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Higgs, more Higgs, less Higgs, or Higgsless? John Ellis King’s College, London (& CERN)

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Presentation on theme: "Higgs, more Higgs, less Higgs, or Higgsless? John Ellis King’s College, London (& CERN)"— Presentation transcript:

1 Higgs, more Higgs, less Higgs, or Higgsless? John Ellis King’s College, London (& CERN)

2 The ‘Standard Model’ of Particle Physics Proposed byAbdus Salam, Glashow and Weinberg Tested by experiments at CERN & elsewhere Perfect agreement between theory and experiments in all laboratories

3 Open Questions beyond the Standard Model What is the origin of particle masses? due to a Higgs boson? Why so many flavours of matter particles? What is the dark matter in the Universe? Unification of fundamental forces? Quantum theory of gravity? LHC

4 Why do Things Weigh? 0 Wheredothemasses come from? Newton: Weight proportional to Mass Einstein: Energy related to Mass Neither explained origin of Mass Are masses due to Higgs boson? (the physicists’ Holy Grail)

5 The Seminal Papers

6 The Englert-Brout-Higgs Mechanism Englert & BroutGuralnik, Hagen & Kibble

7 The Higgs Boson Higgs pointed out a massive scalar boson “… an essential feature of [this] type of theory … is the prediction of incomplete multiplets of vector and scalar bosons” Englert, Brout, Guralnik, Hagen & Kibble did not comment on its existence Discussed in detail by Higgs in 1966 paper

8 Mysterious Higgs Potential Mass 2 of Higgs ~ curvature of potential at minimum Vertical scale ~ 10 60 × dark energy

9 A Phenomenological Profile of the Higgs Boson Neutral currents (1973) Charm (1974) Heavy lepton τ (1975) Attention to search for W ±, Z 0 For us, the Big Issue: is there a Higgs boson? Previously ~ 10 papers on Higgs bosons M H > 18 MeV First attempt at systematic survey

10 Higgs decay modes and searches in 1975: A Phenomenological Profile of the Higgs Boson

11 Higgs Boson placed on the Experimental Agenda Searches at LEP: (EG, Yellow report 76-18) e + e -  Z + H (EGN 76, Ioffe & Khoze 76, Lee, Quigg & Thacker 77) Z  H + μ + μ - (EG 76, Bjorken 1976) LEP: M H > 114.4 GeV

12 The State of the Higgs in Mid-2011 High-energy search: –Limit from LEP: m H > 114.4 GeV High-precision electroweak data: –Sensitive to Higgs mass: m H = 96 +30 –24 GeV Combined upper limit: m H < 161 GeV, or 190 GeV including direct limit Exclusion from high-energy search at Tevatron: m H 173 GeV

13 Latest Higgs Searches @ Tevatron Exclude (100,109); (156,177) GeV Standard Model prediction Experimental upper limit

14 Higgs Hunting @ LHC: Status reported on Dec. 13 th, 2011 Exclude 112.7 GeV to 115.5 GeV, 131 GeV to 237 GeV, 251 GeV to 453 GeV Exclude 127 to 600 GeV

15 Has the Higgs Boson been Discovered? Interesting hints around M h = 125 GeV ? CMS sees broad enhancement ATLAS prefers 125 GeV

16 Has the Higgs Boson been Discovered? Interesting hints around 125 GeV in both experiments - but could also be 119 GeV ?

17 ATLAS Signals γγ: 2.8σ ZZ: 2.1σ WW: 1.4σ Combined: 3.6σ

18 CMS Signals Combined: 2.6σ

19 Has the Higgs Boson been Discovered? Unofficial blogger’s combination NOT ENDORSED BY EXPERIMENTS but he was right last time !

20 Combining the Information from Previous Direct Searches and Indirect Data m H = 125 ± 10 GeV Erler: arXiv:1201.0695 m H = 124.5 ± 0.8 GeV Assuming the Standard Model

21 Precision Electroweak data?? Higgs coupling blows up!! Higgs potential collapses Higgs coupling less than in Standard Model viXra Blogger’s Combination of Dec.13 th Data There must be New Physics Beyond the Standard Model

22 Heretical Interpretation of EW Data Do all the data tell the same story? e.g., A L vs A H What attitude towards LEP, NuTeV? What most of us think Chanowitz

