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


Abstract

Measurements are presented of the lifetimes of theMeasurements are presented of the lifetimes of the $B^0, B{^0_s},\Lambda{^0_b}$ and $B{^+_c}$ hadrons using the decay channels ${\mathrm {B}^0}\!\rightarrow \! \mathrm {J}/\psi \mathrm {K^{*}(892)}{}^{0}, {\mathrm {B}^0}\!\rightarrow \! \mathrm {J}/\psi \mathrm {K^0_S},\mathrm {B}^0_\mathrm {s} \!\rightarrow \! \mathrm {J}/\psi \mathrm {\pi ^+}\mathrm {\pi ^-}, \mathrm {B}^0_\mathrm {s} \!\rightarrow \! \mathrm {J}/\psi \mathrm {\phi (1020)}, \varLambda _\mathrm {b}^0\!\rightarrow \!\mathrm {J}/\psi \mathrm {\Lambda }^{0}$ and $\mathrm {B}_\mathrm {c}^+ \!\rightarrow \!\mathrm {J}/\psi \mathrm {\pi ^+}$. 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 √s=8TeV. The $B^0$ lifetime is measured to be $453.0 \pm 1.6\,\text {(stat)} \pm 1.8\,\text {(syst)} \,\mu \text {m}$ in $\mathrm {J}/\psi \mathrm {K^{*}(892)}{}^{0}$ and $457.8 \pm 2.7\,\text {(stat)} \pm 2.8\,\text {(syst)} \,\mu \text {m}$ in $\mathrm {J}/\psi \mathrm {K^0_S}$ which results in a combined measurement of $c\tau _{{\mathrm {B}^0}} = 454.1 \pm 1.4\,\text {(stat)} \pm 1.7\,\text {(syst)} \,\mu \text {m}$. The effective lifetime of the $B{^0_s}$ 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: $c\tau _{\mathrm {B}^0_\mathrm {s} \rightarrow \mathrm {J}/\psi \mathrm {\pi ^+}\mathrm {\pi ^-}} = 502.7 \pm 10.2\,\text {(stat)} \pm 3.4\,\text {(syst)} \,\mu \text {m}$ and $c\tau _{\mathrm {B}^0_\mathrm {s} \rightarrow \mathrm {J}/\psi \mathrm {\phi (1020)}} = 443.9 \pm 2.0\,\text {(stat)} \pm 1.5\,\text {(syst)} \,\mu \text {m}$. The $mathrm {\Lambda }_\mathrm {b} ^0$ 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 $162.3 \pm 7.8\,\text {(stat)} \pm 4.2\,\text {(syst)} \pm 0.1\,(\tau _{{\mathrm {B}^{+}}})\,\mu \text {m}$. All results are in agreement with current world-average values.

Abstract

Measurements are presented of the lifetimes of theMeasurements are presented of the lifetimes of the $B^0, B{^0_s},\Lambda{^0_b}$ and $B{^+_c}$ hadrons using the decay channels ${\mathrm {B}^0}\!\rightarrow \! \mathrm {J}/\psi \mathrm {K^{*}(892)}{}^{0}, {\mathrm {B}^0}\!\rightarrow \! \mathrm {J}/\psi \mathrm {K^0_S},\mathrm {B}^0_\mathrm {s} \!\rightarrow \! \mathrm {J}/\psi \mathrm {\pi ^+}\mathrm {\pi ^-}, \mathrm {B}^0_\mathrm {s} \!\rightarrow \! \mathrm {J}/\psi \mathrm {\phi (1020)}, \varLambda _\mathrm {b}^0\!\rightarrow \!\mathrm {J}/\psi \mathrm {\Lambda }^{0}$ and $\mathrm {B}_\mathrm {c}^+ \!\rightarrow \!\mathrm {J}/\psi \mathrm {\pi ^+}$. 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 √s=8TeV. The $B^0$ lifetime is measured to be $453.0 \pm 1.6\,\text {(stat)} \pm 1.8\,\text {(syst)} \,\mu \text {m}$ in $\mathrm {J}/\psi \mathrm {K^{*}(892)}{}^{0}$ and $457.8 \pm 2.7\,\text {(stat)} \pm 2.8\,\text {(syst)} \,\mu \text {m}$ in $\mathrm {J}/\psi \mathrm {K^0_S}$ which results in a combined measurement of $c\tau _{{\mathrm {B}^0}} = 454.1 \pm 1.4\,\text {(stat)} \pm 1.7\,\text {(syst)} \,\mu \text {m}$. The effective lifetime of the $B{^0_s}$ 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: $c\tau _{\mathrm {B}^0_\mathrm {s} \rightarrow \mathrm {J}/\psi \mathrm {\pi ^+}\mathrm {\pi ^-}} = 502.7 \pm 10.2\,\text {(stat)} \pm 3.4\,\text {(syst)} \,\mu \text {m}$ and $c\tau _{\mathrm {B}^0_\mathrm {s} \rightarrow \mathrm {J}/\psi \mathrm {\phi (1020)}} = 443.9 \pm 2.0\,\text {(stat)} \pm 1.5\,\text {(syst)} \,\mu \text {m}$. The $mathrm {\Lambda }_\mathrm {b} ^0$ 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 $162.3 \pm 7.8\,\text {(stat)} \pm 4.2\,\text {(syst)} \pm 0.1\,(\tau _{{\mathrm {B}^{+}}})\,\mu \text {m}$. All results are in agreement with current world-average values.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Language:English
Date:2018
Deposited On:06 Mar 2019 08:38
Last Modified:06 Oct 2019 05:57
Publisher:Springer
ISSN:1434-6044
Additional Information:Erratum: Eur. Phys. J.C78,no.7,561(2018) https://link.springer.com/article/10.1140%2Fepjc%2Fs10052-018-6014-7
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1140/epjc/s10052-018-5929-3

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