Higgs Results from ATLAS

Transcription

1 Higgs Results from ATLAS Rosy Nikolaidou CEA Saclay On behalf of ATLAS collaboration Rencontres de Moriond QCD and High Energy Interac7ons La Thuile, March 5th - April st, 7

2 Introduction & Outline Ø After the historical discovery of the new particle (5 GeV) in and its consistency with the SM Higgs boson, an extensive and rich research program has been established: Ø measurements of its properties, study of rare decays Ø searches beyond the Standard Model (BSM) Ø Using the Higgs boson as a tool for discovery Ø Latest published results from ATLAS with a subset of Run dataset corresponding to 35 & Ø a couple of selected topics will be shown Ø New results with full 5+6 dataset (L=36. & ) Ø Ηàγγ + ing transverse energy signatures Ø Hàμμ decays Full list of results

3 LHC and ATLAS performance 3 Ø Excellent LHC performance in 6 Ø more data than all other years combined! Ø Peak L =.4 34 cm - s (exceeded design) Ø higher pileup conditions Ø ATLAS: High data taking efficiency (>9%) and data quality efficiency (93-95% ) Run Run Ecm Year Luminosity used in analyses Uncertainty on luminosity 7 TeV 4.5 >.8% final 8 TeV.3 >.8% final 3 TeV 5 3. >.% final 3 TeV > 3.% prel new

4 H(5 GeV) production and decays 4 ~8% ~6.7% ~.6% ~.9% From 8 to 3 TeV σ(h) increased by (~.5) tth increased by ( ~4) Theory progress: (e.g N3LO inclusive ggf cross section, NNLO differential cross section, updated PDF4LHC)

5 Run legacy Production process Measured significance (s) Expected significance (s) VBF WH.4.7 ZH.3.9 VH tth 4.4. Decay channel H! tt H! bb Studies / measurements of properties Ø Angular distributions showed consistency with a particle of spin and even parity ATLAS and CMS Preliminary ATLAS Ø All measured processes in agreement with SM CMS within standard deviations ATLAS + CMS JHEP 8(6) 45 Ø Largest deviation in measured tth cross section From ATLAS+CMS combination production modes Ø observation of ggf, VBF Ø evidence for VH and tth! decay modes Ø observation of Hàγγ,ZZ,WW Ø observation of Hàττ µ ggf µ VBF LHC Run ATLAS+CMS ± σ ± σ 5 ATLAS + CMS PRL 4, 98 ATLAS and CMS Total Stat. Syst. LHC Run Total Stat. Syst. ATLAS H γ γ 6. ±.5 ( ±.43 ±.7) GeV CMS H γ γ 4.7 ±.34 ( ±.3 ±.5) GeV ATLAS H ZZ 4l 4.5 ±.5 ( ±.5 ±.4) GeV CMS H ZZ 4l 5.59 ±.45 ( ±.4 ±.7) GeV ATLAS +CMS γ γ 5.7 ±.9 ( ±.5 ±.4) GeV ATLAS +CMS 4l 5.5 ±.4 ( ±.37 ±.5) GeV ATLAS +CMS γ γ +4l 5.9 ±.4 ( ±. ±.) GeV m H µ WH µ ZH µ tth µ Mass within.% precision m H =5.9±.4 GeV Parameter value

6 6 Flash some of the latest published results with s L=35 fb - Ηàγγ ΗàZZ*à4l, l=e,μ CombinaYon Hàγγ,ΖΖ*

7 H (5) àγγ Ø High resolution channel, rare decay.% Ø Narrow resonance on top of background Ø γγ, γ-jet, jet-jet Ø Event categorization to probe production modes and kinematic properties Ø Signal extracted by fit of m γγ spectrum Ø Observed Significance 4.7 σ Extract fiducial and differential cross-section P T γγ : data & theory overall good agreement ATLAS-CONF-6-67 Signal strength per production mode No significant deviation from SM observed 7 ggf@n3lo ggf@nnlo

