Hadronic Light by Light Contributions to the Muon Anomalous Magnetic Moment With Physical Pions

TL;DR

This paper presents a first-principles lattice calculation of the hadronic light-by-light contribution to the muon g-2 using physical pion masses, addressing key challenges like finite volume effects.

Contribution

It introduces a lattice QCD approach with physical pions to compute HLbL contributions, moving beyond model-dependent estimates.

Findings

First lattice calculation with physical pions for HLbL

Implementation of noise reduction techniques

Discussion of finite volume effects and remaining challenges

Abstract

The current measurement of muonic $g - 2$ disagrees with the theoretical calculation by about 3 standard deviations. Hadronic vacuum polarization (HVP) and hadronic light by light (HLbL) are the two types of processes that contribute most to the theoretical uncertainty. The current value for HLbL is still given by models. I will describe results from a first-principles lattice calculation with a 139 MeV pion in a box of 5.5 fm extent. Our current numerical strategies, including noise reduction techniques, evaluating the HLbL amplitude at zero external momentum transfer, and important remaining challenges, in particular those associated with finite volume effects, will be discussed.