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3. Search for $K^+$ decays into the $\pi^+e^+e^-e^+e^-$ final state

Author

Cortina Gil, Eduardo, Minucci, Elisa, Padolski, Sergey, Petrov, Plamen, Velghe, Bob, Bryman, Douglas, Fu, Ji, Numao, Toshio, Petrov, Yevgeniy, Wong, Vincent Wai Sum, Husek, Tomas, Kampf, Karol, Zamkovsky, Michal, Jerhot, Jan, Aliberti, Riccardo, Khoriauli, Gia, Kunze, Jonas, Lomidze, David, Marchevski, Radoslav, Peruzzo, Letizia, Vormstein, Mario, Wanke, Rainer, Cotta Ramusino, Angelo, Dalpiaz, Pietro, Fiorini, Massimiliano, Gamberini, Enrico, Gianoli, Alberto, Neri, Ilaria, Norton, Alan, Petrucci, Ferruccio, Wahl, Heinrich, Bizzeti, Andrea, Bucci, Francesca, Iacopini, Enrico, Latino, Giuseppe, Lenti, Massimo, Parenti, Andrea, Volpe, Roberta, Antonelli, Antonella, Gonnella, Francesco, Lamanna, Gianluca, Lanfranchi, Gaia, Tinti, Gemma, Martellotti, Silvia, Moulson, Matthew, Kozhuharov, Venelin, Litov, Leandar, Georgiev, Georgi, Raggi, Mauro, Spadaro, Tommaso, Ambrosino, Fabio, Fiorenza, Renato, Capussela, Tiziana, Corvino, Michele, Di Filippo, Domenico, Massarotti, Paolo, Mirra, Marco, Napolitano, Marco, Saracino, Giulio, Anzivino, Giuseppina, Imbergamo, Ermanno, Lollini, Riccardo, Santoni, Cristiano, Brizioli, Francesco, Barbanera, Mattia, Cenci, Patrizia, Checcucci, Bruno, Duk, Viacheslav, Lupi, Matteo, Pepe, Monica, Piccini, Mauro, Lubrano, Pasquale, Costantini, Flavio, Doble, Niels, Giorgi, Marcello, Giudici, Sergio, Lari, Enrico, Pinzino, Jacopo, Pontisso, Luca, Sozzi, Marco, Di Lella, Luigi, Mannelli, Italo, Cerri, Claudio, Fantechi, Riccardo, Pedreschi, Elena, Piandani, Roberto, Spinella, Franco, Biagioni, Andrea, d'Agostini, Giulio, Leonardi, Emanuele, Lonardo, Alessandro, Valente, Paolo, Vicini, Piero, Cretaro, Paolo, Turisini, Matteo, Frezza, Ottorino, Ammendola, Roberto, Bonaiuto, Vincenzo, de Simone, Nicola, Federici, Luca, Fucci, Adolfo, Salamon, Andrea, Sargeni, Fausto, Arcidiacono, Roberta, Biino, Cristina, Bloch-Devaux, Brigitte, Boretto, Marco, Filippi, Alessandra, Iacobuzio, Lorenza, Marchetto, Flavio, Menichetti, Ezio, Migliore, Ernesto, Soldi, Dario, Engelfried, Jürgen, Estrada-Tristan, Nora, Bragadireanu, Alexandru Mario, Ghinescu, Stefan Alexandru, Hutanu, Ovidiu Emanuel, Enik, Temur, Falaleev, Valeri, Kekelidze, Vladimir, Korotkova, Anna, Madigozhin, Dmitry, Misheva, Milena, Molokanova, Natalia, Movchan, Sergei, Polenkevich, Irina, Potrebenikov, Yuri, Shkarovskiy, Sergey, Zinchenko, Andrey, Baeva, Aigul, Baigarashev, Dosbol, Emelyanov, Dmitry, Fedotov, Sergei, Khotyantsev, Alexey, Gushchin, Evgeny, Kleimenova, Alina, Kudenko, Yury, Kurochka, Viktoriia, Medvedeva, Mariia, Mefodev, Aleksandr, Shaikhiev, Artur, Kholodenko, Sergey, Kurshetsov, Viktor, Obraztsov, Vladimir, Ostankov, Aleksandr, Semenov, Vitali, Sugonyaev, Valentin, Yushchenko, Oleg, Bician, Lubos, Blazek, Tomas, Cerny, Vladimir, Koval, Michal, Kucerova, Zuzana, Ceccucci, Augusto, Bernhard, Johannes, Danielsson, Hans, Döbrich, Babette, Duval, Francois, Gatignon, Lau, Guida, Roberto, Hahn, Ferdinand, Holzer, Eva Barbara, Jenninger, Berthold, Laycock, Paul, Lehmann Miotto, Giovanna, Lichard, Peter, Mapelli, Alessandro, Noy, Matthew, Palladino, Vito, Perrin-Terrin, Mathieu, Ruggiero, Giuseppe, Ryjov, Vladimir, Schuchmann, Simone, Venditti, Stefano, Brunetti, Maria Brigida, Bache, Thomas, Goudzovski, Evgueni, Henshaw, Jack, Tomczak, Adam, Lazzeroni, Cristina, Fascianelli, Valeria, Lurkin, Nicolas, Newson, Francis, Parkinson, Christopher, Romano, Angela, Sergi, Antonino, Sturgess, Andrew, Swallow, Joel, Heath, Helen, Page, Ryan, Trilov, Stoyan, Angelucci, Bruno, Britton, David, Protopopescu, Dan, Graham, Connor, Jones, Roger William Lewis, Dainton, John Bourke, Fry, John Richard, Fulton, Liam, Hutchcroft, David, Carmignani, Joseph, Massri, Karim, Maurice, Emilie, Wrona, Bozydar, Conovaloff, Adam, Cooper, Peter, Coward, David, Rubin, Philip David, Hives, Zdenko, Akmete, Atakan Tugberk, Soldani, Mattia, Bandiera, Laura, Mazzolari, Andrea, Romagnoni, Marco, Sytov, Alexei, Panichi, Ilaria, Lo Chiatto, Prisco, d'Errico, Mariaelena, Giordano, Raffaele, Briano Olvera, Alejandro, Reyes Santos, Marco Antonio, Boboc, Petre, Kereibay, Dias, Gorshanov, Konstantin, Okhotnikov, Artem, Sadovskiy, Alexander, Sanders, Jack, Kenworthy, Chandler, de Martino, Bianca, Rosa, Ilaria, Ceoletta, Marco, Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and NA62

