Astrophysical Consequences of a Neutrinophilic Two-Higgs-Doublet Model

In a recently proposed neutrinophilic two-Higgs doublet model, the low-energy (sub-MeV) effective theory consists of a real scalar with a vev of O(0.1) eV and three Dirac neutrinos. Other models could lead to the same low energy theory. In this Brief Report, we study constraints on the parameter space of the model, including vacuum stability, unitarity, perturbativity and the effects on the invisible Z width. Interestingly, we find that all neutrinos become massless at temperatures above approximately 1000 K, but can find no phenomenological effects of this finding. The most direct test of the model is that it predicts that in a galactic supernova, the energy distributions of the electron, muon and tau neutrinos will be Fermi-Dirac with identical temperatures, unlike the conventional distributions.