Chiral extrapolations for nucleon magnetic moments

TL;DR

This paper uses chiral effective field theory to analyze lattice QCD data for nucleon magnetic moments, addressing finite-volume effects and extrapolating to physical pion masses with results consistent with experiments.

Contribution

It provides a detailed chiral extrapolation method for nucleon magnetic moments, highlighting finite-volume effects and achieving compatibility with experimental values.

Findings

Finite-volume effects are significant and require lattice sizes > 5 fm.

Extrapolated magnetic moments agree with experimental data within 10%.

Strong dependence of results on lattice volume and pion mass.

Abstract

Lattice QCD simulations have made significant progress in the calculation of nucleon electromagnetic form factors in the chiral regime in recent years. With simulation results achieving pion masses of order ~180 MeV, there is an apparent challenge as to how the physical regime is approached. By using contemporary methods in chiral effective field theory, both the quark-mass and finite-volume dependence of the isovector nucleon magnetic moment are carefully examined. The extrapolation to the physical point yields a result that is compatible with experiment, albeit with a combined statistical and systematic uncertainty of 10%. The extrapolation shows a strong finite-volume dependence; lattice sizes of L > 5 fm must be used to simulate results within 2% of the infinite-volume result for the magnetic moment at the physical pion mass.