CMS-PAS-BPH-25-009

CMS-PAS-BPH-25-009
Observation of a peaking structure in the $ \Upsilon(1S) \phi(1020) $ channel in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
2026-05-18

Abstract: The $ \Upsilon(1S) \phi(1020) $ invariant mass spectrum is investigated with an event sample of proton-proton collisions at $ \sqrt{s}= $ 13 TeV, collected by the CMS experiment at the LHC in 2016--2018 and corresponding to an integrated luminosity of 140 fb$^{-1}$. A peaking structure is observed at a $ \Upsilon(1S) \phi(1020) $ invariant mass of $ M_{\Upsilon\phi} = 10, $ 512.60 $ \pm $ 0.21 (stat) $ \pm $ 0.20 (syst) $ \pm 0.11\;(M_{\Upsilon}) \text{MeV} $, where the last uncertainty reflects the precision of the world-average determination of the $ \Upsilon(1S) $ meson mass. The width of this structure is consistent with the instrumental mass resolution, as estimated from simulation. While the mass measurement in this hadronic decay mode is consistent with the current measurement of $ \chi_{b1}{3P} $ mass, obtained from the analysis of the radiative decay to $ \Upsilon(3S)\gamma $, a possible exotic interpretation of the observed structure, such as a four-quark $ b\bar{b}s\bar{s} $ state or a hybrid state, cannot be excluded, since the well-established $ \chi_{b2}{3P} $ partner is not seen in this channel with the present data.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The $ K^{+}K^{-} $ invariant mass for the $ \Upsilon KK $ candidates, within a $ \pm $ 4.8 MeV window around the mass value of the $ \Upsilon \phi $ peak, is presented with the fit result (and its components) superimposed. The $ \phi $ signal is modelled with a Voigtian function where the mass resolution is fixed at the value (1.21 MeV) obtained by simulation studies. The fit estimates a mass value 1019.35 $ \pm $ 0.26 MeV consistent with the PDG average of the $ \phi $ meson ( 1019.46 $ \pm $ 0.02 MeV), and a natural width value ( 4.11 $ \pm $ 1.17 MeV) consistent with the PDG average ( 4.24 $ \pm $ 0.01 MeV) as well.
png pdf	Figure 2: The $ \Upsilon KK $ invariant mass distribution in data (black points with error bars) when $ \|M(\mathrm{K^+} \mathrm{K^-})-m_{\phi}^{\text{PDG}}\| < $ 6.15 MeV. The fit result (solid blue line) is superimposed and is a sum of two components, the signal (dashed red line) and the background (long-dashed green line). The details of the fit model are described in the main text. The lower panel shows the pull distribution, defined as the difference between the data and the fit value in each bin, divided by the combined uncertainty.
png pdf	Figure 3: The $ \Upsilon KK $ invariant mass distribution in data (black points with error bars) when $ \|M(\mathrm{K^+} \mathrm{K^-})-m_{\phi}^{\text{PDG}}\| < $ 6.15 MeV and, additionally, the $ \Upsilon{\textrm{(2S)}} $-veto is applied on the top of the selection criteria discussed in the main text. The model of the superimposed fit includes two Gaussian functions for two signals with means fixed and the two widths fixed at the values of the mass resolutions estimated from simulation. The yield of the observed signal is also fixed to the value estimated in a fit without the possible second signal so that, in this fit, only the yield of the second possible signal is left free to vary in the two-states signal model. Consequently the statistical significance of the second possible signal is estimated to be slightly above 1 standard deviation.

Summary

In summary, a peaking structure with an estimated yield of $450 \pm 59$ candidates and the mass of $10,512.60 \pm 0.21$ (stat) $ \pm 0.20$ (syst) $\pm 0.11 (M_{\Upsilon})$ MeV, where the last uncertainty is associated to the use of the ${\Upsilon}P{1S}$ mass [49] as kinematic constraint in the vertex fit, has been observed by investigating the ${\Upsilon}P{1S}K^+K^-$ invariant mass spectrum with the dikaon invariant mass within a narrow window around the $\phi$ meson. The observation is based on proton-proton collision data collected by the CMS experiment at $\sqrt{s} = 13$ TeV during 2016--2018. The width of the observed peak is compatible with the instrumental mass resolution, and its mass is compatible within 1.5 standard deviations with the mass for the bottomonium excited state $\chi_{b1}{3P}$ of $10,513.42 \pm 0.41$ (stat) $ \pm 0.18$ (syst) MeV measured in its radiative decays [11]. Assuming the observed peaking structure is the $\chi_{b1}{3P}$ state, the local statistical significance of the signal is estimated to exceed 10 standard deviations. However, the absence of a statistically significant signal for the $\chi_{b2}$ spin-2 partner in the same channel, despite the expectations of a similar rate for the two processes (or at least a not strongly suppressed spin-2 partner), may suggest an alternative nonconventional interpretation of the observed signal as a new exotic state. Thus, whereas the identification with $\chi_{b1}{3P}$ seems plausible, no definitive conclusion about the nature of this resonance can be drawn with the analysed data.

