NA62 CollaborationGil, E. CortinaKleimenova, AlinaMinucci, E.Padolski, S.Petrov, P.Shaikhiev, A.Volpe, R.Numao, T.Petrov, Y.Velghe, B.Wong, W. S.Bryman, D.Fu, J.Hives, Z.Husek, T.Jerhot, J.Kampf, K.Zamkovsky, M.De Martino, B.Perrin-Terrin, M.Doebrich, B.Lezki, S.Akmete, A. T.Aliberti, R.Khoriauli, G.Kunze, J.Lomidze, D.Peruzzo, L.Vormstein, M.Wanke, R.Dalpiaz, P.Fiorini, M.Mazzolari, A.Neri, I.Norton, A.Petrucci, F.Soldani, M.Wahl, H.Bandiera, L.Ramusino, A. CottaGianoli, A.Romagnoni, M.Sytov, A.Iacopini, E.Latino, G.Lenti, M.Lo Chiatto, P.Panichi, I.Parenti, A.Bizzeti, A.Bucci, F.Antonelli, A.Georgiev, G.Kozhuharov, V.Lanfranchi, G.Martellotti, S.Moulson, M.Spadaro, T.Tinti, G.Ambrosino, F.Capussela, T.Corvino, M.D'Errico, M.Di Filippo, D.Fiorenza, R.Giordano, R.Massarotti, P.Mirra, M.Napolitano, M.Rosa, I.Saracino, G.Anzivino, G.Brizioli, F.Imbergamo, E.Lollini, R.Piandani, R.Santoni, C.Barbanera, M.Cenci, P.Checcucci, B.Lubrano, P.Lupi, M.Pepe, M.Piccini, M.Costantini, F.Di Lella, L.Doble, N.Giorgi, M.Giudici, S.Lamanna, G.Lari, E.Pedreschi, E.Sozzi, M.Cerri, C.Fantechi, R.Pontisso, L.Spinella, F.Mannelli, I.D'Agostini, G.Raggi, M.Biagioni, A.Cretaro, P.Frezza, O.Leonardi, E.Lonardo, A.Turisini, M.Valente, P.Vicini, P.Ammendola, R.Bonaiuto, V.Fucci, A.Salamon, A.Sargeni, F.Arcidiacono, R.Bloch-Devaux, B.Boretto, M.Menichetti, E.Migliore, E.Soldi, D.Biino, C.Filippi, A.Marchetto, F.Briano Olvera, A.Engelfried, J.Estrada-Tristan, N.Reyes Santos, M. A.Rodriguez Rivera, K. A.Boboc, P.Bragadireanu, A. M.Ghinescu, S. A.Hutanu, O. E.Bician, L.Blazek, T.Cerny, V.Kucerova, Z.Bernhard, J.Ceccucci, A.Ceoletta, M.Danielsson, H.De Simone, N.Duval, F.Federici, L.Gamberini, E.Gatignon, L.Guida, R.Hahn, F.Holzer, E. B.Jenninger, B.Koval, M.Laycock, P.Miotto, G. LehmannLichard, P.Mapelli, A.Marchevski, RadoslavMassri, K.Noy, M.Palladino, V.Pinzino, J.Ryjov, V.Schuchmann, S.Venditti, S.Bache, T.Brunetti, M. B.Duk, V.Fascianelli, V.Fry, J. R.Gonnella, F.Goudzovski, E.Henshaw, J.Iacobuzio, L.Kenworthy, C.Lazzeroni, C.Lurkin, N.Newson, F.Parkinson, C.Romano, A.Sanders, J.Sergi, A.Sturgess, A.Swallow, J.Tomczak, A.Heath, H.Page, R.Trilov, S.Angelucci, B.Britton, D.Graham, C.Protopopescu, D.Carmignani, J.Dainton, J. B.Jones, R. W. L.Ruggiero, G.Fulton, L.Hutchcroft, D.Maurice, E.Wrona, B.Conovaloff, A.Cooper, P.Coward, D.Rubin, P.Baeva, A.Baigarashev, D.Emelyanov, D.Enik, T.Falaleev, V.Fedotov, S.Gorshanov, K.Gushchin, E.Kekelidze, V.Kereibay, D.Kholodenko, S.Khotyantsev, A.Korotkova, A.Kudenko, Y.Kurochka, V.Kurshetsov, V.Litov, L.Madigozhin, D.Medvedeva, M.Mefodev, A.Misheva, M.Molokanova, N.Movchan, S.Obraztsov, V.Okhotnikov, A.Ostankov, A.Polenkevich, I.Potrebenikov, Yu.Sadovskiy, A.Semenov, V.Shkarovskiy, S.Sugonyaev, V.Yushchenko, O.Zinchenko, A.2024-04-172024-04-172024-04-172024-02-1310.1016/j.physletb.2024.138513https://infoscience.epfl.ch/handle/20.500.14299/207284WOS:001190818700001A sample of 3984 candidates of the K+ -> pi(+)gamma gamma decay, with an estimated background of 291 +/- 14 events, was collected by the NA62 experiment at CERN during 2017-2018. In order to describe the observed di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be (9.61 +/- 0.17) x 10(-7). The first search for production and prompt decay of an axion-like particle with gluon coupling in the process K+ -> pi(+) a, a -> gamma gamma is also reported.Physical SciencesRadiative Kaon DecaysPi(+/-)Gamma-Gamma DecaySearchtext::journal::journal article::research article