The Z3-invariant next-to-minimal supersymmetric standard model (NMSSM) can
provide a candidate for dark matter (DM). It can also be used to explain the
hypothesis that the Higgs signal observed on the Large Hadron Collider (LHC)
comes from the contribution of the two lightest CP-even Higgs bosons, whose
masses are near 125 GeV. At present, XENON1T, LUX, and PandaX experiments have
imposed very strict restrictions on direct collision cross sections of {dark
matter}. In this paper, we consider a scenario that the observed Higgs signal
is the superposition of two mass-degenerate Higgs in the Z3-invariant NMSSM
and scan the seven-dimension parameter space composing of λ,κ,tanβ,μ,Ak,At,M1 via the Markov chain Monte Carlo (MCMC) method.
We find that the DM relic density, as well as the LHC searches for sparticles,
especially the DM direct detections, has provided a strong limit on the
parameter space. %Please check intended meaning has been retained. The allowed
parameter space is featured by a relatively small μ≤300 GeV and about
tanβ∈(10,20). In addition, the DM is Higgsino-dominated because of
∣λ2κ∣>1. Moreover, the co-annihilation between
χ~10 and χ~1± must be taken into account to
obtain the reasonable DM relic density