Anomaly-free axion dark matter in three Higgs doublet model and its phenomenological implications

Understand

We study phenomenological implications of an axion that arises as a pseudo Nambu-Goldstone boson due to the spontaneous breaking of anomaly-free global flavor symmetry.

• One interesting possibility for such anomaly-free axion to explain dark matter (DM) is when it has a mass of order keV and an intermediate scale decay constant, since it can be explored through direct search experiments, X-ray observations, various stellar cooling processes, and the misalignment mechanism naturally explains the DM abundance.
• As a concrete renormalizable model of such axion, we consider an extended Higgs sector with global flavor symmetry, which consists of three Higgs doublet fields and three singlet Higgs fields with $U(1)_{\rm B-L}$ charges.
• We identify viable parameter regions that satisfy theoretical bounds on the Higgs potential and various experimental limits on this model, and evaluate the mass spectra of the axion and extra Higgs bosons.