Proton polarizabilities from polarized Compton scattering: low-energy expansion

TL;DR

This paper analyzes the low-energy behavior of polarized Compton scattering on protons, revealing that beam asymmetry is primarily sensitive to magnetic polarizability, and proposes a method to extract this property from experimental data.

Contribution

It demonstrates that the leading non-Born contribution to beam asymmetry depends only on magnetic polarizability and introduces a way to determine it experimentally.

Findings

Beam asymmetry is dominated by magnetic polarizability at low energies.

Electric polarizability cancels out in the beam asymmetry.

Low-energy expansion allows extraction of spin polarizabilities.

Abstract

We reexamine the low-energy expansion of polarized Compton scattering off the proton and show that the leading non-Born contribution to the beam asymmetry of low-energy Compton scattering is given by the magnetic polarizability alone, the electric polarizability cancels out. Based on this fact we propose to determine the magnetic dipole polarizability of the proton from the beam asymmetry. We also present the low-energy expansion of doubly-polarized observables, from which the spin polarizabilities can be extracted.