Leading SU(3)-Breaking Corrections to the Baryon Magnetic Moments in Chiral Perturbation Theory

We calculate the baryon magnetic moments using covariant chiral perturbation theory (chi PT) within the extended-on-mass-shell renormalization scheme. By fitting the two available low-energy constants, we improve the Coleman-Glashow description of the data when we include the leading SU(3)-breaking effects coming from the lowest-order loops. This success is in dramatic contrast with previous attempts at the same order using heavy-baryon chi PT and covariant infrared chi PT. We also analyze the source of this improvement with particular attention to the comparison between the covariant results.