Search for heavy neutral leptons in π+ decays to positrons

Bloch-Devaux, B; Cortina Gil, E; Lurkin, N; Minucci, E; Padolski, S; Petrov, P; Numao, T; Petrov, Y; Shang, V; Velghe, B; Wong, Vws; Bryman, D; Fu, J; Bician, L; Hives, Z; Husek, T; Kampf, K; Kolesar, M; Koval, M; De Martino, B; Perrin-Terrin, M; Petit, L; Dobrich, B; Jerhot, J; Lezki, S; Schubert, J; Akmete, At; Aliberti, R; Ceoletta, M; Di Lella, L; Doble, N; Khoriauli, G; Kunze, J; Lomidze, D; Peruzzo, L; Polivka, C; Schuchmann, S; Vormstein, M; Wahl, H; Wanke, R; Bandiera, L; Canale, N; Gianoli, A; Romagnoni, M; Dalpiaz, P; Fiorini, M; Negrello, R; Neri, I; Petrucci, F; Bizzeti, A; Bucci, F; Iacopini, E; Latino, G; Lenti, M; Lo Chiatto, P; Panichi, I; Parenti, A; Ruggiero, G; Antonelli, A; Georgiev, G; Kozhuharov, V; Lanfranchi, G; Martellotti, S; Moulson, M; Plini, L; Soldani, M; Spadaro, T; Swallow, J; Tinti, G; Ambrosino, F; Capussela, T; Corvino, M; D'Errico, M; Di Filippo, D; Fiorenza, R; Francesconi, M; Giordano, R; Massarotti, P; Mirra, M; Napolitano, M; Rosa, I; Saracino, G; Barbanera, M; Cenci, P; Checcucci, B; Duk, V; Falaleev, V; Lubrano, P; Lupi, M; Pepe, M; Piccini, M; Anzivino, G; Imbergamo, E; Lollini, R; Santoni, C; Cerri, C; Fantechi, R; Kholodenko, S; Spinella, F; Costantini, F; Giorgi, M; Giudici, S; Lamanna, G; Lari, E; Pedreschi, E; Pinzino, J; Sozzi, M; Mannelli, I; Biagioni, A; Cretaro, P; Frezza, O; Leonardi, E; Lonardo, A; Pontisso, L; Turisini, M; Valente, P; Vicini, P; D'Agostini, G; Raggi, M; Ammendola, R; Bonaiuto, V; Fucci, A; Salamon, A; Sargeni, F; Biino, C; Filippi, A; Marchetto, F; Arcidiacono, R; Menichetti, E; Migliore, E; Soldi, D; Mukhamejanov, Y; Mukhamejanova, A; Saduyev, N; Sakhiyev, S; Briano Olvera, A; Engelfried, J; Estrada-Tristan, N; Piandani, R; Reyes Santos, Ma; Rodriguez Rivera, Ka; Boboc, P; Bragadireanu, Am; Ghinescu, Sa; Hutanu, Oe; Blazek, T; Cerny, V; Velas, T; Volpe, R; Bernhard, J; Boretto, M; Brizioli, F; Ceccucci, A; Danielsson, H; De Simone, N; Duval, F; Federici, L; Gamberini, E; Guida, R; Hahn, F; Holzer, Eb; Jenninger, B; Kucerova, Z; Laycock, P; Lehmann Miotto, G; Lichard, P; Mapelli, A; Noy, M; Palladino, V; Ryjov, V; Venditti, S; Zamkovsky, M; Chang, X; Kleimenova, A; Marchevski, R; Bache, T; Brunetti, Mb; Fascianelli, V; Fry, Jr; Gonnella, F; Goudzovski, E; Henshaw, J; Iacobuzio, L; Kenworthy, C; Lazzeroni, C; Newson, F; Parkinson, C; Romano, A; Sam, C; Sanders, J; Sergi, A; Sturgess, A; Tomczak, A; Heath, H; Page, R; Trilov, S; Angelucci, B; Britton, D; Graham, C; Norton, A; Protopopescu, D; Carmignani, J; Dainton, Jb; Gatignon, L; Jones, Rwl; Massri, K; Shaikhiev, A; Fulton, L; Hutchcroft, D; Maurice, E; Wrona, B; Conovaloff, A; Cooper, P; Coward, D; Rubin, P; Baeva, A; Baigarashev, D; Bautin, V; Emelyanov, D; Enik, T; Gorshanov, K; Kekelidze, V; Kereibay, D; Korotkova, A; Litov, L; Madigozhin, D; Misheva, M; Molokanova, N; Movchan, S; Okhotnikov, A; Polenkevich, I; Potrebenikov, Y; Sadovskiy, A; Salamatin, K; Shkarovskiy, S; Zinchenko, A; Fedotov, S; Gushchin, E; Khotyantsev, A; Kudenko, Y; Kurochka, V; Kurshetsov, V; Medvedeva, M; Mefodev, A; Obraztsov, V; Ostankov, A; Semenov, V; Sugonyaev, V; Yushchenko, O

doi:10.1016/j.physletb.2025.140119

A search for heavy neutral lepton (N) production in π+→e+N in-flight decays using data collected by the NA62 experiment at CERN in 2017–2024 is reported. Upper limits for the extended neutrino mixing matrix element |Ue4|2 are established at the level of 10−8 for heavy neutral leptons with mass in the range 95–126 MeV/c2 and lifetime exceeding 50 ns.

Bloch-Devaux, B., Cortina Gil, E., Lurkin, N., Minucci, E., Padolski, S., Petrov, P., et al. (2026). Search for heavy neutral leptons in π+ decays to positrons. PHYSICS LETTERS. SECTION B, 872 [10.1016/j.physletb.2025.140119].