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

The CMS collaboration
Eur.Phys.J.C 78 (2018) 457, 2018.

Abstract (data abstract)
CERN-LHC. Measurements are presented of the lifetimes of the $B^{0}$, $B_{s}^{0}$, $\Lambda_{b}$ and $B_{c}^{+}$ hadrons using the decay channels $B^{0} \to J/\psi K^{*}(892)$, $B^{0} \to J/\psi K_{s}^{0}$, $B_s^{0} \to J/\psi \pi \pi$, $B_s^{0} \to J/\psi\phi(1020)$, $\Lambda_{b} \to J/\psi\Lambda$ amd $B_{c}^{+} \to J/\psi\pi$. The data sample, corresponding to an integrated luminosity of 19.7fb$^{-1}$, 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 $J/\psi K^{*}(892)$ and $457.8 \pm 2.7(stat) \pm 2.8(syst)$ $\mu$m in $J/\psi K_{s}^{0}$, which results in a combined measurement of $c\tau_{B^{0}} = 454.1 \pm 1.4(stat) \pm 1.7(syst)$ $\mu$m. The effective lifetime of the $B_{s}^{0}$ 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: $c\tau_{B_s^{0} \to J/\psi\pi\pi} = 502.7 \pm 10.2(stat)\pm 3.4(syst)$ $\mu$m and $c\tau_{B_s^{0} \to J/\psi\phi(1020)} = 443.9 \pm 2.0(stat) \pm1.5(syst)$ $\mu$m. The $\Lambda_{b}$ lifetime is found to be $442.9 \pm 8.2(stat) \pm 2.8(syst)$ $\mu$m. The precision from each of these channels is as good as or better than previous measurements. The $B_{c}^{+}$ lifetime, measured with respect to the $B^{+}$ to reduce the systematic uncertainty, is $162.3 \pm 7.8(stat) \pm 4.2(syst) \pm 0.1\,(\tau_{B^{+}})$ $\mu$m . All results are in agreement with current world-average values.

  • Table 1


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

  • Table 2


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

  • Table 3


    Estimate $\Gamma_\mathrm{d}$ and $\Delta \Gamma_\mathrm{d}$ in pp collisions at $\sqrt{s}=8$TeV.

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