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| CMS-PAS-BPH-22-001 | ||
| Measurement of the $ \mathrm{B}^0_\mathrm{s} $ effective lifetime in the decay $ \mathrm{B}^0_\mathrm{s}\to\mathrm{J}/\psi\,\mathrm{K}^0_\mathrm{S} $ from pp collisions at $ \sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 28 March 2024 | ||
| Abstract: The effective lifetime of the $ \mathrm{B}^0_\mathrm{s} $ meson in the decay $ \mathrm{B}^0_\mathrm{s}\to\mathrm{J}/\psi \, \mathrm{K}^0_\mathrm{S} $ is measured using data collected during 2016-2018 with the CMS detector in $ \sqrt{s}= $ 13 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 140 fb$ ^{-1} $. The effective lifetime is determined by performing a two-dimensional unbinned maximum likelihood fit to the $ \mathrm{B}^0_\mathrm{s}\to\mathrm{J}/\psi\, \mathrm{K}^0_\mathrm{S} $ meson invariant mass and proper decay time distributions. The resulting value is 1.59 $ \pm $ 0.07 (stat) $ \pm $ 0.03 (syst) ps, where the first uncertainty represents the statistical uncertainty and the latter corresponds to the systematic uncertainty. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to JHEP. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
The tree-level (left) and penguin (right) diagrams for the decay $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $. |
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Figure 1-a:
The tree-level (left) and penguin (right) diagrams for the decay $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $. |
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Figure 1-b:
The tree-level (left) and penguin (right) diagrams for the decay $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $. |
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Figure 2:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and proper decay time (right) from data (points) and the results from the 2D UML fit. The plots show the complete data set from 2016-2018. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted lines and solid lines show the $ \mathrm{B}_{s}^{0} $ signal, $ {\mathrm{B}^0} $ control channel, combinatorial background, and total fit contributions, respectively. |
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Figure 2-a:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and proper decay time (right) from data (points) and the results from the 2D UML fit. The plots show the complete data set from 2016-2018. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted lines and solid lines show the $ \mathrm{B}_{s}^{0} $ signal, $ {\mathrm{B}^0} $ control channel, combinatorial background, and total fit contributions, respectively. |
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Figure 2-b:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and proper decay time (right) from data (points) and the results from the 2D UML fit. The plots show the complete data set from 2016-2018. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted lines and solid lines show the $ \mathrm{B}_{s}^{0} $ signal, $ {\mathrm{B}^0} $ control channel, combinatorial background, and total fit contributions, respectively. |
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Figure 3:
The proper decay time distribution from data (points) for events in the $ \mathrm{B}_{s}^{0} $ signal region with $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass in the range 5.34-5.42 GeV. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted lines and solid lines show the $ \mathrm{B}_{s}^{0} $ signal, $ {\mathrm{B}^0} $ control channel, combinatorial background, and total fit contributions, respectively. |
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Figure 4:
The signal efficiency as a function of the decay time for the $ {\mathrm{B}^0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (left) and $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (right) decays from simulation for each of the three data-taking years. The vertical bars indicate the statistical uncertainty, and the horizontal bars give the bin width. The curves show the projections of the fit to the simulated event samples. |
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Figure 4-a:
The signal efficiency as a function of the decay time for the $ {\mathrm{B}^0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (left) and $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (right) decays from simulation for each of the three data-taking years. The vertical bars indicate the statistical uncertainty, and the horizontal bars give the bin width. The curves show the projections of the fit to the simulated event samples. |
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Figure 4-b:
The signal efficiency as a function of the decay time for the $ {\mathrm{B}^0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (left) and $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (right) decays from simulation for each of the three data-taking years. The vertical bars indicate the statistical uncertainty, and the horizontal bars give the bin width. The curves show the projections of the fit to the simulated event samples. |
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Figure 4-c:
