First Measurement of the ${\nu }_e$ and ${\nu }_{\mu }$ Interaction Cross Sections at the LHC with FASER's Emulsion Detector

Abstract

This paper presents the first results of the study of high-energy electron and muon neutrino charged-current interactions in the FASER$\nu$ emulsion/tungsten detector of the FASER experiment at the LHC. A subset of the FASER$\nu$ volume, which corresponds to a target mass of 128.6~kg, was exposed to neutrinos from the LHC $pp$ collisions with a centre-of-mass energy of 13.6~TeV and an integrated luminosity of 9.5 fb${}^{-1}$. Applying stringent selections requiring electrons with reconstructed energy above 200~GeV, four electron neutrino interaction candidate events are observed with an expected background of $0.025_{-0.010}^{+0.015}$, leading to a statistical significance of 5.2$\sigma$. This is the first direct observation of electron neutrino interactions at a particle collider. Eight muon neutrino interaction candidate events are also detected, with an expected background of $0.22_{-0.07}^{+0.09}$, leading to a statistical significance of 5.7$\sigma$. The signal events include neutrinos with energies in the TeV range, the highest-energy electron and muon neutrinos ever detected from an artificial source. The energy-independent part of the interaction cross section per nucleon is measured over an energy range of 560--1740 GeV (520--1760 GeV) for ${\nu }_e$ (${\nu }_{\mu }$) to be $(1.2_{-0.7}^{+0.8})\times 10^{-38}{\mathrm{cm}}^2{\mathrm{GeV}}^{-1}$ ($(0.5\pm 0.2)\times 10^{-38}{\mathrm{cm}}^2{\mathrm{GeV}}^{-1}$), consistent with Standard Model predictions. These are the first measurements of neutrino interaction cross sections in those energy ranges.

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• The LHC as a TeV Muon Beam Dump: Muonphilic Scalars at FASER
• Constraining neutrinophilic mediators at FASER$\nu$, FLArE and FASER$\nu$2
• Neutrino-Portal Dark Matter Detection Prospects at a Future Muon Collider
• New determination of the neutrino hadronic production cross sections from GeV to beyond PeV energies
• Forward neutrino production and event rates at the Future Circular Collider for hadron collisions
• Measurement of the inelasticity distribution of neutrino-nucleon interactions for $80\mathbf{GeV}<{\mathbf{E}}_{\nu }<560\mathbf{GeV}$ with IceCube DeepCore
• A SHIFT of Perspective: Observing Neutrinos at CMS and ATLAS
• Muon trident process at far-forward LHC detectors