LHC: Higgs, less Higgs, or more Higgs?

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

Has the Higgs been Excluded?

Interesting hints around M h = 125 GeV ?

ATLAS excludes < 122.5, > 129, < 539 GeV CMS excludes > 127.5, < 600 GeV

Has the Higgs been Discovered?

Interesting hints around M h = 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: X 2  γγ (flat for X 0 ) • Azimuthal angle distribution: X 0  WW (flat for X 2 ) JE, Hwang: arXiv:1202.6660

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:1202.6660

Measuring Higgs Couplings @ LHC Current LHC hint @ 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 ✕ 10 -5

STANDARD MODEL

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

Higgs potential collapses Data Higgs coupling less than in Standard Model Precision Electroweak data??

Higgs coupling blows up!!

Estimates of m H 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., A L vs A H

What most of us think Chanowitz

Elementary Higgs or Composite?

• Higgs field: <0|H|0> ≠ 0 • Quantum loop problems Cutoff Λ = 10 TeV Cut-off Λ ~ 1 TeV with Supersymmetry?

• 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?

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: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 –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 <0|χ|0> =

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:

1000 900 800 700

• Γ(gg) may be enhanced • Γ(γγ) may be suppressed Pseudo-baryons as dark matter?

Campbell, JE, Olive: arXiv:1111.4495

600 500 400 300 200 100 200

constraints precision data

300 400 m (GeV) 500

N g = 3

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

Z

2 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 cold dark matter: smaller than required for • 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 Dark mattter Scattering rate • Within range of future experiments Campbell, JE, Olive: arXiv:1111.4495

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: 10 60 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?