References
1	E288 Collaboration	Observation of a Dimuon Resonance at 9.5 GeV in 400 GeV Proton-Nucleus Collisions	PRL 39 (1977) 252
2	K. Ueno et al.	Evidence for the $ \Upsilon^{\prime\prime} $ and a Search for New Narrow Resonances	PRL 42 (1979) 486
3	J. K. Bienlein et al.	Observation of a Narrow Resonance at 10.02-GeV in e+ e- Annihilations	PLB 78 (1978) 360
4	K. Han et al.	Observation of $ P $-wave $ \mathrm{b} \overline{\mathrm{b}} $ bound states	PRL 49 (1982) 1612
5	C. Klopfenstein et al.	Observation of the Lowest $ P $ Wave $ b \bar{b} $ Bound States	PRL 51 (1983) 160
6	BaBar Collaboration	Observation of the bottomonium ground state in the decay $ \Upsilon{\textrm{(3S)}} \to \gamma \eta_\mathrm{b} $	[Erratum: 10.1103/PhysRevLett.102.01] PRL 101 (2008) 071801	0807.1086
7	CLEO Collaboration	First observation of a \PGUP1D state	PRD 70 (2004) 032001	hep-ex/0404021
8	BaBar Collaboration	Observation of the $ \Upsilon{1^3D_J} $ Bottomonium State through Decays to $ \pi^+\pi^-\Upsilon{1S} $	PRD 82 (2010) 111102	1004.0175
9	Belle Collaboration	Evidence for the $ \eta_b(2S) $ and observation of $ h_b(1P) \to \eta_b(1S) \gamma $ and $ h_b(2P) \to \eta_b(1S) \gamma $	PRL 109 (2012) 232002	1205.6351
10	ATLAS Collaboration	Observation of a new $ \chi_b $ state in radiative transitions to $ \Upsilon(1S) $ and $ \Upsilon(2S) $ at ATLAS	PRL 108 (2012) 152001	1112.5154
11	CMS Collaboration	Observation of the $ \chi_\mathrm{b1} $(3P) and $ \chi_\mathrm{b2} $(3P) and measurement of their masses	PRL 121 (2018) 092002	CMS-BPH-17-008 1805.11192
12	C. Oswald and T. K. Pedlar	Results in $ B_s $ physics and bottomonium spectroscopy using the Belle $ \Upsilon({\rm 5S}) $ data	Mod. Phys. Lett. A 28 (2013) 1330036	1311.3547
13	Belle Collaboration	Observation of a new structure near 10.75 gev in the energy dependence of the $ e^+e^{-} \to \Upsilon(ns) \pi^{+}\pi^{-} $ (n = 1, 2, 3) cross sections	JHEP 10 (2019) 220	1905.05521
14	CLEO Collaboration	Observation of the hadronic transitions $ \chi_{\mathrm{b}1,2} $(2P) $ \to \omega \Upsilon (1S) $	PRL 92 (2004) 222002	hep-ex/0307034
15	Belle Collaboration	Study of $ \chi_{bJ}(2P) \to \omega \Upsilon(1S) $ at Belle	PRL 135 (2025) 121902	2407.00879
16	BaBar Collaboration	Study of $ \chi_{b1,2}(2P) \to \omega \Upsilon(1S) $ transitions in $ \Upsilon(3S) \to \gamma \chi_{b1,2}(2P) $ decays at BaBar		2512.08363
17	Belle Collaboration	Observation of $ e^+e^- \to \pi^+ \pi^- \pi^0 \chi_{bJ} $ and Search for $ X_b \to \omega \Upsilon(1S) $ at $ \sqrt{s}= $ 10.867 GeV	PRL 113 (2014) 142001	1408.0504
18	Belle II Collaboration	Observation of $ {e}^{+}{e}^{-}\rightarrow\omega{\chi}_{bJ}(1p) $ and search for $ {X}_{b}\rightarrow\omega\Upsilon(1s) $ at $ \sqrt{s} $ near 10.75 gev	PRL 130 (2023) 091902
19	Belle Collaboration	Observation of anomalous $ \Upsilon{\textrm{(1S)}}\pi^{+}\pi^{-} $ and $ \Upsilon{\textrm{(2S)}}\pi^{+}\pi^{-} $ production near the $ \Upsilon{\textrm{(5S)}} $ resonance	PRL 100 (2008) 112001	0710.2577
20	LHCb Collaboration	Amplitude analysis of $ B^+\to J/\psi \phi K^+ $ decays	PRD 95 (2017) 012002	1606.07898
21	LHCb Collaboration	Observation of structure in the $ J /\psi $ -pair mass spectrum	Sci. Bull. 65 (2020) 1983	2006.16957
22	ATLAS Collaboration	Observation of an Excess of Dicharmonium Events in the Four-Muon Final State with the ATLAS Detector	PRL 131 (2023) 151902	2304.08962
23	CMS Collaboration	New Structures in the J/\ensuremath\psiJ/\ensuremath\psi Mass Spectrum in Proton-Proton Collisions at s=13 TeV	PRL 132 (2024) 111901	CMS-BPH-21-003 2306.07164
24	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
25	G.-J. Ding	Possible Molecular States of D(s) anti-D(s) System and Y(4140)	EPJC 64 (2009) 297	0904.1782
26	E. Braaten, L.-P. He, and A. Mohapatra	Masses of doubly heavy tetraquarks with error bars	PRD 103 (2021) 016001	2006.08650
27	Y. Song and D. Jia	Mass spectra of doubly heavy tetraquarks in diquark\ensuremath-antidiquark picture	Commun. Theor. Phys. 75 (2023) 055201	2301.00376
