Measurement of the mass and lifetime of the $\hat{I}{\text{c◯}}_b^{-}$ baryon

Abstract

A proton-proton collision data sample, corresponding to an integrated luminosity of 3 fb${}^{-1}$ collected by LHCb at $\sqrt{s}=7$ and 8 TeV, is used to reconstruct $63\pm 9$ $\hat{I}{\text{c◯}}_b^{-}\to \hat{I}{\text{c◯}}_c^0\ddot{I}{€}^{-}$, $\hat{I}{\text{c◯}}_c^0\to p{K}^{-}{K}^{-}\ddot{I}{€}^{+}$ decays. Using the $\hat{I}{ž}_b^{-}\to \hat{I}{ž}_c^0\ddot{I}{€}^{-}$, $\hat{I}{ž}_c^0\to p{K}^{-}{K}^{-}\ddot{I}{€}^{+}$ decay mode for calibration, the lifetime ratio and absolute lifetime of the $\hat{I}{\text{c◯}}_b^{-}$ baryon are measured to be \begin{align*} \frac{τ_{Ω_b^-}}{τ_{Ξ_b^-}} &= 1.11\pm0.16\pm0.03, \\ τ_{Ω_b^-} &= 1.78\pm0.26\pm0.05\pm0.06~{\rm ps}, \end{align*} where the uncertainties are statistical, systematic and from the calibration mode (for $\ddot{I}{„}_{\hat{I}{\text{c◯}}_b^{-}}$ only). A measurement is also made of the mass difference, $m_{\hat{I}{\text{c◯}}_b^{-}}-m_{\hat{I}{ž}_b^{-}}$, and the corresponding $\hat{I}{\text{c◯}}_b^{-}$ mass, which yields \begin{align*} m_{Ω_b^-}-m_{Ξ_b^-} &= 247.4\pm3.2\pm0.5~{\rm MeV}/c^2, \\ m_{Ω_b^-} &= 6045.1\pm3.2\pm 0.5\pm0.6~{\rm MeV}/c^2. \end{align*} These results are consistent with previous measurements.

11 pages, 5 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-2016-008.html