Multi-Boson Interactions CMS HL-LHC Multi-boson Physics Prospect

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1 Multi-Boson Interactions CMS HL-LHC Multi-boson Physics Prospect J. Lauwers on behalf of the CMS collaboration University of Antwerp MBI Madison, Wisconsin - 26 August 1 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

2 High Luminosity LHC The High Luminosity LHC will shine a bright light on the dark corners of the SM. 2 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

3 The HL-LHC - A challenging environment s (TeV) Instan. L (cm 2 s 1 ) Integr. L (fb 1 ) < PU > 3 Baseline Scenario J. Lauwers Upper limit times current Luminosity CMS Run 2 and HL-LHC Multi-boson Physics Prospect

4 CMS Phase II 4 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

5 MBI Physics Goals at HL Gauge sector physics is central component of the SM HL program: High statistics studies of diboson states Observation of triple gauge boson production Observation of vector boson scattering Measurement of quartic gauge coupling constants (WWγγ, WWZγ, WWWW, WWZZ) Searches for higher mass scale physics through atgc and aqgc Higgs sector has multi-boson interaction within reach at HL: Measurement of di-higgs production 5 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

6 CMS MBI studies for the HL-LHC Vector Boson Scattering: Precision measurement in the electroweak sector with sensitivity to the electroweak symmetry breaking Test of the Higgs boson nature: V L V L scattering unitarity relies on strong cancellations with Higgs diagrams Higgs pair production: Measurement of the Higgs boson self coupling Probe third derivative Higgs eld potential at its minimum to discriminate against BSM models g t H g t H H g H g H 6 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

7 Vector Boson Scattering Topology Two highly energetic, forward 'tag jets' (identied as highest p T jets) with large m jj and η jj Central leptons, MET Low amount of soft, hadronic activity in central-rapidity region CMS Phase II: Measurement is enabled by improved forward jet reconstruction from tracker and calorimeter extensions and higher granularity. 7 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

8 VBS nal states Study of W ± W ± and WZ scatting in the fully leptonic nal states: q q q q W + W + W + W + ν l + ν W h W Z ν l + l l + Z l + q q q q pp W ± W ± jj l ± ν l ± ν jj W ± W ± jj backgrounds: Jets misidentied as leptons (semi-leptonic t t, W+jets) WW QCD, WZ and charge misassignment pp W ± Z jj l ± ν l + l jj W ± Zjj backgrounds: Fake lepton background negligible (η lep < 2.5) WZ QCD and ZZ 8 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

9 Benchmarks Cross section measurement Longitudinal scattering cross section: V L V L V L V L unitarized through the presence of the Higgs boson Partial unitarization: In theories involving more than a single Higgs boson, unitarization of VBS is only partially operated by the Higgs boson. Anomalous couplings (EFT): New physics in the EWK sector at a high mass scale could lead to strong enhancements in the cross section at high energy 9 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

10 Detector congurations To assess VBS sensitivity at the HL-LHC three scenarios are studied: Phase II, 140 PU Phase I aged, 140 PU: Without phase II upgrade and including radiation damage after 1 ab 1 Phase I, 50 PU: Current non-aged detector and data conditions Target: Maintain the Phase I conguration performance throughout HL period Detector simulation with Delphes: Fast multipurpose detector response simulation framework Simplied detector geometries and parameterization of eciencies and resolutions Parameterizations tuned and veried by comparison to full CMS GEANT4-based simulation 10 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

11 Fake lepton background Backgrounds containing a jet misidentied as a lepton (probability 10 5 ) Dominant background W ± W ± scattering from semi-leptonic ttbar events Measure fake lepton probability from detailed-simulation sample: step 1: Determine probability for a jet to be geometrically matched to a fake lepton (i.e. not produced by the generator) step 2: Correlation matrix between the matched jet P T and the fake lepton P T Both steps calculated separately for b jets and non-b jets The results are cross-checked on several detailed-simulation samples. To account for non-reliable normalization of the fake rate probability measured from simulation, results of the analysis are plotted as a function of a global fake rate scale factor. 11 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

12 Event Selection Basic objects: tight leptons with p T > 20 GeV and η < 2.5 At least 2 jets with p T > 30 GeV MET > GeV extra loose lepton veto VBS topology cuts: m jj > GeV η jj > 3 4 WW cuts: Z mass veto b veto (loose b-tagging WP) soft muon veto (in jet cone) η l1 and η l2 between η jets H T (track jets) < 125 GeV (150GeV for phase II ) m ll > 40 GeV R(JJ,LL) < 6 η ll < 2 WZ cuts: Z mass selection m ll > 20 GeV for same avour opposite charge lepton pairs 12 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

13 Analysis strategy Classify events according to lepton avour and charge: WW: Flavour: EE/MM/EM/ME Charge: ++ / WZ: Flavour: EEE/UUU/EEU/UUE TeV, 3000 fb, PU = 140 Perform 2D binned t for each category and for every benchmark Events / CMS Phase II Delphes Simulation fakelepton WWQCD WZEWK wrongcharge WZ WW (H ) QCD EWK 126 Best variables chosen with a scan on a large set of combinations 600 WW (noh ) WW -H ) EWK 126 EWK (noh φ ll 13 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

