Neutrinophilic nonstandard interactions

We construct UV-complete models for nonstandard neutrino interactions mediated by a sub-GeV gauge boson Z' coupled to baryon number B or B - L. A flavor-dependent Z' coupling to neutrinos is induced by mixing a U(1)'-charged Dirac fermion with the active neutrinos, naturally suppressing flavor violation or nonuniversality of the charged leptons to the loop level. We show that these models can give rise to large flavor-conserving as well as flavor-violating nonstandard neutral-current neutrino interactions potentially observable in current or future oscillation experiments such as DUNE without being in conflict with other constraints such as neutrino scattering or lepton-flavor-violating decays. In particular, the LMA-Dark solution to the solar-neutrino anomaly can be obtained for U(1)(B), but not for Ud(1)(B-L).