Naturalness and Fine Tuning in the NMSSM: Implications of Early LHC Results

TL;DR

This paper analyzes the fine tuning in the semi-constrained NMSSM, showing that early LHC results significantly restrict parameter space and increase the required fine tuning, especially in scenarios with large Higgs mixing or decays.

Contribution

It provides a detailed study of fine tuning dependence on soft SUSY parameters in the NMSSM and assesses the impact of early LHC results on these models.

Findings

Early LHC results exclude large parts of low fine-tuning parameter space.

Scenarios with large singlet-doublet Higgs mixing are more constrained.

Fine tuning remains significant in the semi-constrained NMSSM after LHC constraints.

Abstract

We study the fine tuning in the parameter space of the semi-constrained NMSSM, where most soft Susy breaking parameters are universal at the GUT scale. We discuss the dependence of the fine tuning on the soft Susy breaking parameters M_1/2 and m0, and on the Higgs masses in NMSSM specific scenarios involving large singlet-doublet Higgs mixing or dominant Higgs-to-Higgs decays. Whereas these latter scenarios allow a priori for considerably less fine tuning than the constrained MSSM, the early LHC results rule out a large part of the parameter space of the semi-constrained NMSSM corresponding to low values of the fine tuning.