23 Higgs + Higher-Order Operators Precision EW data suggest they are small: why? But conspiracies are possible: m H could be large, even if believe EW data …? Do not discard possibility of heavy Higgs Corridor to heavy Higgs? Barbieri, Strumia

24 Elementary Higgs or Composite? Higgs field: ≠ 0 Quantum loop problems Fermion-antifermion condensate Just like QCD, BCS superconductivity Top-antitop condensate? needed m t > 200 GeV New technicolour force? inconsistent with precision electroweak data? Cut-off Λ ~ 1 TeV with Supersymmetry? Cutoff Λ = 10 TeV

25 Interpolating Models Combination of Higgs boson and vector ρ Two main parameters: m ρ and coupling g ρ Equivalently ratio weak/strong scale: g ρ / m ρ Grojean, Giudice, Pomarol, Rattazzi

26 What if the Higgs is not quite a Higgs? Tree-level Higgs couplings ~ masses –Coefficient ~ 1/v Couplings ~ dilaton of scale invariance Broken by Higgs mass term –μ 2, anomalies –Cannot remove μ 2 (Coleman-Weinberg) –Anomalies give couplings to γγ, gg Generalize to pseudo-dilaton of new (nearly) conformal strongly-interacting sector Couplings ~ m/V (V > v?), additions to anomalies

27 A Phenomenological Profile of a Pseudo-Dilaton New strongly-interacting sector at scale ~ V Pseudo-dilaton only particle with mass << V Universal suppression of couplings to Standard Model particles ~ v/V Γ(gg) may be enhanced Γ(γγ) may be suppressed Modified self-couplings Pseudo-baryons as dark matter? Compilation of constraints Campbell, JE, Olive: arXiv:1111.4495 Updated with Dec. 11 constraints

28 Higgsless Models? Four-dimensional versions: Strong WW scattering @ TeV, incompatible with precision data? Break EW symmetry by boundary conditions in extra dimension: delay strong WW scattering to ~ 10 TeV? Kaluza-Klein modes: m KK > 300 GeV? compatibility with precision data? Warped extra dimension + brane kinetic terms? Lightest KK mode @ few 00 GeV, strong WW @ 6-7 TeV

29 Theoretical Constraints on Higgs Mass Large M h → large self-coupling → blow up at low-energy scale Λ due to renormalization Small: renormalization due to t quark drives quartic coupling < 0 at some scale Λ → vacuum unstable Vacuum could be stabilized by supersymmetry Espinosa, JE, Giudice, Hoecker, Riotto, arXiv0906.0954 LHC 95% exclusion

30 SUSY vs Data Electroweak precision observables Flavour physics observables g μ - 2 Higgs mass Dark matter LHC MasterCode: O.Buchmueller, JE et al.

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32 68% & 95% CL contours ….. pre-LHC ___ LHC 1/fb

33 Favoured values of M h ~ 119 GeV: Range consistent with evidence from LHC ! Higgs mass χ 2 price to pay if M h = 125 GeV is < 2 Buchmueller, JE et al: arXiv:1112.3564

34 ….. pre-Higgs ___ Higgs @ 125 68% & 95% CL contours Buchmueller, JE et al: arXiv:1112.3564

35 Favoured values of gluino mass significantly above pre-LHC, > 2 TeV Gluino mass --- pre-Higgs ___ Higgs @ 125 … H@125, no g-2 Buchmueller, JE et al: arXiv:1112.3564

36 The Stakes in the Higgs Search How is gauge symmetry broken? Is there any elementary scalar field? Would have caused phase transition in the Universe when it was about 10 -12 seconds old May have generated then the matter in the Universe: electroweak baryogenesis A related inflaton might have expanded the Universe when it was about 10 -35 seconds old Contributes to today’s dark energy: 10 60 too much!

37 Measurements of Higgs Couplings Some decays limited by statistics Others limited by systematics

38 The Spin of the Higgs Boson @ LHC Higher mass: angular correlations in H → ZZ decays Low mass: if H →γγ, It cannot have spin 1

39 Higgs Self-coupling @ Hi-Lumi LHC? Measure triple-Higgs-boson coupling with accuracy comparable to 0.5 TeV ILC? Awaits confirmation by detailed experimental simulation

40 The Fun is just Beginning LHC7 may well resolve Higgs issue LHC7 (or 8) unlikely to resolve SUSY issue (or other BSM scenarios) Premium on increasing E cm towards 14 TeV Prospects for L factor 500 with Hi-Lumi LHC What will follow the LHC? –Higgs factory? CLIC? High-E LHC? A new era about to open: AH (anno Higgsi)

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42 Quo Vadis g μ - 2? Strong discrepancy between BNL experiment and e + e - data: –now ~ 3.6 σ –Better agreement between e + e - experiments Increased discrepancy between BNL experiment and τ decay data –now ~ 2.4 σ –Convergence between e + e - experiments and τ decay More credibility?

