Light NMSSM Neutralino Dark Matter in the Wake of CDMS II and a 126 GeV Higgs

TL;DR

This paper explores the parameter space of the NMSSM to identify light neutralino dark matter candidates with large scattering cross-sections, consistent with recent experimental results and Higgs boson observations, considering two annihilation scenarios.

Contribution

It provides a detailed analysis of viable NMSSM regions for light neutralino dark matter compatible with LHC and cosmological constraints, focusing on two distinct annihilation mechanisms.

Findings

Viable parameter space exists for both scalar and pseudoscalar mediated annihilation.

Accidental cancellations can produce Higgs properties consistent with observations.

Constraints from meson decays and Higgs exotic decays are significant.

Abstract

Recent results from the Cryogenic Dark Matter Search (CDMS) experiment have renewed interest in light dark matter with a large spin-independent neutralino-nucleon scattering cross-section. Here, we examine the regions of the Next-to-MSSM (NMSSM) capable of producing a light neutralino with a large spin-independent scattering cross-section, with the scattering mediated by a very light singlet-like scalar, and a 126 GeV Standard Model-like Higgs consistent with the LHC results, while satisfying other relevant cosmological, flavor and collider constraints. We focus on two different scenarios for annihilation in the early universe, namely annihilation mediated by (1) a light scalar or by (2) a light pseudo-scalar. As expected, both cases are highly constrained. Nevertheless, we find that there persists potentially viable parameter space to accommodate either scenario. In the first, accidental cancellations in the couplings allow for a SM-like Higgs with a total width and invisible branching fraction compatible with the observed Higgs boson. Alternatively, the second scenario can occur in regions featuring smaller branching fractions of the SM-like Higgs to pairs of light scalars, pseudoscalars, and neutralinos without cancellations. The strongest constraints in both cases come from rare meson decays and exotic decays of the SM-like Higgs boson into neutralinos and light, CP-even Higgs pairs. We outline the relevant parameter space for both scenarios and comment on prospects for future discovery with various experiments.