Observation of high-energy electron neutrino interactions with FASER's emulsion detector at the LHC

This note presents the first results from the search for high energy electron and muon neutrino charged-current interactions in the FASER$\nu$ emulsion/tungsten sub-detector of FASER. A subset of the FASER$\nu$ volume is used, corresponding to a target mass of 68~kg, exposed to 9.5~$fb^{-1}$ of LHC proton-proton collision data with a centre of mass energy of 13.6~TeV. Following stringent selections requiring a lepton (electron or muon) with reconstructed energy above 200~GeV, three electron neutrino interactions are observed with an expected background of 0.002 $\pm$ 0.003, leading to a statistical significance of the neutrino signal of 5 standard deviations. This is the first direct observation of electron neutrino interactions at a particle collider, and the signal events include neutrinos with $\sim$ TeV energies, the highest energy electron neutrinos detected from an artificial source. Four muon neutrino interactions are also found, with an expected background of 0.5 $\pm$ 0.3, leading to a statistical significance of the muon neutrino signal of 2.5 standard deviations.