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 $63pm9$ $Omega_b^-toOmega_c^0pi^-$, $Omega_c^0to pK^-K^-pi^+$ decays. Using the $Xi_b^-toXi_c^0pi^-$, $Xi_c^0to pK^-K^-pi^+$ decay mode for calibration, the lifetime ratio and absolute lifetime of the $Omega_b^-$ baryon are measured to be begin{align*} frac{tau_{Omega_b^-}}{tau_{Xi_b^-}} &= 1.11pm0.16pm0.03, tau_{Omega_b^-} &= 1.78pm0.26pm0.05pm0.06~{rm ps}, end{align*} where the uncertainties are statistical, systematic and from the calibration mode (for $tau_{Omega_b^-}$ only). A measurement is also made of the mass difference, $m_{Omega_b^-}-m_{Xi_b^-}$, and the corresponding $Omega_b^-$ mass, which yields begin{align*} m_{Omega_b^-}-m_{Xi_b^-} &= 247.4pm3.2pm0.5~{rm MeV}/c^2, m_{Omega_b^-} &= 6045.1pm3.2pm 0.5pm0.6~{rm MeV}/c^2. end{align*} These results are consistent with previous measurements.
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