Subjects
pair production, CERN Lab, quantum chromodynamics, axion, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], anomaly, mediation, branching ratio, hidden sector, NA62, Particle Physics - Experiment, High Energy Physics - Experiment
Abstract

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"., Comment: Version to be submitted to Physics Letters B

Published
2023

4. A study of the $K^+ \to \pi^0 e^+ \nu \gamma$ decay

Author

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

Subjects
Particle Physics - Experiment, High Energy Physics - Experiment
Abstract

A sample of $1.3 \times 10^5 K^+ \to \pi^0 e^+ \nu \gamma$ candidates with less than 1% background was collected by the NA62 experiment at the CERN SPS in 2017-2018. Branching fraction measurements are obtained at percent relative precision in three restricted kinematic regions, improving on existing results by a factor larger than two. An asymmetry, possibly related to T-violation, is investigated with no evidence observed within the achieved precision. A sample of $1.3 \times 10^5$$K^+ \to \pi^0 e^+ \nu \gamma$ candidates with less than 1% background was collected by the NA62 experiment at the CERN SPS in 2017-2018. Branching fraction measurements are obtained at percent relative precision in three restricted kinematic regions, improving on existing results by a factor larger than two. An asymmetry, possibly related to T-violation, is investigated with no evidence observed within the achieved precision.

Published
2023

5. Improved calorimetric particle identification in NA62 using machine learning techniques

Author

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

Subjects
High Energy Physics - Experiment (hep-ex), Physics - Instrumentation and Detectors, FOS: Physical sciences, Instrumentation and Detectors (physics.ins-det), Particle Physics - Experiment, High Energy Physics - Experiment
Abstract

Measurement of the ultra-rare $K^+\to\pi^+\nu\bar\nu$ decay at the NA62 experiment at CERN requires high-performance particle identification to distinguish muons from pions. Calorimetric identification currently in use, based on a boosted decision tree algorithm, achieves a muon misidentification probability of $1.2\times 10^{-5}$ for a pion identification efficiency of 75% in the momentum range of 15-40 GeV/$c$. In this work, calorimetric identification performance is improved by developing an algorithm based on a convolutional neural network classifier augmented by a filter. Muon misidentification probability is reduced by a factor of six with respect to the current value for a fixed pion-identification efficiency of 75%. Alternatively, pion identification efficiency is improved from 72% to 91% for a fixed muon misidentification probability of $10^{-5}$., Comment: Updated author list and Ref. 4

Published
2023
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6. A search for the $K^+ \to \mu^- \nu e^+ e^+$ decay

