Compton scattering from $^4$He at the TUNL HI$\gamma$S facility

TL;DR

This study measures elastic Compton scattering cross sections from helium-4 at 81.3 MeV with high precision, revealing angular asymmetries that challenge existing theories and motivate new effective-field-theory models.

Contribution

It provides high-precision differential cross section data for helium-4 at 81.3 MeV, highlighting asymmetries that prompt development of advanced theoretical models.

Findings

Observation of fore-aft asymmetry in angular distribution

High statistical precision measurements at multiple angles

Data supports development of effective-field-theory calculations

Abstract

Differential cross sections for elastic Compton scattering from $^4$He have been measured with high statistical precision at the High Intensity $\gamma$-ray Source at laboratory scattering angles of $55^\circ$, $90^\circ$, and $125^\circ$ using a quasi-monoenergetic photon beam with a weighted mean energy value of $81.3$ MeV. The results are compared to previous measurements and similar fore-aft asymmetry in the angular distribution of the differential cross sections is observed. This experimental work is expected to strongly motivate the development of effective-field-theory calculations of Compton scattering from $^4$He to fully interpret the data.