Dark matter stability and Dirac neutrinos using only standard model symmetries

We provide a generic framework to obtain stable dark matter along with naturally small Dirac neutrino masses generated at the loop level. This is achieved through the spontaneous breaking of the global U(1)_B-L symmetry already present in the standard model. The U(1)_B-L symmetry is broken down to a residual even Zₙ (n≥4) subgroup. The residual Zₙ symmetry simultaneously guarantees dark matter stability and protects the Dirac nature of neutrinos. The U(1)_B-L symmetry in our setup is anomaly free and can also be gauged in a straightforward way. Finally, we present an explicit example using our framework to show the idea in action.