Author

Cortina Gil, Eduardo, Minucci, Elisa, Padolski, Sergey, Petrov, Plamen, Velghe, Bob, Bryman, Douglas, Fu, Ji, Numao, Toshio, Petrov, Yevgeniy, Wong, Vincent Wai Sum, Husek, Tomas, Kampf, Karol, Zamkovsky, Michal, Jerhot, Jan, Aliberti, Riccardo, Khoriauli, Gia, Kunze, Jonas, Lomidze, David, Marchevski, Radoslav, Peruzzo, Letizia, Vormstein, Mario, Wanke, Rainer, Cotta Ramusino, Angelo, Dalpiaz, Pietro, Fiorini, Massimiliano, Gamberini, Enrico, Gianoli, Alberto, Neri, Ilaria, Norton, Alan, Petrucci, Ferruccio, Wahl, Heinrich, Bizzeti, Andrea, Bucci, Francesca, Iacopini, Enrico, Latino, Giuseppe, Lenti, Massimo, Parenti, Andrea, Volpe, Roberta, Antonelli, Antonella, Gonnella, Francesco, Lamanna, Gianluca, Lanfranchi, Gaia, Tinti, Gemma, Martellotti, Silvia, Moulson, Matthew, Kozhuharov, Venelin, Litov, Leandar, Georgiev, Georgi, Raggi, Mauro, Spadaro, Tommaso, Ambrosino, Fabio, Fiorenza, Renato, Capussela, Tiziana, Corvino, Michele, Di Filippo, Domenico, Massarotti, Paolo, Mirra, Marco, Napolitano, Marco, Saracino, Giulio, Anzivino, Giuseppina, Imbergamo, Ermanno, Lollini, Riccardo, Santoni, Cristiano, Brizioli, Francesco, Barbanera, Mattia, Cenci, Patrizia, Checcucci, Bruno, Duk, Viacheslav, Lupi, Matteo, Pepe, Monica, Piccini, Mauro, Lubrano, Pasquale, Costantini, Flavio, Doble, Niels, Giorgi, Marcello, Giudici, Sergio, Lari, Enrico, Pinzino, Jacopo, Pontisso, Luca, Sozzi, Marco, Di Lella, Luigi, Mannelli, Italo, Cerri, Claudio, Fantechi, Riccardo, Pedreschi, Elena, Piandani, Roberto, Spinella, Franco, Biagioni, Andrea, d'Agostini, Giulio, Leonardi, Emanuele, Lonardo, Alessandro, Valente, Paolo, Vicini, Piero, Cretaro, Paolo, Turisini, Matteo, Frezza, Ottorino, Ammendola, Roberto, Bonaiuto, Vincenzo, de Simone, Nicola, Federici, Luca, Fucci, Adolfo, Salamon, Andrea, Sargeni, Fausto, Arcidiacono, Roberta, Biino, Cristina, Bloch-Devaux, Brigitte, Boretto, Marco, Filippi, Alessandra, Iacobuzio, Lorenza, Marchetto, Flavio, Menichetti, Ezio, Migliore, Ernesto, Soldi, Dario, Engelfried, Jürgen, Estrada-Tristan, Nora, Bragadireanu, Alexandru Mario, Ghinescu, Stefan Alexandru, Hutanu, Ovidiu Emanuel, Enik, Temur, Falaleev, Valeri, Kekelidze, Vladimir, Korotkova, Anna, Madigozhin, Dmitry, Misheva, Milena, Molokanova, Natalia, Movchan, Sergei, Polenkevich, Irina, Potrebenikov, Yuri, Shkarovskiy, Sergey, Zinchenko, Alexander, Baeva, Aigul, Baigarashev, Dosbol, Emelyanov, Dmitry, Fedotov, Sergei, Khotyantsev, Alexey, Gushchin, Evgeny, Kleimenova, Alina, Kudenko, Yury, Kurochka, Viktoriia, Medvedeva, Mariia, Mefodev, Aleksandr, Shaikhiev, Artur, Kholodenko, Sergey, Kurshetsov, Viktor, Obraztsov, Vladimir, Ostankov, Aleksandr, Semenov, Vitali, Sugonyaev, Valentin, Yushchenko, Oleg, Bician, Lubos, Blazek, Tomas, Cerny, Vladimir, Koval, Michal, Kucerova, Zuzana, Ceccucci, Augusto, Bernhard, Johannes, Danielsson, Hans, Döbrich, Babette, Duval, Francois, Gatignon, Lau, Guida, Roberto, Hahn, Ferdinand, Holzer, Eva Barbara, Jenninger, Berthold, Laycock, Paul, Lehmann Miotto, Giovanna, Lichard, Peter, Mapelli, Alessandro, Noy, Matthew, Palladino, Vito, Perrin-Terrin, Mathieu, Ruggiero, Giuseppe, Ryjov, Vladimir, Schuchmann, Simone, Venditti, Stefano, Brunetti, Maria Brigida, Bache, Thomas, Goudzovski, Evgueni, Henshaw, Jack, Tomczak, Adam, Lazzeroni, Cristina, Fascianelli, Valeria, Lurkin, Nicolas, Newson, Francis, Parkinson, Christopher, Romano, Angela, Sergi, Antonino, Sturgess, Andrew, Swallow, Joel, Heath, Helen, Page, Ryan, Trilov, Stoyan, Angelucci, Bruno, Britton, David, Protopopescu, Dan, Graham, Connor, Jones, Roger William Lewis, Dainton, John Bourke, Fry, John Richard, Fulton, Liam, Hutchcroft, David, Carmignani, Joseph, Massri, Karim, Maurice, Emilie, Wrona, Bozydar, Conovaloff, Adam, Cooper, Peter, Coward, David, Rubin, Philip David, Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and NA62

Subjects
flavor, CERN Lab, lepton, conservation law, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], lepton number, branching ratio, NA62, Particle Physics - Experiment, High Energy Physics - Experiment
Abstract

A search for the $K^+\to\mu^-\nu e^+e^+$ decay, forbidden within the Standard Model by either lepton number or lepton flavour conservation depending on the flavour of the emitted neutrino, has been performed using the dataset collected by the NA62 experiment at CERN in 2016--2018. An upper limit of $8.1\times 10^{-11}$ is obtained for the decay branching fraction at 90% CL, improving by a factor of 250 over the previous search., Comment: Final version, accepted for publication in Physics Letters B

