Electromagnetic Polarizabilities: Lattice QCD in Background Fields

TL;DR

This paper uses lattice QCD with background fields to calculate electromagnetic polarizabilities of hadrons, providing a first-principles approach to test chiral perturbation theory predictions against experimental data.

Contribution

It introduces new lattice QCD techniques for determining hadron electric polarizabilities and magnetic moments, especially near the chiral limit, advancing the understanding of low-energy QCD.

Findings

Demonstrated methods to extract electric polarizabilities from lattice QCD

Studied quark mass dependence of hadron polarizabilities

Provided results relevant for ongoing experiments like COMPASS and HIγS

Abstract

Chiral perturbation theory makes definitive predictions for the extrinsic behavior of hadrons in external electric and magnetic fields. Near the chiral limit, the electric and magnetic polarizabilities of pions, kaons, and nucleons are determined in terms of a few well-known parameters. In this limit, hadrons become quantum mechanically diffuse as polarizabilities scale with the inverse square-root of the quark mass. In some cases, however, such predictions from chiral perturbation theory have not compared well with experimental data. Ultimately we must turn to first principles numerical simulations of QCD to determine properties of hadrons, and confront the predictions of chiral perturbation theory. To address the electromagnetic polarizabilities, we utilize the background field technique. Restricting our attention to calculations in background electric fields, we demonstrate new techniques to determine electric polarizabilities and baryon magnetic moments for both charged and neutral states. As we can study the quark mass dependence of observables with lattice QCD, the lattice will provide a crucial test of our understanding of low-energy QCD, which will be timely in light of ongoing experiments, such as at COMPASS and HI\gamma S.