Elastic Compton Scattering from the Nucleon and Deuteron

TL;DR

This paper uses Chiral Perturbation Theory to analyze elastic Compton scattering from nucleons and deuterons, aiming to determine nucleon polarizabilities, especially for the neutron, by fitting experimental data.

Contribution

It extends Chiral Perturbation Theory to include the Delta resonance and non-perturbative nucleon-nucleon interactions for a unified description of scattering data.

Findings

Determined proton polarizabilities from Compton scattering data.

Estimated neutron polarizabilities by combining proton and deuteron data.

Provided insights into the internal structure of nucleons through polarizability analysis.

Abstract

Goal of this work is the consistent description of elastic Compton scattering from the single nucleon and the deuteron. The theoretical framework chosen is Chiral Perturbation Theory, which is the low-energy formulation of Quantum Chromodynamics, where we extend the spectrum of active degrees of freedom from only pions and nucleons to also the Delta(1232) resonance. In the deuteron sector, we treat the nucleon-nucleon interaction non-perturbatively. Besides the Compton cross sections, our main concern is with the nucleon polarizabilities, which are a useful tool to describe the reaction of the internal nucleonic degrees of freeedom to the external electromagnetic field. Experimentally, only a few nucleon polarizabilities are known. Especially our present knowledge of the neutron polarizabilities is not satisfying. The reason why it is so difficult to determine these quantities experimentally is the finite lifetime of the free neutron. Therefore, we want to contribute to the ongoing discussion of the neutron polarizabilities by fitting the average over proton and neutron polarizabilities to the elastic deuteron Compton-scattering data. Similarly, we determine the proton polarizabilities from fits to the single-proton Compton data. We finally combine both results in order to identify the neutron polarizabilities.