8 H (5) àzz*à(4l),l=e,μ ATLAS-CONF High resolution channel, good S/B, but low yield Event categorization to measure cross section per production mode and provide sensitivity to BSM Extract signal by fitting the shape of discriminants in each category m 4l [89] GeV! p T, j > 3 GeV! or more jets! >= leptons (p T, l > 8 GeV)! jet! jet! m jj < GeV! m jj > GeV! Just counting! Discriminant! BDT-ZZ! Discriminant! BDTj! Discriminant! BDT-jVH!! Discriminant! BDT-jVBF! BDT_ZZ:! p T4l η 4l! KD = log(me HZZ / ME ZZ )! BDT_jet:! p T,j! η j! ΔR 4lj! BDT_jet_VH:! p T,j! p T,j! η j! Δη jj! Δη 4ljj! m jj! min(δr Zj )! BDT_jet_VBF:! p T,j! p T,j! p T,4ljj! Δη jj! Δη 4ljj! m jj! min(δr Zj )!

9 H (5) àzz*à(4l),l=e,μ ATLAS-CONF selection for fiducial cross section Measured cross sections and couplings consistent with SM within σ

10 H(5) : ZZ* + γγ combination Best fit cross-section per production mechanism ATLAS-CONF-6-8 Best fit value (pb) SM prediction (pb) ggf ±.3 VBF ±.7 Total cross-section: Extrapolate fiducial cross section to full phase space VHhad ±.3 VHlep ±. top ±.6 [pb] σ pp H σ pp H m H = 5.9 GeV γ γ 8 6 H H ZZ * 4l comb. data syst. unc. QCD scale uncertainty Tot. uncert. (scale PDF+α s ) cross section consistent with N3LO QCD calculations and NLO EW corrections s [TeV] s = 7 TeV, 4.5 fb s = 8 TeV,.3 fb s = 3 TeV, 3.3 fb (γ γ ), 4.8 fb (ZZ *) 3TeV: σ (pp H + X) = (stat) (syst)pb (ATLAS) σ (pp H + X) = pb (N3LO theory)

11 Two new results with full 5+6 dataset L=36. fb - Ηàγγ + ΜΕΤ signatures Ηàμμ

12 Hàγγ + E new T search Searches for new phenomena (Dark Matter) with H(5)àγγ and E T signature 3 models considered: Z B model q q Z Z Backgrounds: Ø γγ (dominant), γ+jets, Vγ, Vγγ Ø SM Higgs, VH irreducible Discriminating variables: Ø E T significance Ø Z PV γγ Z PV hard Ø P T γγ, P T hard h Z HDM model q q Z A DM coupling to H and Z DM coupling to pseudo-scalar A harder spectrum on E T GeV Events / Data / MC E T / ΣE T 7 Data s = 3 TeV, 36. fb h Z'-HDM, Dirac DM m χ = GeV, m Z' = TeV, m = GeV A Z' B, Dirac DM m χ = GeV, m Z'B Heavy scalar, Scalar DM m χ 5 5 S [ ET GeV] m H Vγγ Vγ = 75 GeV SM Higgs boson γ+jets γγ Syst. Stat. Unc. = GeV = 6 GeV, Heavy scalar: g g H produced via ggf effecyve coupling to DM and SM Higgs Magnitude of vectorial sum of photons and jets Events / GeV Data / MC s = 3 TeV, 36. fb h 5 5 hard p T Data Z'-HDM, Dirac DM m χ = GeV, m Z' = TeV, m = GeV A Z' B, Dirac DM m χ m H = 75 GeV = GeV, m Z'B Heavy scalar, Scalar DM m χ Vγγ Vγ SM Higgs boson γ+jets γγ Syst. Stat. Unc. = GeV = 6 GeV,

