The Higgs Particle Mass, Width and Couplings Seminar Particle Physics at the LHC

Transcription

1 The Higgs Particle, and Seminar Particle Physics at the LHC Freiburg, Albert-Ludwigs-Universität Freiburg Michael Schubert

2 Contents 2/54

3 introduction We found a Higgs boson! So... What now? 3/54

4 introduction what we can measure mass spin CP width couplings 4/54

5 introduction a short reminder about Higgs boson interactios production decay 5/54

6 introduction How do we separate? 6/54

7 significant channels Which Channels are suitable for the mass measurement? H Z 4l 7/54

8 But why? very good knowlegde of detector (e & γ) energy calibration (global & cell specific) behaviour of different layers material in front of the calorimeter controlled with > 7 million events (Z e + e, Z l + l γ, J/ψ e + e ) similar for µ, controlled with 15million events (Z µ + µ, J/ψ µ + µ ) separate for inner detector & muon spectrometer 8/54

9 this channel is good because very good mass resolution (2γ final state) smooth background can be determined from data 9/54

10 many many categories We separate into 10 categories: converted γ vs. unconverted γ different η regions different p Tt regions note p Tt = (p γ 1 T + pγ T 2 ) pγ T 1 pγ 2 T p γ 1 T pγ 2 T = projection orthogonal to thrust axis 10/54

11 the categories 11/54

12 results for illustration each channel is weighted with its signal to background ratio 12/54

13 systematics of course we have systematics to account for relative uncertainties in % 13/54

14 relults, again the ATLAS collaboration measures m H = ± 0.42(stat) ± 0.28(syst)GeV and a signal strength = cross section normalized to SM expectation µ = 1.29 ± /54

15 this channel is good because good signal to background ratio clean final state good mass resolution 15/54

16 the categories here the analysis is split into different final states 4µ 2e2µ 2µ2e 4e 16/54

17 results BDT for better signal/background separation BDT input variables: p T, η, D ZZ ( ) = log M sig 2 M ZZ 2 17/54

18 more results number of events, theory and measurement 18/54

19 likelihood ratios 19/54

20 result the ATLAS collaboration measures m H = ± 0.52(stat) ± 0.06(syst)GeV and a signal strength µ = /54

21 combination Can these be combined? Yes they can! m H = 1.47 ± 0.67(stat) ± 0.28(syst)GeV m H = ± 0.37(stat) ± 0.18(syst)GeV 21/54

22 combination plots 22/54

23 systematics 23/54

24 width Theoretical prediction for the Higgs boson width: 4MeV Experimental energy resolution: 2GeV but CMS did a thing 24/54

25 CMS and the of the Higgs Boson 25/54

26 What now? measure relative contributions to the width measurement of signal strengths and coupling strengths 26/54

27 the basics We have to make some basic assumptions: everything comes from the same single particle this particle is assumed to have zero decay width the particle is a CP-even scalar 27/54

28 reminder modified couplings are introduced 28/54

29 one example matrix element modified by κ 2 t but: W ± contribution interference κ 2 γ(κ F κ V ) = 1.59κ 2 V 0.66κ V κ F κ 2 F 29/54

30 SM only SM contributions only κ V = κ W = κ Z κ F = κ t = κ b = κ τ = κ g σ(gg H) BR(H γγ) κ2 F κ2 γ (κ F κ V ) 0.75κ 2 F +0.25κ2 V σ(qq qq H) BR(H γγ) κ2 V κ2 γ (κ F κ V ) 0.75κ 2 F +0.25κ2 V σ(gg H) BR(H ZZ ( ),H WW ( ) κ ) 2 F κ2 V 0.75κ 2 F +0.25κ2 V σ(qq qq H) BR(H ZZ ( ),H WW ( ) κ ) 2 V κ2 V 0.75κ 2 F +0.25κ2 V σ(qq qq κ H,VH) BR(H ττ,h b b) 2 V κ2 F 0.75κ 2 F +0.25κ2 V 30/54

31 SM only results κ F =1.15±0.08 κ V = /54

32 free total width variable no assumption on total width hide total width in ratios as free parameter κ VV = κ V κ V/κ H λ FV = κ F/κ V only ratios measurable 32/54

33 free total width functionalities σ(gg H) BR(H γγ) λ 2 FV κ2 VV κ2 γ(λ FV,1) σ(qq qq H) BR(H γγ) κ 2 VV κ2 γ(λ FV,1) σ(gg H) BR(H ZZ ( ),H WW ( ) ) λ 2 FV κ2 VV σ(qq qq H) BR(H ZZ ( ),H WW ( ) ) κ 2 VV σ(qq qq H,VH) BR(H ττ,h b b) κ 2 VV λ2 FV 33/54

34 free total width relults λ FV = κ VV = /54

35 custodial symmetry theory predicts same coupling scale factors for W & Z we test it (again no assumption on total width): κ ZZ =κ Z κ Z/κ H λ WZ =κ W/κ Z λ FZ =κ F/κ Z σ(gg H) BR(H γγ) λ 2 FZ κ2 ZZ κ2 γ (λ FZ,1) σ(qq qq H) BR(H γγ) κ 2 VBF (λ WZ,1)κ2 ZZ κ2 γ (λ FZ,1) σ(gg H) BR(H ZZ ( ) ) λ 2 FZ κ2 ZZ σ(qq qq H) BR(H ZZ ( ) ) κ 2 VBF (λ WZ,1)κ2 ZZ σ(gg H) BR(H WW ( ) ) λ 2 FZ κ2 ZZ λ2 WZ σ(qq qq H) BR(H WW ( ) ) κ 2 VBF (λ WZ,1)κ2 ZZ λ2 WZ σ(qq qq H,VH) BR(H ττ,h b b) κ 2 VBF (λ WZ,1)κ2 ZZ λ2 FZ 35/54

