/ hep-ex CMS-BPH-13-008

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$^0_\mathrm{s}$, $\Lambda^0_\mathrm{b}$, and B$_\mathrm{c}^+$ hadrons using the decay channels B$^0\to$J/$\psi$K*(892)$^0$, B$^0\to$J/$\psi$K$^0_\mathrm{S}$, B$^0_\mathrm{s}\to$J/$\psi \pi^+\pi^-$, B$^0_\mathrm{s}\to$J/$\psi\phi$(1020), $\Lambda^0_\mathrm{b}\to$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$1.5 (syst)$\mu$m in J/$\psi$K*(892)$^0$ and 457.8$\pm$2.7 (stat)$\pm$2.7(syst)$\mu$m in J/$\psi$K$^0_\mathrm{S}$, which results in a combined measurement of $c\tau_{\mathrm{B}^0} =$454.1$\pm$1.4(stat)$\pm$1.3(syst)$\mu$m. The effective lifetime of the B$^0_\mathrm{s}$ 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: $c\tau_{\mathrm{B}^0_\mathrm{s} \to \mathrm{J}/\psi \pi^+\pi^-} =$ 502.7$\pm$10.2 (stat)$\pm$3.2 (syst)$\mu$m and $c\tau_{\mathrm{B}^0_\mathrm{s} \to \mathrm{J}/\psi\phi(1020)} =$443.9$\pm$2.0 (stat)$\pm$1.2 (syst)$\mu$m. The $\Lambda^0_\mathrm{b}$ lifetime is found to be 442.9$\pm$8.2 (stat)$\pm$2.7 (syst)$\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$8.2 (stat)$\pm$4.7 (syst)$\pm$0.1 $(\tau_{\mathrm{B}^+})\mu$m. All results are in agreement with current world-average values.

Note: *Temporary entry*; Submitted to Eur. Phys. J. C. All 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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