13 Hàγγ + E T search 3. Event categorizayon to increase the sensiyvity Ø Five categories determined. Signal and background fits per category Ø Signal: Double sided Crystal Ball Ø Background: ExponenYal Ø Modeling bias associated to selected funcyonal form esymated on MC 3. Results: unbinned fit to m γγ spectrum Ø Heavy scalar model: simultaneous fit all categories Ø DM models: fit to Mono-Higgs category Events / GeV Data-Bkg Events / GeV Data-Bkg s = 3 TeV, 36. fb Intermediate-E T h (µ=, m =5.9 GeV) h Heavy scalar, Scalar DM m χ = 6 GeV, m H = 75 GeV Non-resonant bkg Non-resonant bkg + h Total m γγ m γγ 7 h (µ=, m =5.9 GeV) h Heavy scalar, Scalar DM 6 s = 3 TeV, 36. fb m χ = 6 GeV, m H = 75 GeV Non-resonant bkg Different-Vertex 5 Non-resonant bkg + h Inter E T Diff Vertex Total m γγ m γγ Events / GeV Data-Bkg s = 3 TeV, 36. fb Mono-Higgs Mono-Higgs h (µ=, m =5.9 GeV) h Heavy scalar, Scalar DM m χ = 6 GeV, m H = 75 GeV Non-resonant bkg Non-resonant bkg + h Total m γγ Events / GeV Data-Bkg s = 3 TeV, 36. fb High-E T High E T h (µ=, m =5.9 GeV) h Heavy scalar, Scalar DM m χ = 6 GeV, m H = 75 GeV Non-resonant bkg Non-resonant bkg + h Total m γγ m γγ Events / GeV Data-Bkg s = 3 TeV, 36. fb Rest Rest h (µ=, m =5.9 GeV) h Heavy scalar, Scalar DM m χ = 6 GeV, m H = 75 GeV Non-resonant bkg Non-resonant bkg + h Total m γγ m γγ

14 Hàγγ + E new T search 4 hqps://atlas.web.cern.ch/atlas/groups/physics/confnotes/atlas-conf-7-4 Ø No significant excess beyond SM observed à 95% CL limits D upper limit for all models DM simplified models: D contour limits [fb] BR h γγ 95% CL limit on σ pp h χχ 4 3 Observed Expected Expected ± σ Expected ± σ BR σ th s = 3 TeV, 36. fb pp H h( γ γ ) + χ χ, Heavy scalar, Scalar DM = 6 GeV, BR (H hχχ) = % m χ m A m h = m A m Z' s = 3 TeV, 36. fb mono-h(γγ), Z'-HDM, Dirac DM tanβ =., g =.8, m χ = GeV Z' σ obs / σ th = Expected Expected + σ Expected - σ σ obs /σ th 95% CL observed limit on m H m Z' Simplified models: Strong D upper limits on the DM producwon D limits contour on signal strength for both types of the simplified models Heavy scalar: Strong upper limits on the heavy scalar producwon with mass 5-36 GeV

15 Hàμμ decays new 5 Motivation : Ø Sensitive channel to measure Higgs couplings to second generation fermions Characteristics of the channel: Ø Clean experimental signature, small BR ~.8-4 Ø Dominant background Drell Yan Z/γ*à μμ Analysis strategy: Ø Event classification in orthogonal categories for ggf and VBF production Ø Distinguish VBF characteristics by using discriminating variables in a BDT Ø ggf categories based on η, P T μμ Ø Fit dimuon spectra (very good signal resolution, smooth m μμ around m H ) Ø Simultaneous fit to the observed m μμ in all categories ( GeV<m μμ <6 GeV) to extract signal strength and determine background normalization and shapes

