Phenomenology of the nMSSM from colliders to cosmology

TL;DR

The paper analyzes the Nearly Minimal Supersymmetric Standard Model (nMSSM), a singlet-extended MSSM, as a framework addressing the μ problem, electroweak baryogenesis, and dark matter. It details the model’s CP-violation structure, extended Higgs and neutralino/chargino sectors, and the resulting phenomenology, including a characteristic light, singlino-dominated LSP and relatively light electroweak gauginos. It then maps collider prospects at the LHC and ILC (with Giga-Z options) to these cosmological goals, showing that Higgs physics, neutralino/chargino spectroscopy, and threshold scans can constrain the model’s parameters and test EWBG and relic-density predictions. The work emphasizes the synergy between collider measurements and cosmological observables, illustrating how precise mass and coupling determinations at future colliders could validate or falsify the nMSSM’s role in explaining dark matter and baryogenesis, while respecting EDM constraints.

Abstract

Low energy supersymmetric models provide a solution to the hierarchy problem and also have the necessary ingredients to solve two of the most outstanding issues in cosmology: the origin of dark matter and baryonic matter. One of the most attractive features of this framework is that the relevant physical processes are related to interactions at the weak scale and therefore may be tested in collider experiments in the near future. This is true for the Minimal Supersymmetric Standard Model (MSSM) as well as for its extension with the addition of one singlet chiral superfield, the so-called nMSSM. It has been recently shown that within the nMSSM an elegant solution to both the problem of baryogenesis and dark matter may be found, that relies mostly on the mixing of the singlet sector with the Higgs sector of the theory. In this work we review the nMSSM model constraints from cosmology and present the associated collider phenomenology at the LHC and the ILC. We show that the ILC will efficiently probe the neutralino, chargino and Higgs sectors, allowing to confront cosmological observations with computations based on collider measurements. We also investigate the prospects for a direct detection of dark matter and the constraints imposed by the current bounds of the electron electric dipole moment in this model.

Figures (8)

• Figure 1: Fit to $m_{ll}$ distribution for light neutralino production at the LHC. Backgrounds from Standard Model sources are not included, as they are expected to be small.
• Figure 2: Fits to the $m_{jll}$ distribution for (a) $\tilde{\chi}^0_3$ and (b) $\tilde{\chi}^0_2$ production at the LHC. Backgrounds from Standard Model sources are not included, as they are expected to be small.
• Figure 3: Correlation between $m_{\tilde{\chi}^0_{1}}$ and $m_{\tilde{\chi}^0_{2}}$ from LHC measurements.
• Figure 4: Energy distribution for the jet pair originating from the $W$ boson in the decay $\tilde{\chi}_1^\pm \to W^\pm \tilde{\chi}^0_1$ after selection cuts, with a simple fit to the kinematic endpoints.
• Figure 5: Threshold scan for chargino pair production at ILC.