First Measurement of Compton Scattering on ${}^3\text{He}$ at HI$\gamma$S

Abstract

The world's first Compton scattering measurements on a ${}^3$He target were performed to probe neutron electromagnetic polarizabilities. Differential cross sections were measured at laboratory angles of $40^{\circ }$, $55^{\circ }$, $90^{\circ }$, $115^{\circ }$, $150^{\circ }$, using circularly polarized, quasi-monoenergetic photon beams at weighted mean energy values of 61.5 and 97.1 MeV from the High Intensity $\gamma$-ray Source at the Triangle Universities Nuclear Laboratory. Comparisons with chiral effective field theory show good agreement at 97.1 MeV but over-prediction at 61.5 MeV, motivating further theoretical development.

8 pages, 5 figures. Accepted for publication in Physical Review Letters