The magnetic moment of the $\Lambda_c$, $\Xi_{ c1}^+$ and $\Xi_{ c1}^0$ vanish when the charm quark mass is taken to infinity because the light degrees of freedom are in a spin zero configuration. The heavy quark spin-symmetry violating contribution from the light degrees of freedom starts at order $1/m_c$, the same order as the contribution from the heavy charm quark. We compute the leading long-distance contribution to the magnetic moments from the spin-symmetry breaking $\Sigma_c^*-\Sigma_c $ mass splitting in chiral perturbation theory. These are nonanalytic in the pion mass and arise from calculable one-loop graphs. Further, the difference between the magnetic moments of the charged charmed baryons is independent of the charm quark mass and of the subleading local counterterm.
Categories: hep-ph