Precision measurement of the mass and lifetime of the Xi_b^- baryon

TL;DR

This paper presents precise measurements of the Xi_b^- baryon's mass and lifetime using LHCb data, significantly improving the accuracy over previous results and confirming theoretical predictions.

Contribution

First precise measurement of Xi_b^- baryon mass and lifetime with doubled accuracy compared to prior studies.

Findings

Measured mass difference: 178.36 ± 0.46 ± 0.16 MeV/c^2

Measured lifetime ratio: 1.089 ± 0.026 ± 0.011

Results are consistent with theoretical expectations.

Abstract

We report on measurements of the mass and lifetime of the Xi_b^- baryon using about 1800 Xi_b^- decays reconstructed in a proton-proton collision data set corresponding to an integrated luminosity of 3.0 fb^{-1} collected by the LHCb experiment. The decays are reconstructed in the Xi_b^- --> Xi_c^0 pi^-, Xi_c^0 --> pK-K-pi+ channel and the mass and lifetime are measured using the Lambda_b^0 --> Lambda_c^+ pi- mode as a reference. We measure M(Xi_b^-) - M(Lambda_b^0) = 178.36 +- 0.46 +- 0.16 MeV/c^2 and tau(Xi_b^-)/tau(Lambda_b^0) = 1.089 +- 0.026 +- 0.011, where the uncertainties are statistical and systematic, respectively. These results lead to a factor of two better precision on the Xi_b^- mass and lifetime compared to previous best measurements, and are consistent with theoretical expectations.