Published
2022

7. A measurement of the $K^+ \to \pi^+ \mu^+ \mu^-$ decay

Author

Cortina Gil, Eduardo, Minucci, Elisa, Padolski, Sergey, Petrov, Plamen, Velghe, Bob, Bryman, Douglas, Fu, J., Numao, Toshio, Petrov, Yevgeniy, Wong, Vincent Wai Sum, Husek, Tomas, Kampf, Karol, Zamkovsky, Michal, Jerhot, Jan, Aliberti, Riccardo, Khoriauli, Gia, Kunze, Jonas, Lomidze, David, Potrebenikov, Yu., Marchevski, Radoslav, Peruzzo, Letizia, Vormstein, Mario, Wanke, Rainer, Cotta Ramusino, Angelo, Dalpiaz, Pietro, Fiorini, Massimiliano, Gamberini, Enrico, Gianoli, Alberto, Neri, Ilaria, Norton, Alan, Petrucci, Ferruccio, Wahl, Heinrich, Bizzeti, Andrea, Bucci, Francesca, Iacopini, Enrico, Latino, Giuseppe, Lenti, Massimo, Parenti, Andrea, Volpe, Roberta, Antonelli, Antonella, Gonnella, Francesco, Lamanna, Gianluca, Lanfranchi, Gaia, Tinti, Gemma, Martellotti, Silvia, Moulson, Matthew, Kozhuharov, Venelin, Litov, Leandar, Georgiev, Georgi, Raggi, Mauro, Spadaro, Tommaso, Ambrosino, Fabio, Fiorenza, Renato, Capussela, Tiziana, Corvino, Michele, Di Filippo, Domenico, Massarotti, Paolo, Mirra, Marco, Napolitano, Marco, Saracino, Giulio, Anzivino, Giuseppina, Imbergamo, Ermanno, Lollini, Riccardo, Santoni, Cristiano, Brizioli, Francesco, Barbanera, Mattia, Cenci, Patrizia, Checcucci, Bruno, Duk, Viacheslav, Lupi, Matteo, Pepe, Monica, Piccini, Mauro, Lubrano, Pasquale, Costantini, Flavio, Doble, Niels, Giorgi, Marcello, Giudici, Sergio, Lari, Enrico, Pinzino, Jacopo, Pontisso, Luca, Sozzi, Marco, Di Lella, Luigi, Mannelli, Italo, Cerri, Claudio, Fantechi, Riccardo, Pedreschi, Elena, Piandani, Roberto, Spinella, Franco, Biagioni, Andrea, d'Agostini, Giulio, Leonardi, Emanuele, Lonardo, Alessandro, Valente, Paolo, Vicini, Piero, Cretaro, Paolo, Turisini, Matteo, Frezza, Ottorino, Ammendola, Roberto, Bonaiuto, Vincenzo, de Simone, Nicola, Federici, Luca, Fucci, Adolfo, Salamon, Andrea, Sargeni, Fausto, Arcidiacono, Roberta, Biino, Cristina, Bloch-Devaux, Brigitte, Boretto, Marco, Filippi, Alessandra, Iacobuzio, Lorenza, Marchetto, Flavio, Menichetti, Ezio, Migliore, Ernesto, Soldi, Dario, Engelfried, Jürgen, Estrada-Tristan, Nora, Bragadireanu, Alexandru Mario, Ghinescu, Stefan Alexandru, Hutanu, Ovidiu Emanuel, Enik, Temur, Falaleev, Valeri, Kekelidze, Vladimir, Korotkova, Anna, Madigozhin, Dmitry, Misheva, Milena, Molokanova, Natalia, Movchan, Sergei, Polenkevich, Irina, Potrebenikov, Yuri, Shkarovskiy, Sergey, Zinchenko, Alexander, Baeva, Aigul, Baigarashev, Dosbol, Emelyanov, Dmitry, Fedotov, Sergei, Khotyantsev, Alexey, Gushchin, Evgeny, Kleimenova, Alina, Kudenko, Yury, Kurochka, Viktoriia, Medvedeva, Mariia, Mefodev, Aleksandr, Shaikhiev, Artur, Kholodenko, Sergey, Kurshetsov, Viktor, Obraztsov, Vladimir, Ostankov, Aleksandr, Semenov, Vitali, Sugonyaev, Valentin, Yushchenko, Oleg, Bician, Lubos, Blazek, Tomas, Cerny, Vladimir, Koval, Michal, Kucerova, Zuzana, Ceccucci, Augusto, Bernhard, Johannes, Danielsson, Hans, Döbrich, Babette, Duval, Francois, Gatignon, Lau, Guida, Roberto, Hahn, Ferdinand, Holzer, Eva Barbara, Jenninger, Berthold, Laycock, Paul, Lehmann Miotto, Giovanna, Lichard, Peter, Mapelli, Alessandro, Noy, Matthew, Palladino, Vito, Perrin-Terrin, Mathieu, Ruggiero, Giuseppe, Ryjov, Vladimir, Schuchmann, Simone, Venditti, Stefano, Brunetti, Maria Brigida, Bache, Thomas, Goudzovski, Evgueni, Henshaw, Jack, Tomczak, Adam, Lazzeroni, Cristina, Fascianelli, Valeria, Lurkin, Nicolas, Newson, Francis, Parkinson, Christopher, Romano, Angela, Sergi, Antonino, Sturgess, Andrew, Swallow, Joel, Heath, Helen, Page, Ryan, Trilov, Stoyan, Angelucci, Bruno, Britton, David, Protopopescu, Dan, Graham, Connor, Jones, Roger William Lewis, Dainton, John Bourke, Fry, John Richard, Fulton, Liam, Hutchcroft, David, Carmignani, Joseph, Massri, Karim, Maurice, Emilie, Wrona, Bozydar, Conovaloff, Adam, Cooper, Peter, Coward, David, Rubin, Philip David, Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and NA62

Subjects
Fixed Target Experiments, data analysis method, background, Flavour Changing Neutral Currents, perturbation theory: chiral, dimuon: mass spectrum, CERN SPS, pi+, mass dependence, NA62, High Energy Physics - Experiment, muon: pair production, K+: semileptonic decay, +pi%2B+muon%2B+muon%22">K+ --> pi+ muon+ muon, branching ratio: measured, Rare Decay, K+: branching ratio, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], decay: form factor, Branching fraction, K+: secondary beam, Particle Physics - Experiment, K: form factor, experimental results
Abstract

