Lattice QCD analysis of the strangeness magnetic moment of the nucleon - art. no. 074505

The outcome of the SAMPLE experiment suggests that the strange-quark contri bution to the nucleon magnetic moment, G(M)(s)(0), may be greater than zero . This result is very difficult to reconcile with expectations based on the successful baryon magnetic-moment phenomenology of the constituent quark m odel. We show that cartful consideration of chiral symmetry reveals some ra ther unexpected properties of QCD. In particular, it is found that the vale nce u-quark contribution to the magnetic moment of the neutron can differ b y more than 50% from its contribution to the Xi(o) magnetic moment. This hi therto unforeseen result leads to the value G(M)(s)(0)=-0.16+/-0.18 with a systematic error, arising from the relatively large strange quark mass used in existing lattice calculations, that would tend to shift G(M)(s)(0) towa rds small positive values.