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 (χPT) 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 χPT and covariant infrared χPT. We also analyze the source of this improvement with particular attention to the comparison between the covariant results.