Study of the $\Xi_b^-$ baryon decay at CMS

A preliminary measurement of the $\Xi_b^-$ baryon lifetime through the decay chain $\Xi_b^-$ → J/ψ$\Xi^-$ −, where J/ψ → µ$^{+}$µ$^{−}$, $\Xi^-$ → Λ$^{0}$π$^{−}$ and Λ$^{0}$ → pπ$^{−}$, using 5.1 fb$^{−1}$ of integrated luminosity of data from proton-proton collisions with a center-of-mass energy of 7 T eV collected by the Compact Muon Solenoid CMS at CERN is presented. After the reconstruction and selection of the $\Xi_b^-$ baryon from the data, 65 candidates with a mass of 5.798 ± 0.015 GeV/c$^{2}$ were found. Then, the reduced proper time of the $\Xi_b^-$ candidates were calculated in order to use the binned maximum likelihood method to measure the lifetime of the particle. Finally, the preliminary lifetime τ = 1.597 ±$\frac{0.293}{0.262}$ ±0.060 ps was measured, where the first error is statistical and the second is systematic.