Observation of $\hat{I}{ž}_b^0\to \hat{I}{ž}_c^{+}{D}_s^{-}$ and $\hat{I}{ž}_b^{-}\to \hat{I}{ž}_c^0{D}_s^{-}$ decays

Abstract

The $\hat{I}{ž}_b^0\to \hat{I}{ž}_c^{+}{D}_s^{-}$ and $\hat{I}{ž}_b^{-}\to \hat{I}{ž}_c^0{D}_s^{-}$ decays are observed for the first time using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$, corresponding to an integrated luminosity of $5.1{\mathrm{fb}}^{-1}$. The relative branching fractions times the beauty-baryon production cross-sections are measured to be \begin{align*} \mathcal{R}\left(\frac{Ξ_b^0}{Λ_b^0}\right) \equiv \frac{σ\left(Ξ_b^0\right)}{σ\left(Λ_b^0\right)} \times \frac{\mathcal{B}\left(Ξ_b^0 \rightarrow Ξ_c^+ D_s^-\right)}{\mathcal{B}\left(Λ_b^0 \rightarrow Λ_c^0 D_s^-\right)} =(15.8\pm1.1\pm0.6\pm7.7)\%, \mathcal{R}\left(\frac{Ξ_b^-}{Λ_b^0}\right) \equiv \frac{σ\left(Ξ_b^-\right)}{σ\left(Λ_b^0\right)} \times \frac{\mathcal{B}\left(Ξ_b^- \rightarrow Ξ_c^0 D_s^-\right)}{\mathcal{B}\left(Λ_b^0 \rightarrow Λ_c^0 D_s^-\right)} =(16.9\pm1.3\pm0.9\pm4.3)\%, \end{align*} where the first uncertainties are statistical, the second systematic, and the third due to the uncertainties on the branching fractions of relevant charm-baryon decays. The masses of $\hat{I}{ž}_b^0$ and $\hat{I}{ž}_b^{-}$ baryons are measured to be $m_{\hat{I}{ž}_b^0}=5791.12\pm 0.60\pm 0.45\pm 0.24\mathrm{MeV}/c^2$ and $m_{\hat{I}{ž}_b^{-}}=5797.02\pm 0.63\pm 0.49\pm 0.29\mathrm{MeV}/c^2$, where the uncertainties are statistical, systematic, and those due to charm-hadron masses, respectively.

All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-017.html (LHCb public pages)