arXiv · 2507.23552
Latest neutrino results from the FASER experiment and their implications for forward hadron production
Abstract
The muon puzzle -- an excess of muons relative to simulation predictions in ultra-high-energy cosmic-ray air showers -- has been reported by many experiments. This suggests that forward particle production in hadronic interactions is not fully understood. Some of the scenarios proposed to resolve this predict reduced production of forward neutral pions and enhanced production of forward kaons (or other particles). The FASER experiment at the LHC is located 480 m downstream of the ATLAS interaction point and is sensitive to neutrinos and muons, which are the decay products of forward charged pions and kaons. In this study, the latest measurements of electron and muon neutrino fluxes are presented using the data corresponding to 9.5 $\mathrm{fb^{-1}}$ and 65.6 $\mathrm{fb^{-1}}$ of proton-proton collisions with $\sqrt{s}=13.6~\mathrm{TeV}$ by the FASER$\nu$ and the FASER electronic detector, respectively. These fluxes are compared with predictions from recent hadronic interaction models, including EPOS-LHCr, SIBYLL 2.3e, and QGSJET 3. The predictions are generally consistent with the measured fluxes from FASER, although some discrepancies appear in certain energy bins. More precise flux measurements with additional data will follow soon, enabling validation of pion, kaon, and charm meson production with finer energy binning, reduced uncertainties, and multi-differential analyses.
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FASER Collaboration, Roshan Mammen Abraham, Xiaocong Ai, Saul Alonso Monsalve, John Anders, Claire Antel, Akitaka Ariga, Tomoko Ariga, Jeremy Atkinson, Florian U. Bernlochner, Tobias Boeckh, Jamie Boyd, Lydia Brenner, Angela Burger, Franck Cadoux, Roberto Cardella, David W. Casper, Charlotte Cavanagh, Xin Chen, Dhruv Chouhan, Andrea Coccaro, Stephane Débieux, Ansh Desai, Sergey Dmitrievsky, Radu Dobre, Monica D'Onofrio, Sinead Eley, Yannick Favre, Jonathan L. Feng, Carlo Alberto Fenoglio, Didier Ferrere, Max Fieg, Wissal Filali, Elena Firu, Haruhi Fujimori, Edward Galantay, Ali Garabaglu, Stephen Gibson, Sergio Gonzalez-Sevilla, Yuri Gornushkin, Yotam Granov, Carl Gwilliam, Daiki Hayakawa, Michael Holzbock, Shih-Chieh Hsu, Zhen Hu, Giuseppe Iacobucci, Tomohiro Inada, Luca Iodice, Sune Jakobsen, Hans Joos, Enrique Kajomovitz, Hiroaki Kawahara, Alex Keyken, Felix Kling, Daniela Köck, Pantelis Kontaxakis, Umut Kose, Rafaella Kotitsa, Peter Krack, Susanne Kuehn, Thanushan Kugathasan, Sebastian Laudage, Lorne Levinson, Botao Li, Jinfeng Liu, Yi Liu, Margaret S. Lutz, Jack MacDonald, Chiara Magliocca, Toni Mäkelä, Lawson McCoy, Josh McFayden, Andrea Pizarro Medina, Matteo Milanesio, Théo Moretti, Keiko Moriyama, Mitsuhiro Nakamura, Toshiyuki Nakano, Laurie Nevay, Ken Ohashi, Hidetoshi Otono, Lorenzo Paolozzi, Pawan Pawan, Brian Petersen, Titi Preda, Markus Prim, Michaela Queitsch-Maitland, Juan Rojo, Hiroki Rokujo, André Rubbia, Jorge Sabater-Iglesias, Osamu Sato, Paola Scampoli, Kristof Schmieden, Matthias Schott, Christiano Sebastiani, Anna Sfyrla, Davide Sgalaberna, Mansoora Shamim. 2025-07-31. Latest neutrino results from the FASER experiment and their implications for forward hadron production. https://arxiv.org/abs/2507.23552
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