CMS-PAS-BPH-14-008

CMS-PAS-BPH-14-008
Observation of $\Upsilon(1S)$ pair production at CMS
CMS Collaboration
May 2016

Abstract: The simultaneous production of two $\Upsilon(1S)$ mesons in proton-proton collisions is observed by CMS at $\sqrt s = $ 8 TeV at LHC in a data sample corresponding to an integrated luminosity of 20.7 fb$^{-1}$. The statistical significance is well in excess of 5 standard deviations. Both $\Upsilon$ candidates are fully reconstructed via their decays into $\mu^{+}\mu^{-}$. The acceptance region is defined by the individual $\Upsilon$ rapidity, $y(\Upsilon)$, and transverse momentum, $p_{\mathrm{T}}(\Upsilon)$: $\|y(\Upsilon)\| <$ 2.0 and $p_{\mathrm{T}}(\Upsilon)<$ 50 GeV. The total cross section for the production of $\Upsilon(1S)$ pairs assuming that both $\Upsilon(1S)$ mesons decay isotropically, is measured to be 68.8 $\pm$ 12.7 (stat) $\pm$ 7.4 (syst) $\pm$ 2.8 (BR) pb, where the third uncertainty results from the uncertainty in the $\Upsilon(1S) \rightarrow \mu^{+}\mu^{-}$ branching fraction. Different assumptions about the $\Upsilon(1S)$ polarization imply modifications to the cross section ranging from -38% to 36%.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, JHEP 05 (2017) 013. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Lego plot of $M^{(1)}_{\mu \mu }$ vs $M^{(2)}_{\mu \mu }$.
png pdf	Figure 2-a: Projections of the 2D fit. (a) invariant mass of higher mass muon pairs, $M^{(1)}_{\mu \mu }$. (b) invariant mass of lower mass muon pairs, $M^{(2)}_{\mu \mu }$. The lower pads show the difference between the total fit curve and data, with red lines corresponding to a difference of $\pm $2 standard deviations.
png pdf	Figure 2-b: Projections of the 2D fit. (a) invariant mass of higher mass muon pairs, $M^{(1)}_{\mu \mu }$. (b) invariant mass of lower mass muon pairs, $M^{(2)}_{\mu \mu }$. The lower pads show the difference between the total fit curve and data, with red lines corresponding to a difference of $\pm $2 standard deviations.

Tables
png pdf	Table 1: Summary of relative systematic uncertainties in the $\Upsilon $ pair production cross section.
png pdf	Table 2: Relative change of acceptance corrected yield for different polarization assumptions.

Summary

The $\Upsilon(1S)$ meson pair production where both $\Upsilon(1S)$ mesons originate from the common vertex is observed with the CMS detector in proton-proton collisions at $\sqrt s=$ 8 TeV at the LHC from a sample corresponding to an integrated luminosity of 20.7 fb$^{-1}$. A signal yield of 38 $\pm$ 7 $\Upsilon(1S)\Upsilon(1S)$ events is measured with the local significance, including systematics, that exceeds five standard deviations. Using the measured muon kinematics in the data, an event-based acceptance and efficiency correction method is applied, minimizing the model dependence of the cross section measurement. The total cross section of $\Upsilon(1S)$ pair production measured within the single $\Upsilon$ acceptance, $|y(\Upsilon)|<$ 2.0 and $p_{\mathrm{T}}(\Upsilon)<$ 50 GeV, is found to be $\sigma_{\mathrm{T}} = $ 68.8 $\pm$ 12.7 (stat) $\pm$ 7.4 (syst) $\pm$ 2.8 (BR) pb, where the $\Upsilon(1S)$ decay into muons is assumed to be isotropic. Different assumptions about the $\Upsilon(1S)$ polarization imply modifications to the cross section ranging from -38% to 36%.

