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

TL;DR

Neutrino trident production is a highly sensitive method for detecting new physics beyond the Standard Model, especially for constraining new gauge bosons like Z' that couple to muon number, with current experiments already limiting many models.

Contribution

This paper demonstrates that neutrino trident production provides the strongest constraints on new neutral currents involving muons, especially for models with a Z' gauge boson, and discusses future experimental prospects.

Findings

Existing experiments constrain Z' models with mass > 400 MeV.

Neutrino trident production constrains L_mu-L_tau gauge interactions.

Future high-intensity neutrino experiments can further probe new physics.

Abstract

The production of a mu+mu- pair from the scattering of a muon-neutrino off the Coulomb field of a nucleus, known as neutrino trident production, is a sub-weak 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_mu-L_tau. The new gauge boson, Z', increases the rate of neutrino trident production by inducing additional $(\bar\mu \gamma_\alpha \mu)(\bar\nu \gamma^\alpha \nu)$ 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_mu, 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.