Perspectives of Higgs measurements at High-Luminosity LHC

Transcription

1 Perspectives of Higgs measurements at High-Luminosity LHC Alessandro Calandri (Centre de Physique des Particules de Marseille & Aix-Marseille Université) on behalf of the ATLAS and the CMS Collaborations LCWS International Workshop on Future Linear Colliders - Strasbourg, October 23rd 207

2 Outline of the talk The High-Luminosity LHC (HL-LHC) program The ATLAS and CMS upgrade programs HL-LHC environment and object performance The analysis procedure and treatment of the systematic uncertainties for studies on Higgs measurements Higgs analysis prospects Higgs boson couplings, differential measurements Higgs boson self-couplings (HH bbγγ, HH bbττ, HH bbbb) Rare decays (H J/Ψ γ, H μμ) Studies on vector boson fusion Higgs production in ZZ and WW channel Extraction of the Higgs boson width Wrapping-up and conclusions 2

3 The High-Luminosity LHC program Now ( s=3 TeV), < > 25 Phase-II Atlas and CMS Upgrade Peak luminosity (cm -2 s ) μ (pile-up) Increased instantaneous luminosity and mean number of interactions per bunch-crossing (pile-up) Current HL-LHC baseline HL-LHC ultimate Integrated luminosity collected during HL-LHC 3000 fb Precision measurements on the Higgs sector (couplings, selfcouplings, VBF production), raredecays 3

4 A sketch of the ATLAS Phase-II Upgrade Upgrade trigger system track trigger modification of the data acquisition system to deal with the high rate at HL- LHC Inner tracker (all-silicon, pixel and strip sensors) extended to η =4 New muon trigger chambers in the barrel CERN-LHCC (Scoping Document, SD) High-granularity timing detector (still under discussion) Upgrade electronics for Liquid-Argon electromagnetic and for Tile hadronic calorimeter 4

5 A sketch of the CMS Phase-II Upgrade Upgrade trigger system L track trigger, improved rate capability and extension of the L latency Silicon inner tracker with extended coverage to η =4 High granularity calorimeters using silicon technology Upgrade barrel calorimeter electronics and photodetectors Muon system coverage in.5< η <2.5 improved and extension to η =3.0 CERN-LHCC

6 HL-LHC environment and object performance Very challenging environment at HL-LHC detector requirements to maximize benefits from high luminosity large integrated radiation dose mitigation of pile-up effects sustain large event rate with more sophisticated trigger and data acquisition systems Important to keep good control over performance of physics objects (identification and reconstruction, background rejection) CMS-DP-207- Tracking track resolution, pile-up jet rejection, background rejection for b-tagging, identifications of electrons and photons CMS-DP b-tagging Photon Isolation and Identification efficiency ATL-PHYS-PUB ATLAS Simulation Preliminary VBF H"!!, <µ> = 200 HL-LHC ITk-LoI Photons p T,! [GeV] mass (B) [MeV] ATL-PHYS-PUB ATLAS Simulation Preliminary ID/ITk tracks Muons 0 Bs -! +! Run-2 Layout HL-LHC ITk Inclined Layout (B) 6

7 Analysis strategy and treatment of the uncertainties CMS uses extrapolation of current analyses accomplished with 205 or 206 dataset at 3 TeV Several scenarios for systematic uncertainties (results also provided for statistics-only scenario) S: systematic uncertainties kept constant with (S+) or without (S) presence of high pile-up and detector improvements S2: systematic uncertainties are scaled wrt Run 2 analyses (theory /2, experimental /L ATLAS uses generator-level 4 TeV samples Particles (e, μ, τ, missing energy, jets) at eventgenerator level are smeared in pt and energy according to functions that take into account the upgraded detector layout Smearing functions extracted from fullysimulated samples in HL-LHC configuration Some results rely on Run/Run 2 results being extrapolated to HL-LHC and same detector performance and analysis strategy Pile-up included in the simulation (<μ>=40 and <μ>=200) Theoretical systematic uncertainties: same as Run / Run 2 analysis, reduced by /2 or absent Experimental uncertainties: scaled wrt current analyses in Run /Run 2 7