References
1	A. Berezhnoy, A. Likhoded, A. Luchinsky, and A. Novoselov	Double J/psi-meson Production at LHC and 4c-tetraquark state	Phys.Rev. D84 (2011) 094023	1101.5881
2	A. V. Berezhnoy, A. V. Luchinsky, and A. A. Novoselov	Tetraquarks Composed of 4 Heavy Quarks	PRD86 (2012) 034004	1111.1867
3	NA3 Collaboration Collaboration	Evidence for $ \psi \psi $ Production in $ \pi^- $ Interactions at 150-GeV/$ c $ and 280-GeV/$ c $	Phys.Lett. B114 (1982) 457
4	LHCb Collaboration Collaboration	Observation of $ J/\psi $ pair production in $ pp $ collisions at $ \sqrt{s} = $ 7 TeV	Phys.Lett. B707 (2012) 52--59	1109.0963
5	CMS Collaboration	Measurement of prompt $ J/\psi $ pair production in pp collisions at $ \sqrt{s} $ = 7 TeV	JHEP 09 (2014) 094	CMS-BPH-11-021 1406.0484
6	D0 Collaboration	Evidence for simultaneous production of $ J/\psi $ and $ \Upsilon $ mesons	PRL 116 (2016), no. 8, 082002	1511.02428
7	B. L. Ioffe, V. A. Khoze, and L. N. Lipatov	Hard processes. vol. 1: phenomenology, quark parton model	1985
8	P. Bartalini et al.	Multi-Parton Interactions at the LHC	2011	1111.0469
9	Quarkonium Working Group Collaboration	Heavy quarkonium physics		hep-ph/0412158
10	S. D. Ellis, M. B. Einhorn, and C. Quigg	Comment on Hadronic Production of Psions	PRL 36 (1976) 1263
11	C. E. Carlson and R. Suaya	Hadronic Production of psi/J Mesons	PRD14 (1976) 3115
12	J. H. Kuhn	Hadronic Production of $ P $ Wave Charmonium States	PLB89 (1980) 385
13	F. Halzen and S. Matsuda	Hadroproduction of Quark Flavors	PRD17 (1978) 1344
14	E. Braaten and S. Fleming	Color octet fragmentation and the psi-prime surplus at the Tevatron	PRL 74 (1995) 3327--3330	hep-ph/9411365
15	M. Gluck, J. F. Owens, and E. Reya	Gluon Contribution to Hadronic J/psi Production	PRD17 (1978) 2324
16	H. Fritzsch	Theoretical Aspects of e+ e--Annihilation Into Hadrons	PRD10 (1974) 1624
17	F. Yuan and K.-T. Chao	High $ p_{T} \psi \psi $ production as strong signals for double parton scattering at the Tevatron	J.Phys. G24 (1998) 1105--1112	hep-ph/9706293
18	A. Novoselov	Double parton scattering as a source of quarkonia pairs in LHCb		1106.2184
19	S. Baranov, A. Snigirev, and N. Zotov	Double heavy meson production through double parton scattering in hadronic collisions	Phys.Lett. B705 (2011) 116--119	1105.6276
20	P. Ko, C. Yu, and J. Lee	Inclusive double-quarkonium production at the Large Hadron Collider	JHEP 1101 (2011) 070	1007.3095
21	ATLAS Collaboration	Measurement of Upsilon production in 7 TeV pp collisions at ATLAS	PRD87 (2013), no. 5, 052004	1211.7255
22	CMS Collaboration Collaboration	Measurement of the $ \Upsilon(1S), \Upsilon(2S) $, and $ \Upsilon(3S) $ cross sections in pp collisions at $ \sqrt{s} $ = 7 TeV	Phys.Lett. B727 (2013) 101--125	1303.5900
23	LHCb Collaboration	Measurement of Upsilon production in pp collisions at $ \sqrt{s} $ = 7 TeV	EPJC72 (2012) 2025	1202.6579
24	CMS Collaboration	Description and performance of track and primary-vertex reconstruction with the CMS tracker	JINST 9 (2014), no. 10, P10009	CMS-TRK-11-001 1405.6569
25	CMS Collaboration	Performance of CMS muon reconstruction in pp collision events at $ \sqrt{s}=7 $ TeV	JINST 7 (2012) P10002	CMS-MUO-10-004 1206.4071
26	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
27	H. Jung et al.	The CCFM Monte Carlo generator CASCADE version 2.2.03	Eur.Phys.J. C70 (2010) 1237--1249	1008.0152
28	T. Sjostrand, S. Mrenna, and P. Z. Skands	A Brief Introduction to PYTHIA 8.1	Comput.Phys.Commun. 178 (2008) 852--867	0710.3820
29	GEANT4 Collaboration	GEANT4: A Simulation toolkit	NIMA506 (2003) 250--303
30	R. Fruhwirth	Application of Kalman filtering to track and vertex fitting	NIMA262 (1987) 444--450
31	M. Oreglia	{A Study of the Reactions $\psi? \to \gamma\gamma \psi$}	PhD thesis, Standford University, 1980SLAC Report SLAC-R-236
32	W. Verkerke and D. P. Kirkby	The RooFit toolkit for data modeling	eConf C0303241 (2003) MOLT007, [,186(2003)]	physics/0306116
33	S. S. Wilks	The Large-Sample Distribution of the Likelihood Ratio for Testing Composite Hypotheses	The Annals of Mathematical Statistics 9 (1938), no. 1, 60--62
34	L. Moneta et al.	The RooStats Project	PoS ACAT2010 (2010) 057	1009.1003
35	CMS Collaboration Collaboration	CMS Luminosity Based on Pixel Cluster Counting - Summer 2013 Update	Technical Report CMS-PAS-LUM-13-001, CERN, Geneva
36	Particle Data Group Collaboration	Review of Particle Physics (RPP)	PRD86 (2012) 010001
37	CMS Collaboration	Measurement of the $ Y(1S), Y(2S) $ and $ Y(3S) $ polarizations in $ pp $ collisions at $ \sqrt{s}=7 $ TeV	PRL 110 (2013), no. 8, 081802	CMS-BPH-11-023 1209.2922