Search for $K^+$ decays into the $\pi^+e^+e^-e^+e^-$ final state
Creators: name: Cortina Gil, Eduardo
name: Minucci, Elisa
name: Padolski, Sergey
name: Petrov, Plamen
name: Velghe, Bob
name: Bryman, Douglas
name: Fu, Ji
name: Numao, Toshio
name: Petrov, Yevgeniy
name: Wong, Vincent Wai Sum
name: Husek, Tomas
name: Kampf, Karol
name: Zamkovsky, Michal
name: Jerhot, Jan
name: Aliberti, Riccardo
name: Khoriauli, Gia
name: Kunze, Jonas
name: Lomidze, David
name: Marchevski, Radoslav
name: Peruzzo, Letizia
name: Vormstein, Mario
name: Wanke, Rainer
name: Cotta Ramusino, Angelo
name: Dalpiaz, Pietro
name: Fiorini, Massimiliano
name: Gamberini, Enrico
name: Gianoli, Alberto
name: Neri, Ilaria
name: Norton, Alan
name: Petrucci, Ferruccio
name: Wahl, Heinrich
name: Bizzeti, Andrea
name: Bucci, Francesca
name: Iacopini, Enrico
name: Latino, Giuseppe
name: Lenti, Massimo
name: Parenti, Andrea
name: Volpe, Roberta
name: Antonelli, Antonella
name: Gonnella, Francesco
name: Lamanna, Gianluca
name: Lanfranchi, Gaia
name: Tinti, Gemma
name: Martellotti, Silvia
name: Moulson, Matthew
name: Kozhuharov, Venelin
name: Litov, Leandar
name: Georgiev, Georgi
name: Raggi, Mauro
name: Spadaro, Tommaso
name: Ambrosino, Fabio
name: Fiorenza, Renato
name: Capussela, Tiziana
name: Corvino, Michele
name: Di Filippo, Domenico
name: Massarotti, Paolo
name: Mirra, Marco
name: Napolitano, Marco
name: Saracino, Giulio
name: Anzivino, Giuseppina
name: Imbergamo, Ermanno
name: Lollini, Riccardo
name: Santoni, Cristiano
name: Brizioli, Francesco
name: Barbanera, Mattia
name: Cenci, Patrizia
name: Checcucci, Bruno
name: Duk, Viacheslav
name: Lupi, Matteo
name: Pepe, Monica
name: Piccini, Mauro
name: Lubrano, Pasquale
name: Costantini, Flavio
name: Doble, Niels
name: Giorgi, Marcello
name: Giudici, Sergio
name: Lari, Enrico
name: Pinzino, Jacopo
name: Pontisso, Luca
name: Sozzi, Marco
name: Di Lella, Luigi
name: Mannelli, Italo
name: Cerri, Claudio
name: Fantechi, Riccardo
name: Pedreschi, Elena
name: Piandani, Roberto
name: Spinella, Franco
name: Biagioni, Andrea
name: D'Agostini, Giulio
name: Leonardi, Emanuele
name: Lonardo, Alessandro
name: Valente, Paolo
name: Vicini, Piero
name: Cretaro, Paolo
name: Turisini, Matteo
name: Frezza, Ottorino
name: Ammendola, Roberto
name: Bonaiuto, Vincenzo
name: De Simone, Nicola
name: Federici, Luca
name: Fucci, Adolfo
name: Salamon, Andrea
name: Sargeni, Fausto
name: Arcidiacono, Roberta
name: Biino, Cristina
name: Bloch-Devaux, Brigitte
name: Boretto, Marco
name: Filippi, Alessandra
name: Iacobuzio, Lorenza
name: Marchetto, Flavio
name: Menichetti, Ezio
name: Migliore, Ernesto
name: Soldi, Dario
name: Engelfried, Jürgen
name: Estrada-Tristan, Nora
name: Bragadireanu, Alexandru Mario
name: Ghinescu, Stefan Alexandru
name: Hutanu, Ovidiu Emanuel
name: Enik, Temur
name: Falaleev, Valeri
name: Kekelidze, Vladimir
name: Korotkova, Anna
name: Madigozhin, Dmitry
name: Misheva, Milena
name: Molokanova, Natalia
name: Movchan, Sergei
name: Polenkevich, Irina
name: Potrebenikov, Yuri
name: Shkarovskiy, Sergey
name: Zinchenko, Andrey
name: Baeva, Aigul
name: Baigarashev, Dosbol
name: Emelyanov, Dmitry
name: Fedotov, Sergei
name: Khotyantsev, Alexey
name: Gushchin, Evgeny
name: Kleimenova, Alina
name: Kudenko, Yury
name: Kurochka, Viktoriia
name: Medvedeva, Mariia
name: Mefodev, Aleksandr
name: Shaikhiev, Artur
