How to solve the Free Parameter Problem in SUSY ?

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Discussion Overview

The discussion revolves around the Free Parameter Problem in Supersymmetry (SUSY), particularly in relation to the numerous free parameters present in the Standard Model and how they compare to those in SUSY models. Participants explore potential solutions and implications of these parameters within theoretical frameworks.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that the Standard Model has 19 free parameters, while Supersymmetric Models have over 100, raising the question of how to address this issue.
  • Another participant suggests embedding SUSY into string theory, proposing that this could replace the numerous free parameters with a discrete choice from a vast number of false vacua, although it remains uncertain if any of these would reduce to the Standard Model.
  • A different viewpoint indicates that depending on the specifics of the model, SUSY may only add a few extra degrees of freedom, with the majority of the parameters arising from the soft breaking sector, which is more of a phenomenological issue due to the unknown nature of SUSY breaking.
  • One participant expresses curiosity about mSugra extensions that reportedly reduce nearly 100 free parameters to just 5, seeking clarification on how this reduction is achieved.

Areas of Agreement / Disagreement

Participants express differing views on the nature and implications of the free parameters in SUSY, with no consensus reached on a definitive solution to the Free Parameter Problem.

Contextual Notes

The discussion highlights the complexity of SUSY models and the challenges associated with understanding supersymmetry breaking, which remains unresolved and is dependent on various theoretical assumptions.

ophase
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How to solve the Free Parameter Problem in SUSY ??

In Standard Model, we have 19 free parameters:

me Electron mass 511 keV
mμ Muon mass 106 MeV
mτ Tauon mass 1.78 GeV
mu Up quark mass () 1.9 MeV
md Down quark mass () 4.4 MeV
ms Strange quark mass () 87 MeV
mc Charm quark mass () 1.32 GeV
mb Bottom quark mass () 4.24 GeV
mt Top quark mass (on-shell scheme) 172.7 GeV
θ12 CKM 12-mixing angle 0.229
θ23 CKM 23-mixing angle 0.042
θ13 CKM 13-mixing angle 0.004
δ CKM CP-violating Phase 0.995
g1 U(1) gauge coupling () 0.357
g2 SU(2) gauge coupling () 0.652
g3 SU(3) gauge coupling () 1.221
θQCD QCD Vacuum Angle ~0
μ Higgs quadratic coupling Unknown
λ Higgs self-coupling strength Unknown

Note that We have even more (above 100) free parameters in Supersymmetric Models while we solved another problems of SM (hierarchy problem).
Is there a way to solve this problem in SUSY??
 
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Yep. You embed your SUSY into a string theory and replace your 100 free parameters with a discrete choice of one of [tex]10^{500}[/tex] false vacua. Unfortunately, at the present time it's unknown whether anyone of them reduces to SM. But the number of possibilities is so huge that you can probably find any combination of constants in there.
 
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Actually, depending on some specifics of the model, supersymmetry basically only adds a few extra degrees of freedom (for instance 5). The immense majority of the rest ~100 are contained in the soft breaking sector of the lagrangian and is more a phenomenology problem than a theoretical one, since we don't know how supersymmetry breaking actually occurs and must effectively parametrize our ignorance. If we had an accelerator that could probe the full SUSY parameter space, we'd find relationships between all those 'free' parameters and be able to pin down exactly how the breaking is accomplished.
 


I heard that some of mSugra extensions reduce almost 100 free parameters to 5!
I wonder what these numbers are and how can one reduce such a huge number to only 5??
 

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