Pseudo-Nambu-Goldstone dark matter and two-Higgs-doublet models

Understand

We study a dark matter model with one singlet complex scalar and two Higgs doublets.

• The scalar potential respects a softly broken global symmetry, which makes the imaginary part of the singlet become a pseudo-Nambu-Goldstone boson acting as a dark matter candidate.
• The pseudo-Nambu-Goldstone nature of the boson leads to the vanishing of its tree-level scattering amplitude off nucleons at zero momentum transfer.
• Therefore, although the interaction strength could be sufficiently large to yield a viable relic abundance via thermal mechanism, direct detection is incapable of probing this candidate.