Speaker
Description
In this work we study the one-loop realizations of the d = 5 operator $\bar L \tilde H N_R S$ that leads to Dirac neutrino masses, where $S$ is a singlet scalar field that hosts the QCD axion, $N_R$ represents three right-handed neutrinos, $L$ is the lepton doublet and $H$ is the SM Higgs boson. As usual, the axion arises from the breaking of the Peccei-Quinn symmetry, which in our setup we use to not only solve the strong CP problem, but also to forbid the operator $\bar L \tilde H N_R S$ (which generates Dirac neutrino masses at tree level) and the tree-level realizations of $\bar L \tilde H N_R S$. Thus, the neutrino masses are directly correlated to the axion mass (via the PQ symmetry breaking scale $v_S$) and their smallness is due to the radiative character besides the mass suppression of the loop mediators. Furthermore, the PQ symmetry breaking leaves a residual $Z_N$ symmetry that allow us to guarantee the stability of the lightest of the
mediators in the one-loop neutrino mass diagrams (as happens in the scotogenic models), thus leading naturally to multicomponent DM scenarios with axions and WIMPs. We illustrate our proposal by considering a specific model, where simple numerical estimates allow us to show the effectiveness of the scheme regarding neutrino masses, DM and lepton flavor violating processes.
