Isospin splittings in baryons with two heavy quarks

Isospin splittings in baryons with two heavy quarks and a u or d quark are calculated using simple methods proposed previously by the authors. The results are M(Ξcc++)-M(Ξcc+)=1.41±0.12+0.76 MeV, M(Ξbb0)-M(Ξbb-)=-4.78±0.06+0.03 MeV, and M(Ξbc+)-M(Ξbc0)=-1.69±0.07+0.39 MeV, where the statistical errors reflect uncertainties in input mass splittings, and the systematic errors are associated with the choice of constituent-quark masses.