A sample of $2.8 \times 10^4$ $K^{+} \to \pi^{+} \mu^{+} \mu^{-}$ candidates with negligible background was collected by the NA62 experiment at the CERN SPS in 2017--2018. The model-independent branching fraction is measured to be $(9.15 \pm 0.08)\times 10^{-8}$, a factor three more precise than previous measurements. The decay form factor is presented as a function of the squared dimuon mass. A measurement of the form factor parameters and their uncertainties is performed using a description based on Chiral Perturbation Theory at $\mathcal{O}(p^6)$., Comment: 17 pages, 5 figures. Updated version (6 October 2022) accepted for publication in JHEP

Published
2022

11. Search for lepton number and flavour violation in $K^+ $ and $\pi^0$ decays

Author

Cortina Gil, Eduardo, Minucci, Elisa, Padolski, Sergey, Petrov, Plamen, Potrebenikov, Yu., Velghe, Bob, Bryman, Douglas, Fu, Ji, Numao, Toshio, Petrov, Yevgeniy, Husek, Tomas, Kampf, Karol, Zamkovsky, Michal, Jerhot, Jan, Aliberti, Riccardo, Khoriauli, Gia, Kunze, Jonas, Lomidze, David, Marchevski, Radoslav, Peruzzo, Letizia, Vormstein, Mario, Wanke, Rainer, Cotta Ramusino, Angelo, Dalpiaz, Pietro, Fiorini, Massimiliano, Gamberini, Enrico, Gianoli, Alberto, Neri, Ilaria, Norton, Alan, Petrucci, Ferruccio, Wahl, Heinrich, Bizzeti, Andrea, Bucci, Francesca, Iacopini, Enrico, Latino, Giuseppe, Lenti, Massimo, Parenti, Andrea, Volpe, Roberta, Antonelli, Antonella, Gonnella, Francesco, Lamanna, Gianluca, Lanfranchi, Gaia, Martellotti, Silvia, Moulson, Matthew, Kozhuharov, Venelin, Litov, Leandar, Georgiev, Georgi, Raggi, Mauro, Spadaro, Tommaso, Ambrosino, Fabio, Capussela, Tiziana, Corvino, Michele, Di Filippo, Domenico, Massarotti, Paolo, Mirra, Marco, Napolitano, Marco, Saracino, Giulio, Anzivino, Giuseppina, Imbergamo, Ermanno, Lollini, Riccardo, Santoni, Cristiano, Brizioli, Francesco, Barbanera, Mattia, Cenci, Patrizia, Checcucci, Bruno, Duk, Viacheslav, Lupi, Matteo, Pepe, Monica, Piccini, Mauro, Lubrano, Pasquale, Costantini, Flavio, Doble, Niels, Giorgi, Marcello, Giudici, Sergio, Lari, Enrico, Pinzino, Jacopo, Pontisso, Luca, Sozzi, Marco, Di Lella, Luigi, Mannelli, Italo, Cerri, Claudio, Fantechi, Riccardo, Pedreschi, Elena, Piandani, Roberto, Spinella, Franco, Biagioni, Andrea, D'Agostini, Giulio, Leonardi, Emanuele, Lonardo, Alessandro, Valente, Paolo, Vicini, Piero, Ammendola, Roberto, Bonaiuto, Vincenzo, De Simone, Nicola, Federici, Luca, Fucci, Adolfo, Salamon, Andrea, Sargeni, Fausto, Arcidiacono, Roberta, Biino, Cristina, Bloch-Devaux, Brigitte, Boretto, Marco, Filippi, Alessandra, Iacobuzio, Lorenza, Marchetto, Flavio, Menichetti, Ezio, Migliore, Ernesto, Soldi, Dario, Engelfried, Jürgen, Estrada-Tristan, Nora, Bragadireanu, Alexandru Mario, Ghinescu, Stefan Alexandru, Hutanu, Ovidiu Emanuel, Enik, Temur, Falaleev, Valeri, Kekelidze, Vladimir, Korotkova, Anna, Madigozhin, Dmitry, Misheva, Milena, Molokanova, Natalia, Movchan, Sergei, Polenkevich, Irina, Potrebenikov, Yuri, Shkarovskiy, Sergey, Zinchenko, Alexander, Baeva, Aigul, Baigarashev, Dosbol, Emelyanov, Dmitry, Fedotov, Sergei, Khotyantsev, Alexey, Gushchin, Evgeny, Kleimenova, Alina, Kudenko, Yury, Kurochka, Viktoriia, Medvedeva, Mariia, Mefodev, Aleksandr, Shaikhiev, Artur, Kholodenko, Sergey, Kurshetsov, Viktor, Obraztsov, Vladimir, Ostankov, Aleksandr, Semenov, Vitali, Sugonyaev, Valentin, Yushchenko, Oleg, Bician, Lubos, Blazek, Tomas, Cerny, Vladimir, Koval, Michal, Kucerova, Zuzana, Ceccucci, Augusto, Bernhard, Johannes, Danielsson, Hans, Döbrich, Babette, Duval, Francois, Gatignon, Lau, Guida, Roberto, Hahn, Ferdinand, Holzer, Eva Barbara, Jenninger, Berthold, Laycock, Paul, Lehmann Miotto, Giovanna, Lichard, Peter, Mapelli, Alessandro, Noy, Matthew, Palladino, Vito, Perrin-Terrin, Mathieu, Ruggiero, Giuseppe, Ryjov, Vladimir, Schuchmann, Simone, Venditti, Stefano, Brunetti, Maria Brigida, Bache, Thomas, Goudzovski, Evgueni, Henshaw, Jack, Lazzeroni, Cristina, Fascianelli, Valeria, Lurkin, Nicolas, Newson, Francis, Parkinson, Christopher, Romano, Angela, Sergi, Antonino, Sturgess, Andrew, Swallow, Joel, Heath, Helen, Page, Ryan, Trilov, Stoyan, Angelucci, Bruno, Britton, David, Protopopescu, Dan, Graham, Connor, Jones, Roger William Lewis, Dainton, John Bourke, Fry, John Richard, Fulton, Liam, Hutchcroft, David, Carmignani, Joseph, Massri, Karim, Maurice, Emilie, Wrona, Bozydar, Conovaloff, Adam, Cooper, Peter, Coward, David, and Rubin, Philip David

