Observation of $\hat{I}{›}_b^0\to \ddot{I}ˆ(2S)p{K}^{-}$ and $\hat{I}{›}_b^0\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^{-}p{K}^{-}$ decays and a measurement of the $\hat{I}{›}_b^0$ baryon mass

Abstract

The decays $\hat{I}{›}_b^0\to \ddot{I}ˆ(2S)p{K}^{-}$ and $\hat{I}{›}_b^0\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^{-}p{K}^{-}$ are observed in a data sample corresponding to an integrated luminosity of 3fb${}^{-1}$, collected in proton-proton collisions at 7 and 8TeV centre-of-mass energies by the LHCb detector. The $\ddot{I}ˆ(2S)$ mesons are reconstructed through the decay modes $\ddot{I}ˆ(2S)\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}$ and $\ddot{I}ˆ(2S)\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^{-}$. The branching fractions relative to that of $\hat{I}{›}_b^0\to J/\ddot{I}ˆp{K}^{-}$ are measured to be \begin{eqnarray*} \frac{\mathcal{B}(Λ_b^0 \to ψ(2S) pK^-)} {\mathcal{B}(Λ_b^0 \to J/ψpK^-)} & = & (20.70\pm 0.76\pm 0.46\pm 0.37)\times10^{-2} \,, \frac{\mathcal{B}(Λ_b^0 \to J/ψπ^+ π^- pK^-)} {\mathcal{B}(Λ_b^0 \to J/ψpK^-)} & = & (20.86\pm 0.96\pm 1.34)\times10^{-2} \,, \end{eqnarray*} where the first uncertainties are statistical, the second are systematic and the third is related to the knowledge of $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(2S)$ branching fractions. The mass of the $\hat{I}{›}_b^0$ baryon is measured to be $$M(\hat{I}{›}_b^0)=5619.65\pm 0.17\pm 0.17\mathrm{MeV}/c^2,$$ where the uncertainties are statistical and systematic.

21 pages, 6 figures. All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-060.html