First Measurement of the $ν_e$ and $ν_μ$ Interaction Cross Sections at the LHC with FASER's Emulsion Detector
Creators: name: FASER Collaboration
name: Abraham, Roshan Mammen
name: Anders, John
name: Antel, Claire
name: Ariga, Akitaka
name: Ariga, Tomoko
name: Atkinson, Jeremy
name: Bernlochner, Florian U.
name: Boeckh, Tobias
name: Boyd, Jamie
name: Brenner, Lydia
name: Burger, Angela
name: Cadoux, Franck
name: Cardella, Roberto
name: Casper, David W.
name: Cavanagh, Charlotte
name: Chen, Xin
name: Coccaro, Andrea
name: Debieux, Stephane
name: D'Onofrio, Monica
name: Desai, Ansh
name: Dmitrievsky, Sergey
name: Eley, Sinead
name: Favre, Yannick
name: Fellers, Deion
name: Feng, Jonathan L.
name: Fenoglio, Carlo Alberto
name: Ferrere, Didier
name: Fieg, Max
name: Filali, Wissal
name: Fujimori, Haruhi
name: Garabaglu, Ali
name: Gibson, Stephen
name: Gonzalez-Sevilla, Sergio
name: Gornushkin, Yuri
name: Gwilliam, Carl
name: Hayakawa, Daiki
name: Hsu, Shih-Chieh
name: Hu, Zhen
name: Iacobucci, Giuseppe
name: Inada, Tomohiro
name: Iodice, Luca
name: Jakobsen, Sune
name: Joos, Hans
name: Kajomovitz, Enrique
name: Kanai, Takumi
name: Kawahara, Hiroaki
name: Keyken, Alex
name: Kling, Felix
name: Kock, Daniela
name: Kontaxakis, Pantelis
name: Kose, Umut
name: Kotitsa, Rafaella
name: Kuehn, Susanne
name: Kugathasan, Thanushan
name: Lefebvre, Helena
name: Levinson, Lorne
name: Li, Ke
name: Liu, Jinfeng
name: Lutz, Margaret S.
name: MacDonald, Jack
name: Magliocca, Chiara
name: Martinelli, Fulvio
name: McCoy, Lawson
name: McFayden, Josh
name: Medina, Andrea Pizarro
name: Milanesio, Matteo
name: Moretti, Theo
name: Munker, Magdalena
name: Nakamura, Mitsuhiro
name: Nakano, Toshiyuki
name: Neuhaus, Friedemann
name: Nevay, Laurie
name: Nonaka, Motoya
name: Okui, Kazuaki
name: Ohashi, Ken
name: Otono, Hidetoshi
name: Pang, Hao
name: Paolozzi, Lorenzo
name: Petersen, Brian
name: Prim, Markus
name: Queitsch-Maitland, Michaela
name: Rokujo, Hiroki
name: Ruiz-Choliz, Elisa
name: Rubbia, André
name: Sabater-Iglesias, Jorge
name: Sato, Osamu
name: Scampoli, Paola
name: Schmieden, Kristof
name: Schott, Matthias
name: Sfyrla, Anna
name: Shamim, Mansoora
name: Shively, Savannah
name: Takubo, Yosuke
name: Tarannum, Noshin
name: Theiner, Ondrej
name: Torrence, Eric
name: Vasina, Svetlana
name: Vormwald, Benedikt
name: Wang, Di
name: Wang, Yuxiao
name: Welch, Eli
name: Zahorec, Samuel
name: Zambito, Stefano
name: Zhang, Shunliang
Publisher: name: arXiv
Year: 2024
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: This paper presents the first results of the study of high-energy electron and muon neutrino charged-current interactions in the FASER$ν$ emulsion/tungsten detector of the FASER experiment at the LHC. A subset of the FASER$ν$ 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 $0.025^{+0.015}_{-0.010}$, leading to a statistical significance of 5.2$σ$. 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 $0.22^{+0.09}_{-0.07}$, leading to a statistical significance of 5.7$σ$. 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 $ν_e$ ($ν_μ$) to be $(1.2_{-0.7}^{+0.8}) \times 10^{-38}~\mathrm{cm}^{2}\,\mathrm{GeV}^{-1}$ ($(0.5\pm0.2) \times 10^{-38}~\mathrm{cm}^{2}\,\mathrm{GeV}^{-1}$), consistent with Standard Model predictions. These are the first measurements of neutrino interaction cross sections in those energy ranges.