Dirac neutrinos from a second Higgs doublet

Abstract

We propose a minimal extension of the standard model in which neutrinos are Dirac particles and their tiny masses are explained without requiring tiny Yukawa couplings. A second Higgs doublet with a tiny vacuum expectation value provides neutrino masses while simultaneously improving the naturalness of the model by allowing a heavier standard-model-like Higgs boson consistent with electroweak precision data. The model predicts a $\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}$ rate potentially detectable in the current round of experiments, as well as distinctive signatures in the production and decay of the charged Higgs ${H}^{+}$ of the second doublet which can be tested at future colliders. Neutrinoless double beta decay is absent.