The signal efficiency as a function of the decay time for the $ {\mathrm{B}^0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (left) and $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (right) decays from simulation for each of the three data-taking years. The vertical bars indicate the statistical uncertainty, and the horizontal bars give the bin width. The curves show the projections of the fit to the simulated event samples. |
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Figure 4-d:
The signal efficiency as a function of the decay time for the $ {\mathrm{B}^0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (left) and $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (right) decays from simulation for each of the three data-taking years. The vertical bars indicate the statistical uncertainty, and the horizontal bars give the bin width. The curves show the projections of the fit to the simulated event samples. |
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Figure 4-e:
The signal efficiency as a function of the decay time for the $ {\mathrm{B}^0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (left) and $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (right) decays from simulation for each of the three data-taking years. The vertical bars indicate the statistical uncertainty, and the horizontal bars give the bin width. The curves show the projections of the fit to the simulated event samples. |
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Figure 4-f:
The signal efficiency as a function of the decay time for the $ {\mathrm{B}^0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (left) and $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ (right) decays from simulation for each of the three data-taking years. The vertical bars indicate the statistical uncertainty, and the horizontal bars give the bin width. The curves show the projections of the fit to the simulated event samples. |
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Figure 5:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and decay time (right) from data (points), along with the projections from the 2D UML fit for each year of data taking. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted and solid lines represent the signal, control channel, combinational background, and total fit contributions respectively. |
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Figure 5-a:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and decay time (right) from data (points), along with the projections from the 2D UML fit for each year of data taking. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted and solid lines represent the signal, control channel, combinational background, and total fit contributions respectively. |
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Figure 5-b:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and decay time (right) from data (points), along with the projections from the 2D UML fit for each year of data taking. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted and solid lines represent the signal, control channel, combinational background, and total fit contributions respectively. |
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Figure 5-c:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and decay time (right) from data (points), along with the projections from the 2D UML fit for each year of data taking. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted and solid lines represent the signal, control channel, combinational background, and total fit contributions respectively. |
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Figure 5-d:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and decay time (right) from data (points), along with the projections from the 2D UML fit for each year of data taking. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted and solid lines represent the signal, control channel, combinational background, and total fit contributions respectively. |
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Figure 5-e:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and decay time (right) from data (points), along with the projections from the 2D UML fit for each year of data taking. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted and solid lines represent the signal, control channel, combinational background, and total fit contributions respectively. |
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Figure 5-f:
Distributions of the $ \mathrm{J}/\psi\mathrm{K^0_S} $ invariant mass (left) and decay time (right) from data (points), along with the projections from the 2D UML fit for each year of data taking. The vertical bars on the data points indicate the statistical uncertainty. The dashed, dotted-dashed, dotted and solid lines represent the signal, control channel, combinational background, and total fit contributions respectively. |
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Figure 6:
The 2D UML fit projection on the decay time axis for mass range 5.17 $ < m < $ 5.22 GeV for 2016, 2017 and 2018 respectively. |
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Figure 6-a:
The 2D UML fit projection on the decay time axis for mass range 5.17 $ < m < $ 5.22 GeV for 2016, 2017 and 2018 respectively. |
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Figure 6-b:
The 2D UML fit projection on the decay time axis for mass range 5.17 $ < m < $ 5.22 GeV for 2016, 2017 and 2018 respectively. |
