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Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to EPJC. The superseded preliminary plots can be found here.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.

References
1	LHCb Collaboration	Observation of $ \mathrm{J}/\psi \mathrm{p} $ resonances consistent with pentaquark states in $ \Lambda_{b}^{0}\to\mathrm{J}/\psi\mathrm{p}\mathrm{K^-} $ decays	PRL 115 (2015) 072001	1507.03414
2	L. Maiani, A. D. Polosa, and V. Riquer	The new pentaquarks in the diquark model	PLB 749 (2015) 289	1507.04980
3	E. Santopinto and A. Giachino	Compact pentaquark structures	PRD 96 (2017) 014014	1604.03769
4	L. Roca, J. Nieves, and E. Oset	LHCb pentaquark as a $ \bar{D}^\Sigma_c-\bar{D}^\Sigma_c^* $ molecular state	PRD 92 (2015) 094003	1507.04249
5	M. I. Eides, V. Y. Petrov, and M. V. Polyakov	Pentaquarks with hidden charm as hadroquarkonia	EPJC 78 (2018) 36	1709.09523
6	M.-L. Du et al.	Interpretation of the LHCb $ P_c $ states as hadronic molecules and hints of a narrow $ P_c(4380) $	PRL 124 (2020) 072001	1910.11846
7	S. X. Nakamura	$ P_c(4312)^+ $, $ P_c(4380)^+ $, and $ P_c(4457)^+ $ as double triangle cusps	PRD 103 (2021) 111503	2103.06817
8	LHCb Collaboration	Observation of a narrow pentaquark state, $ P_c(4312)^+ $, and of two-peak structure of the $ P_c(4450)^+ $	PRL 122 (2019) 222001	1904.03947
9	LHCb Collaboration	Evidence of a $ \mathrm{J}/\psi\Lambda $ structure and observation of excited $ \Xi^{-} $ states in the $ \Xi_{b}^{-} \to \mathrm{J}/\psi\Lambda \mathrm{K^-} $ decay	Sci. Bull. 66 (2021) 1278	2012.10380
10	LHCb Collaboration	Evidence for a new structure in the $ \mathrm{J}/\psi\mathrm{p} $ and $ \mathrm{J}/\psi\overline{\mathrm{p}} $ systems in $ \mathrm{B}_{s}^{0}\to\mathrm{J}/\psi\mathrm{p}\overline{\mathrm{p}} $ decays	PRL 128 (2022) 062001	2108.04720
11	LHCb Collaboration	Observation of a $ \mathrm{J}/\psi\Lambda $ resonance consistent with a strange pentaquark candidate in $ {\mathrm{B}^{-}}\to \mathrm{J}/\psi\Lambda\bar{p} $ decays		2210.10346
12	K. Azizi, Y. Sarac, and H. Sundu	Investigation of hidden-charm double strange pentaquark candidate $ P_{css} $ via its mass and strong decays	EPJC 82 (2022) 543	2112.15543
13	F.-L. Wang, X.-D. Yang, R. Chen, and X. Liu	Hidden-charm pentaquarks with triple strangeness due to the $ \Omega_{c}^{()}\bar{D}_s^{()} $ interactions	PRD 103 (2021) 054025	2101.11200
14	CMS Collaboration	Precision luminosity measurement in proton-proton collisions at $ \sqrt{s} = $ 13 TeV in 2015 and 2016 at CMS	EPJC 81 (2021) 800	CMS-LUM-17-003 2104.01927
15	CMS Collaboration	CMS luminosity measurements for the 2016 data taking period	CMS Physics Analysis Summary, 2017 CMS-PAS-LUM-17-001	CMS-PAS-LUM-17-001
16	CMS Collaboration	CMS luminosity measurement for the 2017 data-taking period at $ \sqrt{s} = $ 13 TeV	CMS Physics Analysis Summary, 2018 CMS-PAS-LUM-17-004	CMS-PAS-LUM-17-004
17	CMS Collaboration	CMS luminosity measurement for the 2018 data-taking period at $ \sqrt{s} = $ 13 TeV	CMS Physics Analysis Summary, 2019 CMS-PAS-LUM-18-002	CMS-PAS-LUM-18-002
