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

Abstract

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 ${\mathrm{\ensuremath{\Xi}}}_{cc}$, ${\mathrm{\ensuremath{\Xi}}}_{bb}$, and ${\mathrm{\ensuremath{\Xi}}}_{bc}$, 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 $M({\mathrm{\ensuremath{\Xi}}}_{cc})=3627\ifmmode\pm\else\textpm\fi{}12\text{ }\text{ }\mathrm{MeV}$, $M({\mathrm{\ensuremath{\Xi}}}_{cc}^{*})=3690\ifmmode\pm\else\textpm\fi{}12\text{ }\text{ }\mathrm{MeV}$, $M({\mathrm{\ensuremath{\Xi}}}_{bb})=10162\ifmmode\pm\else\textpm\fi{}12\text{ }\text{ }\mathrm{MeV}$, $M({\mathrm{\ensuremath{\Xi}}}_{bb}^{*})=10184\ifmmode\pm\else\textpm\fi{}12\text{ }\text{ }\mathrm{MeV}$, $M({\mathrm{\ensuremath{\Xi}}}_{bc})=6914\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}13\text{ }\text{ }\mathrm{MeV}$, $M({{\mathrm{\ensuremath{\Xi}}}^{\ensuremath{'}}}_{bc})=6933\ifmmode\pm\else\textpm\fi{}12\text{ }\text{ }\mathrm{MeV}$, and $M({\mathrm{\ensuremath{\Xi}}}_{bc}^{*})=6969\ifmmode\pm\else\textpm\fi{}14\text{ }\text{ }\mathrm{MeV}$. As a byproduct, we estimate the hyperfine splitting between ${B}_{c}^{*}$ and ${B}_{c}$ mesons to be $68\ifmmode\pm\else\textpm\fi{}8\text{ }\text{ }\mathrm{MeV}$. We discuss P-wave excitations, production mechanisms, decay modes, lifetimes, and prospects for detection of the doubly heavy baryons.