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Free keywords:
High Energy Physics - Experiment, hep-ex
MPINP:
LHCb - Abteilung Hofmann
Abstract:
A search for previously unobserved decays of beauty baryons to the final
states $K^0_{\rm\scriptscriptstyle S} p \pi^{-}$ and
$K^0_{\rm\scriptscriptstyle S}p K^{-}$ is reported. The analysis is based on a
data sample corresponding to an integrated luminosity of $1.0\,$fb$^{-1}$ of
$pp$ collisions. The $\Lambda^0_{b} \rightarrow \overline{\kern -0.2em
K}^0_{\rm\scriptscriptstyle S}p \pi^{-}$ decay is observed with a significance
of $8.6\,\sigma$, with branching fraction \begin{eqnarray*}
{\cal{B}}(\Lambda^0_{b} \rightarrow \overline{\kern -0.2em K}^0 p \pi^{-}) &
= & \left(1.26 \pm 0.19 \pm 0.09 \pm 0.34 \pm 0.05 \right) \times 10^{-5} \,,
\end{eqnarray*} where the uncertainties are statistical, systematic, from the
ratio of fragmentation fractions $f_{\Lambda}/f_{d}$, and from the branching
fraction of the $B^0 \rightarrow K^0_{\rm\scriptscriptstyle S}\pi^{+}\pi^{-}$
normalisation channel, respectively. A first measurement is made of the $CP$
asymmetry, giving \begin{eqnarray*}
A_{C/!P} (\Lambda^0_{b} \rightarrow \overline{\kern -0.2em K}^0 p \pi^{-}) &
= & 0.22 \pm 0.13\mathrm{\,(stat)} \pm 0.03\mathrm{\,(syst)} \, .
\end{eqnarray*} No significant signals are seen for $\Lambda^0_{b} \rightarrow
K^0_{\rm\scriptscriptstyle S}p K^{-}$ decays, $\Xi^{0}_{b}$ decays to both the
$K^0_{\rm\scriptscriptstyle S}p \pi^{-}$ and $K^0_{\rm\scriptscriptstyle S}p
K^{-}$ final states, and the $\Lambda^0_{b} \rightarrow D^{-}_{s} (\rightarrow
K^0_{\rm\scriptscriptstyle S} K^{-}) p$ decay, and upper limits on their
branching fractions are reported.
