Measurement of cross sections and properties of the Higgs boson in decays to bosons with the ATLAS experiment Lake Louise Winter Insitute 2019 Ruggero Turra on behalf of the ATLAS Collaboration INFN Milano 11 February, 2019
References for Run2 13 TeV 36 fb − 1 and 80 fb − 1 Latest Summer Run 2 results with 80 fb − 1 13 TeV: H → γγ : ATLAS-CONF-2018-028 H → 4 ℓ : ATLAS-CONF-2018-018 combination γγ + 4 ℓ + e νµν + ττ + VH( bb ) + µµ + ttH(bb and multilepton): ATLAS-CONF-2018-031 combination ttH γγ + 4 ℓ + bb + multilepton (5 . 8 σ ): -1 160 fb ATLAS Phys. Lett. B 784 (2018) 173 s = 13 TeV Total Integrated Luminosity Preliminary 140 -1 Delivered: 158 fb LHC Delivered -1 120 Recorded: 149 fb ATLAS Recorded 100 80 fb-1 Latest Run 2 results with 36 fb − 1 13 TeV: 80 Mass γγ +4 ℓ : Phys. Lett. B 784 (2018) 345 60 36 fb-1 Initial 2018 calibration 40 xsections combination γγ +4 ℓ : Phys. Lett. B 786 20 (2018) 114 0 Jan '15 Jul '15 Jan '16 Jul '16 Jan '17 Jul '17 Jan '18 Jul '18 H → γγ : Phys. Rev. D 98 (2018) 052005 Month in Year H → 4 ℓ : JHEP 03 (2018) 095 EFT interpretation γγ +4 ℓ : ATL-PHYS-PUB-2017-018 H → WW → e νµν : Phys. Lett. B 789 (2019) 508 R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 2 / 27
Table of contents 1 Higgs boson and its properties 2 Decay channels ( γγ , ZZ ∗ → 4 ℓ , WW ∗ → e νµν ) 3 Combination 4 Conclusions R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 3 / 27
Higgs properties Excess compatible with Higgs boson firmly established by ATLAS+CMS in 2012. Measurements Mass: m H known at 0.2% (single experiment) σ × Br : inclusive, for each production-mode, fiducial region (STXS), decay (strong SM assumption: very optimized analyses, acceptance extrapolations) Fiducial cross sections (minimal model dependence) Differential kinematic distributions for each decay in fiducial regions (minimal model dependence) Interpretations Spin and parity: 0 + , other models excluded in Run 1 Signal strengths: µ i = σ i /σ SM , µ f = BR f / BR SM (inclusive, i f per-production-mode, . . . ) Coupling modifiers to SM particles (k-framework) EFT interpretations R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 4 / 27
Higgs properties Excess compatible with Higgs boson firmly established by ATLAS+CMS in 2012. Measurements Mass: m H known at 0.2% (single experiment) σ × Br : inclusive, for each production-mode, fiducial region (STXS), decay (strong SM assumption: very optimized analyses, acceptance extrapolations) Fiducial cross sections (minimal model dependence) Differential kinematic distributions for each decay in fiducial regions (minimal model dependence) Interpretations Spin and parity: 0 + , other models excluded in Run 1 Signal strengths: µ i = σ i /σ SM , µ f = BR f / BR SM (inclusive, i f per-production-mode, . . . ) Coupling modifiers to SM particles (k-framework) EFT interpretations R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 4 / 27
Simplified template cross sections (STXS) stage 1 Defined in the CERN Yellow Report 4 Exclusive fiducial regions defined by production mode, p H T , N j , VBF-topology, p j 1 T , p Hjj T , p V T STXS bins interpr. Design measurement to split events according to STXS R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 5 / 27
γγ , ZZ ∗ → 4 ℓ , WW ∗ → e νµν BR/10 − 3 sig. eff. mass resolution Backgrounds γγ 2 . 27 42% 1 . 41–2 . 10 GeV Large: q ¯ q / gg → γγ and fakes q / gg → ZZ ∗ and fakes 4 ℓ 0 . 124 24% 1.6–2.4 GeV Small: q ¯ q / gg → WW ∗ , t ¯ e νµν 5 . 04 ∼ 11% Transverse mass q ¯ t , Wt , . . . R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 6 / 27
