CMS-PAS-BPH-19-002

CMS-PAS-BPH-19-002
Observation of the $\Lambda_{\mathrm{b}} \to \mathrm{J}/\psi \Lambda \phi$ decay in proton-proton collisions at $\sqrt{s}=$ 13 TeV
CMS Collaboration
August 2019

Abstract: We report a first observation of the $\Lambda_{\mathrm{b}} \to \mathrm{J}/\psi \Lambda \phi$ decay using proton-proton collision data collected at $\sqrt{s}$= 13 TeV by the CMS experiment at the LHC, and corresponding to an integrated luminosity of 60 fb$^{-1}$. The ratio of the branching fractions ${\cal B}(\Lambda_{\mathrm{b}} \to \mathrm{J}/\psi \Lambda \phi)/{\cal B}(\Lambda_{\mathrm{b}}\to \psi\mathrm{(2S)} \Lambda)$ 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 third is due to the uncertainties in the world-average branching fractions.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 802 (2020) 135203. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The invariant mass distribution $M({\mathrm{J}/\psi} \Lambda {{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}})$ (left) and the background-subtracted distribution of $M({{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}})$ (right). The choice of the fit function is explained in the text.
png pdf	Figure 1-a: The invariant mass distribution $M({\mathrm{J}/\psi} \Lambda {{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}})$ (left) and the background-subtracted distribution of $M({{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}})$ (right). The choice of the fit function is explained in the text.
png pdf	Figure 1-b: The invariant mass distribution $M({\mathrm{J}/\psi} \Lambda {{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}})$ (left) and the background-subtracted distribution of $M({{\mathrm{K}} ^{+}} {{\mathrm{K}} ^{-}})$ (right). The choice of the fit function is explained in the text.
png pdf	Figure 2: The invariant mass distribution of $\Lambda_{\mathrm{b}} \to \psi\mathrm{(2S)}\Lambda $ candidates. The points are data and the curve is the result of the fit described in the text.

Tables
png pdf	Table 1: Summary of the relative systematic uncertainties in ${\cal B}(\Lambda_{\mathrm{b}} \to {\mathrm{J}/\psi} \Lambda \phi)/{\cal B}(\Lambda_{\mathrm{b}} \to \psi\mathrm{(2S)}\Lambda)$.

Summary

We report the first observation of the $\Lambda_{\mathrm{b}} \to \mathrm{J}/\psi\Lambda \phi$ decay and the measurement of the relative branching fraction ${\cal B}(\Lambda_{\mathrm{b}} \to \mathrm{J}/\psi\Lambda \phi)/{\cal B}(\Lambda_{\mathrm{b}} \to \psi\mathrm{(2S)} \Lambda)$ using a data sample of pp collisions at $\sqrt{s} = $ 13 TeV recorded in 2018 and corresponding to an integrated luminosity of 60 fb$^{-1}$. The branching fraction ratio ${\cal B}(\Lambda_{\mathrm{b}} \to \mathrm{J}/\psi\Lambda \phi)/{\cal B}(\Lambda_{\mathrm{b}} \to \psi\mathrm{(2S)} \Lambda)$ is measured to be (8.26 $\pm$ 0.90 (stat) $\pm$ 0.68 (syst) $\pm$ 0.11 (${\cal B}$) )$\times 10^{-2}$.

