Axionic Dirac seesaw mechanism and electroweak vacuum stability

Abstract

We explore the connection between tree-level Dirac neutrino masses and axion physics in a scenario where the Peccei-Quinn (PQ) symmetry enforces lepton number conservation perturbatively. Requiring that the PQ scale ${f}_{a}$ is the only heavy scale to play a role in neutrino mass generation, we are led to the construction of a Kim--Shifman--Vainshtein--Zakharov-type model where Dirac neutrino masses are inversely proportional to ${f}_{a}$, provided a real scalar triplet (zero hypercharge) is added to the standard model scalar sector. We analyze this extended scalar sector, focusing on the stabilization of the electroweak vacuum. The contribution of the triplet vacuum expectation value to the $W$ mass may also be responsible for the recent hint of beyond-the-SM physics by the CDF collaboration.