16 Muon performance ggf H(5)àμμ new 6 hqps://atlas.web.cern.ch/atlas/groups/physics/plots/muon-7-/index.html Efficiency Data / MC s = 3 TeV, 33.3 fb Medium muons No TRT selection applied η >. Stat only Sys Stat muon efficiency versus P T J/ψ µµ Data J/ψ µµ MC Z µµ Data Z µµ MC p T di-muon invariant mass resolution versus η Entries /.5 GeV.4 ATLAS Simulation Preliminary Central low p µµ T FWHM=5.6 GeV s = 3 TeV, 36. fb ggf [5] Signal model m µµ m µµ signal model fit in low P T μμ category Entries /.5 GeV ATLAS Simulation Preliminary Central high p µµ T FWHM=6.3 GeV s = 3 TeV, 36. fb ggf [5] Signal model signal model fit in high P T μμ category

17 Hà μμ decays 7 new hqps://atlas.web.cern.ch/atlas/groups/physics/confnotes/atlas-conf-7-4/ Events / GeV s = 3 TeV, 36. fb Data Drell-Yan Top Diboson ggf VBF VH Entries / GeV 35 3 χ µ s = /ndof = 3.7/ ATLAS VBF tight Preliminary s = 3 TeV, 36. fb Data Background model Signal [5] Data/MC m µµ Pull mll m µµ Data set Upper C L Observed (expected) Signal Strength μ s Run (3 TeV) 3. (3.) -.7 ±.5 Run+Run (7+8+3 TeV).7 (.8) -.3 ±.4

18 Summary / Conclusions 8 Ø ATLAS in full speed to prepare the final publications on Higgs searches with the full dataset available from TeV Ø Two new analyses presented in this talk Ø Hàμμ, Hàγγ+ E T Ø No significant excess w.r.t SM observed Ø Improved limits w.r.t. Run or previous Run results Ø Many more analyses in preparation, coming soon Ø Stay tuned

19 BACKUP 9

20 Hàγγ + E new T search 9% CL Z B limits reinterpreted as DMnucleon scaqering cross secyon as a funcyon of DM mass, for a spinindependent scenario ] DM-nucleon cross section [cm pp h( γ γ ) + sinθ =.3, g q Spin-independent χ χ, Z', Dirac DM B = /3, g = χ supercdms CRESST-II 6 ATLAS Preliminary s = 3 TeV, 36. fb PandaX-II LUX6 9% CL DM mass m χ 3

21 Run studies Exploring the higher energy regime and increased statistics in Run and the progress from the theory side. Measuring Higgs boson TeV (indirect search for new physics) Ø decays to bosons : Hàγγ,ZZ*, WW* Ø Access to all production modes Ø Study of BEH kinematics, spin/parity properties, improve mass measurement, width studies Ø Access to rare decays HàZγ Ø Decays to fermions: Hàμμ, bb,ττ In this talk Ø Study of Yukawa couplings to quarks and leptons Ø Challenging either to large background (bb,ττ channels) or to tiny BR (μμ) Ø tth production mode search Ø Unique channel to study directly the top Yukawa coupling Ø Profit from the increased cross TeV Ø Use of H as a tool for new physics Ø (example Dark Matter search Hàγγ +E T ) In this talk. BSM studies (direct search for new physics) Ø Many models are studied HDM, MSSM in order to understand the Higgs sector, assuming additional Higgs bosons neutral or charged decaying to bosons or fermions In this talk

22 Hà μμ: previous ATLAS results Run: 8TeV Run with L= 3 & 95% CL Limit on µ Observed Bkg. Expected ± σ ± σ + - H µ µ Ldt =.7 fb s = 8 TeV BR(H µµ) [pb] s = 3 TeV, 3. fb H µµ Observed Expected ± σ ± σ SM Higgs m H 95% CL Limit on σ m H 95% CL Observed (expected) limit = 9.8 (8.) x SM hqp://atlas.web.cern.ch/atlas/groups/ PHYSICS/CONFNOTES/ATLAS- CONF-3-/ 95% CL Observed (expected) limit = 4.4 (5.5) x SM hqps://atlas.web.cern.ch/atlas/groups/ PHYSICS/CONFNOTES/ATLAS- CONF-6-4/

23 Hà μμ decays 3 The background model fits to the m μμ distribuyon in different categories. Signal is scaled x