References
1	UA1 Collaboration	First observation of the beauty baryon $\Lambda_{\mathrm{b}}$ in the decay channel $ \Lambda_{\mathrm{b}} \to \mathrm{J}/\psi \Lambda $ at the CERN proton - anti-proton collider	PLB 273 (1991) 540
2	CDF Collaboration	Search for $ \Lambda_b \to J/\psi \Lambda^0 $ in $ p\bar{p} $ collisions at $ \sqrt{s} = $ 1.8 TeV	PRD 47 (1993) R2639
3	CDF Collaboration	Measurement of $ \Lambda_b^0 $ lifetime using $ \Lambda_b^0 \to \Lambda_c^+ \ell^- \bar{\nu} $	PRL 77 (1996) 1439
4	CDF Collaboration	Observation of $ \Lambda_b^0 \to J/\psi \Lambda $ at the Fermilab proton antiproton collider	PRD 55 (1997) 1142
5	CDF Collaboration	Search for $ \Lambda_b \to p \pi $ and $ \Lambda_b \to p K $ decays in $ p\bar{p} $ collisions at $ \sqrt{s} = $ 1.96 TeV	PRD 72 (2005) 051104	hep-ex/0507067
6	CDF Collaboration	Measurement of $ \sigma(\Lambda_b^0)/\sigma(\bar{B}^0) \times {\rm BR}(\Lambda_b^0 \to \Lambda_c^+ \pi^-)/{\rm BR}(\bar{B}^0 \to D^+ \pi^-) $ in $ p\bar{p} $ collisions at $ \sqrt{s} = $ 1.96-TeV.	PRL 98 (2007) 122002	hep-ex/0601003
7	CDF Collaboration	Measurement of the $ \Lambda^0_{b} $ Lifetime in $ \Lambda^0_{b} \to J/\psi \Lambda^0 $ in $ p \bar{p} $ Collisions at $ \sqrt{s} = $ 1.96-TeV	PRL 98 (2007) 122001	hep-ex/0609021
8	CDF Collaboration	First Measurement of the Ratio of Branching Fractions $ B(\Lambda^0_b \to \Lambda^+_{c} \mu^{-} \bar{\nu}_\mu / B(Lambda^0_b \to \Lambda^+_{c} \pi^{-}) $	PRD 79 (2009) 032001	0810.3213
9	CDF Collaboration	Measurement of the $ \Lambda_b $ Lifetime in $ \Lambda_b \to \Lambda_c^+ \pi^- $ Decays in $ p\bar{p} $ Collisions at $ \sqrt{s} = $ 1.96 TeV	PRL 104 (2010) 102002	0912.3566
10	CDF Collaboration	Observation of the Baryonic Flavor-Changing Neutral Current Decay $ \Lambda_{b} \to \Lambda \mu^{+} \mu^{-} $	PRL 107 (2011) 201802	1107.3753
11	CDF Collaboration	Measurement of the branching fraction $ {\mathcal{B}}(\Lambda^0_b\rightarrow \Lambda^+_c\pi^-\pi^+\pi^-) $ at CDF	PRD 85 (2012) 032003	1112.3334
12	D0 Collaboration	Measurement of the $ \Lambda_b^0 $ lifetime in the decay $ \Lambda_b^0 \to J/\psi \Lambda^0 $ with the D$ \O\ $ detector	PRL 94 (2005) 102001	hep-ex/0410054
13	D0 Collaboration	Measurement of the $ \Lambda_b $ Lifetime in the Exclusive Decay $ \Lambda_b \to J/\psi \Lambda $	PRL 99 (2007) 142001	0704.3909
14	D0 Collaboration	Measurement of the $ \Lambda_b^0 $ lifetime using semileptonic decays	PRL 99 (2007) 182001	0706.2358
15	D0 Collaboration	Measurement of the production fraction times branching fraction $ f(b\to\Lambda_{b})\cdot \mathcal{B}(\Lambda_{b}\to J/\psi \Lambda) $	PRD 84 (2011) 031102	1105.0690
16	D0 Collaboration	Measurement of the $ \Lambda_b^0 $ lifetime in the exclusive decay $ \Lambda_b^0 \to J/\psi \Lambda^0 $ in $ p\bar{p} $ collisions at $ \sqrt{s}= $ 1.96 TeV	PRD 85 (2012) 112003	1204.2340
17	D0 Collaboration	Measurement of the Forward-Backward Asymmetry in $ ?_b^0 $ and $ \bar{?}_b^0 $ Baryon Production in $ p\bar{p} $ Collisions at $ \sqrt{s} = $ 1.96 TeV	PRD 91 (2015) 072008	1503.03917
18	LHCb Collaboration	Observation of the decays $ \Lambda_b^0 \to \chi_{c1} p K^- $ and $ \Lambda_b^0 \to \chi_{c2} p K^- $	PRL 119 (2017) 062001	1704.07900
19	LHCb Collaboration	Observation of excited $ \Lambda_b^0 $ baryons	PRL 109 (2012) 172003	1205.3452
