Study of the K-+/- -> pi(+/-)gamma gamma decay by the NA62 experiment

Lazzeroni, C; 1 Romano A,; 1 Ceccucci A,; 2 Danielsson H,; 2 Falaleev V,; 2 Gatignon L,; 2 Lopez SG,; 2 Hallgren B,; 2 Maier A,; 2 Peters A,; 2 Piccini Mauro 2 Riedler P,; 2 Frabetti PL,; 3 Gersabeck E,; 3 Kekelidze V,; 3 Madigozhin D,; 3 Misheva M,; 3 Molokanova N,; 3 Movchan S,; 3 Potrebenikov Y,; 3 Shkarovskiy S,; 3 Zinchenko A,; 3 Rubin P,; 4 Baldini Wander 5, 6 CottaRamusino A; 5,; 6 Dalpiaz Pietro 5,; 6 Fiorini Massimiliano 5,; 6 Gianoli Alberto 5,; 6 Norton Alan Robert 5,; 6 Petrucci Ferruccio 5,; 6 Savrie' Mauro 5,; 6 Wahl Heinrich 5,; 6 Bizzeti Andrea 7,; 30 Bucci Francesca, 7; 31 Iacopini Enrico,; Massimo, Lenti; Veltri, Michele; 8 Moulson Matthew David 8 Raggi Mauro 8 Spadaro Tommaso 8 Eppard K, Antonelli Antonella; 9 Hita Hochgesand M,; 9 Kleinknecht K,; 9 Renk B,; 9 Wanke R,; 9 Winhart A,; 9 Winston R,; 10 Bolotov, V; 11 Duk, V; 11 Gushchin, E; 11 Ambrosino Fabio 12,; 13 Di Filippo Domenico 12,; 13 Massarotti Paolo 12,; 13 Napolitano Marco 12,; 13 Palladino Vittorio 12,; 13 Saracino Giulio 12,; 13 Anzivino Giuseppina 14,; 15 Imbergamo Ermanno 14,; 15 Piandani Roberto 14,; 15 Sergi Antonino 14,; 15 Cenci Patrizia 15 Pepe Monica 15 Costantini Flavio 16,; 17 Doble, N; 16,; 17 Giudici Sergio 16,; 17 Pierazzini Giuseppe 16,; 17 Sozzi Marco 16,; 17 Venditti Stefano 16,; 17 Balev Spasimir 17,; 18 Collazuol Gianmaria 17,; 18 DiLella, L; 17,; 18 Gallorini Stefano 17,; 18 Goudzovski, E; 17,; 18 Lamanna Gianluca 17,; 18 Mannelli Italo 17,; 18 Ruggiero Giuseppe 17,; 18 Cerri Claudio 17 Fantechi Riccardo 17 Kholodenko, S; 19 Kurshetsov, V; 19 Obraztsov, V; 19 Semenov, V; 19 Yushchenko, O; 19 D'Agostini Giulio 20, 21 Leonardi Emanuele 21 Serra Marco 21 Valente Paolo 21 Fucci Adolfo 22 Salamon Andrea 22 Bloch Devaux B; 23 Peyaud, B; 23 Engelfried, J; 24 Coward, D; 25 Kozhuharov Venelin 26 Litov, L; 26 Arcidiacono Roberta 27,; 28 Bifani Simone 27,; 28 Biino Cristina 28 Dellacasa Giulio 28 Marchetto Flavio Pietro 28 Numao, T; 29 Retiere, F; 29,

doi:10.1016/j.physletb.2014.03.016

A study of the dynamics of the rare decay K-+/- -> pi(+/-)gamma gamma has been performed on a sample of 232 decay candidates, with an estimated background of 17.4 +/- 1.1 events, collected by the NA62 experiment at CERN in 2007. The results are combined with those from a measurement conducted by the NA48/2 Collaboration at CERN. The combined model-independent branching ratio in the kinematic range z = (m gamma gamma/m(K))(2) > 0.2 is B-MI(z > 0.2) = (0.965 +/- 0.063) x 10(-6), and the combined branching ratio in the full kinematic range assuming a Chiral Perturbation Theory description is B(K-pi gamma gamma) = (1.003 +/- 0.056) x 10(-6). A detailed comparison of the results with the previous measurements is performed. (C) 2014 The Authors. Published by Elsevier B.V.