CERN Accelerating science

Preprint
Report number	arXiv:2412.12015 ; CERN-EP-2024-343
Title	Observation of the $K^+ \to \pi^+ \nu \bar\nu$ decay and measurement of its branching ratio
Author(s)	Cortina Gil, Eduardo (Louvain U., CP3) ; Jerhot, Jan (Louvain U., CP3 ; Munich, Max Planck Inst.) ; Lurkin, Nicolas (Louvain U., CP3) ; Bryman, Douglas (British Columbia U. ; TRIUMF) ; Numao, Toshio (TRIUMF) ; Velghe, Bob (TRIUMF) ; Wong, Vincent Wai Sum (TRIUMF) ; Hives, Zdenko (Charles U.) ; Husek, Tomas (Charles U. ; Birmingham U.) ; Kampf, Karol (Charles U.) ; Kolesar, Marian (Charles U.) ; Koval, Michal (Charles U.) ; De Martino, Bianca (Marseille, CPPM) ; Perrin-Terrin, Mathieu (Marseille, CPPM) ; Petit, Lucie (Marseille, CPPM) ; Döbrich, Babette (Munich, Max Planck Inst.) ; Lezki, Samet (Munich, Max Planck Inst.) ; Schubert, Jonathan (Munich, Max Planck Inst. ; Tech. U., Munich (main)) ; Akmete, Atakan Tugberk (Mainz U., Inst. Phys.) ; Aliberti, Riccardo (Mainz U., Inst. Phys. ; Helmholtz Inst., Mainz) ; Ceoletta, Marco (Mainz U., Inst. Phys. ; CERN) ; Doble, Niels (Mainz U., Inst. Phys.) ; Di Lella, Luigi (Mainz U., Inst. Phys.) ; Peruzzo, Letizia (Mainz U., Inst. Phys.) ; Polivka, Celia (Mainz U., Inst. Phys.) ; Schuchmann, Simone (Mainz U., Inst. Phys.) ; Wahl, Heinrich (Mainz U., Inst. Phys.) ; Wanke, Rainer (Mainz U., Inst. Phys.) ; Dalpiaz, Pietro (Ferrara U.) ; Negrello, Riccardo (Ferrara U.) ; Neri, Ilaria (Ferrara U.) ; Petrucci, Ferruccio (Ferrara U.) ; Soldani, Mattia (Ferrara U.) ; Bandiera, Laura (INFN, Ferrara) ; Canale, Nicola (INFN, Ferrara) ; Cotta Ramusino, Angelo (INFN, Ferrara) ; Gianoli, Alberto (INFN, Ferrara) ; Romagnoni, Marco (INFN, Ferrara) ; Sytov, Alexei (INFN, Ferrara) ; Bizzeti, Andrea (INFN, Florence ; Modena U.) ; Bucci, Francesca (INFN, Florence) ; Lenti, Massimo (Florence U.) ; Panichi, Ilaria (Florence U.) ; Lo Chiatto, Prisco (Florence U.) ; Ruggiero, Giuseppe (Florence U.) ; Antonelli, Antonella (Frascati) ; Lanfranchi, Gaia (Frascati) ; Tinti, Gemma (Frascati) ; Martellotti, Silvia (Frascati) ; Moulson, Matthew (Frascati) ; Kozhuharov, Venelin (Frascati ; Sofiya U.) ; Spadaro, Tommaso (Frascati) ; Ambrosino, Fabio (Naples U.) ; Fiorenza, Renato (Naples U. ; SSM, Naples) ; D'Errico, Mariaelena (Naples U.) ; Giordano, Raffaele (Naples U.) ; Massarotti, Paolo (Naples U.) ; Mirra, Marco (Naples U.) ; Napolitano, Marco (Naples U.) ; Saracino, Giulio (Naples U.) ; Anzivino, Giuseppina (Perugia U.) ; Lollini, Riccardo (INFN, Perugia) ; Brizioli, Francesco (CERN ; INFN, Perugia) ; Cenci, Patrizia (INFN, Perugia) ; Duk, Viacheslav (INFN, Perugia) ; Pepe, Monica (INFN, Perugia) ; Piccini, Mauro (INFN, Perugia) ; Lubrano, Pasquale (INFN, Perugia) ; Costantini, Flavio (Pisa U.) ; Giorgi, Marcello (Pisa U.) ; Giudici, Sergio (Pisa U.) ; Lari, Enrico (Pisa U.) ; Pinzino, Jacopo (Pisa U.) ; Lamanna, Gianluca (Pisa U.) ; Pedreschi, Elena (Pisa U.) ; Sozzi, Marco (Pisa U.) ; Mannelli, Italo (Pisa, Scuola Normale Superiore) ; Fantechi, Riccardo (INFN, Pisa) ; Spinella, Franco (INFN, Pisa) ; Raggi, Mauro (Rome U.) ; Biagioni, Andrea (INFN, Rome) ; Lonardo, Alessandro (INFN, Rome) ; Vicini, Piero (INFN, Rome) ; Cretaro, Paolo (INFN, Rome) ; Turisini, Matteo (INFN, Rome) ; Frezza, Ottorino (INFN, Rome) ; Ammendola, Roberto (Rome U., Tor Vergata) ; Bonaiuto, Vincenzo (Rome U., Tor Vergata) ; Fucci, Adolfo (Rome U., Tor Vergata) ; Salamon, Andrea (Rome U., Tor Vergata) ; Sargeni, Fausto (Rome U., Tor Vergata) ; Arcidiacono, Roberta (Turin U. ; Piemonte Orientale U., Novara) ; Bloch-Devaux, Brigitte (Turin U. ; Louvain U., CP3 ; Birmingham U.) ; Menichetti, Ezio (Turin U.) ; Migliore, Ernesto (Turin U.) ; Biino, Cristina (INFN, Turin) ; Filippi, Alessandra (INFN, Turin) ; Marchetto, Flavio (INFN, Turin) ; Soldi, Dario (INFN, Turin) ; Engelfried, Jürgen (San Luis Potosi U.) ; Briano Olvera, Alejandro (San Luis Potosi U.) ; Estrada-Tristan, Nora (San Luis Potosi U. ; Guanajuato U.) ; Reyes Santos, Marco Antonio (San Luis Potosi U. ; Guanajuato U.) ; Piandani, Roberto (San Luis Potosi U.) ; Rodriguez Rivera, Kevin Alexander (San Luis Potosi U.) ; Boboc, Petre (Bucharest, IFIN-HH) ; Bragadireanu, Alexandru Mario (Bucharest, IFIN-HH) ; Ghinescu, Stefan Alexandru (Bucharest, IFIN-HH) ; Hutanu, Ovidiu Emanuel (Bucharest, IFIN-HH) ; Enik, Temur ; Falaleev, Valeri (INFN, Perugia) ; Kekelidze, Vladimir ; Korotkova, Anna ; Madigozhin, Dmitry ; Misheva, Milena (Sofiya, Inst. Nucl. Res.) ; Molokanova, Natalia ; Kereibay, Dias ; Polenkevich, Irina ; Potrebenikov, Yuri ; Shkarovskiy, Sergey ; Baeva, Aigul ; Baigarashev, Dosbol (Eurasian Nat. U., Astana) ; Emelyanov, Dmitry ; Litov, Leandar (Sofiya U.) ; Fedotov, Sergei ; Khotyantsev, Alexey ; Gorshanov, Konstantin ; Gushchin, Evgeny ; Kudenko, Yury ; Kurochka, Viktoriia ; Mefodev, Aleksandr ; Kholodenko, Sergey (INFN, Pisa) ; Kurshetsov, Viktor ; Obraztsov, Vladimir ; Okhotnikov, Artem ; Sadovskiy, Alexander ; Sugonyaev, Valentin ; Yushchenko, Oleg ; Blazek, Tomas (Comenius U.) ; Cerny, Vladimir (Comenius U.) ; Kucerova, Zuzana (CERN) ; Volpe, Roberta (Comenius U. ; INFN, Perugia) ; Ceccucci, Augusto (CERN) ; Bernhard, Johannes (CERN) ; Bician, Lubos (CERN ; Charles U.) ; Boretto, Marco (CERN) ; Corvino, Michele (CERN) ; Danielsson, Hans (CERN) ; Mukhamejanov, Yerzhan (Inst. Nucl. Phys., Almaty) ; Mukhamejanova, Assel (Inst. Nucl. Phys., Almaty) ; Saduyev, Nurzhan (Inst. Nucl. Phys., Almaty) ; Sakhiyev, Sayabek (Inst. Nucl. Phys., Almaty) ; Zamkovsky, Michal (CERN) ; Duval, Francois (CERN) ; Federici, Luca (CERN) ; Gamberini, Enrico (CERN) ; Guida, Roberto (CERN) ; Holzer, Eva Barbara (CERN) ; Jenninger, Berthold (CERN) ; Lehmann Miotto, Giovanna (CERN) ; Lichard, Peter (CERN) ; Massri, Karim (CERN ; Lancaster U.) ; Minucci, Elisa (CERN ; Syracuse U.) ; Noy, Matthew (CERN) ; Ryjov, Vladimir (CERN) ; Swallow, Joel (CERN ; Frascati) ; Chang, Xiafei (EPFL) ; Marchevski, Radoslav (EPFL) ; Kleimenova, Alina (EPFL) ; Goudzovski, Evgueni (Birmingham U.) ; Henshaw, Jack (Birmingham U.) ; Tomczak, Adam (Birmingham U.) ; Lazzeroni, Cristina (Birmingham U.) ; Fry, John Richard (Birmingham U.) ; Gonnella, Francesco (Birmingham U.) ; Parkinson, Christopher (Birmingham U.) ; Romano, Angela (Birmingham U.) ; Sanders, Jack (Birmingham U.) ; Sam, Ceyhan (Birmingham U.) ; Kenworthy, Chandler (Birmingham U.) ; Sergi, Antonino (Birmingham U. ; Genoa U.) ; Shaikhiev, Artur (Birmingham U. ; Lancaster U.) ; Heath, Helen (Bristol U.) ; Britton, David (Glasgow U.) ; Norton, Alan (Glasgow U.) ; Protopopescu, Dan (Glasgow U.) ; Gatignon, Lau (Lancaster U.) ; Jones, Roger William Lewis (Lancaster U.) ; Dainton, John Bourke (Lancaster U.) ; Cooper, Peter (George Mason U.) ; Coward, David (George Mason U. ; SLAC) ; Rubin, Philip David (George Mason U.) ; Rosa, Ilaria (Naples U.) ; Bautin, Vitalii ; Salamatin, Kirill ; Velas, Tomas (Comenius U.) ; Francesconi, Marco (Naples U.)
Corporate author(s)	The NA62 collaboration
Publication	2024
Imprint	13 Dec 2024
Number of pages	29
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN SPS ; NA62
Keywords	electroweak interaction ; flavor physics ; branching fraction ; rare decay ; experimental results ; very rare kaon decay ; New Physics sensitivity
Abstract	A measurement of the $K^+ \to \pi^+ \nu \bar\nu$ decay by the NA62 experiment at the CERN SPS is presented, using data collected in 2021 and 2022. This dataset was recorded, after modifications to the beamline and detectors, at a higher instantaneous beam intensity with respect to the 2016–2018 data taking. Combining NA62 data collected in 2016–2022, a measurement of B($K^+ \to \pi^+ \nu \bar\nu$) = $(13.0^{+3.3}_{-3.0}) \times 10^{−11} $ is reported. With 51 signal candidates observed and an expected background of $18^{+3}_{−2}$ events, B($K^+ \to \pi^+ \nu \bar\nu$) becomes the smallest branching ratio measured with a signal significance above 5 $\sigma$.
Other source	Inspire
Copyright/License	Preprint: © 2024 CERN (License: CC-BY-4.0)
Submitted by	[email protected]