Search for Rare Higgs - Boson Decays into Quarkonium Pairs
Himal Acharya
University of Tennessee CMS Collaboration
PAS Publication arXiv
DPF Meeting 2019 July 30 Outline
● Motivation 4 Search Channels ● Muon Detection pp → X → J/�J/� → 4 � pp → X → YY → 4 �
● Results X = Higgs , Z – boson ● Polarization Y=Y(nS) (n=1,2,3) ● Summary & Outlook
2 Himal Acharya, DPF Meeting - 2019 Motivation: BF calculation ― - SM: expect Higgs-boson decays into quarkonium pairs (access to ―cc, bb Yukawa couplings) - Predictions of the SM branching fractions are still a moving target …
Typical diagrams Previous Calculation [1] Most recent calculation [2] Direct coupling + Indirect coupling -10 -9 BF(H→ΥΥ ) ≈ 6 ⨉ 10-5 BF (H →J/�J/� ≈ 1.5 ⨉ 10 ; H→ΥΥ ≈ 2 ⨉ 10 )
[1] M. Bander, A. Soni, PLB 82 (1979) 411 ⊕ Internal motion of quarks [2] [2] V. Kartvelishvili, A.V. Luchinsky, A.A. Novoselov, PRD 79 (2009) 114015 3 Himal Acharya, DPF Meeting - 2019 Motivation: Possible modification in BF ● In SM additional diagrams exists e.g. related to H → J/� g with g → g * ; g * → J/�, Y [1]
● Many BSM models predict additional diagrams e.g. related to H → Y g ; can cause orders of magnitude increase of BF [2]
….not yet calculated for quarkonium pairs
J/y, U H J/y, U H …⊕ ⊕ ⊕ BSM J/y, U J/y, U
Enhancement ? [1] K. Abe et al. , Phys. Rev. Lett. 89 (2002) 142001 [2] Geoffrey Bodwin et.al. Phys. Rev. D 88, 053003
4 Himal Acharya, DPF Meeting - 2019 CMS Detector: Muon Detection CMS detector Cross-Sectional View
Trigger Muon Chambers: 1. Drift Tube Chambers 2. Cathode Strip Chambers Track 3. Resistive Plate Chamber (Trigger) Match Inner/Outer Track 5 Himal Acharya, DPF Meeting - 2019 CMS Detector: Event Display & Trigger e.g. H→YY Simulated Event Trigger Muons + Dimuon Invariant Mass (HLT)
Dedicated Triggers require 3 muons + ● Di-muon resonance + Muon ● Efficiencies > 85 %
6 Himal Acharya, DPF Meeting - 2019 Efficiencies
Tag & Probe Method [1] Low-level Muon Trigger Efficiency ● Compare efficiencies to full-detector (MC) -1 simulation CMS Work in Progress 10 fb (13 TeV) ● Exploit di-muon decay of J/�
J/� → �trigger . � J/� Signal [2] tag probe � ≈ 30 MeV L3 Efficiency L3 ⊕ Selection (L3)
e.g. Barrel
10 100 Muon pT [GeV] ● Total efficiencies agree closely between [1] https://twiki.cern.ch/twiki/bin/view/CMSPublic/TagAndProbe data and MC (scale factor ≈ 1); [2] https://cds.cern.ch/record/2276459 ● Uncertainty ≈ 3% 7 Himal Acharya, DPF Meeting - 2019 Reconstruction
CMS Work in progress 37.5 fb-1 (13 TeV) Strategy: 20 J/ 350 µ µ y
• 300 Modest requirement on kinematics and topology [ GeV ] 15 T Trigger Data Trigger 250
200 Muon: muon p 10 150
• pT > 3 GeV & |h| < 2.4 5 100
50
0 0 0 0.5 1 1.5 2 Dimuon: | muon h | • Kalman vertex fit Muon Acceptance CMS Simulation Work in progress (13 TeV) 20 • pT > 3.5 GeV 45
+ - 40 H→J/
• µ µ invariant mass range [ GeV ] T 15 35
30 y 25 muon p
10 J/ Four-Muon: 20 y
15 • Kalman vertex fit 5 10
• |ΔU| < 3.0 5 Efficiency ⨉ Acceptance ~ 25 % 0 0 0 0.5 1 1.5 2 | muon h | 8 Himal Acharya, DPF Meeting - 2019 Results: J/�J/� Channel Fit
