Delta Baryon Magnetic Moments From Lattice QCD

TL;DR

This paper uses lattice QCD and effective field theory to predict Delta baryon magnetic moments, revealing nonanalytic chiral behaviour and surprising results about proton and Delta^+ moments.

Contribution

It introduces a finite-range regulated effective field theory approach to lattice QCD data, capturing chiral nonanalytic behaviour of Delta baryon magnetic moments.

Findings

Delta++ magnetic moment estimated at 4.99 ± 0.56 μ_N

Results align with Particle Data Group and experimental data

Proton moment may exceed Delta^+ moment, contrary to expectations

Abstract

Theoretical predictions for the magnetic moments of the physical Delta baryons are extracted from lattice QCD calculations. We utilize finite-range regulated effective field theory that is constructed to have the correct Dirac moment mass dependence in the region where the up and down quark masses are heavy. Of particular interest is the chiral nonanalytic behaviour encountered as the nucleon-pion decay channel opens. We find a Delta^++ magnetic moment (at the Delta pole) of 4.99 \pm 0.56 \mu_N. This result is within the Particle Data Group range of 3.7-7.5 \mu_N and compares well with the experimental result of Bosshard et al. of 4.52 \pm 0.51 \pm 0.45 \mu_N. The interplay between the different pion-loop contributions to the Delta^+ magnetic moment leads to the surprising result that the proton moment may exceed that of the Delta^+, contrary to conventional expectations.