Stability constraints in triplet extension of MSSM

TL;DR

This paper investigates stability constraints in a triplet extension of the MSSM, showing how these constraints limit the parameter space and affect phenomenological predictions like Higgs decay rates and fine-tuning.

Contribution

The study derives stability constraints for the triplet-extended MSSM and analyzes their impact on the model's viable parameter space and phenomenological features.

Findings

Only about 25% of parameter points are stable.

Stable points have Higgs and soft masses below 1 TeV.

Higgs decay to diphoton shows larger deviations from MSSM.

Abstract

We study the stability constraints on the parameter space of a triplet extension of MSSM. Existence of unbounded from below directions in the potential can spoil successful Electroweak (EW) symmetry breaking by making the corresponding minimum unstable, and hence the model should be free from those directions. Avoiding those directions restricts the parameter space of the model. We derive four stability constraints, of which only three independent from each other. After scanning the model's parameter space for phenomenologically viable data points, we impose the stability constraints and find that only about a quarter of the data points features a stable EW minimum. At those data points featuring stability, $\mu$ and the up Higgs soft mass turn out to be smaller than about a TeV in absolute value, which make the mass of the lightest chargino and neutralino smaller than about 700 GeV. Two relevant phenomenological consequences of lifting the unbounded from below directions are that the lightest Higgs boson decay rate to diphoton predicted by the triplet extension of MSSM generally features larger deviations from MSSM and fine tuning is actually higher, that what each of the two would be without imposing stability constraints.