The BEH-Mechanism in the SM. m f = λ f. Coupling of Higgs boson to other particles fixed by particle mass and vev

Transcription

1

2

3 The BEH-Mechanism in the SM Most general renormalizable gauge invariant potential: V(φ) ' µ 2 φ φ+λ(φ φ) 2 µ 2,λ > 0 Condensate v hides symmetry of underlying Langrangian M W = g 2 v m f = λ f 2 v M H = λv v = r 2µ 2 λ = 247GeV Coupling of Higgs boson to other particles fixed by particle mass and vev Higgs boson mass: - enters production and decay rates via phase space - determines Higgs boson self coupling 3

4

5 Higgs Boson Decays in the Standard Model Hà fermions H b,τ,.. b,τ +,.. HàWW(ZZ)à4 fermions (l=e,µ) BR (H XX) (M H = GeV) bb 58.1% WW 21.5% gg 8.18% ττ 6.25% cc 2.88% ZZ 2.64% H W,Z W,Z WW lνlν γγ Zγ ZZ 4ν 1.02% 0.23% 0.15% 0.11% Hàγγ / Zγ H t,w γ 10 4 µµ 0.022% ZZ 4l 0.012% γ fermionic channels discovery channels Higgs-Boson life time 1.6 x s BR from LHCHXSWG

6

7

8 Reaction Probabilities at LHC Standard Model Production Cross Section Measurements Status: March 2017 σ [pb] total (x2) ATLAS Preliminary inelastic Theory incl. 0.1<p T<2TeV dijets 0.3<m jj<5tev p T>25 GeV p T>125GeV n j 0 n j 1 p T>100GeV n j 2n j 1 n j 1 n j 3n j 2 n j 2 n n j 4 j 3 n j 3 n j 4 n j 5 n j 4 n j 5 n j 6 n j 5 n j 6 n j 7 n j 0 n n j 7 j 6 n j 7 total n j 4 n j 5 n j 6 n j 7 n j 8 t-chan Wt s-chan Run 1,2 WW WW WW WZ WZ ZZ WZ ZZ ZZ s =7,8,13TeV total ggf H WW H ττ VBF H WW H γγ H ZZ 4l Zγ Wγ Zγ LHC pp s =7TeV m jj>500gev m jj>1tev Data fb 1 LHC pp s =8TeV Data 20.3 fb 1 LHC pp s =13TeV Data fb 1 W ± W ± WZ pp Jets R=0.4 γ fid. W fid. Z fid. t t fid. t tot. VV tot. γγ fid. H fid. Vγ fid. t twt tzt tγ tot. tot. fid. Wjj EWK fid. Zjj EWK fid. WW Excl. tot. ZγγWγγZγjjVVjj EWK EWK fid. fid. fid. fid. Excellent agreement between theory prediction and experimental measurements due to very precise calculations and very good understanding of detector performance 8

9 July 2012: Discovery in the Search for the SM Higgs 9 Observation in bosonic decay modes: Hàγγ, HàZZà4l and HàWWàlνlν Events / 2 GeV ATLAS -1 s=7 TeV, Ldt=4.8fb -1 s=8 TeV, Ldt=5.9fb Data Sig+Bkg Fit (m =126.5 GeV) H Bkg (4th order polynomial) H γ γ p-wert 1 0σ 1σσ σ 10 4 ATLAS 4σ 10 6 CMS 5σ ~5 fb -1 at 7 TeV and ~5 fb -1 at 8 TeV m H in GeV/c 2 6σ Events - Bkg m γ γ [GeV] Neutral boson and mass of 125 to 126 GeV Spin = 1 excluded from Hàγγ (Landau Yang theorem)

10 ? Is it a Higgs Boson? My definition of a Higgs boson: Excitation of field, which provides vev for generation of M W and M Z Higgs boson has to be scalar, in order not to break isotropy of space At least one Higgs field has to couple to W and Z bosons to provide mass terms à associated Higgs boson H has HVV vertex with CP-even SM coupling structure ATLAS Spring 2013 ) P alt ( J CL s H γγ s = 8 TeV Ldt = 20.7 fb H ZZ* 4l P - J = 0-1 s = 7 TeV Ldt = 4.6 fb s = 8 TeV Ldt = 20.7 fb H WW* eνµν/µνeν s = 8 TeV Ldt = 20.7 fb P + J = 1 Data CL s expected P assuming J = 0 ± 1 σ P - P + J = 1 J = 2 m + 1σ 2σ 3σ 4σ Significance of exclusion Z 2M 2 V v gµν Now all alternative J CP hypotheses excluded with 99.9% CL First evidence for scalar nature in spring 2013 à Since then It is a Higgs boson CMS has excluded twenty spin=2 models 10

