Radiative Dirac neutrino mass, neutrinoless quadruple beta decay, and dark matter in B-L extension of the standard model

We propose that neutrino Dirac masses can be generated through a scotogenic scenario while violating the lepton number by four units by extending the standard model to have an anomaly free U(1)B-L, which is spontaneously broken to a residual Z4 symmetry. Z4 symmetry ensures the Dirac nature of neutrinos and simultaneously stabilizes dark matter. Although neutrinoless double beta decay is exactly absent, this model predicts a nonzero neutrinoless quadruple beta decay (0ν4β). It is shown that the 0ν4β can be enhanced thanks to the introduction of a new scalar field without affecting tiny neutrino masses and the relic density of dark matter. We perform numerical analysis for a 0ν4β, dark matter, and direct detection by imposing cosmological, collider, and theoretical constraints.