Delta baryon magnetic moments from lattice QCD

.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 u and d quark masses are heavy. Of particular interest is the chiral nonanalytic behaviour encountered as the Npi decay channel opens. We find a Delta(++) magnetic moment (at the A pole) of muDelta(++) = (4.99 +/- 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 mu(Delta)++ = (4.52 +/- 0.51 +/- 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. (C) 2003 Elsevier Science B.V. All rights reserved.