20	ATLAS Collaboration	Measurement of the $ \Lambda_b^0 $ lifetime and mass in the ATLAS experiment	PRD 87 (2013) 032002	1207.2284
21	LHCb Collaboration	Precision measurement of the ratio of the $ \Lambda^0_b $ to $ \overline{B}^0 $ lifetimes	PLB 734 (2014) 122	1402.6242
22	CMS Collaboration	Measurement of the $ \Lambda_b $ polarization and angular parameters in $ \Lambda_b\to J/\psi \Lambda $ decays from pp collisions at $ \sqrt{s}= $ 7 and 8 TeV	PRD 97 (2018) 072010	CMS-BPH-15-002 1802.04867
23	CMS Collaboration	Measurement of b hadron lifetimes in pp collisions at $ \sqrt{s} = $ 8 TeV	EPJC 78 (2018) 457	CMS-BPH-13-008 1710.08949
24	ATLAS Collaboration	Measurement of the branching ratio $ \Gamma(\Lambda_b^0 \rightarrow \psi(2S)\Lambda^0)/\Gamma(\Lambda_b^0 \rightarrow J/\psi\Lambda^0) $ with the ATLAS detector	Phys. Lett.B 751 (2015) 63	1507.08202
25	LHCb Collaboration	Observation of $ \Lambda_b^0 \to \psi(2S)pK^- $ and $ \Lambda_b^0 \to J/\psi \pi^+ \pi^- pK^- $ decays and a measurement of the $ \Lambda_b^0 $ baryon mass	JHEP 05 (2016) 132	1603.06961
26	LHCb Collaboration	Observation of the $ \Lambda_b^0\rightarrow \chi_{c1}(3872)pK^- $ decay		1907.00954
27	LHCb Collaboration	Observation of $ J/\psi p $ resonances consistent with pentaquark states in $ \Lambda_b^0 \to J/\psi K^- p $ decays	PRL 115 (2015) 072001	1507.03414
28	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
29	Particle Data Group Collaboration	Review of Particle Physics	PRD 98 (2018) 030001
30	Y. Chen et al., eds.	Heavy Quark Effective Theory	Springer, Berlin, Heidelberg, 2004 , ISBN 978-3-540-20692-7
31	CDF Collaboration	Observation of the $ Y(4140) $ structure in the $ J/\psi\phi $ mass spectrum in $ B^\pm\to J/\psi\phi K^\pm $ decays	MPLA32 (2017) 1750139	1101.6058
32	CMS Collaboration	Observation of a peaking structure in the $ J/\psi \phi $ mass spectrum from $ B^{\pm} \to J/\psi \phi K^{\pm} $ decays	PLB 734 (2014) 261	CMS-BPH-11-026 1309.6920
33	D0 Collaboration	Inclusive Production of the X(4140) State in $ p \overline p $ Collisions at D0	PRL 115 (2015) 232001	1508.07846
34	LHCb Collaboration	Observation of $ J/\psi\phi $ structures consistent with exotic states from amplitude analysis of $ B^+\to J/\psi \phi K^+ $ decays	PRL 118 (2017) 022003	1606.07895
35	CMS Collaboration	Performance of CMS muon reconstruction in $ {\mathrm{p}}{\mathrm{p}} $ collision events at $ \sqrt{s}= $ 7 TeV	JINST 7 (2012) P10002	CMS-MUO-10-004 1206.4071
36	CMS Collaboration	The CMS trigger system	JINST 12 (2017) P01020	CMS-TRG-12-001 1609.02366
37	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
38	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
39	CMS Collaboration	CMS tracking performance results from early LHC operation	EPJC 70 (2010) 1165	CMS-TRK-10-001 1007.1988
40	T. Sjostrand et al.	An Introduction to PYTHIA 8.2	CPC 191 (2015) 159	1410.3012
41	D. J. Lange	The EVTGEN particle decay simulation package	NIMA 462 (2001) 152
42	S. Agostinelli et al.	GEANT4--A simulation toolkit	NIMA 506 (2003) 250
43	M. Pivk and F. R. Le Diberder	SPlot: A statistical tool to unfold data distributions	NIMA 555 (2005) 356	physics/0402083
44	M. J. Oreglia	A study of the reactions $\psi' \to \gamma\gamma \psi$	PhD thesis, Stanford University, 1980 SLAC Report SLAC-R-236, see A
45	J. Gaiser	Charmonium Spectroscopy From Radiative Decays of the $\mathrm{J}/\psi$	PhD thesis, SLAC