11

12

13

14

15

16

17

18

19 LO Coupling Modifiers / Kappa-Framework Cross section in narrow width approximation: LO coupling modifiers κ i: σ(i f)= σ i Γ f Γ tot Look for deviation of κ from SM value = 1 κ = g P g SM P σ i = κ 2 i σ SM i Γ f = κ 2 f Γf,SM Example: ggàhàww (ZZ): σ gg H = κ 2 gσ SM gg H σ gg H = f(κ t,κ b )σ SM gg H t t t H H W,Z W,Z Γ W/Z = κ 2 W/Z ΓW/Z SM Total width Γ H, SM = 4.1 MeV (<< mass resolution in Hà 4l and Hàγγ) - scales all observed event rates - lower limit from observed event rates à constrain total width with model dependent assumptions 19

20

21

22

23

24

25

26

27

28

29 Open Questions & Possible Connection to Higgs 29 Dark Matter contributes with ~25% to energy content of the universe In specific models (Higgs portal) Dark Matter (DM) particle couples only to Higgs boson à e.g. search for Hà invisible decays for M DM < ½ M H Baryon Asymmetry of the universe η = baryon / photon density ~ 5x10-11 CP violation needed to explain asymmetry CKM-CP violation too small to explain obs. η à search for new sources of CP-violation in the Higgs sector Matter Anti-Matter

30

31

32 New Sources of CP-Violation in the HVV Vertex? Ansatz: L = L SM +λ CP L CPodd Strength of CP-violation: λ CP 2M 2 V v gµν + à modified tensor structure and kinematics λ CP µνρσ p V 1 ρ p V 2 σ HVV-vertex accessible in: a) decay HàVV b) VBF, qqàhqq c) Higgs-Strahlung VàVH R R Optimal observables combine information from multidim. phase space in two scalars OO 1 = 2Re(M SMM CP odd ) M SM 2 OO 2 = M CP odd 2 M SM 2 CP-odd, sensitive to small λ CP λ CP 0 à <OO 1 > 0, asymmetry CP-even, sensitive to larger λ CP 32

33

34

35

36

37 Application: Constraining MCHM Parameters In minimal composite Higgs models (MCHM) common reduction of coupling strength ξ=v 2 / f 2 f compositeness scale MCHM4 κ=κ V =κ F = p 1 ξ MCHM5 κ V = p 1 ξ κ F = 1 2ξ 1 ξ κ F ATLAS -1 s = 7 TeV, fb -1 s = 8 TeV, 20.3 fb MCHM4 ξ=0.3 ξ=0.3 ξ=0.2 ξ=0.2 MCHM5 ξ=0.1 ξ=0.1 ξ=0.0 Best fit Obs. 68% CL Obs. 95% CL SM Exp. 68% CL Exp. 95% CL κ V 95% CL limits on f Model Lower limit on f Obs. Exp. MCHM4 710 GeV 510 GeV MCHM5 780 GeV 600 GeV Rule of thumb for deviations g(f)/sm =1+(3 9)%! 2 1TeV f 37

38

39

40

41

42 Limits on some Rare, LFV, Invisible Decay Modes Hà (95% CL limits (exp)) ATLAS CMS µ(µµ) Run1 /Run 2 Combined 7.0 (7.2) / 3.2(3.3) 2.8 (2.9) 7.4( (6.5) µ(ee) 3.7 x 10 5 µ(zγ) 11(9) 9.5 (10) µ(llγ) with m ll <20GeV 7.7 (6.4) BR(Υ(1S,2S,3S) γ) 1.3/1.9/1.3 x10-3 (1.8/2.1/1.8) BR(J/Ψ γ) 1.5 (1.2) x10-3 BR(φ γ) 1.4 (1.5) x10-3 LFV BR(τµ) Run (1.01) % 1.51 (0.75) % Run 2 (2.3 fb -1 ) 1.20 (1.62) % LFV BR(τe) Run (1.21) % 0.69 (0.75) % Non universal coupling to leptons. H->J/Ψγ: test coupling to charm quark SM: BR= 2.9±0.2 x 10-6 Hàφγ : test coupling to strange quark SM: BR= 2.3±0.1 x 10-6 Lepton flavour violation (LFV): 2.3σ excess at CMS Hàτµ in Run1 42

43 - Search for Hà Quarkonia (qq) + Photon Hàφγ : test coupling to strange quark H->J/Ψγ: test coupling to charm quark SM: BR= 2.3±0.1 x 10-6 Limit 95% 1.4 x 10-3 (exp 1.5) x 10-3 SM: BR= 2.9±0.2 x 10-6 Limit 95% 1.5 x 10-3 (exp 1.2) x 10-3 Events/ 5 GeV Data/Fit 120 ATLAS s=13 TeV, 2.7 fb Data Background Fit ±1σ Background -3 B(H φ γ )=10-6 B(Z φ γ )= [GeV] m - K + K γ Events / 4 GeV ATLAS s=8 TeV m µ µ γ Data S+B Fit Ldt = 19.2 fb Background -3 H [B=10 ] -6 Z [B=10 ] -1 [GeV] No hints for decays to quarkonia Limits ~ 500 x SM prediction 43

44

45