Determination of the scalar polarizabilities of the proton using beam asymmetry $\Sigma_{3}$ in Compton scattering

TL;DR

This paper reports the first measurement of the beam asymmetry $oldsymbol{oldsymbol{ extSigma_{3}}}$ in Compton scattering below pion threshold at MAMI, providing an alternative method to determine proton scalar polarizabilities.

Contribution

It introduces a novel experimental approach using beam asymmetry measurements to extract proton scalar polarizabilities, complementing traditional cross section analyses.

Findings

First measurement of $oldsymbol{ extSigma_{3}}$ below pion threshold

Comparison with model calculations shows consistency

Data influence on polarizability extraction assessed

Abstract

The scalar dipole polarizabilities, $\alpha_{E1}$ and $\beta_{M1}$, are fundamental properties related to the internal dynamics of the nucleon. The currently accepted values of the proton polarizabilities were determined by fitting to unpolarized proton Compton scattering cross section data. The measurement of the beam asymmetry $\Sigma_{3}$ in a certain kinematical range provides an alternative approach to the extraction of the scalar polarizabilities. At the Mainz Microtron (MAMI) the beam asymmetry was measured for Compton scattering below pion photoproduction threshold for the first time. The results are compared with model calculations and the influence of the experimental data on the extraction of the scalar polarizabilities is determined.