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| CMS-BPH-19-002 ; CERN-EP-2019-224 | ||
| Observation of the $\Lambda_{\mathrm{b}}^0 \to \mathrm{J}/\psi \Lambda \phi$ decay in proton-proton collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 9 November 2019 | ||
| Phys. Lett. B 802 (2020) 135203 | ||
| Abstract: The observation of the $\Lambda_{\mathrm{b}}^0 \to \mathrm{J}/\psi \Lambda \phi$ decay is reported using proton-proton collision data collected at $\sqrt{s} = $ 13 TeV by the CMS experiment at the LHC in 2018, corresponding to an integrated luminosity of 60 fb$^{-1}$. The ratio of the branching fractions ${\cal B}(\Lambda_{\mathrm{b}}^0 \to \mathrm{J}/\psi \Lambda \phi)/{\cal B}(\Lambda_{\mathrm{b}}^0\to \psi{\mathrm{(2S)}} \Lambda)$ is measured to be (8.26 $\pm$ 0.90 (stat) $\pm$ 0.68 (syst) $\pm$ 0.11 (${\cal B}$) ) $\times 10^{-2}$, where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of $\phi$ and $\psi{\mathrm{(2S)}}$ decays to the reconstructed final states. | ||
| Links: e-print arXiv:1911.03789 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
The invariant mass distributions of (left) ${\mathrm{J}/\psi} \Lambda {{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}} $ and (right) background-subtracted $ {{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}} $. The points are the data, with the vertical bars giving the statistical uncertainties, and the lines show the results of the fits described in the text. |
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Figure 1-a:
The invariant mass distribution of ${\mathrm{J}/\psi} \Lambda {{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}} $. The points are the data, with the vertical bars giving the statistical uncertainties, and the lines show the results of the fits described in the text. |
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Figure 1-b:
The invariant mass distribution of background-subtracted $ {{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}} $. The points are the data, with the vertical bars giving the statistical uncertainties, and the lines show the results of the fits described in the text. |
png pdf |
Figure 2:
The invariant mass distribution of $\Lambda _{\mathrm {b}}^0\to \psi{\mathrm{(2S)}}\Lambda $ candidates. The points are the data and the lines give the result of the fit described in the text. |
| Tables | |
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Table 1:
Summary of the relative systematic uncertainties in ${\cal B}(\Lambda _{\mathrm {b}}^0\to {\mathrm{J}/\psi} \Lambda \phi)/{\cal B}(\Lambda _{\mathrm {b}}^0\to \psi{\mathrm{(2S)}}\Lambda)$. |
| Summary |
| The observation of the $\Lambda_{\mathrm{b}}^0 \to \mathrm{J}/\psi\Lambda \phi$ decay and the measurement of the branching fraction ratio ${\cal B}(\Lambda_{\mathrm{b}}^0 \to \mathrm{J}/\psi\Lambda \phi)/{\cal B}(\Lambda_{\mathrm{b}}^0 \to \psi{\mathrm{(2S)}} \Lambda)$ is presented using a data sample of proton-proton collisions at $\sqrt{s} = $ 13 TeV collected in 2018 by the CMS experiment and corresponding to an integrated luminosity of 60 fb$^{-1}$. The ratio ${\cal B}(\Lambda_{\mathrm{b}}^0 \to \mathrm{J}/\psi\Lambda \phi)/{\cal B}(\Lambda_{\mathrm{b}}^0 \to \psi{\mathrm{(2S)}} \Lambda)$ is measured to be (8.26 $\pm$ 0.90 (stat) $\pm$ 0.68 (syst) $\pm$ 0.11 (${\cal B}$) )$\times 10^{-2}$, where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of $\phi$ and $\psi{\mathrm{(2S)}}$ decays to the reconstructed final states. The observation of the $\Lambda_{\mathrm{b}}^0 \to \mathrm{J}/\psi\Lambda \phi$ decay opens a window on future searches for new resonances in the $\mathrm{J}/\psi\Lambda$ and $\mathrm{J}/\psi\phi$ mass spectra, once a sufficient number of signal events is observed. |
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