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 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? 4

5 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 5

6 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) 089 6

7 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 7

8 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 8

9 Spin-parity: ATLAS H WW ATLAS H WW results: Graviton-like Higgs (Jp = 2+) excluded at 99% CL for arbitrary fraction of gg fusion in the production process. 9

10 Higgs coupling: signal strength Summer 2012: 10

11 Higgs coupling: Search for fermionic decays H bb, cc: H ττ : + BF 60% (3%) - huge dijet backgrounds use VH production mode - BF smaller 6% + backgrounds managable, Zττ, dijets in addition: fermionic coupling in production: tth, H xx: small cross section 11

12 H ττ production Largest cross section for gg fusion process but larger backgrounds Boosted Higgs: gg H production VBF Higgs: in association with jets Tag two forward jets Veto central jet activity 12

13 H ττ production Signal: H ττ Background: Z ττ Z Z boosted p p p p Large boost along the beam Large transverse Z pipe (z) Large rapidity Other backgrounds: - multi-jet production - Top quark production momentum pt 13

14 H ττ decays 2-4 neutrinos in the final state: underconstrained system π0, π±,.. ν Z Z ττ: visible mass: Only visible decay products Z ττ: MMC most probable mass: probability distributions for v τ τ ν ptmiss ν e,μ 14

15 ATLAs: search for H ττ Backgrounds: Zττ: Embeded simulated τ in Zμμ data and simulated Zττ Zμμ/Zee: simulation, normalized in CR Fakes: Measured Jet τ Fake Rate applied to anti- τ-id- ed control region Others: simulation ATLAS-CONF

16 ATLAS: search for H ττ VBF category: 2 well separated jets Boosted category: large pt(h) Rest category: control region Boosted p p p VBF VBF p p 16

17 ATLAS: Search for H ττ Input variable: m(jj) Training of 6 boosted decision trees (BDT) for optimal separation of m(h)=125 signal and background BDT score: VBF leplhad 6-9 input variables per BDT: MMC di-tau mass Tagging jets topology General event topology... Validation in dedicated control regions 17

18 ATLAS: Search for H ττ Signal extraction and background estimation in a single fit: Signal strength parameter (μ) Background normalisations (Z ττ / Top / Z ll / Multijet ) Nuisance Parameters (parametrize systematic uncertainties) All 6 BDTs sorted by S/B μ = σ excess mhmmc weighted by ln(1+s/b) Nov 2013: First evidence for H ττ decay 18

19 ATLAS: Search for H ττ First Firstevidence evidencefor forhh ττττ: : ATLAS: ATLAS: σσ(3.2 (3.2σσexpected) expected) CMS: CMS: σσ(3.2 (3.2σσexpected) expected) 19

20 ATLAS: Search for H bb Categories: 0/1/2 leptons+2b jets, pt(v), 0/1 additional jet ATLAS preliminary results: cut-based selection Important backgrounds: W+bb, Z+bb, Top, WZ Systematics: - b-tagging - Modelling of Top, W+bb, Z+bb: pt(v), m(bb), ΔΦ(bb) ATLAS-CONF

21 ATLAS: Search for H bb Categories: 0/1/2 leptons+2b jets, pt(v), 0/1 additional jet ATLAS preliminary results: cut-based selection (v) (v) m(bb) after subtraction of bkg: V(H bb) and V (Z bb) Important backgrounds: W+bb, Z+bb, Top, WZ Fit of the Higgs signal strength & Top, V+bb normalization Systematics: - b-tagging - Modelling of Top, W+bb, Z+bb: pt(v), m(bb), ΔΦ(bb) 21

22 ATLAS: Search for H bb Cross check: Search for VZ production - Fit of W(Z bb)+z(z bb) cross section - V(H bb) as background Main result: Search for VH production - Fit of V(H bb) cross section - W(Z bb)+z(z bb) as background 22

23 Higgs coupling ATLAS and CMS Higgs searches: ( Introduce parameter κi, κf parametrizing new physics ) SF for ii, ff Example: ggh γγ SF for total width 23

24 Higgs coupling scaling Fundamental parameters: 24

25 Higgs coupling scaling: examples VBF H ggh, H gg Case 1: No new particles g g Case 2: new particles effective parameter 25

26 Higgs coupling scaling H γγ Case 1: No new particles Case 2: effective parameter Total width Case 1: No new particles Case 2: effective parameter! If we allow new BSM particles, we can only fit ratios, one of which is κi /κh 26

27 Higgs coupling scaling Generic models: - Only SM particles, free parameters: - Allowing for new particles (loops, width): Approximative relations (assuming no new BSM particles) 27

28 Higgs coupling: benchmarks Simple benchmark model: common scale parameter Ignores diffent coupling mechanisms to fermions and bosons 28

29 Higgs coupling scaling Benchmark: Common fermion and common boson SF, no additional particles 29

30 Higgs coupling scaling Benchmark: Common fermion and common boson SF, no additional particles Benchmark: Common fermion and common boson SF, additional particles 30

31 Higgs coupling scaling Probing custodial SU(2) symmetry W/Z Probing custodial SU(2) symmetry W/Z, allowing for new particles 31

32 Higgs coupling scaling Probing fermion up/down symmetry Probing fermion up/down symmetry, allowing fore new particles 32

33 Higgs coupling scaling Probing new contribution to lops (no new undetectable contributions) Probing new contribution to lops (no new undetectable contributions) 33

34 Higgs coupling scaling: summary 34

35 Higgs coupling: ATLAS results Input data: 35

36 Higgs coupling: ATLAS results 2-Parameter benchmark model, 68% CL contours no contribution from BSM particles 36

37 Higgs coupling: ATLAS results 2-Parameter benchmark model, no contribution from BSM particles κf< 0 SM SM κf> 0 Fit of Κv with ΚF profiled Fit of ΚF with Κv profiled 37

38 Higgs coupling: ATLAS results 2-Parameter benchmark model, allow for BSM particles Fit of Κvv with λfv profiled Fit of λfv with Κvv profiled 38

39 Higgs coupling: ATLAS results Probing custodial SU(2) W/Z symmetry, allowing for BSM particles Fit of λwz with λfz and Κzz profiled Fit of λfz with λwz and Κzz profiled 39

40 Higgs coupling: ATLAS results Generic model Benchmark models 40

41 Higgs coupling: CMS results Fermion vs Vector boson couplings: 68% CL contours, no BSM particles Additional particles in loops:: Constrain BSM contribution: BR(BSM) < 52% 41

42 Higgs coupling: CMS results Generic coupling fits: dependence of coupling on mass 42

43 Higgs coupling: Outlook LHC upgrades: now Larger cms energy larger cross section More interactions per bunch crossing : Int. lumi: 300fb-1, s = 13-14TeV HL LHC: Int. lumi: 3000fb-1, s = 13-14TeV 43

44 Higgs coupling: Outlook 300fb fb-1 Expected precision on coupling parameters: LHC: 300 fb-1: 5-20% HL-LHC: 3000 fb-1: 2-10% 44

45 Higgs coupling: Outlook Linear e+e- Collider, example: ILC: Crcular Collider, example: FCC - FCC-hh: hadron collider - FCCee: e+e- colllider 45

46 Higgs coupling: Outlook e+e- collider: measure couplings at 1% precision or below 46