Separation of proton polarizabilities with the beam asymmetry of Compton scattering

TL;DR

This paper proposes using the beam asymmetry in low-energy Compton scattering to directly measure the proton's magnetic polarizability, effectively isolating it from the electric polarizability.

Contribution

It introduces a method to extract the proton's magnetic polarizability directly from beam asymmetry measurements, simplifying the separation from electric polarizability.

Findings

Beam asymmetry isolates magnetic polarizability.

Higher-order effects are suppressed in forward kinematics.

Proposes experimental feasibility at MAMI and HIGS.

Abstract

We propose to determine the magnetic dipole polarizability of the proton directly from the beam asymmetry of low-energy Compton scattering based on the fact that the leading non-Born contribution to the asymmetry is due to the magnetic polarizability alone; the electric polarizability cancels out. The beam asymmetry thus provides the simplest observable with a clean separation of the magnetic polarizability from the electric one. Introducing polarizabilities in a Lorentz-invariant fashion we compute the higher-order (recoil) effects of polarizabilities on beam asymmetry and show that these effects are most suppressed in forward kinematics. With the prospects of precision Compton experiments at the MAMI and HIGS facilities in mind, we argue why the beam asymmetry could be the best way to measure the elusive magnetic polarizability of the proton.