CMS-PAS-BPH-22-002

CMS-PAS-BPH-22-002
Observation of the $\Lambda^{0}_{\mathrm{b}} \to \mathrm{J}/{\psi}\,\Xi^{-}\,\mathrm{K}^{+}$ decay
CMS Collaboration
21 May 2023

Abstract: Using pp collision data corresponding to an integrated luminosity of about 140 fb $^{-1}$ collected by the CMS experiment at $\sqrt{s}=$ 13 TeV in 2016--2018, the $\Lambda^{0}_{\mathrm{b}} \to \mathrm{J}/{\psi}\,\Xi^{-}\,\mathrm{K}^{+}$ decay is observed for the first time with a significance exceeding 5 standard deviations. The relative branching fraction, with respect to the $\Lambda^{0}_{\mathrm{b}} \to \psi(\mathrm{2S})\,\Lambda$ decay, is measured to be $\mathcal{B}(\Lambda^{0}_{\mathrm{b}} \to \mathrm{J}/{\psi}\,\Xi^{-}\,\mathrm{K}^{+})/\mathcal{B}(\Lambda^{0}_{\mathrm{b}} \to \psi(\mathrm{2S})\,\Lambda) =$ [ 2.5 $\pm$ 0.8 $\pm$ 0.9 ]%, where the first uncertainty is statistical and the second one is systematic.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to EPJC. The superseded preliminary plots can be found here.

Figures & Tables	Summary	Additional Figures	References	CMS Publications

Figures
png pdf	Figure 1: The measured $\psi({2\mathrm{S}})\Lambda$ invariant mass distribution with the fit results overlaid ( $\chi^2/\text{ndf}$ = 45.1/54).
png pdf	Figure 2: The measured $\mathrm{J}/\psi\Xi^{-}\mathrm{K^+}$ invariant mass distribution with the fit results overlaid ( $\chi^2/\text{ndf}$ = 30.1/45).

Tables
png pdf	Table 1: Relative systematic uncertainties on the ratio $\mathcal{R}$ in %.

Summary

The

$\Lambda_{b}^{0}\to\mathrm{J}/\psi\Xi^{-}\mathrm{K^+}$ decay is observed with a significance exceeding 5 standard deviations using 13 TeV proton-proton collision data collected by the CMS experiment, corresponding to an integrated luminosity of about 140 fb

$^{-1}$ . The branching fraction is measured with respect to the

$\Lambda_{b}^{0}\to\psi(\text{2S})\Lambda$ decay to be

$\mathcal{B}(\Lambda_{b}^{0}\to\mathrm{J}/\psi\Xi^{-}\mathrm{K^+})/\mathcal{B}(\Lambda_{b}^{0}\to\psi(\text{2S})\Lambda) =$ [ 2.5

$\pm$ 0.8 (stat)

$\pm$ 0.9 (syst) ]%. This is the first discovered multibody decay containing the

$\mathrm{J}/\psi\Xi^{-}$ system, which opens the possibility to search for doubly-strange hidden-charm pentaquarks once more data are collected. The obtained results are important for understanding the strong interaction processes in hadronic decays of beauty baryons and the possible formation of exotic states.

Additional Figures
png pdf	Additional Figure 1: Intermediate invariant mass distributions of the $\Lambda_{b}^{0}\to\mathrm{J}/\psi\Xi^{-}\mathrm{K^+}$ decay. Black points represent the background-subtracted data, while red ones show the predictions of phase space simulation.
png pdf	Additional Figure 1-a: Intermediate invariant mass distributions of the $\Lambda_{b}^{0}\to\mathrm{J}/\psi\Xi^{-}\mathrm{K^+}$ decay. Black points represent the background-subtracted data, while red ones show the predictions of phase space simulation.
png pdf	Additional Figure 1-b: Intermediate invariant mass distributions of the $\Lambda_{b}^{0}\to\mathrm{J}/\psi\Xi^{-}\mathrm{K^+}$ decay. Black points represent the background-subtracted data, while red ones show the predictions of phase space simulation.
png pdf	Additional Figure 1-c: Intermediate invariant mass distributions of the $\Lambda_{b}^{0}\to\mathrm{J}/\psi\Xi^{-}\mathrm{K^+}$ decay. Black points represent the background-subtracted data, while red ones show the predictions of phase space simulation.

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