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

CMS excludes > 127.5, < 600 GeV ATLAS excludes 129, < 539 GeV Has the Higgs been Excluded? Interesting hints around M h = 125 GeV ?

CMS prefers < 125 GeV ATLAS prefers > 125 GeV Has the Higgs been Discovered? Interesting hints around M h = 125 GeV ?

Unofficial Combination of Higgs Search Data from March 7th Is this the Higgs Boson? 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: X 2  γγ (flat for X 0 ) Azimuthal angle distribution: X 0  WW (flat for X 2 ) JE, Hwang: arXiv:

Does the ‘Higgs’ have Spin Zero ? Polar angle distribution for X 2  W + W - Polar angle distribution for X 0  W + W - (for φ = π) JE, Hwang: arXiv:

Measuring Higgs LHC Current LHC M h = 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 BR(μe) must be < 2 ✕ Blankenburg, JE, Isidori: arXiv:

STANDARD MODEL John Ellis, King’s College London (& CERN)

Precision Electroweak data?? Higgs coupling blows up!! Higgs potential collapses Higgs coupling less than in Standard Model viXra Blogger’s Combination of March 7 th Data There must be New Physics Beyond the Standard Model

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

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

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? -Heavy scalar resonance? -Inconsistent with precision electroweak data? Cut-off Λ ~ 1 TeV with Supersymmetry? Cutoff Λ = 10 TeV

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

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 (a 2 > 1), must have non-zero scattering with I = 2 Fialkowski, Rychkov, Urban: arXiv:

Higgs as a Pseudo-Goldstone Boson Loop cancellation mechanism SupersymmetryLittle Higgs ‘Little Higgs’ models (breakdown of larger symmetry)

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 –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 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 Effective χ potential à la Coleman-Weinberg, with small coefficient B: Large = V >> electroweak scale v JE 1970

A Phenomenological Profile of a Pseudo-Dilaton Universal suppression of couplings to Standard Model particles: a = c = v/V Effective potential: Self-couplings: Γ(gg) may be enhanced Γ(γγ) may be suppressed Compilation of constraints Campbell, JE, Olive: arXiv: Updated with Dec. 11 constraints Pseudo-baryons as dark matter?

General Analysis of ‘Less Higgs’ Models Parameterization of effective Lagrangian: Fits a ≠ c Azatov, Contino, Galloway: arXiv: Espinosa, Grojean, Muhlleitner, Trott: arXiv:

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 Z 2 quantum number –Sp(N) gauge theory: baryons decay to mesons Campbell, JE, Olive: arXiv:

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:

Cosmological Phase Transition Critical temperature with ~ V: But supercooling to nucleation temperature: First-order phase transition Percolation ~ immediate Short phase of non-adiabatic expansion Campbell, JE, Olive: arXiv:

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 Campbell, JE, Olive: arXiv:

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:

Can we look for them with the LHC? Electroweak baryons ?

Electroweak Baryons as Dark Matter Fermions with I = J = ½? Expect mass of charged partner > neutral: Estimate mass difference ~ GeV –β-decay lifetime ~ 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:

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: Dark mattter Scattering rate

Classic Supersymmetric Signature Missing transverse energy carried away by dark matter particles

Limits on Heavy MSSM Higgses

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

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 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 seconds old Contributes to today’s dark energy: 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 Wouldn’t it be better if they found what you predicted? Then we would not learn anything!