Electromagnetic processes in a $\chi$EFT framework

TL;DR

This paper develops a chiral effective field theory framework for electromagnetic processes in nuclear physics, deriving two-nucleon potentials and currents up to N$^3$LO, and applying them to neutron capture reactions.

Contribution

It introduces a consistent chiral EFT approach including N$^3$LO corrections for nuclear electromagnetic currents and applies it to radiative neutron capture processes.

Findings

LECs are fitted to phase shifts and magnetic moments.

The EFT current operator successfully reproduces experimental capture data.

The role of LECs is crucial in matching experimental observations.

Abstract

Recently, we have derived a two--nucleon potential and consistent nuclear electromagnetic currents in chiral effective field theory with pions and nucleons as explicit degrees of freedom. The calculation of the currents has been carried out to include N$^3$LO corrections, consisting of two--pion exchange and contact contributions. The latter involve unknown low-energy constants (LECs), some of which have been fixed by fitting the $np$ S- and P-wave phase shifts up to 100 MeV lab energies. The remaining LECs entering the current operator are determined so as to reproduce the experimental deuteron and trinucleon magnetic moments, as well as the $np$ cross section. This electromagnetic current operator is utilized to study the $nd$ and $n^3$He radiative captures at thermal neutron energies. Here we discuss our results stressing on the important role played by the LECs in reproducing the experimental data.