Analyzing the Effects of Neutron Polarizabilities in Elastic Compton Scattering off ${}^3$He

TL;DR

This paper investigates how neutron electromagnetic polarizabilities influence elastic Compton scattering off helium-3, proposing measurements of unpolarized and double-polarization observables to extract neutron polarizability information.

Contribution

It provides a theoretical analysis using chiral perturbation theory to next-to-leading order, identifying observables sensitive to neutron polarizabilities in helium-3 scattering.

Findings

Unpolarized cross section can measure neutron electric and magnetic polarizabilities.

Double-polarization observables are sensitive to neutron spin polarizabilities.

Numerical results have been corrected in an erratum, with detailed data available online.

Abstract

Motivated by the fact that a polarized ${}^3$He nucleus behaves as an `effective' neutron target, we examine manifestations of neutron electromagnetic polarizabilities in elastic Compton scattering from the Helium-3 nucleus. We calculate both unpolarized and double-polarization observables using chiral perturbation theory to next-to-leading order (${\mathcal O}(e^2 Q)$) at energies, $\omega \leq m_{\pi}$, where $m_{\pi}$ is the pion mass. Our results show that the unpolarized differential cross section can be used to measure neutron electric and magnetic polarizabilities, while two double-polarization observables are sensitive to different linear combinations of the four neutron spin polarizabilities. [Note added in 2018] The qualitative conclusions and analytic formulae presented in this paper are correct, but several of the numerical results are wrong: see the erratum posted as arXiv:1804.01206 for further details. A full suite of corrected numerical results for cross sections and asymmetries can be found in Margaryan et al., arXiv:1804.00956. They can also be obtained as an interactive Mathematica notebook by emailing hgrie@gwu.edu.