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Figure 6-c:
The 2D UML fit projection on the decay time axis for mass range 5.17 $ < m < $ 5.22 GeV for 2016, 2017 and 2018 respectively. |
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Figure 7:
The 2D UML fit projection on the decay time axis for mass range 5.22 $ < m < $ 5.34 GeV for 2016, 2017 and 2018 respectively. |
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Figure 7-a:
The 2D UML fit projection on the decay time axis for mass range 5.22 $ < m < $ 5.34 GeV for 2016, 2017 and 2018 respectively. |
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Figure 7-b:
The 2D UML fit projection on the decay time axis for mass range 5.22 $ < m < $ 5.34 GeV for 2016, 2017 and 2018 respectively. |
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Figure 7-c:
The 2D UML fit projection on the decay time axis for mass range 5.22 $ < m < $ 5.34 GeV for 2016, 2017 and 2018 respectively. |
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Figure 8:
The 2D UML fit projection on the decay time axis for mass range 5.42 $ < m < $ 5.57 GeV for 2016, 2017 and 2018 respectively. |
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Figure 8-a:
The 2D UML fit projection on the decay time axis for mass range 5.42 $ < m < $ 5.57 GeV for 2016, 2017 and 2018 respectively. |
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Figure 8-b:
The 2D UML fit projection on the decay time axis for mass range 5.42 $ < m < $ 5.57 GeV for 2016, 2017 and 2018 respectively. |
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Figure 8-c:
The 2D UML fit projection on the decay time axis for mass range 5.42 $ < m < $ 5.57 GeV for 2016, 2017 and 2018 respectively. |
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Figure 9:
The 2D UML fit projection plots on the mass axis for decay time range 0.2 $ < t < $ 2.5 ps for 2016, 2017 and 2018 respectively. |
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Figure 9-a:
The 2D UML fit projection plots on the mass axis for decay time range 0.2 $ < t < $ 2.5 ps for 2016, 2017 and 2018 respectively. |
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Figure 9-b:
The 2D UML fit projection plots on the mass axis for decay time range 0.2 $ < t < $ 2.5 ps for 2016, 2017 and 2018 respectively. |
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Figure 9-c:
The 2D UML fit projection plots on the mass axis for decay time range 0.2 $ < t < $ 2.5 ps for 2016, 2017 and 2018 respectively. |
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Figure 10:
The 2D UML fit projection plots on the mass axis for decay time range 2.5 $ < t < $ 3.5 ps for 2016, 2017 and 2018 respectively. |
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Figure 10-a:
The 2D UML fit projection plots on the mass axis for decay time range 2.5 $ < t < $ 3.5 ps for 2016, 2017 and 2018 respectively. |
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Figure 10-b:
The 2D UML fit projection plots on the mass axis for decay time range 2.5 $ < t < $ 3.5 ps for 2016, 2017 and 2018 respectively. |
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Figure 10-c:
The 2D UML fit projection plots on the mass axis for decay time range 2.5 $ < t < $ 3.5 ps for 2016, 2017 and 2018 respectively. |
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Figure 11:
The 2D UML fit projection plots on the mass axis for decay time range 3.5 $ < t < $ 10 ps for 2016, 2017 and 2018 respectively. |
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Figure 11-a:
The 2D UML fit projection plots on the mass axis for decay time range 3.5 $ < t < $ 10 ps for 2016, 2017 and 2018 respectively. |
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Figure 11-b:
The 2D UML fit projection plots on the mass axis for decay time range 3.5 $ < t < $ 10 ps for 2016, 2017 and 2018 respectively. |
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Figure 11-c:
The 2D UML fit projection plots on the mass axis for decay time range 3.5 $ < t < $ 10 ps for 2016, 2017 and 2018 respectively. |
| Tables | |
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Table 1:
Sources of systematic uncertainties in the $ \mathrm{B}_{s}^{0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ effective lifetime measurement and their estimated values, along with the total systematic uncertainty. |
| Summary |
| The effective lifetime of the $ \mathrm{B}_{s}^{0} $ meson in the $ \mathrm{J}/\psi\mathrm{K^0_S} $ decay channel is measured using the data collected during 2016-2018 by the CMS detector in proton-proton collision events at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 140 fb$ ^{-1} $. Throughout the analysis, the decay $ {\mathrm{B}^0} \to \mathrm{J}/\psi\mathrm{K^0_S} $ with larger event yield is used as a reference at multiple stages validating analysis method. The measured effective lifetime is found to be 1.59 $ \pm $ 0.07 (stat) $ \pm $ 0.03 (syst) ps. This measurement is compatible within 2.1$ \sigma $ with a previous measurement conducted by the LHCb experiment and shows strong agreement with the SM prediction of 1.62 $ \pm $ 0.02 ps. |
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Compact Muon Solenoid LHC, CERN |
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