36 custodial symmetry results λ WZ = λ FZ [ 0.91, 0.63] [0.65,1.00] κ ZZ = /54

37 SM loop contents set everything to SM values effective couplings at loops (for γ & g): κ 2 g σ(gg H) BR(H γγ) κ2 γ 0.085κ 2 g κ2 γ σ(qq qq κ 2 γ H) BR(H γγ) 0.085κ 2 g κ2 γ σ(gg H) BR(H ZZ ( ),H WW ( ) κ 2 g ) 0.085κ 2 g κ2 γ σ(qq qq H) BR(H ZZ ( ),H WW ( ) 1 ) 0.085κ 2 g κ2 γ σ(qq qq 1 H,VH) BR(H ττ,h b b) 0.085κ 2 g κ2 γ /54

38 SM loop contents results κ g = κ γ = /54

39 BSM loop contents H invis possible BSM decays Γ H = κ 2 H (κ i) Γ SM H 1 BR inv,undet κ 2 g σ(gg H) BR(H γγ) κ2 γ 0.085κ 2 (1 BR inv,undet) g κ2 γ σ(qq qq κ 2 γ H) BR(H γγ) 0.085κ 2 (1 BR inv,undet) g κ2 γ σ(gg H) BR(H ZZ ( ),H WW ( ) κ 2 g ) 0.085κ 2 (1 BR inv,undet) g κ2 γ σ(qq qq H) BR(H ZZ ( ),H WW ( ) 1 ) 0.085κ 2 (1 BR inv,undet) g κ2 γ σ(qq qq 1 H,VH) BR(H ττ,h b b) 0.085κ 2 (1 BR inv,undet) g κ2 γ /54

40 BSM loop contents results κ g= κ γ= BR inv,undet = /54

41 In the end... 41/54

42 summary mass: m H = ± 0.41GeV signal strength: µ = 1.30 ± 0.20 all those couplings SM validated within 2σ 42/54

43 The End The End? 43/54

44 no end jet But wait there s more! CMS has results, too m H = (stat) (syst) 44/54

45 CMS coupling 45/54

46 references I [1] ATLAS Collaboration, Measurement of the Higgs boson mass from the and H ZZ ( ) 4l channels with the ATLAS detector using 25 fb 1 of pp collision data, arxiv: v1, 15. Jun 2014 [2] ATLAS Collaboration, Combined coupling measurement of the Higgs-like boson with the ATLAS detector using up to 25 fb 1 of proton-proton collision data, ATLAS-CONF , 13. Mar 2013 [3] ATLAS Collaboration, Updated coupling measurement of the Higgs-like boson with the ATLAS detector using up to 25 fb 1 of proton-proton collision data, ATLAS-CONF , 20. Mar /54

47 references II [4] ATLAS Collaboration, Measurement of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC, Physics Letters B 726 (2013) , Aug 2013 [5] CMS Collaboration, Measurement of the properties of the new boson with a mass near 125 GeV, CMS PAS HIG , 17. Apr 2013 [6] CMS Collaboration, Constraints on the Higgs boson width from off-shell production and decay of Z-boson pairs, arxiv: v1, 14. May /54

48 Thanks for your attention! Questions? Remarks? 48/54

49 backup 49/54

50 differences 50/54

51 free loop content allow BSM loop contents loose the sign information and get λ FV = κ F/κ V λ γv = κ γ/κ V κ VV = κ V κ V/κ H σ(gg H) BR(H γγ) λ 2 FV κ2 VV λ2 γv σ(qq qq H) BR(H γγ) κ 2 VV λ2 γv σ(gg H) BR(H ZZ ( ),H WW ( ) ) λ 2 FV κ2 VV σ(qq qq H) BR(H ZZ ( ),H WW ( ) ) κ 2 VV σ(qq qq H,VH) BR(H ττ,h b b) κ 2 VV λ2 FV 51/54

52 free loop contents result λ FV = λ γv = κ VV =1.15± /54

53 custodial symmetry BSM testing custodial symmetry again, with free loop content: κ ZZ =κ Z κ Z/κ H λ WZ =κ W/κ Z λ γz =κγ/κ Z λ FZ =κ F/κ Z σ(gg H) BR(H γγ) λ 2 FZ κ2 ZZ λ2 γz σ(qq qq H) BR(H γγ) κ 2 VBF (λ WZ,1)κ2 ZZ λ2 γz σ(gg H) BR(H ZZ ( ) ) λ 2 FZ κ2 ZZ σ(qq qq H) BR(H ZZ ( ) ) κ 2 VBF (λ WZ,1)κ2 ZZ σ(gg H) BR(H WW ( ) ) λ 2 FZ κ2 ZZ λ2 WZ σ(qq qq H) BR(H WW ( ) ) κ 2 VBF (λ WZ,1)κ2 ZZ λ2 WZ σ(qq qq H,VH) BR(H ττ,h b b) κ 2 VBF (λ WZ,1)κ2 ZZ λ2 FZ 53/54

54 custodial symmetry BSM results λ WZ = 0.80 ± 0.15 λ FZ = λ γz = 1.10 ± 0.18 κ ZZ = /54