Observation of New Charmless Decays of Bottom Hadrons

Abstract

We search for new charmless decays of neutral $b$ hadrons to pairs of charged hadrons, using $1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected by the CDF II detector at the Fermilab Tevatron. We report the first observation of the ${B}_{s}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ decay and measure $\mathcal{B}({B}_{s}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=\mathbf{(}5.0\ifmmode\pm\else\textpm\fi{}0.7(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.8(\mathrm{syst})\mathbf{)}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. We also report the first observation of charmless $b$-baryon decays, and measure $\mathcal{B}({\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}})=\mathbf{(}3.5\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.9(\mathrm{syst})\mathbf{)}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $\mathcal{B}({\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}})=\mathbf{(}5.6\ifmmode\pm\else\textpm\fi{}0.8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.5(\mathrm{syst})\mathbf{)}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. No evidence is found for other modes, and we set the limit $\mathcal{B}({B}_{s}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})<1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ at 90% C.L.