14 Cross section results EWK W ± W ± jj XS uncertainty at the order of 5%, close to the systematic limit, after 3ab 1 EWK WZ scattering XS uncertainty at the order of 10% after 3ab 1 Systematics: Theoretical uncertainties are taken from RunI analysis Experimental uncertainties: PhaseI and PhaseII: uncertainties from RunI analysis Phase I aged: several systematics are downgraded (from detailed simulation comparison) 14 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

15 Partial unitarization results Use (noh - H) excess as signal and SM contribution as background Expected 95% CL exclusion limit can be calculated on fraction of dierence SM /(noh SM) Excluded signal strength is well below 1 for 3ab 1 Events / TeV, 3000 fb, PU = 140 CMS Phase II Delphes Simulation fakelepton WWQCD WZEWK wrongcharge WZ WW (H ) QCD EWK 126 WW WW 600 WW EWK (noh ) WW (noh -H ) 126 EWK φ ll Combined WW and WZ result: Phase I Phase II Phase I aged noh 95% CL exclusion Samples generated with Phantom Phase II scenario recovers performance phase I scenario. 15 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

16 Longitudinal scattering V L V L component is considered as signal, V L V T and V T V T as backgrounds Signal is much reduced w.r.t. the total EWK scattering W L W L W L W L Sensitivity from the low lepton P T region. Madgraph v decay package 16 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

17 Electroweak V L V L jj results Expected signicance after 3ab 1 at the level of 2σ for W ± W ± jj and 1σ for WZjj WW WW Expected significance (σ) 2 CMS Delphes Simulation TeV WZ Phase I 50 PU 0.5 Phase I aged 140 PU Phase II 140 PU Luminosity (fb ) Combined result: Phase I Phase II Phase I aged V L V L scattering signicance (σ) Phase II performs better due to improved lepton reconstruction for low P T leptons. 17 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

18 W ± W ± jj EFT New physics eects are parametrized by including higher dimension operators (8th order) in SM Lagrangian Exclusion limits on associated coecients set through binned template t on m ll ( c (6) i L = L SM + i Λ 2 O (6) i )+ i c (8) i Λ 4 O (8) i +... ] L T,0 = Tr[Ŵµν Ŵ µν Tr [Ŵαβ ] Ŵ αβ 18 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

19 W ± W ± jj EFT results Expected upper 95% CL limits on the coecients for the dimension eight operators Combination S0-S1: only modies SM quartic gauge coupling phase I phase II phase I aged S S M M M M T T T Limits from the 8 TeV analysis are times higher ) -4 S 1 (TeV Phase I 50PU Phase I aged 140PU Phase II 140PU TeV, 3000 fb CMS Delphes Simulation S 0 (TeV ) 19 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

20 VBS expectations Run 2 (100fb 1 ): Expected discovery of EWK W ± W ± jj production Run 3 (300fb 1 ): Expected discovery of EWK WZjj production Precision on the total XS of the EWK VBS processes at the order of 10 20%, Sensitivity to partially-unitarized models is expected: 95% CL exclusion for 0.6 times the (noh - H) dierence HL-LHC (3000fb 1 ): Sensitivity to partially-unitarized models: 95% CL exclusion for 0.14 times the (noh - H) dierence Sensitivity to aqgc strongly enhanced Detecting the longitudinal component of the VV scattering remains challenging, expected signicance of 2.75 σ Room for improvements: Conservative estimates for pixel detector performance, possible improvements in reconstruction algorithms b-tagging only up to η < 2.5 Longitudinal scattering analysis strategy Semi-leptonic nal states unexplored 20 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

21 Di-Higgs nal states Study of Higgs pair production in three nal states Destructive interference gives very low NNLO cross section of 40fb 1 in gluon fusion production mode, 1000 times smaller than single Higgs production Without Higgs self-coupling cross section x 2 g t H g t H H g H g H HH bbγγ Exp. events (3ab 1 ): 320 MC with smearing functions HH bbττ Exp. events (3ab 1 ): 9000 Combination of MC and Delphes HH bbww bblνlν Exp. events (3ab 1 ): 1500 Delphes simulation 21 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

22 HH bbγγ Backgrounds: Resonant: ZH, t th, b bh Non-resonant: b bγγ, jjγγ, b bjγ, b bjj, jjjj and t t(γ) Produced at generator level and weighted by mis-tagging eciencies and mis-identication rates. Two categories: 2 photons in barrel / at least 1 photon in endcap Dominant backgrounds: b bγγ, b bjγ / b bjγ, b bjj g γ q γ light j b 1% c b 20% e γ 1% k-factor Event Selection: 2 photons with P T > 40, 25 GeV and η < b-tagged jets with P T > 30 GeV and η < 2.4 loose lepton veto #jets < 4 R γ,γ < 2.0 R bb < 2.0 min ( R γb ) > J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