18	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004
19	CMS Collaboration	Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $ \sqrt{s}= $ 13 TeV	JINST 13 (2018) P06015	CMS-MUO-16-001 1804.04528
20	CMS Collaboration	Description and performance of track and primary-vertex reconstruction with the CMS tracker	JINST 9 (2014) P10009	CMS-TRK-11-001 1405.6569
21	CMS Tracker Group Collaboration	The CMS Phase-1 pixel detector upgrade	JINST 16 (2021) P02027	2012.14304
22	CMS Collaboration	Track impact parameter resolution for the full pseudo rapidity coverage in the 2017 dataset with the CMS Phase-1 pixel detector	CMS Detector Performance Summary CMS-DP-2020-049, 2020 CDS
23	CMS Collaboration	The CMS trigger system	JINST 12 (2017) P01020	CMS-TRG-12-001 1609.02366
24	CMS Collaboration	Performance of the CMS Level-1 trigger in proton-proton collisions at $ \sqrt{s} = $ 13 TeV	JINST 15 (2020) P10017	CMS-TRG-17-001 2006.10165
25	T. Sjöstrand et al.	An introduction to PYTHIA 8.2	Comput. Phys. Commun. 191 (2015) 159	1410.3012
26	D. J. Lange	The EvtGen particle decay simulation package	NIM A 462 (2001) 152
27	E. Barberio and Z. Was	PHOTOS --- a universal Monte Carlo for QED radiative corrections: version 2.0	Comput. Phys. Commun. 79 (1994) 291
28	GEANT4 Collaboration	GEANT 4---A simulation toolkit	NIM A 506 (2003) 250
29	CMS Collaboration	CMS tracking performance results from early LHC operation	EPJC 70 (2010) 1165	CMS-TRK-10-001 1007.1988
30	Particle Data Group Collaboration	Review of particle physics	PTEP 2022 (2022) 083C01
31	CMS Collaboration	Observation of the $ \mathrm{B}_{s}^{0}\to\mathrm{X}(3872)\phi $ decay	PRL 125 (2020) 152001	CMS-BPH-17-005 2005.04764
32	CMS Collaboration	Measurement of $ \mathrm{B}_{c} $(2S)$ ^+ $ and $ \mathrm{B}_{c}^{*} $(2S)$ ^+ $ cross section ratios in proton-proton collisions at $ \sqrt{s} = $ 13 TeV	no.~9, 09, 2020 PRD 102 (2020)	CMS-BPH-19-001 2008.08629
33	CMS Collaboration	Observation of a new excited beauty strange baryon decaying to $ \Xi_{b}^{-}\pi^{+}\pi^{-} $	PRL 126 (2021) 252003	CMS-BPH-20-004 2102.04524
34	CMS Collaboration	Observation of $ {\mathrm{B}^0}\to \psi(\text{2S})\mathrm{K^0_S}\pi^{+}\pi^{-} $ and $ \mathrm{B}_{s}^{0}\to \psi(\text{2S})\mathrm{K^0_S} $ decays	EPJC 82 (2022) 499	CMS-BPH-18-004 2201.09131
35	G. Punzi	Sensitivity of searches for new signals and its optimization	eConf C030908 MODT002, 2003	physics/0308063
36	S. Jackman	Bayesian analysis for the social sciences	John Wiley \& Sons, New Jersey, USA, 2009 link
37	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727
38	S. S. Wilks	The large-sample distribution of the likelihood ratio for testing composite hypotheses	Annals Math. Statist. 9 (1938) 60
39	N. L. Johnson	Systems of frequency curves generated by methods of translation	Biometrika 36 (1949) 149
40	M. Pivk and F. R. Le Diberder	$ _\mathrm{{s}}\mathcal{P}\mathrm{lot} $: a statistical tool to unfold data distributions	NIM A 555 (2005) 356	physics/0402083
41	CMS Collaboration	Tracking performances for charged pions with Run2 legacy data	CMS Detector Performance Report CMS-DP-2022-012, 2022 CDS