Measurement of b hadron lifetimes in pp collisions at $\sqrt{s}=$ 8 TeV

Abstract

Measurements are presented of the lifetimes of the B${}^0$, B${}_{\mathrm{s}}^0$, ${\Lambda }_{\mathrm{b}}^0$, and B${}_{\mathrm{c}}^{+}$ hadrons using the decay channels B${}^0\to$ J/$\psi$K*(892)${}^0$, B${}^0\to$J/$\psi$K${}_{\mathrm{S}}^0$, B${}_{\mathrm{s}}^0\to$J/$\psi {\pi }^{+}{\pi }^{-}$, B${}_{\mathrm{s}}^0\to$J/$\psi \varphi$(1020), ${\Lambda }_{\mathrm{b}}^0\to$J/$\psi {\Lambda }^0$, and B${}_{\mathrm{c}}\to$J/$\psi {\pi }^{+}$. The data sample, corresponding to an integrated luminosity of 19.7 fb${}^{-1}$, was collected by the CMS detector at the LHC in proton-proton collisions at $\sqrt{s}=$ 8 TeV. The B${}^0$ lifetime is measured to be 453.0 $\pm$ 1.6 (stat) $\pm$ 1.8 (syst) $\mu$m in J/$\psi$K*(892)${}^0$ and 457.8 $\pm$ 2.7 (stat) $\pm$ 2.8 (syst) $\mu$m in J/$\psi$K${}_{\mathrm{S}}^0$, which results in a combined measurement of $c{\tau }_{{\mathrm{B}}^0}=$ 454.1 $\pm$ 1.4 (stat) $\pm$ 1.7 (syst) $\mu$m. The effective lifetime of the B${}_{\mathrm{s}}^0$ meson is measured in two decay modes, with contributions from different amounts of the heavy and light eigenstates. This results in two different measured lifetimes: $c{\tau }_{{\mathrm{B}}_{\mathrm{s}}^0\to \mathrm{J}/\psi {\pi }^{+}{\pi }^{-}}=$ 502.7 $\pm$ 10.2 (stat) $\pm$ 3.4 (syst) $\mu$m and $c{\tau }_{{\mathrm{B}}_{\mathrm{s}}^0\to \mathrm{J}/\psi \varphi (1020)}=$ 443.9 $\pm$ 2.0 (stat) $\pm$ 1.5 (syst) $\mu$m. The ${\Lambda }_{\mathrm{b}}^0$ lifetime is found to be 443.9 $\pm$ 8.2 (stat) $\pm$ 2.8 (syst) $\mu$m. The precision from each of these channels is as good as or better than previous measurements. The B${}_{\mathrm{c}}^{+}$ lifetime, measured with respect to the B${}^{+}$ to reduce the systematic uncertainty, is 162.3 $\pm$ 7.8 (stat) $\pm$ 4.2 (syst) $\pm$ 0.1 $({\tau }_{{\mathrm{B}}^{+}})$ $\mu$m. All results are in agreement with current world-average values.

Replaced with the published version, including some corrections. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/BPH-13-008 (CMS Public Pages)

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