Precision measurement of the Lambda_b baryon lifetime

TL;DR

This paper reports a precise measurement of the mbda_b baryon lifetime relative to the B0 meson using LHC data, including the first observation of mbda_b in a specific decay mode, confirming theoretical predictions.

Contribution

It provides the first observation of mbda_b in the mbda_b -> J/si pK- decay mode and measures its lifetime with high precision, aligning with heavy quark expansion theories.

Findings

The mbda_b to B0 lifetime ratio is 0.976 b1 0.012 b1 0.006.

The mbda_b lifetime is measured as 1.482 b1 0.018 b1 0.012 ps.

First observation of mbda_b in the decay mode mbda_b -> J/si pK-.

Abstract

The ratio of the \Lambda b baryon lifetime to that of the B0 meson is measured using 1.0/fb of integrated luminosity in 7 TeV center-of-mass energy pp collisions at the LHC. The \Lambda b baryon is observed for the first time in the decay mode \Lambda b -> J/\psi pK-, while the B0 meson decay used is the well known B0 -> J/\psi pi+K- mode, where the pi+ 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 B0 meson lifetime, the \Lambda 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.