Determination of baryon magnetic moments from QCD sum rules.

Abstract

The magnetic moment ${\ensuremath{\mu}}_{B}$ of a baryon B with quark content (aab) is written as ${\ensuremath{\mu}}_{B}$=4${e}_{a}$(1+${\ensuremath{\delta}}_{B}$)e\ensuremath{\Elzxh}/2${\mathrm{cM}}_{B}$, where ${e}_{a}$ is the charge of the quark of flavor type a. The experimental values of ${\ensuremath{\delta}}_{B}$ have a simple pattern and have a natural explanation within QCD. Using the ratio method, the QCD sum rules are analyzed and the values of ${\ensuremath{\delta}}_{B}$ are computed. We find good agreement with data (\ensuremath{\approxeq}10%) for the nucleons and the \ensuremath{\Sigma} multiplet while for the cascade the agreement is not as good. In our analysis we have incorporated additional terms in the operator-product expansion as compared to previous authors. We also clarify some points of disagreement between the previous authors. External-field-induced correlations describing the magnetic properties of the vacuum are estimated from the baryon magnetic-moment sum rules themselves as well as by independent spectral representations and the results are contrasted.