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Beyond the MSSM: Solving the Little Hierarchy Problem and Exploring the Baryon Asymmetry of the Universe

This research explores the limitations of the Minimal Supersymmetric Standard Model (MSSM) in solving the little hierarchy problem and proposes the Beyond MSSM (BMSSM) as a potential solution. The study also investigates the implications of BMSSM on vacuum stability, dark matter, and electroweak baryogenesis.

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Beyond the MSSM: Solving the Little Hierarchy Problem and Exploring the Baryon Asymmetry of the Universe

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  1. Beyond the MSSMFrom the little hierarchy problem to the Baryon Asymmetry of the Universe Kfir Blum Advisors: Yossi Nir and Eli Waxman

  2. 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

  3. 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? 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

  4. See e.g. Dine, Seiberg & Thomas, Phys.Rev.D76:095004,2007 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

  5. MSSM BMSSM Blum & Nir, Phys.Rev.D78:035005,2009 Bernal, Blum, Losada & Nir, JHEP 0908:053,2009 Blum, Delaunay, Losada, Nir, Tulin, Work in progress 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

  6. Vacuum stability BMSSM Higgs potential non trivial. Raise mH tunneling problem ? • …SUSY implies: • Constraints remain: • Must not overcome gauge couplings • Upper bound on M

  7. MSSM BMSSM BMSSM Electroweak Baryogenesis • 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 •  biglittle hierarchy BMSSM: • Can have 2 light stops! No hierarchy • New couplings  CP violation • Spontaneous EWBG

  8. 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

  9. Thanks!

  10. Xtras

  11. 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

  12. Choice of basis Leading mass shift Dimension 6 scalar term, and condition for neglecting it 2-loop thermal corrections associated with dim 6 term

  13. Effective potential

  14. EWPT I

  15. 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

  16. BMSSM higgsinos Chargino-chargino-scalar-scalar terms and modifications to the mass matrices exist as well

  17. BMSSM Dark Matter Most natural parameter space for MSSM DM: Bino annihilates via light sfermion exchange. Example – mSUGRA Bulk Region. If sfermion spectrum correlated (light sleptons  light stops), LEPII kills bulk region, since stops must be heavy. • BMSSM: • mH decoupled from mst • efficient sfermion t-channel, • bulk region lives • Stop co-annihilation region • Also: • Higgs resonance channel, • Modified Higgsino couplings

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