Neutrino-axion-dilaton interconnection

Abstract

We show that a recently proposed framework that provides a simple connection between Majorana neutrinos and an invisible axion in minimal scalar extensions of the standard electroweak model can be naturally embedded in a classically scale-invariant setup. The explicit breaking of the scale invariance \`a la Coleman-Weinberg generates the Peccei-Quinn and electroweak scales. The spontaneous breaking of the chiral $U(1)_{PQ}$ triggers the generation of neutrino masses via Type-II seesaw and, at the same time, provides a dynamical solution to the strong CP problem as well as the axion as a dark matter candidate. The electroweak and neutrino mass scales are obtained via a technically natural ultraweak limit of the singlet scalar interactions. Accordingly, a realistic and perturbatively stable scalar spectrum, possibly in the reach of the LHC, is naturally obtained. A very light pseudodilaton characterizes such a setting. The vacuum stability of the extended setup is discussed.