Shining light on the dark sector: search for axion-like particles and other new physics in photonic final states with FASER
Creators: name: Mammen Abraham, Roshan
name: Ai, Xiaocong
name: Anders, John
name: Antel, Claire
name: Ariga, Akitaka
name: Ariga, Tomoko
name: Atkinson, Jeremy
name: Bernlochner, Florian U.
name: Bianchi, Emma
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: Cho, Eunhyung
name: Chouhan, Dhruv
name: Coccaro, Andrea
name: Débieux, Stephane
name: D'Onofrio, Monica
name: Desai, Ansh
name: Dmitrievsky, Sergey
name: Dobre, Radu
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: Firu, Elena
name: Galantay, Edward
name: Garabaglu, Ali
name: Gibson, Stephen
name: Gonzalez-Sevilla, Sergio
name: Gornushkin, Yuri
name: Gwilliam, Carl
name: Hayakawa, Daiki
name: Holzbock, Michael
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: Kawahara, Hiroaki
name: Keyken, Alex
name: Kling, Felix
name: Köck, Daniela
name: Kontaxakis, Pantelis
name: Kose, Umut
name: Kotitsa, Rafaella
name: Kuehn, Susanne
name: Kugathasan, Thanushan
name: Levinson, Lorne
name: Li, Ke
name: Liu, Jinfeng
name: Liu, Yi
name: Lutz, Margaret S.
name: MacDonald, Jack
name: Magliocca, Chiara
name: Mäkelä, Toni
name: McCoy, Lawson
name: McFayden, Josh
name: Medina, Andrea Pizarro
name: Milanesio, Matteo
name: Moretti, Théo
name: Nakamura, Mitsuhiro
name: Nakano, Toshiyuki
name: Nevay, Laurie
name: Ohashi, Ken
name: Otono, Hidetoshi
name: Paolozzi, Lorenzo
name: Petersen, Brian
name: Preda, Titi
name: Prim, Markus
name: Queitsch-Maitland, Michaela
name: Rokujo, Hiroki
name: Rubbia, André
name: Sabater-Iglesias, Jorge
name: Sato, Osamu
name: Scampoli, Paola
name: Schmieden, Kristof
name: Schott, Matthias
name: Sfyrla, Anna
name: Sgalaberna, Davide
name: Shamim, Mansoora
name: Shively, Savannah
name: Takubo, Yosuke
name: Tarannum, Noshin
name: Theiner, Ondrej
name: Torrence, Eric
name: Martinez, Oscar Ivan Valdes
name: Vasina, Svetlana
name: Vormwald, Benedikt
name: Wang, Di
name: Wang, Yuxiao
name: Welch, Eli
name: Xu, Yue
name: Zahorec, Samuel
name: Zambito, Stefano
name: Zhang, Shunliang
name: FASER Collaboration
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2024
Subjects: subject: 530
subject: Beyond Standard Model
subject: Dark Matter
subject: Forward Physics
subject: Hadron-Hadron Scattering

description: 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 $ \sqrt{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, g$_{aWW}$, 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.[graphic not available: see fulltext]