H → γγ coupling Decay with loop: can probe coupling to both fermions and vectors; sensitive to BSM Model large smooth background as a functional form, fitted on data Difficult to validate the potential bias on the signal: important systematics Lot of data: categorize the events in a fine way, targeting STXS Observable: diphoton mass, direction from calorimeter pointing ATLAS Preliminary Total Stat. Syst. SM −1 = 13 TeV, 79.8 fb s H , |y | < 2.5 → γ γ Total Stat. Syst. ( ) H + 0.23 + 0.16 ggF, 0j 0.92 ( ± 0.17 ) − 0.22 − 0.14 H + 0.68 + 0.43 ggF, 1j, 0<p <60 GeV 1.23 ( ± 0.52 ) − 0.61 − 0.31 T H + 0.50 + 0.43 + 0.27 ggF, 1j, 60<p <120 GeV 0.89 ( ) − 0.47 − 0.42 − 0.21 T H + 0.85 + 0.70 + 0.49 ggF, 1j, 120<p <200 GeV 1.51 ( ) − 0.76 − 0.68 − 0.35 T + 0.56 + 0.29 ggF, >= 2j 0.65 ( 0.47 ) ± − 0.52 − 0.21 j + 0.47 + 0.36 + 0.30 qq → Hqq, 0<p <200 GeV 1.40 ( ) − 0.40 − 0.34 − 0.21 T + 0.50 + 0.45 ggF + qq → Hqq, BSM−like 0.76 ( ± 0.23 ) − 0.49 − 0.43 + 0.71 + 0.65 + 0.29 VH, leptonic 1.38 ( ) − 0.64 − 0.59 − 0.25 + 0.44 + 0.37 + 0.23 Top 1.13 ( ) − 0.38 − 0.34 − 0.19 2 1 0 1 2 3 4 5 − − ( σ x B) / ( σ x B) SM ✞ ☎ ✞ ☎ Difficult to separate ggF 0j/ggF 1j p T < 60 GeV and qq → Hqq /ggF 2j ✝ ✆ ✝ ✆ R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 7 / 27
H → γγ coupling categorization To measure many cross-sections with small correlation split events in pure categories ttH VH VBF 29 reco-categories inspired by STXS ggF prod modes R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 8 / 27
H → γγ cross sections With 80 fb − 1 unfolded (bin by bin) distribution for p γγ T , y γγ , p j 1 T , N b − jets (lepton-veto) 80 [fb/GeV] | [fb] [fb/GeV] [fb] ATLAS Preliminary → γ γ , -1 ATLAS Preliminary → γ γ , -1 ATLAS Preliminary → γ γ , -1 3 ATLAS Preliminary → γ γ , -1 H s = 13 TeV, 79.8 fb H s = 13 TeV, 79.8 fb H s = 13 TeV, 79.8 fb 10 H s = 13 TeV, 79.8 fb fid Data, tot. unc. Syst. unc. data, tot. unc. syst. unc. data, tot. unc. syst. unc. data, tot. unc. syst. unc. γ σ γ y 1 / d| 1 gg → H default MC + XH gg → H default MC + XH gg → H default MC + XH 2 gg → H default MC + XH γ 60 j1 T 10 γ T p p fid / d ⊕ gg → H SCETlib+MCFM8 + XH / d gg → H NNLOJET + XH NNLOJET SCET + XH σ XH = VBF+ VH + ttH + bbH d fid fid → SCETlib (STWZ) + XH = VBF+ VH + ttH + bbH XH = VBF+ VH + ttH + bbH σ gg H XH 10 ttH σ d d N (p > 30 GeV, | η | < 2.5) ≥ 1, N = 0 − 40 − XH = VBF+ VH + ttH + bbH jets µ 10 1 10 1 T e+ ≥ anti k R = 0.4, N 0 t jets 1 20 − 1 − 10 10 2 − 2 10 − 2 10 0 0 50 100 150 200 250 300 350 0 1 2 0 200 1 2 3 4 XH XH 2 XH 2 XH 2 2 Ratio to default MC + Ratio to default MC + Ratio to default MC + Ratio to default MC + 1 1 1 1 0 0 0 = 0 = 1 ≥ 2 0 50 100 150 200 250 300 350 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 0 50 100 150 200 250 300 350 γ γ | y | j1 p [GeV] p [GeV] N γ γ b-jets T T Define fiducial regions only with kinematic cuts, close to the ones used in the analysis: small model dependency. p-value( χ 2 ) data/SM > 30% -1 σ H → γ γ , s = 13 TeV, 36.1 fb , m = 125.09 GeV H HW σ Can be used as input of EFT interpretation Δ ATLAS 0.4 ~ c (36 fb − 1 ): c = c HB HW 0.2 R ~ ~ u c = c n R 1 HB HW u n 9 5 1 % 6 introduce additional CP-even and 8 C % L − C L 0 CP-odd interactions in SILH framework − − ⊕ 0.2 inputs: p γγ T , N j , m jj , | ∆ φ jj | , p j 1 ⊕ ⊕ T and − 68% CL their correlations 95% CL γ γ 0.4 Standard Model contours hold 68%, 95% CL 0.2 0.1 0 0.1 0.2 c HW R.Turra (INFN Milano) Higgs to bosons (ATLAS) 11 February, 2019 9 / 27
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