standard model. precision electroweak data?? higgs coupling blows up!! higgs potential collapses...
TRANSCRIPT
STANDARD MODEL
Precision
Electroweak
data??
Higgs
coupling
blows up!!
Higgs
potential
collapses
Higgs coupling less
than in Standard Model
viXra Blogger’s Combination
of Dec.13th Data
There must be New Physics
Beyond the Standard Model
Theorists getting Cold Feet
• Composite Higgs model?conflicts with precision electroweak data
• Interpretation of EW data?consistency of measurements? Discard some?
• Higgs + higher-dimensional operators?corridors to higher Higgs masses?
• Little Higgs models?extra `Top’, gauge bosons, `Higgses’
• Higgsless models?strong WW scattering, extra D?
Heretical Interpretation of EW Data
Do all the data
tell the same story?
e.g., AL vs AH
What attitude towards LEP, NuTeV?
What most
of us think
Chanowitz
Spread looks natural: no significant disagreement
Estimates of mH from different Measurements
Higgs + Higher-Order Operators
Precision EW data suggest they are small: why?
But conspiracies
are possible: mH
could be large,
even if believe
EW data …?
Do not discard possibility of heavy Higgs
Corridor to
heavy Higgs?
Barbieri, Strumia
Elementary Higgs or Composite?
• Higgs field:
<0|H|0> ≠ 0• Quantum loop problems
• Fermion-antifermion condensate
• Just like QCD, BCS superconductivity
• Top-antitop condensate? needed mt > 200 GeV
New technicolour force?-Heavy scalar resonance?-Inconsistent with precision electroweak data?
Cut-off Λ ~ 1 TeV with
Supersymmetry?
Cutoff
Λ = 10 TeV
Comparison between Weakly- and Strongly-coupled Models
Interpolating Models
• Combination of Higgs boson and vector ρ
• Two main parameters: mρ and coupling gρ
• Equivalently ratio weak/strong scale:
gρ / mρ
Grojean, Giudice, Pomarol, Rattazzi
Intermediate Models
Effects on Higgs Decays
• Dependences on ξ of Higgs branching ratios
• Standard Model recovered in limit ξ0
Grojean, Giudice, Pomarol, Rattazzi
Higgs as a Pseudo-Goldstone
Boson
Loop cancellation mechanism
SupersymmetryLittle Higgs
‘Little Higgs’ models
(breakdown of larger symmetry)
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 heavyNot as complete as susy: more physics > 10 TeV
MT < 2 TeV (mh / 200 GeV)2
MW’ < 6 TeV (mh / 200 GeV)2
MH++ < 10 TeV
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
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:1111.4495
Updated
with Dec. 11
constraints
Pseudo-baryons as dark matter?
General Analysis of ‘Less Higgs’ Models
• Parameterization of effective Lagrangian:
• Fitsa ≠ c
Azatov, Contino, Galloway: arXiv:1202.3415 Espinosa, Grojean, Muhlleitner, Trott: arXiv:1202.3697
General Analysis of ‘Less Higgs’ Models
• Separate fits to CMS and ATLAS data:
Azatov, Contino, Galloway: arXiv:1202.3415
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
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: mKK > 300 GeV?
compatibility with precision data?• Warped extra dimension + brane kinetic terms?
Lightest KK mode @ few 00 GeV, strong WW @ 6-7 TeV
Particle Spectrum in Simplest Model with Extra Dimensions
Lowest-lying states have flat wave functions (n = 0)
Excitations (Kaluza-Klein) have nodes (n > 0):
Mass ~ n/R (R = radius of circle)
‘Fold’ Circle: Orbifold
• Identify two halves of circle: up to a minus sign
• ‘Even’ particles include massless: odd ones all massive• A way to give masses to particles that are asymmetric
Mechanism to break Gauge Symmetry
• Identify two halves up to a group transformation U
• Unbroken part of gauge group commutes with U• Masses for asymmetric particles:
– e.g., SU(2) × U(1) U(1)
Search for Vector Resonance in Higgsless Model
Vector resonance structure in WZ scattering
Simulation of resonance structure in mWZ @ LHC