Discovering neutrino tridents at the Large Hadron Collider

Neutrino trident production of dilepton pairs is well recognized as a sensitive probe of both electroweak physics and physics beyond the Standard Model. Although a rare process, it could be significantly boosted by such new physics, and it also allows the electroweak theory to be tested in a new regime. We demonstrate that the forward neutrino physics program at the Large Hadron Collider offers a promising opportunity to measure for the first time, dimuon neutrino tridents with a statistical significance exceeding 5σ, improving on the previous claims at the ∼3σ level by the CHARM-II and CCFR collaborations while accounting for additional backgrounds later identified by the NuTeV collaboration. We present predictions for various proposed experiments and outline a specific experimental strategy to identify the signal and mitigate backgrounds, based on “reverse tracking” dimuon pairs in the FASERν2 detector. We also discuss prospects for constraining beyond Standard Model contributions to neutrino trident rates at high energies.

Published by the American Physical Society 2024

First Measurement of ν_{e} and ν_{μ} Interaction Cross Sections at the LHC with FASER's Emulsion Detector

The first results of the study of high-energy electron neutrino (ν_{e}) and muon neutrino (ν_{μ}) charged-current interactions in the FASERν emulsion-tungsten detector of the FASER experiment at the LHC are presented. A 128.8 kg subset of the FASERν volume was analyzed after exposure to 9.5  fb^{-1} of sqrt[s]=13.6  TeV pp data. Four (eight) ν_{e} (ν_{μ}) interaction candidate events are observed with a statistical significance of 5.2σ (5.7σ). This is the first direct observation of ν_{e} interactions at a particle collider and includes the highest-energy ν_{e} and ν_{μ} ever detected from an artificial source. The interaction cross section per nucleon σ/E_{ν} is measured over an energy range of 560-1740 GeV (520-1760 GeV) for ν_{e} (ν_{μ}) to be (1.2_{-0.7}^{+0.8})×10^{-38}  cm^{2} GeV^{-1} [(0.5±0.2)×10^{-38}  cm^{2} GeV^{-1}], consistent with standard model predictions. These are the first measurements of neutrino interaction cross sections in those energy ranges.