8 i CMS-PAS-FTR6-002 ATLAS Simulation Preliminary s = 4 TeV: H H ZZ H WW H Z H bb H (comb.) (comb.) (comb.) (incl.) (comb.) (VBF-like) Ldt=300 fb ; Ldt=3000 fb Higgs boson couplings ATLAS performs an extrapolation from Run analysis using <μ>=40 CMS makes projections for different Higgs couplings in production using the H γγ and H ZZ 4l decay channels Run : Δμ/μ (H γγ)=23%, Δμ/μ (H ZZ)=24%, Δμ/μ (H WW)=33% y Expected precision on couplings to W/Z around 3%, to muons 7%, to τ, b, t approximately 3000 fb -2-3 ATLAS Simulation Preliminary h, h ZZ* 4l, h WW* l l h, h bb, h!!, h Z [ Z, W, t, b,,! ] BR i,u =0! b s = 4 TeV W Ldt = 300 fb Z Ldt = 3000 fb t!"#!"#$%&'(#)!!! ::6 789! 6 &&6!;9<=(>?(!;9<=(>2? C 3/// DE /0/(BH&,&0A(! /0/I(B$"#0A(! /0/=(B&F$G0A! /0/(BH&,&0A(! /0/2(B$"#0A(! /0/3(B&F$G0A /0 / /0 /02 /03 /04 /05 CMS Projection H! ZZ*! 4l!"#$%&$'()*%$+&,-*& fb (3 TeV) µ ZZ ± 0.02 (stat.) ± 0.04 (exp.) ± 0.07 (theo.) µ ZZ ggh µ ZZ VBF ATL-PHYS-PUB Systematic uncertainties in the present and in the HL-LHC conditions ECFA6 S+ ECFA6 S2+ ± 0.02 (stat.) ± 0.03 (exp.) ± 0.03 (theo.) H!! (comb.) !/! Ratio to SM [GeV] m i 2 µ ZZ VH µ ZZ tth

9 CMS-PAS-FTR6-002 H->ZZ*->4l (differential) Measurements of differential cross section as a function of the Higgs transverse momentum allow to probe the high pt phase space and be sensitive to possible deviations from Standard Model expectations - fiducial region matching the expected experimental acceptance for HL-LHC - statistical component in the measurement of the high pt spectrum is still large at HL-LHC CMS Projection 300 fb (3 TeV) CMS Projection 3000 fb (3 TeV) (H) [fb/gev] T d! fid /dp " "2 "3 Toy Data (stat.#sys. unc.) Systematic uncertainty (ECFA6 S) Systematic uncertainty (ECFA6 S2) gg$h (POWHEG+JHUGen) + XH XH = VBF + VH + tth (H)>200 GeV) T!(p 50 (H) [fb/gev] T d! fid /dp " "2 "3 Toy Data (stat.#sys. unc.) Systematic uncertainty (ECFA6 S+) Systematic uncertainty (ECFA6 S2+) gg$h (POWHEG+JHUGen) + XH XH = VBF + VH + tth (H)>200 GeV) T!(p 50 Ratio to POWHEG " p (H) [GeV] T Ratio to POWHEG " p (H) [GeV] T 9

10 CMS-PAS-FTR6-002 Higgs self-couplings - HH bbbb ATL-PHYS-PUB Measure the Higgs boson trilinear self-couplings decay channels with b-jets (bbbb, bbww) have higher BR - fundamental to achieve excellent b-tagging performance at HL-LHC - largest systematics from b-tagging and treatment of ttbar background HH bbbb - both ATLAS and CMS employ an extrapolation (<μ>=200) from Run 2 analysis with 205 (CMS) / fraction of 206 (ATLAS) data ( fb ) and systematic uncertainties as in 205/206 analysis H!! H! H ATLAS-TDR-025! H! H Results given as signal significance, expected uncertainty on μbbbb (CMS) or limits on the trilinear couplings (λhhh) wrt SM predictions (ATLAS) CMS Projection s = 3 TeV SM gg $ HH µ ##bb µ ""bb µ VVbb ECFA6 S2 ECFA6 S2+ Stat. Only µ bbbb! 2! expected uncertainty [fb] pp# hh # bbbb $ ATLAS Preliminary Internal s = 4 TeV, L = 3000 fb Non-resonant prediction Expected Limit (95% CL) Expected ± $ Expected ± 2$ " " SM! HHH /! HHH ATLAS: results as a function of the trigger pt threshold for pt threshold at 30 GeV: -3.5<λHHH/λSM< (current systematic 95% CL CMS: expected uncertainty on μbbbb 2.4 (with systematics)

