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