43 MSSM: > 100 parameters Minimal Flavour Violation: 13 parameters (+ 6 violating CP) SU(5) unification: 7 parameters NUHM2: 6 parameters NUHM1 = SO(10): 5 parameters CMSSM: 4 parameters mSUGRA: 3 parameters String?

44 … nevertheless Supersymmetric Dark Matter in View of 1/fb of LHC Data

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46 68% & 95% CL contours ….. pre-LHC ___ LHC 1/fb MasterCode: O.Buchmueller, JE et al.

47 Dropping g μ - 2 allows masses up to dark matter limit ….. pre-LHC ___ LHC 1/fb Impact of dropping g μ -2 constraint MasterCode: O.Buchmueller, JE et al.

48 Favoured values of gluino mass significantly above pre-LHC, > 1 TeV ….. pre-LHC ___ LHC 1/fb Gluino mass MasterCode: O.Buchmueller, JE et al.

49 Favoured values of BR(B s  μ + μ - ) above SM value ! (due to increase in tan β) + LHCb Bs μ+μ-Bs μ+μ- ….. pre-LHC ___ LHC 1/fb --- with CDF MasterCode: O.Buchmueller, JE et al.

50 Favoured values of Mh ~ 119 GeV: Coincides with value consistent with LHC ! Higgs mass

51 Generic Little Higgs Models Loop cancellation mechanism SupersymmetryLittle Higgs (Higgs as pseudo-Goldstone boson of larger symmetry)

52 Little Higgs Models Embed SM in larger gauge group Higgs as pseudo-Goldstone boson Cancel top loop with new heavy T quark New gauge bosons, Higgses Higgs light, other new physics heavy Not as complete as susy: more physics > 10 TeV M T < 2 TeV (m h / 200 GeV) 2 M W’ < 6 TeV (m h / 200 GeV) 2 M H++ < 10 TeV

53 Searches for Extra Particles in Little Higgs Models

54 Spread looks natural: no significant disagreement Estimates of m H from different Measurements

55 Intermediate Models

56 Effects on Higgs Decays Dependences on  of Higgs branching ratios Standard Model recovered in limit   0 Grojean, Giudice, Pomarol, Rattazzi

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58 What if no Higgs? Higgs must discriminate between different types of particles: –Some have masses, some do not –Masses of different particles are different In mathematical jargon, symmetry must be broken: how? –Break symmetry in equations? –Or in solutions to symmetric equations? This is the route proposed by Higgs –Is there another way?

59 Where to Break the Symmetry? Throughout all space? –Route proposed by Higgs –Universal Higgs (snow)field breaks symmetry –If so, what type of field? Or at the edge of space? –Break symmetry at the boundary? Not possible in 3-dimensional space –No boundaries –Postulate extra dimensions of space Different particles behave differently in the extra dimension(s)

60 Higgs Hunting @ Tevatron Exclude (100,109); (156,177) GeV

61 Comparison between Weakly- and Strongly-coupled Models

62 X ENON 100 & other Experiments Aprile et al: arXiv:1104.2549

63 Supersymmetry Searches in ATLAS Jets + missing energy + 0 lepton

64 X ENON 100 Experiment Aprile et al: arXiv:1104.2549

65 Early Phenomenological Bounds Emission from stars: M H > 0.7 m e (Sato & Sato, 1975) Neutron-electron scattering: M H > 0.7 MeV (Rafelski, Muller, Soff & Greiner; Watson & Sundaresan; Adler, Dashen & Treiman; 1974) Neutron-nucleus scattering: M H > 13 MeV (Barbieri & Ericson, 1975) Nuclear 0 + – 0 + transitions: M H > 18 MeV (Kohler, Watson & Becker, 1974)

66 Supersymmetry Searches @ LHC Jets + missing energy (+ lepton(s)) Applicable to NUHM, CMSSM, VCMSSM, mSUGRA but need other strategies for other models


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