Naturalness in low-scale SUSY models and “non-linear” MSSM

In MSSM models with various boundary conditions for the soft breaking terms ( m soft ) and for a Higgs mass of 126 GeV, there is a (minimal) electroweak fine-tuning Δ ≈ 800 to 1000 for the constrained MSSM and Δ ≈ 500 for non-universal gaugino masses. These values, often regarded as unacceptably lar...

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Bibliographic Details
Published in:The European physical journal. C, Particles and fields Particles and fields, 2014-09, Vol.74 (9), p.3050-13, Article 3050
Main Authors: Antoniadis, I., Babalic, E. M., Ghilencea, D. M.
Format: Article
Language:English
Subjects:
Acceptability
Astronomy
Astrophysics and Cosmology
Boundary conditions
Breaking
Constraints
Couplings
Elementary Particles
Gravitation
Hadrons
Heavy Ions
Measurement Science and Instrumentation
Nonlinearity
Nuclear Energy
Nuclear Physics
Physics
Physics and Astronomy
Quantum Field Theories
Quantum Field Theory
Regular - Theoretical Physics
Regular Article - Theoretical Physics
String Theory
Supersymmetry
Texts
Tuning
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Summary:In MSSM models with various boundary conditions for the soft breaking terms ( m soft ) and for a Higgs mass of 126 GeV, there is a (minimal) electroweak fine-tuning Δ ≈ 800 to 1000 for the constrained MSSM and Δ ≈ 500 for non-universal gaugino masses. These values, often regarded as unacceptably large, may indicate a problem of supersymmetry (SUSY) breaking, rather than of SUSY itself. A minimal modification of these models is to lower the SUSY breaking scale in the hidden sector ( f ) to few TeV, which we show to restore naturalness to more acceptable levels Δ ≈ 80 for the most conservative case of low tan β and ultraviolet boundary conditions as in the constrained MSSM. This is done without introducing additional fields in the visible sector, unlike other models that attempt to reduce Δ . In the present case Δ is reduced due to additional (effective) quartic Higgs couplings proportional to the ratio m soft / f of the visible to the hidden sector SUSY breaking scales. These couplings are generated by the auxiliary component of the goldstino superfield. The model is discussed in the limit its sgoldstino component is integrated out so this superfield is realized non-linearly (hence the name of the model) while the other MSSM superfields are in their linear realization. By increasing the hidden sector scale f one obtains a continuous transition for fine-tuning values, from this model to the usual (gravity mediated) MSSM-like models.
ISSN:1434-6044
1434-6052
DOI:10.1140/epjc/s10052-014-3050-9