Precision measurement of the $\Xi^-_b$ baryon lifetime

TL;DR

This paper reports a precise measurement of the $ ext{Xi}_b^-$ baryon lifetime using LHCb data, significantly improving the accuracy of previous measurements and aligning well with theoretical predictions.

Contribution

The study provides the most precise measurement of the $ ext{Xi}_b^-$ baryon lifetime to date, combining Run 1 and Run 2 data for enhanced accuracy.

Findings

Measured the ratio of $ ext{Xi}_b^-$ to $ ext{Lambda}_b^0$ lifetime as 1.078±0.012±0.007.

Derived the $ ext{Xi}_b^-$ lifetime as 1.578±0.018±0.010±0.011 ps.

Result agrees with recent theoretical models.

Abstract

A sample of $pp$ collision data, corresponding to an integrated luminosity of 5.5 fb$^{-1}$ and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the $\Xi^-_b$ baryon to that of the $\Lambda^0_b$ baryon, $r_{\tau}\equiv\tau_{\Xi^-_b}/\tau_{\Lambda^0_b}$. The value ${r_{\tau}=1.076\pm0.013\pm0.006}$ is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain ${r_{\tau}^{\rm Run\,1,2} = 1.078\pm0.012\pm0.007}$. Multiplying by the world-average value of the $\Lambda^0_b$ lifetime yields $\tau_{\Xi^-_b}^{\rm Run~1,2} = 1.578\pm0.018\pm0.010\pm0.011$ ps, where the uncertainties are statistical, systematic, and due to the limited knowledge of the $\Lambda^0_b$ lifetime. This measurement improves the precision of the current world average of the $\Xi^-_b$ lifetime by about a factor of two, and is in good agreement with the most recent theoretical predictions.