Neutrino Trident Production: A Powerful Probe of New Physics with Neutrino Beams

The production of a μ⁺μ^- pair from the scattering of a muon neutrino off the Coulomb field of a nucleus, known as neutrino trident production, is a subweak process that has been observed in only a couple of experiments. As such, we show that it constitutes an exquisitely sensitive probe in the search for new neutral currents among leptons, putting the strongest constraints on well-motivated and well-hidden extensions of the standard model gauge group, including the one coupled to the difference of the lepton number between the muon and tau flavor, L_μ-L_τ. The new gauge boson Z^', increases the rate of neutrino trident production by inducing additional (μγ_αμ)(νγ^αν) interactions, which interfere constructively with the standard model contribution. Existing experimental results put significant restrictions on the parameter space of any model coupled to muon number L_μ, and disfavor a putative resolution to the muon g-2 discrepancy via the loop of Z^' for any mass m_Z^'400 MeV. The reach to the models' parameter space can be widened with future searches of the trident production at high-intensity neutrino facilities such as the LBNE.