Measurement of b hadron lifetimes in pp collisions at s = 8 TeV

Abstract

Measurements are presented of the lifetimes of the $B^0$ , $B_s^0$ , ${\Lambda }_b^0$ , and $B_c^{+}$ hadrons using the decay channels $B^0\to J/\psi K^{\ast }\left(892\right){}^0$ , $B^0\to J/\psi K_S^0$ , $B_s^0\to J/\psi {\pi }^{+}{\pi }^{-}$ , $B_s^0\to J/\psi \varphi \left(1020\right)$ , ${\Lambda }_b^0\to J/\psi {\Lambda }^0$ , and $B_c^{+}\to J/\psi {\pi }^{+}$ . The data sample, corresponding to an integrated luminosity of 19.7 ${\text{fb}}^{\text{-1}}$ , was collected by the CMS detector at the LHC in proton-proton collisions at $\sqrt{s}=8\text{TeV}$ . The $B^0$ lifetime is measured to be $453.0\pm 1.6\text{(stat)}\pm 1.8\text{(syst)}\mu \text{m}$ in $J/\psi K^{\ast }\left(892\right){}^0$ and $457.8\pm 2.7\text{(stat)}\pm 2.8\text{(syst)}\mu \text{m}$ in $J/\psi K_S^0$ , which results in a combined measurement of $c{\tau }_{B^0}=454.1\pm 1.4\text{(stat)}\pm 1.7\text{(syst)}\mu \text{m}$ . 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: $c{\tau }_{B_s^0\to J/\psi {\pi }^{+}{\pi }^{-}}=502.7\pm 10.2\text{(stat)}\pm 3.4\text{(syst)}\mu \text{m}$ and $c{\tau }_{B_s^0\to J/\psi \varphi \left(1020\right)}=443.9\pm 2.0\text{(stat)}\pm 1.5\text{(syst)}\mu \text{m}$ . The ${\Lambda }_b^0$ lifetime is found to be $442.9\pm 8.2\text{(stat)}\pm 2.8\text{(syst)}\mu \text{m}$ . 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 $162.3\pm 7.8\text{(stat)}\pm 4.2\text{(syst)}\pm 0.1\left({\tau }_{B^{+}}\right)\mu \text{m}$ . All results are in agreement with current world-average values.