28	V. Patel, J. Oudichhya, and A. K. Rai	Spectroscopic study of $ \mathrm{s}\mathrm{s}\overline{\mathrm{b}}\overline{\mathrm{b}} $ and $ \mathrm{b}\mathrm{b}\overline{\mathrm{b}}\overline{\mathrm{b}} $ tetraquarks using Regge phenomenology	Int. J. Mod. Phys. A 40 (2025) 2550152	2509.23149
29	W.-X. Zhang, H. Xu, and D. Jia	Masses and magnetic moments of hadrons with one and two open heavy quarks: Heavy baryons and tetraquarks	PRD 104 (2021) 114011	2109.07040
30	S.-Q. Luo et al.	Exotic tetraquark states with the $ qq\bar{Q}\bar{Q} $ configuration	EPJC 77 (2017) 709	1707.01180
31	P. Junnarkar, N. Mathur, and M. Padmanath	Study of doubly heavy tetraquarks in Lattice QCD	PRD 99 (2019) 034507	1810.12285
32	H.-X. Chen et al.	Understanding the internal structures of the $ X(4140) $, $ X(4274) $, $ X(4500) $ and $ X(4700) $	EPJC 77 (2017) 160	1606.03179
33	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
34	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
35	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
36	CMS Collaboration	HEPData record for this analysis	link
37	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004
38	CMS Collaboration	Development of the CMS detector for the CERN LHC Run 3	JINST 19 (2024) P05064	CMS-PRF-21-001 2309.05466
39	CMS Collaboration	The CMS trigger system	JINST 12 (2017) P01020	CMS-TRG-12-001 1609.02366
40	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
41	CMS Collaboration	Performance of the CMS high-level trigger during LHC Run 2	JINST 19 (2024) P11021	CMS-TRG-19-001 2410.17038
42	CMS Collaboration	Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC	JINST 16 (2021) P05014	CMS-EGM-17-001 2012.06888
43	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
44	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
45	CMS Collaboration	Particle-flow reconstruction and global event description with the CMS detector	JINST 12 (2017) P10003	CMS-PRF-14-001 1706.04965
46	CMS Collaboration	Strategies and performance of the CMS silicon tracker alignment during LHC Run 2	NIM A 1037 (2022) 166795	CMS-TRK-20-001 2111.08757
47	CMS Tracker Group Collaboration	The CMS phase-1 pixel detector upgrade	JINST 16 (2021) P02027	2012.14304
48	CMS Collaboration	Technical proposal for the Phase-II upgrade of the Compact Muon Solenoid	CMS Technical Proposal CERN-LHCC-2015-010, CMS-TDR-15-02, 2015 CDS
49	Particle Data Group Collaboration	Review of particle physics	PRD 110 (2024) 030001
50	T. Sjöstrand et al.	An introduction to PYTHIA 8.2	Comput. Phys. Commun. 191 (2015) 159	1410.3012
51	CMS Collaboration	Extraction and validation of a new set of CMS PYTHIA8 tunes from underlying-event measurements	EPJC 80 (2020) 4	CMS-GEN-17-001 1903.12179
52	D. J. Lange	The EvtGen particle decay simulation package	NIM A 462 (2001) 152
53	E. Barberio, B. van Eijk, and Z. W \c a s	PHOTOS: A universal Monte Carlo for QED radiative corrections in decays	Comput. Phys. Commun. 66 (1991) 115
54	E. Barberio and Z. W \c a s	PHOTOS: A universal Monte Carlo for QED radiative corrections. version 2.0	Comput. Phys. Commun. 79 (1994) 291
55	GEANT4 Collaboration	GEANT 4---a simulation toolkit	NIM A 506 (2003) 250
56	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727
57	S. S. Wilks	The large-sample distribution of the likelihood ratio for testing composite hypotheses	Annals Math. Statist. 9 (1938) 60
58	S. Jackman	Bayesian analysis for the social sciences	John Wiley & Sons, New Jersey, USA, 2009 link
59	CMS Collaboration	CMS Software	link
60	ARGUS Collaboration	Search for hadronic $ b \to u $ decays	PLB 241 (1990) 278
61	CMS Collaboration	Measurement of the production cross section ratio sigma(chi[b2](1P)) / sigma(chi[b1](1P)) in pp collisions at $ \sqrt{s} = $ 8 TeV	PLB 743 (2015) 383	CMS-BPH-13-005 1409.5761
62	E. Gross and O. Vitells	Trial factors for the look elsewhere effect in high energy physics	EPJC 70 (2010) 525	1005.1891