LHC: Higgs, less Higgs, or more Higgs? John Ellis, King’s College London (& CERN) Has the Higgs been Excluded? Interesting hints around Mh = 125 GeV ? ATLAS excludes < 122.5, > 129, < 539 GeV CMS excludes > 127.5, < 600 GeV Has the Higgs been Discovered? Interesting hints around Mh = 125 GeV ? CMS prefers < 125 GeV ATLAS prefers > 125 GeV Unofficial Combination of Higgs Search Data from March 7th Is this the Higgs Boson? No Higgs here! No Higgs here! The Particle Higgsaw Puzzle Is LHC finding the missing piece? Is it the right shape? Is it the right size? Do we already know the ‘Higgs’ has Spin Zero ? • Decays into γγ, so cannot have spin 1 • 0 or 2? • If it decays into ττ or b-bar: spin 0 or 1 or orbital angular momentum • Can diagnose spin via – angular distribution of γγ – angular correlations of leptons in WW, ZZ decays • Does selection of WW events mean spin 2? Does the ‘Higgs’ have Spin Zero ? • Polar angle distribution: • Azimuthal angle X2 γγ distribution: X0 WW (flat for X0) JE, Hwang: arXiv:1202.6660 (flat for X2) Does the ‘Higgs’ have Spin Zero ? • Polar angle distribution for X2 W+W• Polar angle distribution for X0 W+W(for φ = π) JE, Hwang: arXiv:1202.6660 Measuring Higgs Couplings @ LHC Current LHC hint @ Mh = 125 GeV Flavour-Changing Couplings? • Upper limits from FCNC, EDMs, … • Quark FCNC bounds exclude observability of quark-flavour-violating h decays • Lepton-flavour-violating h decays could be large: BR(τμ) or BR(τe) could be O(10)% B Blankenburg, JE, Isidori: arXiv:1202.5704 BR(μe) must be < 2 ✕ 10-5 STANDARD MODE John Ellis, King’s College London (& CERN) There be New Physics viXramust Blogger’s Combination March 7th Data Model Beyondofthe Standard Higgs potential collapses Higgs coupling less than in Standard Model Precision Electroweak data?? Higgs coupling blows up!! Estimates of mH from different Measurements Spread looks natural: no significant disagreement Heretical Interpretation of EW Data What attitude towards LEP, NuTeV? Do all the data tell the same story? e.g., AL vs AH Chanowitz What most of us think Elementary Higgs or Composite? • Higgs field: <0|H|0> ≠ 0 • Quantum loop problems • Fermion-antifermion condensate • Just like QCD, BCS superconductivity Cutoff Λ = 10 TeV • Top-antitop condensate? needed mt > 200 GeV Cut-off Λ ~ 1 TeV with Supersymmetry? New technicolour force? - Heavy scalar resonance? - Inconsistent with precision electroweak data? Interpolating Models • Combination of Higgs boson and vector ρ • Two main parameters: mρ and coupling gρ • Equivalently ratio weak/strong scale: g ρ / mρ Grojean, Giudice, Pomarol, Rattazzi Sum Rule for More or Less Higgs Models • What if Higgs-V-V couplings differ from SM? • Unitarity imposes sum rule on scattering in different isospin channels: • If Higgs coupling > Standard Model (a2 > 1), must have non-zero scattering with I = 2 Fialkowski, Rychkov, Urban: arXiv:1202.1532 Higgs as a Pseudo-Goldstone Boson ‘Little Higgs’ models (breakdown of larger symmetry) Loop cancellation mechanism Little Higgs Supersymmetry Examples of Higgs as Pseudo-Goldstone Boson • Parameterization of effective Lagrangian: • Examples: • To be measured! 