Precision Measurement of the Λ0b Baryon Lifetime

Abstract

The ratio of the Λ 0 b 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 p p collisions at the LHC. The Λ 0 b baryon is observed for the first time in the decay mode Λ 0 b → J / ψ p K − , while the ¯¯¯ B 0 meson decay used is the well known ¯¯¯ B 0 → J / ψ π + K − mode, where the π + K − mass is consistent with that of the ¯¯¯¯ K * 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 ¯¯¯ B 0 meson lifetime, the Λ 0 b lifetime is found to be 1.482 ± 0.018 ± 0.012 ps . In both cases, the first uncertainty is statistical and the second systematic.