Examination of the strangeness contribution to the nucleon magnetic moment

Abstract

We examine the nucleon strangeness magnetic moment ${\ensuremath{\mu}}_{s}$ with a lowest order meson cloud model. We observe that (1) strangeness in the nucleon is a natural requirement of the empirical relation ${\ensuremath{\mu}}_{p}∕{\ensuremath{\mu}}_{n}=\ensuremath{-}3∕2$, which favors an SU(3) octet meson cloud instead of merely the SU(2) pions. (2) In a consistent perturbative calculation, the quark vertex contribution to ${\ensuremath{\mu}}_{s}$ is divergently positive, the meson cloud contribution to ${\ensuremath{\mu}}_{s}$ is divergently negative, and the sum is convergent and negative. (3) In the rest frame of the nucleon, ${\ensuremath{\mu}}_{s}$ cannot be separated into a quark part and an antiquark part, neither can ${\ensuremath{\mu}}_{s}$ be calculated via the spin and orbital angular momentum of the strange quarks and antiquarks. (4) While the overall sign of ${\ensuremath{\mu}}_{s}$ is under debate, the spin part of ${\ensuremath{\mu}}_{s}$ (which is related to the strange quark tensor charge) is better known to be negative.