Neutrino tridents at the LHC

The production of dilepton pairs in neutrino trident scattering off a nucleus N, ν N→ν' l ^- l' ⁺ N, is well recognized as a sensitive probe of both electroweak physics and physics beyond the Standard Model. This rare process could be significantly boosted by new physics effects, and allows testing the electroweak theory in a new regime. The forward neutrino physics program at the Large Hadron Collider offers a promising opportunity to measure dimuon neutrino tridents with a statistical significance exceeding 5 sigma for the first time, improving on previous claims at the 3 sigma level by the CHARM-II and CCFR collaborations while accounting for additional backgrounds identified in a later analysis by the NuTeV collaboration. Predictions for various proposed experiments are presented, along with an outline for an experimental strategy for identifying the signal and mitigating backgrounds, based on “reverse tracking” dimuon pairs in the FASERν2 detector. We show that even a O(10 ton) detector yields tens of di-muon trident events, while the relevant backgrounds can be made negligible, and suffices for constraining beyond the Standard Model contributions to neutrino trident rates at high energies.