beyond the mssm from the little hierarchy problem to the baryon asymmetry of the universe
DESCRIPTION
Beyond the MSSM From the little hierarchy problem to the Baryon Asymmetry of the Universe. Kfir Blum Advisors: Yossi Nir and Eli Waxman. Supersymmetry (SUSY) is a great idea It fixes the fine tuning problem. MSSM = simplest SUSY extension of SM Higgs sector extremely predictive: - PowerPoint PPT PresentationTRANSCRIPT
Beyond the MSSM
From the little hierarchy problem to the Baryon Asymmetry of the Universe
Kfir Blum
Advisors:
Yossi Nir and Eli Waxman
Supersymmetry (SUSY) is a great idea
It fixes the fine tuning problem
MSSM = simplest SUSY extension of SM Higgs sector extremely predictive:
more so than in SM!
…But it does not completely solve the tuning – little hierarchy problem remains
The little hierarchy problem
MSSM: at classical level, mH< mZ=91 GeV ! LEPII: mH>114 GeV
need large quantum corrections; can do with very heavy stops, mst>TeV
This implies % tuning
If additional DOF heavy M >> mZ, general way to proceed is via effective field theory:
Beyond MSSM
MSSM ain’t the whole story(we know this: for one, it isn’t enough to break SUSY)
Can additional DOF solve little hierarchy problem?
BMSSM
• Expand in powers of m/M, m ~ mZ << M
• Higgs sector:
)Approx’( SUSY + leading m/M Only two operators !
• In the scalar potential:
For M < 10 TeV,
More than enough to lift mH above LEP at classical level
See e.g. Dine, Seiberg & Thomas,
Phys.Rev.D76:095004,2007
BMSSM: Implications for vacuum stability and Cosmology
• Vacuum stability
• Dark Matter
• The electroweak phase transition and electroweak baryogenesis
Blum, Delaunay & Hochberg,
Phys.Rev.D80:075004,2009
Bernal, Blum, Losada & Nir ,
JHEP 0908:053,2009
Blum, Delaunay, Losada, Nir, Tulin,Work in progress
Bernal, Blum, Losada & Nir ,
JHEP 0908:053,2009 Blum & Nir ,
Phys.Rev.D78:035005,2009
MSSM
BMSSM
BMSSM Higgs potential non trivial.
Raise mH tunneling problem ?
Vacuum stability
…SUSY implies:
Constraints remain:
• Must not overcome gauge couplings• Upper bound on M
MSSM
BMSSM
Baryon Asymmetry of the Universe cannot be solved within SM
MSSM EWBG – little hierarchy amplified
need mH~114 GeV, but also light stop
other stop very heavy big little hierarchy
BMSSM:• Can have 2 light stops! No hierarchy• New couplings CP violation• Spontaneous EWBG
BMSSM
Electroweak Baryogenesis
Summary
* MSSM little hierarchy problem – due to constrained Higgs sector, solved Beyond-MSSM * Vacuum stability – SUSY renders effective theory simple & consistent
* Implications for Cosmology
– Natural EW Baryogenesis with 2 light stops – DM scenarios )bulk region reopens(
Outlook
* Spontaneous EW Baryogenesis
* Light stop phenomenology
* Microscopic realizations
Thanks!
Xtras
If…
•BMSSM respects R-parity
•Approximately SUSY (msoft<<M)
SUSY breaking via spurions
Pure Higgs:
Only 2 new operators!…enough to solve little hierarchy problem
Choice of basis
Leading mass shift
Dimension 6 scalar term,
and condition for neglecting it
2-loop thermal corrections associated with dim 6 term
Effective potential
EWPT I
EWPT – Barrier Formation
• First order: barrier forms between EW breaking and conserving minima
• Barrier height depends on light scalar dof coupling to the higgs field, and on thermal screening
• In SM, only gauge bosons contribute to barrier
• In MSSM, negative soft squared-mass can reduce thermal screening for stops, making them the dominant player by far
BMSSM higgsinos
Chargino-chargino-scalar-scalar
terms and modifications to the mass
matrices exist as well
Most natural parameter spacefor MSSM DM:Bino annihilates via lightsfermion exchange.
Example – mSUGRA Bulk Region.
If sfermion spectrum correlated )light sleptons light stops(,LEPII kills bulk region, since stopsmust be heavy.
BMSSM Dark Matter
BMSSM:
• mH decoupled from mst
efficient sfermion t-channel,
bulk region lives• Stop co-annihilation region
Also:
• Higgs resonance channel,
• Modified Higgsino couplings