Determination of baryon magnetic moments from QCD sum rules

Abstract

The magnetic moment μ _B of a baryon B with quark content (aab) is written as μ _B=4e_a(1+δ _B)eh/2cM_B, where e_a is the charge of the quark of flavor type a. The experimental values of δ 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 δ_B are computed. We find good agreement with data (Λ 10%) for the nucleons and the Σ 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.