Scotogenic $U(1{)}_{\chi }$ Dirac Neutrinos

The standard model of quarks and leptons is extended to include the gauge symmetry $U(1{)}_{\chi }$ which comes from $SO(10)\to SU(5)\times U(1{)}_{\chi }$. The radiative generation of Dirac neutrino masses through dark matter is discussed in two examples. One allows for light Dirac fermion dark matter. The other allows for self-interacting scalar dark matter with a light scalar mediator which decays only to two neutrinos.