The Scale-Invariant NMSSM and the 126 GeV Higgs Boson

TL;DR

The paper investigates the scale-invariant NMSSM as a natural extension of the MSSM to accommodate the 126 GeV Higgs, analyzing its parameter space under current experimental constraints and its testability at the 14 TeV LHC.

Contribution

It provides a detailed analysis of the naturalness and parameter space of the scale-invariant NMSSM considering recent experimental constraints, highlighting regions with low tuning and their LHC prospects.

Findings

TeV-scale stop masses are compatible with low tuning (~5%) at a 20 TeV messenger scale.

Larger Higgs-singlet coupling increases tuning, constraining superpartner masses.

The natural parameter space will be fully probed at the 14 TeV LHC.

Abstract

The recent LHC discovery of a Higgs-like resonance at 126 GeV suggests that the minimal supersymmetric standard model must be modified in order to preserve naturalness. A simple extension is to include a singlet superfield and consider the scale-invariant NMSSM, whose renormalizable superpotential contains no dimensionful parameters. This extension not only solves the \mu-problem, but can easily accommodate a 126 GeV Higgs. We study the naturalness of the scale-invariant NMSSM taking into account the recent constraints from LHC searches, flavor physics and electroweak precision tests. We show that TeV-scale stop masses are still allowed in much of the parameter space with 5% tuning for a low messenger scale of 20 TeV, split families (with third-generation sleptons decoupled) and Higgs-singlet coupling \lambda of order one. For larger values of the Higgs-singlet coupling, which can relieve the tuning in the Higgs VEV, an additional tuning in the Higgs mass limits increasing the (lightest) stop mass beyond 1.2 TeV, the gluino mass above 3 TeV, and electroweak charginos and neutralinos beyond 400 GeV for a combined tuning better than 5%. This implies that the natural region of parameter space for the scale-invariant NMSSM will be fully explored at the 14 TeV LHC.