First Direct Observation of Collider Neutrinos with FASER at the LHC

We report the first direct observation of neutrino interactions at a particle collider experiment. Neutrino candidate events are identified in a 13.6 TeV center-of-mass energy pp collision dataset of 35.4 fb-1 using the active electronic components of the FASER detector at the Large Hadron Collider. The candidates are required to have a track propagating through the entire length of the FASER detector and be consistent with a muon neutrino charged-current interaction. We infer 153 thorn 12-13 neutrino interactions with a significance of 16 standard deviations above the background-only hypothesis. These events are consistent with the characteristics expected from neutrino interactions in terms of secondary particle production and spatial distribution, and they imply the observation of both neutrinos and anti-neutrinos with an incident neutrino energy of significantly above 200 GeV.

Automated summary

This study reports the first direct observation of neutrino interactions at a particle collider experiment. Using the active electronic components of the FASER detector at the Large Hadron Collider, neutrino candidate events were identified in a 13.6 TeV center-of-mass energy pp collision dataset of 35.4 fb-1. The observed events are consistent with the expected characteristics of neutrino interactions in terms of secondary particle production and spatial distribution, indicating the observation of neutrinos and anti-neutrinos with an incident neutrino energy significantly above 200 GeV.