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