11 CMS-PAS-FTR6-002 Higgs self-couplings - HH bbγγ ATL-PHYS-PUB [fb] pp HH bb Clear HH signal extraction thanks to the narrow mass peak of H γγ (low BR, 0.3%) <μ>=200 at 3000 fb - SD performance for photons and updated b-tagging performance Main background component - non resonant bbγγ and bbjγ + single H background production Cut and count analysis based on the identification of isolated photons and a pair of b-tagged jets (main systematic uncertainty on photon/b-tagging performance) - expected signal event 9.5 with S/ B significance.05 (only statistical uncertainties) ATLAS Simulation Preliminary s=4 TeV, 3000 fb Non-resonant HH prediction Expected Limit (95% CL) Expected! Expected! SM HHH / HHH ATLAS: -0.8<λHH/ λsm<7.7 (no 95% CL CMS: expected uncertainty on μbbγγ 3 (with systematics) Events / 5 GeV Events / GeV ATLAS Simulation Preliminary s = 4 TeV, 3000 fb Stat. Unc. HH bb Single H bb Reducible Others [GeV] ATLAS Simulation Preliminary s = 4 TeV, 3000 fb m Stat. Unc. HH bb Single H bb Reducible Others [GeV] m bb

12 CMS-PAS-FTR6-002 Higgs self-couplings - HH bbττ ATL-PHYS-PUB Large BR H ττ decay results in significantly large yield but very complex final state and several background contributions to estimate Significance CMS projection gg"hh"!! bb channel ECFA6 S ECFA6 S2 (3 TeV) Final state divided into sub-channels depending on the decay modes of the τ leptons, leptonic (lep) or hadronic (had) Stat. error only Common irreducible backgrounds i.e. tt and Z( ττ) +jets and di-boson production ZZ, ZH, WH Cut-based analysis with optimization of S/ B with separate event selection optimization for each decay channel Main systematic uncertainty: background modeling uncertainty (Run ) S/ B significance 0.47 (had-had), 0.35 (lep-had in μ- channel), 0.33 (lep-had in the e-channel) combined significance: 0.60 ATLAS -4.0<λ HH/λSM<2 (with systematic uncertainties) / SM 95% CL upper limit on Total luminosity [fb ] / SM as a function of Exp. 95% CL ATLAS Simulation Preliminary / SM 2!! 2 had-had selection L dt = 3000 fb lep-had e selection lep-had " selection s = 4 TeV / SM CMS: expected uncertainty on μ bbττ 3.2 (with systematics) 2

13 Higgs-self couplings - wrapping-up HH bbbb 95% C.L. uncertainty on μ 2.4 (with systematic uncertainties included) HH bbγγ 95% C.L. uncertainty on μ 3.0 (with systematic uncertainties included) HH bbττ 95% C.L. uncertainty on μ 3.2 (with systematic uncertainties included) 3

14 ATLAS-TDR-025 Higgs rare decays H J/Ψ ( μμ) γ - using Run detector performance and <μ>=40 ATL-PHYS-PUB sensitivity to the magnitude c and b quark couplings J/Ψ μμ decays - opposite sign muons with pt>3 GeV η <2.5 consistent with common vertex - Dimuon invariant mass compatible with J/Ψ Multivariate analysis employed using pt (μμ), pt (γ) and μ/γ isolation BR (H J/Ψ γ) < ( % CL where SM expectation H μμ - using Run detector performance and <μ>=200 - very high mass resolution and low BR with very large irreducible background from Z/γ* - with 3000 fb, expected sensitivity of 7σ Key aspect is the reconstruction of the di-muon final state - upgraded layout improves the di-muon invariant mass resolution by 25% 4

15 Vector boson fusion - H ZZ 4l ATL-PHYS-PUB Vector boson fusion (VBF) signature is kinematically highly distinctive, marked by the presence of two energetic final state quark jet at very high rapidity gap - corresponding H boson centrally produced Important role of pile-up jet suppression in the forward region Assuming Run detector performance for e/μ - results for <μ>=200 - Selection requirements: same selection as in Run VBF H ZZ analysis + m(jj)>30 GeV Multivariate approach employed to separate VBF from gluon-fusion + 2jets Higgs production and qq ZZ - definition of the signal region exploited by a cut on BDT to improve resulting VBF H 4l significance - QCD scale variation systematic uncertainty Normalized to unity / ATLAS Simulation Preliminary VBF25 ggf25 qqzz bkg. 0!! 0.8! 0.6! 0.4! <μ>=200, stat+sys Stat+sys Significance 7.2 Δμ/μ 0.8 BDT score Impact of increasing jet tracking coverage in the forward region (η=2.4 4) improves the expected precision on Δμ/μ from 22% to 4% 5

