A neutrinophilic two Higgs doublet model with an A₄ flavour symmetry for Dirac neutrinos

Abstract

We introduce three right-handed sterile neutrinos which acquire mass by coupling to a second Higgs doublet with a tiny vacuum expectation value, giving rise to naturally small neutrino masses. Majorana mass terms are forbidden by an additional global U(1) symmetry. We discuss the phenomenology of this model, placing a special emphasis on processes involving leptons. In addition, an A4 flavour symmetry is introduced in the lepton sector in order to explain the structure of the leptonic mixing matrix and the neutrino masses. We discuss how a tribimaximal leptonic mixing matrix can be achieved in this context and analyse numerically deviations from the exact tribimaximal form, which are required in order to be compatible with the recent experimental findings indicating a rather large θ13. In particular, implications of the presence of this flavour symmetry on the phenomenology of the two Higgs doublet model are studied