A heavy Higgs boson from flavor and electroweak symmetry unification
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Transcript of A heavy Higgs boson from flavor and electroweak symmetry unification
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A heavy Higgs boson from flavor and electroweak symmetry unification
A heavy Higgs boson from flavor and electroweak symmetry unification
Boston, August 2004Boston, August 2004
Little Higgs meets little flavon
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Waiting for the LHCWaiting for the LHC
• Can we guess the mass of the Higgs?
• Is it light (< 200 GeV) or heavy (> 200 GeV)?
• Precision measurements (and SUSY) say it is
light
• Is there any prediction for a heavy mass?
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What is natural (and stable)What is natural (and stable)
• Dirac: dimensionless parameters should be of order one
•‘t Hooft: dimensionful parameters should be of the order
of the largest scale in the problem, unless a symmetry
arises in the limit of the coupling going to zero
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The little hierarchy problemThe little hierarchy problem
• Naturalness in the SM seems to demand new
physics at or around 1 TeV
• Precision measurements do not show any
departure from standard physics up to 10 TeV
How to use this little hierarchy problem to guess new physics?
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Higgs as a pseudo-Goldstone bosonHiggs as a pseudo-Goldstone boson
SU(3) SU(2)
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→
Problem: Goldstone bosons are exactly massless
Explicit breaking of SU(3) to make them into pseudo
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L = L0 + ε1L1
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ε1But is not small in the SM:
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The little-Higgs mechanism: an example [Schmaltz, hep-ph/0210415]
The little-Higgs mechanism: an example [Schmaltz, hep-ph/0210415]
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L = L0 + ε1L1 + ε2L2
collective symmetry breaking:
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Bringing flavor into the gameBringing flavor into the game
• Horizontal flavor symmetry
• Heavy scalar fields, the flavons
• Spontaneous breaking
• Hierarchy in VEV’s explains that in mass
matrices
• Stability (usually problematic to keep v/f<1)
Froggart-Nielsen mechanism
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RequestsRequests
• Unified electroweak and flavor symmetry• Dynamically generated potential with the desired vacuum• Stable scales, i.e., only small radiative corrections (no fine
tuning)• Appropriate textures (from charges and vev)
a little-Higgs inspired scenario
Little Higgs meets little flavon: the flhiggs model
[F. Bazzocchi and MF, hep-ph/0407358]
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Group structureGroup structure
SU(10) [SU(3)xU(1)]WxU(1)X xU(1)F
SO(10)
spontaneous
explicit2 2
2
[SU(3)xU(1)]WxU(1)X xU(1)F
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The sigma modelThe sigma model
vacuum
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The sigma model, IIThe sigma model, II
Lagrangian
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Effective potentialEffective potential
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Example: the right-handed neutrinosExample: the right-handed neutrinos
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Parameters in the potentialParameters in the potential
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flhiggs: 2 triplets of opposite flavor charge, 2 triplets of opposite X charge
this VEV breaksSU(3)xU(1)xU(1)to U(1)Q
Low-energy effective theoryLow-energy effective theory
[SU(3)xU(1)]WxU(1)X xU(1)F
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Experimental constrainsExperimental constrains
• Tree-level deviations in ballpark of radiative corrrections
• T parameter and Weinberg angle (at the 10-2 level)
• Z’ mass > 690 GeV
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Particle spectrum Particle spectrum
• vW fixed by GF
• vF fixed by experimental constrains• f fixed by texture parameter
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TexturesTextures
quarks
leptons
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The numerical analysisThe numerical analysis
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The (lightest) Higgs bosonThe (lightest) Higgs boson
• Gaussian distribution for all parameters of potential around 1 with spread of 20%