23 HH bbγγ - Signal Extraction Fitting the double Higgs peak: 2D maximum likelihood t on M γγ and M bb PDF's tted on MC: Crystal Ball for resonances, decaying exponential for non-resonant backgrounds Correlation M γγ and M bb assumed to be negligible Example toy experiment for category with two photons in barrel: Number of Events CMS Simulation s=14 TeV, PU=140, 3000 fb 1 Toy data Combined fit HH->bbγγ Resonant bkg Non-resonant bkg [GeV/c ] M γγ 23 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

24 HH bbγγ - Results Relative uncertainty on tted signal yield (%): Relative Uncertainty on Fitted Signal Yield [%] CMS Simulation s=14 TeV, PU=140 Nominal Luminosity Integrated Luminosity [10 fb -1 ] Relative Uncertainty on Fitted Signal Yield [%] CMS Simulation s=14 TeV, PU=140 Nominal result Non-resonant Background Scale Factor Expected signicance at 3ab 1 : 1.6σ Result dominated by statistical uncertainties 24 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

25 HH bbγγ - CMS upgrade Relative Uncertainty on Fitted Signal Yield [%] CMS Simulation s=14 TeV, PU=140 Phase II Phase I aged Relative Improvement In Photon Efficiency [%] Relative Uncertainty on Fitted Signal Yield [%] CMS Simulation s=14 TeV, PU=140 Phase II Phase I aged Relative Improvement In B-Tagging Efficiency [%] Small improvement to the selection eciencies would have signicant impact on the analysis sensitivity. 25 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

26 HH bbττ Backgrounds: Resonant: ZH, t th Non-resonant: t t, DY, tv, t tv, VV Combination of Delphes and generator level weighted by eciencies. Two categories: τ h τ h / τ h τ µ τ h : Hadronic tau decays τ µ : Tau decays to µ Event Selection: 2 b-tagged jets with p T > 30GeV, η < 2.4 τ h τ h final state 2 isolated τ h -s with p T > 60GeV or p T > 90/45GeV, η < 2.1 τ µ τ h final state An isolated τ h with p T > 30GeV, η < 2.1 and an isolated τ µ with p T > 30GeV, η < GeV < m bb < 130GeV and 110GeV < m ττ < 140GeV m ττ reconstructed with likelihood based technique (SVFIT), important to discriminate against Z ττ. 26 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

27 HH bbττ - Analysis strategy Dene kinematic bounding variable m T 2 to discriminate against t t : Maximal possible mass of the parent particle (t or H) consistent with the constraints Bounded above by the top mass for t t events, unbounded for di-higgs signal events Events CMS Simulation s=14 TeV, PU=140 HH ττ bb tt tw Z->ττ ttv VV[V] tth ZH Stat. uncertainty τ h τ h Events CMS Simulation s=14 TeV, PU=140 HH ττ bb tt tw Z->ττ ttv VV[V]+jets tth ZH Stat. uncertainty τ µ τ h m T2 [GeV/c ] BDT To further exploit the boosted kinematics of di-higgs production, a BDT is trained on masses, P T, R and m T 2 27 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

28 HH bbττ - Results Signal extraction: τ h τ h : Maximum likelihood t on m T 2 τ µ τ h : Has a much larger leptonic t t background Maximum likelihood t on BDT output Expected signicance: 0.5 and 0.7σ for τ µ τ h and τ h τ h Total: 0.9σ Strong dependance on capability to trigger at level 1 on charged particles with the Phase II CMS detector, otherwise sensitivity reduced by 40%. 28 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

29 HH bbww bblνlν Backgrounds: Dominant background: t t production with fully leptonic decay Other backgrounds negligible Detector simulation with Delphes Event Selection: 2 opposite sign leptons, muon P T > 20 GeV, electron P T > 25 GeV and η < b-tagged jets with P T > 30 GeV and η < 2.5 m ll > 85 GeV 60 GeV < m bb < 160 GeV R ll < 2.0 R bb < 3.1 φ bb,ll > J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

30 HH bbww bblνlν Results A neural network is trained on the kinematic properties, taking into account the correlations Result from cut and count on NN discriminator Small contribution to signicance when combined with the other nal states 30 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

31 Higgs Pair production expectations HL-LHC (3000fb 1 ): Combining bbγγ and bbττ nal states, the expected signicance is 1.9σ Observation might be possible, after improvements and combining CMS and ATLAS results Room for improvements: More sophisticated reconstruction and analysis techniques Additional di-higgs boson production and decay modes remain unexplored, especially promising bbbb nal state when using boosted b-tagging techniques 31 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

32 Conclusions Many interesting future MBI results with the LHC. At the short term: Observation of triple gauge boson states Discovery of EWK VV+2j production Improved measurements of the anomalous triple and quartic gauge couplings At longer term, HL-LHC: Sensitivity to partially-unitarized models Possibility of discovering longitudinal vector boson scattering and di-higgs production, but further study is required Analyses will benet from HL LHC and phase 2 upgrades: Tracker extension improves tag-jets identication in scattering analysis The ability to measure the di-higgs production in the most promising nal states will largely depend on the identication and momentum resolution performance for b-jet, photons and τ 32 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

33 Backup Backup 33 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect

34 HL-LHC plan 34 J. Lauwers CMS Run 2 and HL-LHC Multi-boson Physics Prospect