Study of the $B^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}{K}^{-}$ decay

Abstract

The decay $B^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}{K}^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 ${\mathrm{fb}}^{-1}$ collected by the LHCb experiment. In the ${\Lambda }_c^{+}{K}^{-}$ system, the ${\Xi }_c(2930{)}^0$ state observed at the BaBar and Belle experiments is resolved into two narrower states, ${\Xi }_c(2923{)}^0$ and ${\Xi }_c(2939{)}^0$, whose masses and widths are measured to be $$\begin{gathered} m({\Xi }_c(2923{)}^0)=2924.5\pm 0.4\pm 1.1\mathrm{MeV}, \\ m({\Xi }_c(2939{)}^0)=2938.5\pm 0.9\pm 2.3\mathrm{MeV}, \\ \Gamma ({\Xi }_c(2923{)}^0)=4.8\pm 0.9\pm 1.5\mathrm{MeV}, \\ \Gamma ({\Xi }_c(2939{)}^0)=11.0\pm 1.9\pm 7.5\mathrm{MeV}, \end{gathered}$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt ${\Lambda }_c^{+}{K}^{-}$ sample. Evidence of a new ${\Xi }_c(2880{)}^0$ state is found with a local significance of $3.8\sigma$, whose mass and width are measured to be $2881.8\pm 3.1\pm 8.5\mathrm{MeV}$ and $12.4\pm 5.3\pm 5.8\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode ${\Xi }_c(2790{)}^0\to {\Lambda }_c^{+}{K}^{-}$ is found with a significance of $3.7\sigma$. The relative branching fraction of $B^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}{K}^{-}$ with respect to the $B^{-}\to D^{+}{D}^{-}{K}^{-}$ decay is measured to be $2.36\pm 0.11\pm 0.22\pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.

arXiv commentAll figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages)

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• Refining radiative decay studies in singly heavy baryons
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• Mass spectra of singly heavy baryons in the relativized quark model with heavy-quark dominance
• ${\Xi }_c(3055)$ as a scaling point to establish the excited ${\Xi }_c^{(\prime )}$ family