehensive theoretical calculation of all relevant interaction contributions affecting the Sherman function, including radiative corrections, for improved precision in polarimetry.

Findings

Radiative corrections are estimated to be below 0.5% for typical conditions.

Theoretical analysis covers energies of a few MeV and backward angles.

Main sources of theoretical error are identified and quantified.

Abstract

Electron polarimeters based on Mott scattering are extensively used in different fields in physics such as atomic, nuclear or particle physics. This is because spin-dependent measurements gives additional information on the physical processes under study. The main quantity that needs to be understood in very much detail, both experimentally and theoretically, is the spin-polarization function, so called analyzing power or Sherman function. A detailed theoretical analysis on all the contributions to the effective interaction potential that are relevant at the typical electron beam energies and angles commonly used in the calibration of the experimental apparatus is presented. The main contribution leading the theoretical error on the Sherman function is found to correspond to radiative corrections that have been qualitatively estimated to be below the 0.5% for the considered kinematical conditions: unpolarized electron beams of few MeV elastically scattered from a gold and silver targets at backward angles.