16 Vector boson fusion - H WW eνμν ATL-PHYS-PUB VBF signature is kinematically distinctive - presence of two energetic final state quark jets at very high rapidity gap - corresponding H boson centrally produced VBF H WW* production mode very useful to test detector layouts because of the several objects in the final state which are affected by pile-up Assuming Run detector performance for e/μ - results for <μ>=200 - events with two opposite-sign and different flavour leptons (e/μ) passing quality selection criteria - no other jets present between the VBF jets (events are removed if jet with pt> 30 GeV within the rapidity range of the VBF jets) - Drell-Yan and multi-jet background suppressed by requiring ET miss >20 GeV QCD scale on the VBF jets dominates the systematic uncertainties - theoretical computation will improve with time and will reduce the uncertainty Events / 325 GeV Events / 40 GeV ATLAS Simulation s=4 TeV, 3.0 ab VBF H WW e! tt WW Z+jets ggf H [GeV] 50 ATLAS Simulation s=4 TeV, 3.0 ab VBF H WW e! tt WW Z+jets ggf H m jj m T WZ/ZZ Single Top W+jets VBF H WZ/ZZ Single Top W+jets VBF H [GeV] 6

17 Higgs boson total width Off-shell Higgs production used to indirectly constrain the Higgs boson width, ΓH Using H ZZ* 4l final state with m(4l)>220 GeV to select the high-mass region - m(4l) shape and matrix-element method to discriminate between the Higgs signal and the qq ZZ and gg ZZ backgrounds [fb/gev] d /dm 4l ATL-PHYS-PUB ATLAS Simulation s=4 TeV gg H* ZZ (S) gg ZZ (B) gg (H* ) ZZ (SBI) - signal-to-background interference from same gg-initiated initial states (gg H ZZ 4l and non-resonant gg ZZ) taken into account in the simulation - same treatment of systematic uncertainties as in Run analysis (theory uncertainty on gg ZZ will reduce at HL-LHC) Off-shell signal strength - μ(off-shell)= Combining with the on-shell measurement in the on-peak Higgs region and assuming that the error on the combination is dominated by off-shell - ΓH= MeV Run (ATLAS) limit on Γ H at 22 MeV (ZZ and WW) at 95% CL -2ln [GeV] ATLAS Simulation Ldt = 3000 fb s=4 TeV No systematics Norm systematics Norm+shape systematics m 4l ! 7

18 Wrapping-up and conclusions High-Luminosity LHC will represent an important challenge for the physics program within the Higgs sector of ATLAS and CMS Object and particle performance will have to be re-optimized due to the large pile-up contamination and the upgrades of the two experiments The Higgs program will largely benefit for the high statistics provided during HL-LHC - a lot of studies from ATLAS and CMS covering several topics precision measurements on Higgs boson couplings Higgs width and rare-decays can extend the present sensitivity and explore Higgs-self couplings with good precision Results for prospects on Higgs measurements at HL-LHC from ATLAS and CMS are preliminary detectors are still in the development/optimization phase more advanced analysis techniques and better characterization of the systematics uncertainties will give a more precise picture Very exciting times ahead! 8

19 Additional slides 9

20 Higgs boson total width ATL-PHYS-PUB [fb/gev] d /dm 4l s=4 TeV ATLAS Simulation Events normalized to unit area gg H* ZZ (S) gg (H* )ZZ (SBI) gg ZZ qq ZZ ATLAS Simulation s=4 TeV gg H* ZZ (S) Interference [GeV] m 4l Signal component and signal-to-background interference ME discriminant Matrix element-based discriminant for gg H ZZ (signal), qq ZZ and gg ZZ (backgrounds). The signal-to-background interference is also included 20

21 Higgs boson couplings ATLAS Simulation Preliminary s = 4 TeV: H H ZZ H WW H Z H bb H H!! (comb.) (0j) (j) (VBF-like) (WH-like) (ZH-like) (tth-like) (comb.) (VH-like) (tth-like) (VBF-like) (ggf-like) (comb.) (0j) (j) (VBF-like) (incl.) (comb.) (WH-like) (ZH-like) (VBF-like) (comb.) (incl.) (tth-like) Ldt=300 fb ; Ldt=3000 fb !/! F fb, w/ theory 3000 fb, w/ theory Precision on the signal strength parameter for the different Higgs production modes 68% CL expected likelihood contours for couplings to fermions and bosons at 4 TeV for an assumed integrated luminosity of 300 fb and 3000 fb 300 fb, w/o theory 3000 fb, w/o theory Standard Model ATLAS Simulation Preliminary s = 4 TeV V 2

22 Higgs self-couplings - HH bbbb (ATLAS) ATL-PHYS-PUB Entries/ GeV ATLAS Preliminary Internal s = 4 TeV, L = 3000 fb Multijet tt SM non-resonant HH 3 2! [GeV] m 4j 22

23 CMS-PAS-FTR6-002 Higgs self-couplings - HH bbww (CMS) Phase-II detector simulation Main background: tt+jets 23

24 ATLAS inner tracker 24

25 Higgs rare decays - H->μμ 25