Electromagnetic structure of the low-lying baryons in covariant chiral perturbation theory

Abstract

We report a calculation of the low-lying baryon magnetic moments using covariant chiral perturbation theory within the extended-on-mass-shell renormalization scheme including intermediate octet and decuplet contributions. For the case of the baryon octet, we succeed to improve the Coleman-Glashow description by including the leading SU(3)$_F$-breaking effects coming from the lowest-order loops. We compare with previous attempts at the same order using heavy-baryon and covariant infrared chiral perturbation theory, and discuss the source of the differences. For the case of the decuplet-baryons we fix the only unknown LEC with the well measured magnetic dipole moment of the $\Omega^-$ and predict the corresponding ones of the $\Delta(1232)$ isospin multiplet. In particular we obtain $\mu_{\Delta^{++}}=6.0(6) \mu_N$ and $\mu_{\Delta^{+}}=2.84(34) \mu_N$ that compare well with the current experimental information.