Dark matter physics in neutrino specific two Higgs doublet model

Understand

Although the seesaw mechanism is a natural explanation for the small neutrino masses, there are cases when the Majorana mass terms for the right-handed neutrinos are not allowed due to symmetry.

• In that case, if neutrino-specific Higgs doublet is introduced, neutrinos become Dirac particles and their small masses can be explained by its small VEV.
• We show that the same symmetry, which we assume a global $U(1)_X$, can also be used to explain the stability of dark matter.
• In our model, a new singlet scalar breaks the global symmetry spontaneously down to a discrete $Z_2$ symmetry.