Disconnected contributions to the magnetic polarisability of the neutral pion

TL;DR

This paper investigates the impact of disconnected quark loop contractions on the magnetic polarisability of the neutral pion using lattice QCD, highlighting their significance as indicated by chiral perturbation theory.

Contribution

It presents the first lattice QCD investigation of disconnected contributions to the neutral pion's magnetic polarisability in a background magnetic field.

Findings

Disconnected contractions are significant for accurate polarisability calculations.

Initial results show these contractions provide leading loop-order contributions.

The study advances understanding of charge symmetry breaking effects in lattice QCD.

Abstract

The magnetic polarisability of the neutral pion has been calculated using the background field method in lattice QCD. These early results do not consider the effect of the disconnected loop contractions arising from the breaking of charge symmetry in a background magnetic field. Recent work in chiral perturbation theory has shown that these quark-self-annihilation contractions provide the leading loop-order contributions to the magnetic polarisability. A first investigation of these contractions in a background magnetic field is presented.