RooFit - Extended ML Fit [1]
Signal Model ● H: double Gaussian ● Z: Voigtian function
Background Model ● Source: prompt non-resonant J/� pair production [2] ● Exponential + Uniform function 4 � Invariant Mass
[1] https://root.cern.ch/roofit #186 Candidates [2] C. Qiao, J. Wang, and Y. Zheng, Chin. Phys. C 35 (2011) 209 9 Himal Acharya, DPF Meeting - 2019 Results: ΥΥ Channel
RooFit - Extended ML Fit [1] practically zero counting
Signal Model ● H: double Gaussian ● Z: Voigtian function
Background Model ● Source: non-resonant ΥΥ production [2] ● Exponential function 4 � Invariant Mass [1] https://root.cern.ch/roofit [2] C. Qiao, J. Wang, and Y. Zheng, Chin. Phys. C 35 (2011) 209 #106 Candidates
10 Himal Acharya, DPF Meeting - 2019 Results: Upper limit Exclusion limits @ 95% CL ● Upper limits Calculation CLs, Modified frequentist approach [1,2]. ● Expected limits are set with the background only hypothesis with 68% CL bands ● Impact of systematic uncertainty (including efficiency, momentum scale/resolution, fit, theory, luminosity, BF) on upper limit is less than 2 %
● Observed limit within expected limit bands ● No deviation from SM prediction
[1] J. Thomas, Nucl. Instrum. Meth. A 434 (1999) 435 [2] Read, Alexander L., J. Phys. G 28 (2002) 2693
11 Himal Acharya, DPF Meeting - 2019 Polarization Effect + ● Acceptance depends on decay angular distribution � � CMS Work in Progress J/�
Acceptance H Decreases -
Arbitrary Unit Arbitrary �
2 transversal P(θ)∝ 1 + λθcos θ longitudinal Simulation with λθ = 0
Acceptance Transversely polarized (λθ = + 1) Increases BF upper limits increases by ≈ 13%
● Ref. [1,2] predict longitudinal Longitudinally polarized (λθ = − 1) polarization will dominate BF upper limits decreases by ≈ 26% [1] A. Likhoded and A. Luchinsky, Mod. Phys. Lett. A 33 (2018) 1850078 [2] V. Kartvelishvili, A. Luchinsky, and A. Novoselov, Phys. Rev. D 79 (2009) 114015, 12 Himal Acharya, DPF Meeting - 2019 Summary • Rare decays of Higgs boson are a promising laboratory for the search of new physics beyond SM • Very first searches of Higgs and Z boson decays into J/� and Υ-pairs are performed with the CMS detector at the LHC, and upper limits are accepted for publication in Phys. Lett. B
• Renewed calculations of branching fractions for Higgs decays into quarkonium pairs decays in the SM, and beyond SM are needed
• Only a few positive signal events would indicate the presence of beyond SM physics
13 Himal Acharya, DPF Meeting - 2019 Outlook • In Run 2 obtained 3⨉ more statistics in all-muon final states and additional 2µ 2e final states
• HL-LHC expected to access the Higgs decays with BF ~ 10-5
• Other signals are expected in Quarkonium pair final states such as low mass pseudo-scalar Higgs e.g. predicted in NMSSM [1] and such as tetra-quark bound states [2]
• Measurement of Quarkonium pair final states complements/improves H → a a searches [3]
[1] https://arxiv.org/abs/0805.1115. [2] https://arxiv.org/pdf/1706.00610.pdf [3] https://arxiv.org/pdf/1812.00380.pdf
14 Himal Acharya, DPF Meeting - 2019 Thank You
15 Himal Acharya, DPF Meeting - 2019