Subjects
High Energy Physics::Phenomenology, High Energy Physics::Experiment, Particle Physics - Experiment, High Energy Physics - Experiment
Abstract

Searches for the lepton number violating $K^{+} \rightarrow \pi^{-} \mu^{+} e^{+}$ decay and the lepton flavour violating $K^{+} \rightarrow \pi^{+} \mu^{-} e^{+}$ and $\pi^{0} \rightarrow \mu^{-} e^{+}$ decays are reported using data collected by the NA62 experiment at CERN in $2017$-$2018$. No evidence for these decays is found and upper limits of the branching ratios are obtained at 90% confidence level: $\mathcal{B}(K^{+}\rightarrow\pi^{-}\mu^{+}e^{+}), Comment: 8 pages, 4 figures

Published
2021

13. An investigation of the very rare $K^+\rightarrow\pi^+\nu\bar{\nu}$ decay

Author

Cortina Gil, Eduardo, Minucci, Elisa, Padolski, Sergey, Petrov, Plamen, Velghe, Bob, Bryman, Douglas, Fu, Ji, Numao, Toshio, Husek, Tomas, Kampf, Karol, Zamkovsky, Michal, Jerhot, Jan, Aliberti, Riccardo, Khoriauli, Gia, Kunze, Jonas, Lomidze, David, Marchevski, Radoslav, Peruzzo, Letizia, Vormstein, Mario, Wanke, Rainer, Cotta Ramusino, Angelo, Dalpiaz, Pietro, Fiorini, Massimiliano, Gamberini, Enrico, Gianoli, Alberto, Neri, Ilaria, Norton, Alan, Petrucci, Ferruccio, Wahl, Heinrich, Bizzeti, Andrea, Bucci, Francesca, Iacopini, Enrico, Latino, Giuseppe, Lenti, Massimo, Parenti, Andrea, Volpe, Roberta, Antonelli, Antonella, Gonnella, Francesco, Lamanna, Gianluca, Lanfranchi, Gaia, Martellotti, Silvia, Moulson, Matthew, Kozhuharov, Venelin, Litov, Leandar, Georgiev, Georgi, Raggi, Mauro, Spadaro, Tommaso, Ambrosino, Fabio, Capussela, Tiziana, Corvino, Michele, Di Filippo, Domenico, Massarotti, Paolo, Mirra, Marco, Napolitano, Marco, Saracino, Giulio, Anzivino, Giuseppina, Imbergamo, Ermanno, Lollini, Riccardo, Santoni, Cristiano, Brizioli, Francesco, Barbanera, Mattia, Cenci, Patrizia, Checcucci, Bruno, Duk, Viacheslav, Lupi, Matteo, Pepe, Monica, Piccini, Mauro, Lubrano, Pasquale, Costantini, Flavio, Doble, Niels, Giorgi, Marcello, Giudici, Sergio, Lari, Enrico, Pinzino, Jacopo, Pontisso, Luca, Sozzi, Marco, Di Lella, Luigi, Mannelli, Italo, Cerri, Claudio, Fantechi, Riccardo, Pedreschi, Elena, Piandani, Roberto, Spinella, Franco, Biagioni, Andrea, D'Agostini, Giulio, Leonardi, Emanuele, Lonardo, Alessandro, Valente, Paolo, Vicini, Piero, Ammendola, Roberto, Bonaiuto, Vincenzo, De Simone, Nicola, Federici, Luca, Fucci, Adolfo, Salamon, Andrea, Sargeni, Fausto, Arcidiacono, Roberta, Biino, Cristina, Bloch-Devaux, Brigitte, Boretto, Marco, Filippi, Alessandra, Iacobuzio, Lorenza, Marchetto, Flavio, Menichetti, Ezio, Migliore, Ernesto, Soldi, Dario, Engelfried, Jürgen, Estrada-Tristan, Nora, Bragadireanu, Alexandru Mario, Ghinescu, Stefan Alexandru, Hutanu, Ovidiu Emanuel, Enik, Temur, Falaleev, Valeri, Kekelidze, Vladimir, Korotkova, Anna, Madigozhin, Dmitry, Misheva, Milena, Molokanova, Natalia, Movchan, Sergei, Polenkevich, Irina, Potrebenikov, Yuri, Shkarovskiy, Sergey, Zinchenko, Alexander, Baeva, Aigul, Baigarashev, Dosbol, Emelyanov, Dmitry, Fedotov, Sergei, Khotyantsev, Alexey, Gushchin, Evgeny, Kleimenova, Alina, Kudenko, Yury, Kurochka, Viktoriia, Medvedeva, Mariia, Mefodev, Aleksandr, Shaikhiev, Artur, Kholodenko, Sergey, Kurshetsov, Viktor, Obraztsov, Vladimir, Ostankov, Aleksandr, Semenov, Vitali, Sugonyaev, Valentin, Yushchenko, Oleg, Bician, Lubos, Blazek, Tomas, Cerny, Vladimir, Koval, Michal, Kucerova, Zuzana, Ceccucci, Augusto, Bernhard, Johannes, Danielsson, Hans, Döbrich, Babette, Duval, Francois, Gatignon, Lau, Guida, Roberto, Hahn, Ferdinand, Holzer, Eva Barbara, Jenninger, Berthold, Laycock, Paul, Lehmann Miotto, Giovanna, Lichard, Peter, Mapelli, Alessandro, Noy, Matthew, Palladino, Vito, Perrin-Terrin, Mathieu, Ruggiero, Giuseppe, Ryjov, Vladimir, Schuchmann, Simone, Venditti, Stefano, Brunetti, Maria Brigida, Bache, Thomas, Goudzovski, Evgueni, Lazzeroni, Cristina, Fascianelli, Valeria, Lurkin, Nicolas, Newson, Francis, Parkinson, Christopher, Romano, Angela, Sergi, Antonino, Sturgess, Andrew, Swallow, Joel, Heath, Helen, Page, Ryan, Trilov, Stoyan, Angelucci, Bruno, Britton, David, Protopopescu, Dan, Graham, Connor, Jones, Roger William Lewis, Dainton, John Bourke, Fry, John Richard, Fulton, Liam, Hutchcroft, David, Carmignani, Joseph, Massri, Karim, Maurice, Emilie, Wrona, Bozydar, Conovaloff, Adam, Cooper, Peter, Coward, David, and Rubin, Philip David

