The ratio of the Λb0 baryon lifetime to that of the B ̄0 meson is measured using 1.0 fb-1 of integrated luminosity in 7 TeV center-of-mass energy pp collisions at the LHC. The Λb0 baryon is observed for the first time in the decay mode Λb0→J/ψpK-, while the B̄0 meson decay used is the well known B̄0→J/ψπ+K - mode, where the π+K- mass is consistent with that of the K̄*0(892) meson. The ratio of lifetimes is measured to be 0.976±0.012±0.006, in agreement with theoretical expectations based on the heavy quark expansion. Using previous determinations of the B̄0 meson lifetime, the Λb0 lifetime is found to be 1.482±0.018±0.012 ps. In both cases, the first uncertainty is statistical and the second systematic. © 2013 CERN, for the LHCb Collaboration Published by the American Physical Society under the terms of the http://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
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