Abstract
We perform a systematic analysis of Standard Model extensions with an additional anomaly-free gauge U(1) symmetry, to generate tree-level Dirac neutrino masses. An anomaly-free symmetry demands nontrivial conditions on the charges of the unavoidable new states. An intensive scan was performed, looking for solutions generating neutrino masses by the type-I and type-II tree-level Dirac seesaw mechanism, via operators with dimension 5 and 6, that correspond to active or dark symmetries. Special attention was paid to the cases featuring no extra massless chiral fermions or multicomponent dark matter with unconditional stability.
Highlights
Despite its enormous success, the standard model (SM) has to be extended in order to account for neutrino masses and dark matter (DM)
We look for anomaly-free solutions to SM extensions with an additional U (1) gauge symmetry, giving rise to tree-level Dirac neutrino masses
Studies on tree-level Dirac neutrino masses have typically focused on finding specific anomaly-free solutions for a given kind of symmetry, either for an active or dark symmetry
Summary
The standard model (SM) has to be extended in order to account for neutrino masses and dark matter (DM). Few studies have performed systematic analysis of SM extensions with an additional anomaly-free gauge U (1) symmetry to generate Dirac neutrino masses [30,31]. We continue the effort of performing a systematic analysis of SM extensions, presenting a complete set of relevant anomaly-free solutions to the general problem of the generation of neutrino masses by the type-I and type-II treelevel Dirac seesaw mechanism, via dimension 5 and 6 operators. We look for anomaly-free solutions to SM extensions with an additional U (1) gauge symmetry, giving rise to tree-level Dirac neutrino masses. 3 we discuss solutions giving rise to neutrino masses, by the type-I and type-II tree-level Dirac seesaw mechanism, via operators with dimensions 5 and 6, corresponding to active or dark symmetries.
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