Observation and Mass Measurement of the Baryon $\Xi^-_b$

TL;DR

This paper reports the first observation and precise mass measurement of the bottom, strange baryon $ ext{ extXi}^-_b$ through its decay chain, providing significant evidence with a high statistical significance.

Contribution

It presents the first observation and mass measurement of the $ ext{ extXi}^-_b$ baryon, using decay channels and statistical analysis to establish its existence.

Findings

Observation with 7.7 sigma significance

Mass measured as 5792.9 ± 2.5 (stat) ± 1.7 (syst) MeV/c^2

Strong evidence for the existence of $ ext{ extXi}^-_b$

Abstract

We report the observation and measurement of the mass of the bottom, strange baryon $\Xi^-_b$ through the decay chain $\Xi^-_b \to J/\psi \Xi^-$, where $J/\psi \to \mu^+ \mu^-$, $\Xi^- \to \Lambda \pi^-$, and $\Lambda \to p \pi^-$. Evidence for observation is based on a signal whose probability of arising from the estimated background is 6.6 x 10^{-15}, or 7.7 Gaussian standard deviations. The $\Xi^-_b$ mass is measured to be $5792.9\pm 2.5$ (stat.) $\pm 1.7$ (syst.) MeV/$c^2$.