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Baryons with two heavy quarks: Masses, production, decays, and detection

The large number of $B_c$ mesons observed by LHCb suggests a sizable cross section for producing doubly-heavy baryons in the same experiment. Motivated by this, we estimate masses of the doubly-heavy $J=1/2$ baryons $Ξ_{cc}$, $Ξ_{bb}$, and $Ξ_{bc}$, and their $J=3/2$ hyperfine partners, using a method which accurately predicts the masses of ground-state baryons with a single heavy quark. We obtain $M(Ξ_{cc}) = 3627 \pm 12$ MeV, $M(Ξ_{cc}^*)= 3690 \pm 12$ MeV, $M(Ξ_{bb}) = 10162 \pm 12$ MeV, $M(Ξ_{bb}^*)= 10184 \pm 12$ MeV, $M(Ξ_{bc}) = 6914 \pm 13$ MeV, $M(Ξ'_{bc}) = 6933 \pm 12$ MeV, and $M(Ξ_{bc}^*) = 6969 \pm 14$ MeV. As a byproduct, we estimate the hyperfine splitting between $B_c^*$ and $B_c$ mesons to be $68 \pm 8$ MeV. We discuss P-wave excitations, production mechanisms, decay modes, lifetimes, and prospects for detection of the doubly heavy baryons.