Status and prospects of the nMSSM after LHC Run-1

TL;DR

This paper examines the nMSSM after LHC Run-1, identifying viable parameter regions consistent with collider and dark matter constraints, and explores distinctive collider signatures and detection prospects for the model.

Contribution

It provides a comprehensive analysis of the nMSSM parameter space post-LHC Run-1, highlighting the unique dark matter and collider signatures of the model.

Findings

A light singlino LSP around 5 GeV can account for all dark matter.

Heavier mixed singlinos can only be part of dark matter.

Future ton-scale detectors could probe LSP masses around 65 GeV.

Abstract

The new minimal supersymmetric standard model (nMSSM), a variant of the general next to minimal supersymmetric standard model (NMSSM) without $Z_3$ symmetry, features a naturally light singlino with a mass below 75 GeV. In light of the new constraints from LHC Run-1 on the Higgs couplings, sparticles searches and flavour observables, we define the parameter space of the model which is compatible with both collider and dark matter (DM) properties. Among the regions compatible with these constraints, implemented through NMSSMTools, SModelS and MadAnalysis 5, only one with a singlino lightest supersymmetric particle (LSP) with a mass around 5 GeV can explain all the DM abundance of the universe, while heavier mixed singlinos can only form one of the DM components. Typical collider signatures for each region of the parameter space are investigated. In particular, the decay of the 125 GeV Higgs into light scalars and/or pseudoscalars and the decay of the heavy Higgs into charginos and neutralinos, provide distinctive signatures of the model. Moreover, the sfermion decays usually proceed through heavier neutralinos rather than directly into the LSP, as the couplings to the singlino are suppressed. We also show that direct detection searches are complementary to collider ones, and that a future ton-scale detector could completely probe the region of parameter space with a LSP mass around 65 GeV.