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 –μ2, anomalies – Cannot remove μ2 (Coleman-Weinberg) – Anomalies give couplings to γγ, gg • Generalize to pseudo-dilaton of new (nearly) conformal strongly-interacting sector • Pseudo-Goldstone boson of scale symmetry Effective Lagrangian Framework • • • • Standard Model Higgs sector = linear σ model Replace by nonlinear chiral Lagrangian Assume ~ scale (conformal) symmetry Realized via (pseudo-)dilaton field χ JE 1970 • Effective χ potential à la Coleman-Weinberg, with small coefficient B: • Large <0|χ|0> = V >> electroweak scale v A Phenomenological Profile of a Pseudo-Dilaton • Universal suppression of couplings to Standard Model particles: a = c = v/V • Effective potential: • Self-couplings: Compilation Updated 1000 900 of with constraints Dec. 11 constraints 800 • Γ(gg) may be enhanced • Γ(γγ) may be suppressed V (GeV) 700 Pseudo-baryons as dark matter? Campbell, JE, Olive: arXiv:1111.4495 600 500 400 precision data 300 N =3 g 200 100 200 300 400 m (GeV) 500 600 700 General Analysis of ‘Less Higgs’ Models • Parameterization of effective Lagrangian: • Fits a≠c Azatov, Contino, Galloway: arXiv:1202.3415 Espinosa, Grojean, Muhlleitner, Trott: arXiv:1202.3697 Analysis of ‘Less Higgs’ Models • Rescale couplings: to bosons by a to fermions by c • Standard Model: a=c=1 JE & Tevong You Electroweak Pseudo-Baryons • Chiral Lagrangian has soliton solutions whenever higher-order term present (generic): • Have non-zero topological quantum number • B is integer, can be identified with baryon # • Underlying SU(N) gauge theory: bosons (fermions) with I = J = 0 (1/2) if N even (odd) – SO(N) gauge theory: B is Z2 quantum number – Sp(N) gauge theory: baryons decay to mesons Campbell, JE, Olive: arXiv:1111.4495 Behaviour at Finite Temperature • Corrections to nonlinear effective theory: • Correction to effective dilaton potential: • Critical temperature when equal free energies • More degrees of freedom in confined phase: Campbell, JE, Olive: arXiv:1111.4495 Cosmological Phase Transition • Critical temperature with <0|χ|0> ~ V: • But supercooling to nucleation temperature: • First-order phase transition • Percolation ~ immediate • Short phase of non-adiabatic expansion Campbell, JE, Olive: arXiv:1111.4495 Evolution of the Universe • Universe supercoools • Expansion briefly dominated by field energy • Growth in entropy by factor ~ 7 to 200 • Identify confinement, appearance of electroweak ‘baryons’ with transition to <0|χ|0> ≠ 0 Campbell, JE, Olive: arXiv:1111.4495 Baryon-to-Entropy Ratio • ‘Kibble’ estimate would be large • But thermal equilibrium thought to be restored • Expect smaller density: : freeze-out • Density smaller than required for cold dark matter: • Need electroweak ‘pseudo-baryon’ asymmetry Campbell, JE, Olive: arXiv:1111.4495 Electroweak baryons ? Can we look for them with the LHC? Electroweak Baryons as Dark Matter • Fermions with I = J = ½? • Expect mass of charged partner > neutral: • Estimate mass difference ~ GeV – β-decay lifetime ~ 10-11 sec – thermal equilibrium down to T ~ MeV – Small abundance of charged state • BUT some might be trapped in stable charged ‘pseudo-nuclei’ ✕ experiment Campbell, JE, Olive: arXiv:1111.4495 Pseudo-Baryonic Dark Matter? • No problem if I = J = 0 bosons • Estimate scattering cross section: where: with • Within range of future experiments Campbell, JE, Olive: arXiv:1111.4495 Dark mattter Scattering rate Classic Supersymmetric Signature Missing transverse energy carried away by dark matter particles Limits on Heavy MSSM Higgses Gluino mass --- pre-Higgs ___ Higgs @ 125 … H@125, no g-2 Buchmueller, JE et al: arXiv:1112.3564 Favoured values of gluino mass significantly above pre-LHC, > 2 TeV 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: 1060 too much! Conversation with Mrs Thatcher: 1982 What do you do? Think of things for the experiments to look for, and hope they find something different Then we would not learn anything! Wouldn’t it be better if they found what you predicted?