Mass splittings within heavy baryon isospin multiplets in chiral perturbation theory

We calculate the mass splittings within the heavy baryon isospin multiplets \Sigma_{c(b)} and \Xi_{c(b)}' in chiral perturbation theory to leading one-loop order. The pattern of the mass splittings in the \Sigma_c iso-triplet, which is different from that of any other known isospin multiplet, can be explained. We predict m_{\Xi_c'^+} - m_{\Xi_c'^0}=-0.2\pm0.6 MeV, m_{\Xi_b'^0} - m_{\Xi_b'^-}=-4.0\pm1.9 MeV and the mass of the \Sigma_b^0 to be 5810.3\pm1.9 MeV.