Extracting Neutron Polarizabilities from Compton Scattering on The Quasi-Free Neutrons in $\gamma \text{d}\to \gamma \text{n p}$

Abstract

Compton scattering processes are ideal to study electric and magnetic dipole polarizabilities of nucleons. These fundamental quantities parametrize the responses of the internal degrees of freedoms to a monochromatic photon probe. In this work, the inelastic channel $\gamma d\to \gamma np$ is treated in $\chi$EFT, with a focus on the kinematic region of the neutron quasi-free peak, where the momentum of the outgoing proton is small enough that it is considered to remain at rest. This provides access to the Compton scattering process $\gamma n\to \gamma n$, from which the scalar polarizabilites of the neutron, ${\alpha }_{E1}$ and ${\beta }_{M1}$, are extracted. Using $\chi$EFT, triple differential cross-sections $d^3\sigma /d{E}_{n}d{\Omega }_{{\gamma }^{\prime }}{\Omega }_n$ in the photon energy range of 200-to-400 MeV are computed. The biggest contribution comes from the impulse approximation, with small corrections stemming from final state interactions, meson exchange currents and rescattering. In this presentation, we report progress and preliminary results.

Comments: 9 pages, 10 figures, presented at the 8th International Workshop on Chiral Dynamics (CD2015), accepted for publication in the PoS, PoS(CD15)097