Transcript Phenomenology Beyond the Standard Model

STANDARD MODE
There
be New
Physics
viXramust
Blogger’s
Combination
th Data Model
Dec.13
Beyondofthe
Standard
Higgs coupling less
than in Standard Model
Higgs
potential
collapses
Precision
Electroweak
data??
Higgs
coupling
blows up!!
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
What attitude towards LEP, NuTeV?
Do all the data
tell the same story?
e.g., AL vs AH
Chanowitz
What most
of us think
Estimates of mH from different
Measurements
Spread looks natural: no significant disagreement
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 …?
Barbieri, Strumia
Do not discard possibility of heavy Higgs
Corridor to
heavy Higgs?
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?
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:
g ρ / mρ
Grojean, Giudice, Pomarol, Rattazzi
Intermediate Models
Effects on Higgs Decays
• Dependences on ξ of Higgs branching ratios
• Standard Model recovered in limit ξ0
Grojean, Giudice, Pomarol, Rattazzi
Higgs as a
Pseudo-Goldstone
Boson
‘Little Higgs’ models
(breakdown of larger symmetry)
Loop cancellation mechanism
Little Higgs
Supersymmetry
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
MT < 2 TeV (mh / 200 GeV)2
MW’ < 6 TeV (mh / 200 GeV)2
MH++ < 10 TeV
Not as complete as susy: more physics > 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:
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
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