Physik des Higgs Bosons. Higgs decays V( ) Re( ) Im( ) Figures and calculations from A. Djouadi, Phys.Rept. 457 (2008) 1-216

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1 : Higgs decays V( ) Re( ) Im( ) Figures and calculations from A. Djouadi, Phys.Rept. 457 (2008)

2 Reminder Higgs couplings: 2

3 Reminder Higgs BF as a function of mh Higgs total decay width as a function of mh 3

4 Reminder Tevatron: Main production channels: Gluon fusion: gg H Associated VH production: qq WH, qq ZH 4

5 Reminder Key processes: High mass: H WW Low mass: VH Vbb 5

6 Reminder P-value: probability of an outcome as extreme as that observed, assuming the null hypothesis is true. 6

7 Reminder Mass exclusion 7

8 LHC: Higgs discovery CMS ATLAS LHC: pp Collider circumference: 27 km Ecms = 8 TeV 18 TeV 8

9 LHC: Higgs discovery July 2012: ATLAS and CMS experiments: Discovery of the Higgs Boson, ZZ, γγ and WW channels, 10 fb-1 Phys. Lett. B 716 (2012)1-60 9

10 LHC: Higgs discovery July 2012: ATLAS and CMS experiments: Discovery of the Higgs Boson, ZZ, γγ and WW channels, 10 fb-1 Phys. Lett. B 716 (2012)

11 Higgs ZZ 2013: 25 fb-1, Measurement of H ZZ cross section, production processes, mass, etc. Clean signature, small number of selected events. Low-pT lepton reconstructin and identification Selection categories - gg fusion - VBF H - associated VH Select typical ZZ* kinematics pt(l), m(ll),... 11

12 Higgs γγ 2013: 25 fb-1, Measurement of H γγ cross section, production processes, mass, etc. Signal extraction: common fit of signal+background - signal: cristal ball+gauss (see appendix) - background: Bernstein polynomials (see appendix) Categories VH, V ll VH, V qq VBF H ggh conversions, ptt Backgrounds large: - QCD productionof two photons - QCD γ + jets, jet identified as γ 12

13 Higgs WW H WW lvlv: Higgs mass reconstruction not possible no mass peak to be fitted reduce backgrounds in other ways Ttbar background: N jets, b-tag Increasing top background Z+jets background: ΔΦ(ll), M(ll) Increasing Z+jets (and WW) fraction 13

14 Higgs WW Signal extracted by fit to mt 14

15 Higgs properties Discovery of a Higgs boson: New neutral particle Mass roughly in range expected by SM precission measurements Coupling to ZZ, WW Is it the SM Higgs boson? Mass (vacuum stability without new physics?) Width compatible with expectation? Spin-parity 0+? Couplings to bosons and fermions as expected? Self coupling? 15

16 Higgs mass measurement Mass reconstruction in H ZZ* 4lep and in H γγ ATLAS: ZZ* and γγ masses differ by 1.5GeV (2σ) CMS: ZZ* and γγ masses compatible 16

17 Higgs Mass and vacuum stability Higgs mass and vacuum instability RGE running of quartic coupling λ λ < 0 for energy scale: vacuum instable Buttazzo et al: JHEP12 (2013)

18 Higgs Mass and vacuum stability m(top) D0 m(top) CMS Vacuum stbility excluded at 2.2σ - Higgs mass stability contition (based on measured top mass): - Top mass stability condition (measured Higgs mass): Buttazzo et al: JHEP12 (2013)

19 Higgs Mass shift and width Δm(SM) = MeV 19

20 Higgs width from off-shell H Z*Z* But: contribution to 4-lepton cross section at high mass (8% contribution by SM Higgs) (continuum) Campbell et al

21 Higgs width from off-shell H Z*Z* Hypothetical case: Higgs width larger than ΓSM but same (measured) on-shell cross section larger Higgs couplings larger off-shell cross section (assuming identical on- and off-shell couplings) CMS measurement off-shell 4-lep cross section ΓH < 22 MeV 21

22 Higgs width CMS: ΓH < 22 MeV Δm < 200 MeV 22

23 Spin-parity Wh: H ZZ 3-body decay 23

24 Higgs properties Standard Model: Zerwas et al, Phys.Lett.B553:61-71,

25 Higgs properties Experiments: combinations ob several spin-parity sensitive observables into one discriminant. CMS: Example H ZZ: Likelihood from angles (Θ*,Θ1,Θ2,Φ1,Φ,), mz1, mz2 PseudoSkalar exc. at 99%CL Vector boson Graviton-like Higgs boson excluded at 99%CL excluded at 95% CL 25

26 Spin-parity: ATLAS H WW BDT0 BDT2 Fit to 0+ template Fit to 2+ template Example: 25% VBF fraction in 2+ 26

27 Spin-parity: ATLAS H WW ATLAS H WW results: 2+ hypothesis excluded at 95%-99% CL 27

28 Spin-parity: ATLAS H ZZ Experiments: combinations ob several spin-parity sensitive observables into one discriminant. ATLAS H->ZZ: BDT from angles, mz1, mz2 Graviton-like Higgs (Jp = 2+) excluded at 99% CL for arbitrary fraction of gg fusion in the production process. 28

29 29

30 Anhang: Cristal ball function Gauss funktion with tail towards low values (energy loss) 30

31 Anhang: Bernstein Polynomial Linear combination of Bernstein basis funktions 31

32 Higgs properties Experiments: combinations ob several spin-parity sensitive observables into one discriminant. CMS: Example H ZZ: Likelihood from angles ( Ω), mz1, mz2 Pseudoskalar Vector boson Graviton-like Higgs boson 32