Delta baryon magnetic moments from lattice QCD

Theoretical predictions for the magnetic moments of the physical Δ 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 u and d quark masses are heavy. Of particular interest is the chiral nonanalytic behaviour encountered as the Nπ decay channel opens. We find a Δ++ magnetic moment (at the Δ pole) of μΔ++=(4.99±0.56)μN. This result is within the Particle Data Group range of 3.7–7.5 μN and compares well with the experimental result of Bosshard et al. of μΔ++=(4.52±0.51±0.45)μN. The interplay between the different pion-loop contributions to the Δ+ magnetic moment leads to the surprising result that the proton moment may exceed that of the Δ+, contrary to conventional expectations.