Subjects
hep-ex, Particle Physics - Experiment, High Energy Physics - Experiment
Abstract

A search for heavy neutral lepton (N) production in $K^+\rightarrow\pi^+\nu\bar{\nu}$ decays using the data sample collected by the NA62 experiment at CERN in 2017–2018 is reported. Upper limits of the extended neutrino mixing matrix element $|U_{e4}|^2$ are established at the level of $10^{−9}$ over most of the accessible heavy neutral lepton mass range 144–462 MeV/$c^2$, with the assumption that the lifetime exceeds 50 ns. These limits improve significantly upon those of previous production and decay searches. The $|U_{e4}|^2$ range favoured by Big Bang Nucleosynthesis is excluded up to a mass of about 340 MeV/$c^2$. The NA62 experiment reports an investigation of the $ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $ mode from a sample of K$^{+}$ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10$^{−10}$, corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10$^{−11}$. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10$^{−10}$ for the $ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $ branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of ($ {0.48}_{-0.48}^{+0.72} $) × 10$^{−10}$, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements. The NA62 experiment reports an investigation of the $K^+\rightarrow\pi^+\nu\bar{\nu}$ mode from a sample of $K^+$ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of $(0.389\pm 0.024)\times10^{-10}$, corresponding to 2.2 events assuming the Standard Model branching ratio of $(8.4\pm1.0)\times10^{-11}$. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of $1.78\times10^{-10}$ for the $K^+\rightarrow\pi^+\nu\bar{\nu}$ branching ratio at 90\%\,CL. This, together with the corresponding 68\%\,CL measurement of $(0.48^{+0.72 }_{-0.48})\times10^{-10}$, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.

