Proton Compton Scattering from Linearly Polarized Gamma Rays

TL;DR

This study measures proton Compton scattering cross sections using polarized gamma rays at specific angles and energies, then interprets the results within chiral effective field theory to determine proton polarizabilities.

Contribution

First measurements of differential cross sections at specific angles with polarized gamma rays at ~83 MeV, interpreted through chiral effective field theory to extract proton polarizabilities.

Findings

Measured differential cross sections at 55°, 90°, 125°

Extracted proton electric and magnetic polarizabilities

Results consistent with theoretical predictions

Abstract

Differential cross sections for Compton scattering from the proton have been measured at scattering angles of $55^\circ$, $90^\circ$, and $125^\circ$ in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy value of 83.4\,MeV (81.3\,MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives $\alpha_{E1}^p = 13.8\pm1.2_{\rm stat}\pm0.1_{\rm BSR}\pm0.3_{\rm theo}, \beta_{M1}^p = 0.2\mp1.2_{\rm stat}\pm0.1_{\rm BSR}\mp0.3_{\rm theo}$ in units of 10$^{-4}$\, fm$^3$.