name: Kholodenko, Sergey
name: Kurshetsov, Viktor
name: Obraztsov, Vladimir
name: Ostankov, Aleksandr
name: Semenov, Vitali
name: Sugonyaev, Valentin
name: Yushchenko, Oleg
name: Bician, Lubos
name: Blazek, Tomas
name: Cerny, Vladimir
name: Koval, Michal
name: Kucerova, Zuzana
name: Ceccucci, Augusto
name: Bernhard, Johannes
name: Danielsson, Hans
name: Döbrich, Babette
name: Duval, Francois
name: Gatignon, Lau
name: Guida, Roberto
name: Hahn, Ferdinand
name: Holzer, Eva Barbara
name: Jenninger, Berthold
name: Laycock, Paul
name: Lehmann Miotto, Giovanna
name: Lichard, Peter
name: Mapelli, Alessandro
name: Noy, Matthew
name: Palladino, Vito
name: Perrin-Terrin, Mathieu
name: Ruggiero, Giuseppe
name: Ryjov, Vladimir
name: Schuchmann, Simone
name: Venditti, Stefano
name: Brunetti, Maria Brigida
name: Bache, Thomas
name: Goudzovski, Evgueni
name: Henshaw, Jack
name: Tomczak, Adam
name: Lazzeroni, Cristina
name: Fascianelli, Valeria
name: Lurkin, Nicolas
name: Newson, Francis
name: Parkinson, Christopher
name: Romano, Angela
name: Sergi, Antonino
name: Sturgess, Andrew
name: Swallow, Joel
name: Heath, Helen
name: Page, Ryan
name: Trilov, Stoyan
name: Angelucci, Bruno
name: Britton, David
name: Protopopescu, Dan
name: Graham, Connor
name: Jones, Roger William Lewis
name: Dainton, John Bourke
name: Fry, John Richard
name: Fulton, Liam
name: Hutchcroft, David
name: Carmignani, Joseph
name: Massri, Karim
name: Maurice, Emilie
name: Wrona, Bozydar
name: Conovaloff, Adam
name: Cooper, Peter
name: Coward, David
name: Rubin, Philip David
name: Hives, Zdenko
name: Akmete, Atakan Tugberk
name: Soldani, Mattia
name: Bandiera, Laura
name: Mazzolari, Andrea
name: Romagnoni, Marco
name: Sytov, Alexei
name: Panichi, Ilaria
name: Lo Chiatto, Prisco
name: D'Errico, Mariaelena
name: Giordano, Raffaele
name: Briano Olvera, Alejandro
name: Reyes Santos, Marco Antonio
name: Boboc, Petre
name: Kereibay, Dias
name: Gorshanov, Konstantin
name: Okhotnikov, Artem
name: Sadovskiy, Alexander
name: Sanders, Jack
name: Kenworthy, Chandler
name: De Martino, Bianca
name: Rosa, Ilaria
name: Ceoletta, Marco
name: NA62 Collaboration
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2023
Subjects: subject: 530
subject: K+: secondary beam
subject: K+: semileptonic decay
subject: K+: rare decay
subject: quantum chromodynamics: axion
subject: K+: branching ratio
subject: branching ratio: upper limit
subject: new particle
subject: neutral particle: pair production
subject: CERN Lab
subject: mediation
subject: NA62
subject: CERN SPS
subject: anomaly
subject: photon: hidden sector
subject: experimental results
subject: K+ --&gt; pi+ 2electron 2positron

description: The first search for ultra-rare $K^+$ decays into the $\pi^+e^+e^-e^+e^-$ final state is reported, using a dataset collected by the NA62 experiment at CERN in 2017-2018. An upper limit of $1.4\times 10^{-8}$ at 90% CL is obtained for the branching ratio of the $K^+\to\pi^+e^+e^-e^+e^-$ decay, predicted in the Standard Model to be $(7.2\pm0.7)\times 10^{-11}$. Upper limits at 90% CL are obtained at the level of $10^{-9}$ for the branching ratios of two prompt decay chains involving pair-production of hidden-sector mediators: $K^+\to\pi^+aa$, $a\to e^+e^-$ and $K^+\to\pi^+S$, $S\to A^\prime A^\prime$, $A^\prime\to e^+e^-$. The QCD axion is excluded as a possible explanation of the '17 MeV anomaly'.