Abstract
We perform a global fit within the pseudo-Nambu-Goldstone Dark Matter (DM) model emerging from an additional complex scalar singlet with a softly broken global U (1) symmetry. Leading to a momentum-suppressed DM-nucleon cross section at tree level, the model provides a natural explanation for the null results from direct detection experiments. Our global fit combines constraints from perturbative unitarity, DM relic abundance, Higgs invisible decay, electroweak precision observables and latest Higgs searches at colliders. The results are presented in both frequentist and Bayesian statisical frameworks. Furthermore, post-processing our samples, we include the likelihood from gamma-ray observations of Fermi -LAT dwarf spheroidal galaxies and compute the one-loop DM-nucleon cross section. We find two favoured regions characterised by their dominant annihilation channel: the Higgs funnel and annihilation into Higgs pairs. Both are compatible with current Fermi -LAT observations, and furthermore, can fit the slight excess observed in four dwarfs in a mass range between about 30–300 GeV. While the former region is hard to probe experimentally, the latter can partly be tested by current observations of cosmic-ray antiprotons as well as future gamma-ray observations.
Highlights
Symmetries [15, 16]
We perform a global fit within the pseudo-Nambu-Goldstone Dark Matter (DM) model emerging from an additional complex scalar singlet with a softly broken global U(1) symmetry
The Goldstone nature of the DM particle implies that the pNG DM-nucleon cross section is momentum-suppressed at tree-level [24]
Summary
We extend the SM Lagrangian by adding a new complex scalar field S that couples to the SM particles via a Higgs portal term, Φ†Φ (Φ is the SM Higgs doublet). The model contains a massive Goldstone boson, i.e., a pNG boson. After this symmetry breaking, we are left with a residual Z2 symmetry, S → −S, of the dark U(1) group, which forbids a linear term in S in the above Lagrangians. Eq (2.1) is invariant under a dark CP symmetry:. This symmetry is unbroken by the S vacuum expectation value (VEV) as for positive μS2, the VEV is real. The model spectrum can be analysed by decomposing Φ and S in the unitary gauge as. Given that the S VEV is non-zero in general, the λΦS term in eq (2.2) leads to a mixing between the CP -even interaction eigenstates (φ, s).
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