Lattice Calculation of Hadronic Light-by-Light Contribution to the Muon Anomalous Magnetic Moment

TL;DR

This paper presents a lattice QCD calculation of the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment, achieving significant error reduction with algorithmic improvements and near-physical pion mass simulations.

Contribution

It introduces new algorithmic techniques and applies them to compute the hadronic light-by-light contribution with reduced statistical errors using near-physical pion mass lattice QCD.

Findings

Error reduction by over an order of magnitude

Successful calculation at near-physical pion mass

Use of large volume lattice with improved algorithms

Abstract

The quark-connected part of the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment is computed using lattice QCD with chiral fermions. We report several significant algorithmic improvements and demonstrate their effectiveness through specific calculations which show a reduction in statistical errors by more than an order of magnitude. The most realistic of these calculations is performed with a near-physical, $171$ MeV pion mass on a $(4.6\;\mathrm{fm})^3$ spatial volume using the $32^3\times 64$ Iwasaki+DSDR gauge ensemble of the RBC/UKQCD Collaboration.