Observation of Λb0→Λc+D¯(∗)0K- and Λb0→Λc+Ds∗- decays

Abstract

The decays ${\Lambda }_b^0\to {\Lambda }_c^{+}\overline{D}{}^{(\ast )0}{K}^{-}$ and ${\Lambda }_b^0\to {\Lambda }_c^{+}{D}_s^{\ast -}$ are observed for the first time, in proton-proton collision data at $\sqrt{s}=13\text{Te}\text{V}$, corresponding to an integrated luminosity of 5.4${\text{fb}}^{-1}$ collected with the LHCb detector. Their ratios of branching fractions with respect to the ${\Lambda }_b^0\to {\Lambda }_c^{+}{D}_s^{-}$ mode are measured to be $$\begin{array}{c}\hfill \begin{array}{cc}\hfill \frac{\mathcal{B}\left({\Lambda }_b^0,,\to ,{\Lambda }_c^{+},\overline{D}{}^0,K^{-}\right)}{\mathcal{B}\left({\Lambda }_b^0,,\to ,{\Lambda }_c^{+},D_s^{-}\right)}& =0.1908{}_{-0.0034}^{+0.0036}{}_{-0.0018}^{+0.0016}\pm 0.0038,\hfill \\ \hfill \frac{\mathcal{B}\left({\Lambda }_b^0,,\to ,{\Lambda }_c^{+},\overline{D}{}^{\ast 0},K^{-}\right)}{\mathcal{B}\left({\Lambda }_b^0,,\to ,{\Lambda }_c^{+},D_s^{-}\right)}& =0.589{}_{-0.017}^{+0.018}{}_{-0.018}^{+0.017}\pm 0.012,\hfill \\ \hfill \frac{\mathcal{B}\left({\Lambda }_b^0,,\to ,{\Lambda }_c^{+},D_s^{\ast -}\right)}{\mathcal{B}\left({\Lambda }_b^0,,\to ,{\Lambda }_c^{+},D_s^{-}\right)}& =1.668\pm 0.022{}_{-0.055}^{+0.061},\hfill \end{array}\end{array}$$where the first uncertainties are statistical, the second systematic, and the third, for the ${\Lambda }_b^0\to {\Lambda }_c^{+}\overline{D}{}^{(\ast )0}{K}^{-}$ decays, are due to the uncertainties on the branching fractions of the $D_s^{-}\to K^{-}{K}^{+}{\pi }^{-}$ and $\overline{D}{}^0\to K^{+}{\pi }^{-}$ decay modes. The measured branching fractions probe factorization assumptions in effective theories and provide the normalization for future pentaquark searches in ${\Lambda }_b^0\to {\Lambda }_c^{+}\overline{D}{}^{(\ast )0}{K}^{-}$ decay channels.