The first FASER search for a light, long-lived particle decaying into a pair of photons is reported. The search uses LHC proton-proton collision data at s = 13.6 TeV collected in 2022 and 2023, corresponding to an integrated luminosity of 57.7 fb−1. A model with axion-like particles (ALPs) dominantly coupled to weak gauge bosons is the primary target. Signal events are characterised by high-energy deposits in the electromagnetic calorimeter and no signal in the veto scintillators. One event is observed, compared to a background expectation of 0.44 ± 0.39 events, which is entirely dominated by neutrino interactions. World-leading constraints on ALPs are obtained for masses up to 300 MeV and couplings to the Standard Model W gauge boson, gaWW, around 10−4 GeV−1, testing a previously unexplored region of parameter space. Other new particle models that lead to the same experimental signature, including ALPs coupled to gluons or photons, U(1)B gauge bosons, up-philic scalars, and a Type-I two-Higgs doublet model, are also considered for interpretation, and new constraints on previously viable parameter space are presented in this paper.
Shining light on the dark sector: search for axion-like particles and other new physics in photonic final states with FASER / Null, Null; Abraham, Roshan Mammen; Ai, Xiaocong; Anders, John; Antel, Claire; Ariga, Akitaka; Ariga, Tomoko; Atkinson, Jeremy; Bernlochner, Florian U.; Bianchi, Emma; Boeckh, Tobias; Boyd, Jamie; Brenner, Lydia; Burger, Angela; Cadoux, Franck; Cardella, Roberto; Casper, David W.; Cavanagh, Charlotte; Chen, Xin; Cho, Eunhyung; Chouhan, Dhruv; Coccaro, Andrea; Débieux, Stephane; D'Onofrio, Monica; Desai, Ansh; Dmitrievsky, Sergey; Dobre, Radu; Eley, Sinead; Favre, Yannick; Fellers, Deion; Feng, Jonathan L.; Fenoglio, Carlo Alberto; Ferrere, Didier; Fieg, Max; Filali, Wissal; Firu, Elena; Galantay, Edward; Garabaglu, Ali; Gibson, Stephen; Gonzalez-Sevilla, Sergio; Gornushkin, Yuri; Gwilliam, Carl; Hayakawa, Daiki; Holzbock, Michael; Hsu, Shih-Chieh; Hu, Zhen; Iacobucci, Giuseppe; Inada, Tomohiro; Iodice, Luca; Jakobsen, Sune; Joos, Hans; Kajomovitz, Enrique; Kawahara, Hiroaki; Keyken, Alex; Kling, Felix; Köck, Daniela; Kontaxakis, Pantelis; Kose, Umut; Kotitsa, Rafaella; Kuehn, Susanne; Kugathasan, Thanushan; Levinson, Lorne; Li, Ke; Liu, Jinfeng; Liu, Yi; Lutz, Margaret S.; Macdonald, Jack; Magliocca, Chiara; Mäkelä, Toni; Mccoy, Lawson; Mcfayden, Josh; Medina, Andrea Pizarro; Milanesio, Matteo; Moretti, Théo; Nakamura, Mitsuhiro; Nakano, Toshiyuki; Nevay, Laurie; Ohashi, Ken; Otono, Hidetoshi; Paolozzi, Lorenzo; Petersen, Brian; Preda, Titi; Prim, Markus; Queitsch-Maitland, Michaela; Rokujo, Hiroki; Rubbia, André; Sabater-Iglesias, Jorge; Sato, Osamu; Scampoli, Paola; Schmieden, Kristof; Schott, Matthias; Sfyrla, Anna; Sgalaberna, Davide; Shamim, Mansoora; Shively, Savannah; Takubo, Yosuke; Tarannum, Noshin; Theiner, Ondrej; Torrence, Eric; Valdes Martinez, Oscar Ivan; Vasina, Svetlana; Vormwald, Benedikt; Wang, Di; Wang, Yuxiao; Welch, Eli; Xu, Yue; Zahorec, Samuel; Zambito, Stefano; Zhang, Shunliang. - In: JOURNAL OF HIGH ENERGY PHYSICS. - ISSN 1029-8479. - 2025:1(2025). [10.1007/jhep01(2025)199]
Shining light on the dark sector: search for axion-like particles and other new physics in photonic final states with FASER
Scampoli, PaolaPrimo
;
2025
Abstract
The first FASER search for a light, long-lived particle decaying into a pair of photons is reported. The search uses LHC proton-proton collision data at s = 13.6 TeV collected in 2022 and 2023, corresponding to an integrated luminosity of 57.7 fb−1. A model with axion-like particles (ALPs) dominantly coupled to weak gauge bosons is the primary target. Signal events are characterised by high-energy deposits in the electromagnetic calorimeter and no signal in the veto scintillators. One event is observed, compared to a background expectation of 0.44 ± 0.39 events, which is entirely dominated by neutrino interactions. World-leading constraints on ALPs are obtained for masses up to 300 MeV and couplings to the Standard Model W gauge boson, gaWW, around 10−4 GeV−1, testing a previously unexplored region of parameter space. Other new particle models that lead to the same experimental signature, including ALPs coupled to gluons or photons, U(1)B gauge bosons, up-philic scalars, and a Type-I two-Higgs doublet model, are also considered for interpretation, and new constraints on previously viable parameter space are presented in this paper.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