Published
2020

18. Performance of the NA62 trigger system

Author

Cortina Gil, Eduardo, Potrebenikov, Yuri, Kleimenova, Alina, Minucci, Elisa, Padolski, Sergey, Petrov, Plamen, Shaikhiev, Artur, Volpe, Roberta, Numao, Toshio, Petrov, Yevgeniy, Velghe, Bob, Wong, Vincent Wai Sum, Bryman, Douglas, Fu, Ji, Husek, Tomas, Jerhot, Jan, Kampf, Karol, Zamkovsky, Michal, Aliberti, Riccardo, Khoriauli, Gia, Kunze, Jonas, Lomidze, David, Peruzzo, Letizia, Vormstein, Mario, Wanke, Rainer, Dalpiaz, Pietro, Fiorini, Massimiliano, Neri, Ilaria, Norton, Alan, Petrucci, Ferruccio, Wahl, Heinrich, Cotta Ramusino, Angelo, Gianoli, Alberto, Iacopini, Enrico, Latino, Giuseppe, Lenti, Massimo, Parenti, Andrea, Bizzeti, Andrea, Bucci, Francesca, Antonelli, Antonella, Georgiev, Georgi, Kozhuharov, Venelin, Lanfranchi, Gaia, Martellotti, Silvia, Moulson, Matthew, Spadaro, Tommaso, Tinti, Gemma, Ambrosino, Fabio, Capussela, Tiziana, Corvino, Michele, Di Filippo, Domenico, Fiorenza, Renato, Massarotti, Paolo, Mirra, Marco, Napolitano, Marco, Saracino, Giulio, Anzivino, Giuseppina, Brizioli, Francesco, Imbergamo, Ermanno, Lollini, Riccardo, Piandani, Roberto, Santoni, Cristiano, Barbanera, Mattia, Cenci, Patrizia, Checcucci, Bruno, Lubrano, Pasquale, Lupi, Matteo, Pepe, Monica, Piccini, Mauro, Costantini, Flavio, Di Lella, Luigi, Doble, Niels, Giorgi, Marcello, Giudici, Sergio, Lamanna, Gianluca, Lari, Enrico, Pedreschi, Elena, Sozzi, Marco, Cerri, Claudio, Fantechi, Riccardo, Pontisso, Luca, Spinella, Franco, Mannelli, Italo, D'Agostini, Giulio, Raggi, Mauro, Biagioni, Andrea, Cretaro, Paolo, Frezza, Ottorino, Leonardi, Emanuele, Lonardo, Alessandro, Turisini, Matteo, Valente, Paolo, Vicini, Piero, Ammendola, Roberto, Bonaiuto, Vincenzo, Fucci, Adolfo, Salamon, Andrea, Sargeni, Fausto, Arcidiacono, Roberta, Bloch-Devaux, Brigitte, Boretto, Marco, Menichetti, Ezio, Migliore, Ernesto, Soldi, Dario, Biino, Cristina, Filippi, Alessandra, Marchetto, Flavio, Engelfried, Jürgen, Estrada-Tristan, Nora, Bragadireanu, Alexandru Mario, Ghinescu, Stefan Alexandru, Hutanu, Ovidiu Emanuel, Baeva, Aigul, Baigarashev, Dosbol, Emelyanov, Dmitry, Enik, Temur, Falaleev, Valeri, Kekelidze, Vladimir, Korotkova, Anna, Litov, Leandar, Madigozhin, Dmitry, Misheva, Milena, Molokanova, Natalia, Movchan, Sergei, Polenkevich, Irina, Potrebenikov, Yu., Shkarovskiy, Sergey, Zinchenko, Alexander, Fedotov, Sergei, Gushchin, Evgeny, Khotyantsev, Alexey, Kudenko, Yury, Kurochka, Viktoriia, Medvedeva, Mariia, Mefodev, Aleksandr, Kholodenko, Sergey, Kurshetsov, Viktor, Obraztsov, Vladimir, Ostankov, Aleksandr, Semenov, Vitali, Sugonyaev, Valentin, Yushchenko, Oleg, Bician, Lubos, Blazek, Tomas, Cerny, Vladimir, Kucerova, Zuzana, Bernhard, Johannes, Ceccucci, Augusto, Danielsson, Hans, De Simone, Nicola, Duval, Francois, Döbrich, Babette, Federici, Luca, Gamberini, Enrico, Gatignon, Lau, Guida, Roberto, Hahn, Ferdinand, Holzer, Eva Barbara, Jenninger, Berthold, Koval, Michal, Laycock, Paul, Lehmann Miotto, Giovanna, Lichard, Peter, Mapelli, Alessandro, Marchevski, Radoslav, Massri, Karim, Noy, Matthew, Palladino, Vito, Perrin-Terrin, Mathieu, Pinzino, Jacopo, Ryjov, Vladimir, Schuchmann, Simone, Venditti, Stefano, Bache, Thomas, Brunetti, Maria Brigida, Duk, Viacheslav, Fascianelli, Valeria, Fry, John Richard, Gonnella, Francesco, Goudzovski, Evgueni, Henshaw, Jack, Iacobuzio, Lorenza, Lazzeroni, Cristina, Lurkin, Nicolas, Newson, Francis, Parkinson, Christopher, Romano, Angela, Sergi, Antonino, Sturgess, Andrew, Swallow, Joel, Tomczak, Adam, Heath, Helen, Page, Ryan, Trilov, Stoyan, Angelucci, Bruno, Britton, David, Graham, Connor, Protopopescu, Dan, Carmignani, Joseph, Dainton, John Bourke, Jones, Roger William Lewis, Ruggiero, Giuseppe, Fulton, Liam, Hutchcroft, David, Maurice, Emilie, Wrona, Bozydar, Conovaloff, Adam, Cooper, Peter, Coward, David, Rubin, Philip David, Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and NA62

Subjects
Fixed Target Experiments, Nuclear and High Energy Physics, CERN Lab, Physics - Instrumentation and Detectors, Flavour Physics, Flavour Changing Neutral Currents, K+: rare decay, FOS: Physical sciences, particle: exotic, NA62, High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), +pi%2B+neutrino+antineutrino%22">K+ --> pi+ neutrino antineutrino, Rare Decay, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Detectors and Experimental Techniques, neutrino: pair production, symmetry: violation, Settore FIS/04, Instrumentation and Detectors (physics.ins-det), Trigger, trigger: performance, K+: semileptonic decay, Particle Physics - Experiment, experimental results
Abstract

The NA62 experiment at CERN targets the measurement of the ultra-rare $K^{+} \to \pi^{+}\nu\bar{\nu}$ decay, and carries out a broad physics programme that includes probes for symmetry violations and searches for exotic particles. Data were collected in 2016-2018 using a multi-level trigger system, which is described highlighting performance studies based on 2018 data., Comment: 20 pages; 20 figures

19. First search for $K^+\rightarrow\pi^+\nu\bar{\nu}$ using the decay-in-flight technique

Author

Cortina Gil, Eduardo, Minucci, Elisa, Padolski, Sergey, Petrov, Plamen, Velghe, Bob, Kozhuharov, Venelin, Litov, Leandar, Georgiev, Georgi, Bryman, Douglas, Fu, Ji, Numao, Toshio, Husek, Tomas, Kampf, Karol, Zamkovsky, Michal, Aliberti, Riccardo, Khoriauli, Gia, Kunze, Jonas, Lomidze, David, Marchevski, Radoslav, Peruzzo, Letizia, Vormstein, Mario, Wanke, Rainer, Cotta Ramusino, Angelo, Dalpiaz, Pietro, Fiorini, Massimiliano, Gamberini, Enrico, Gianoli, Alberto, Neri, Ilaria, Norton, Alan, Petrucci, Ferruccio, Wahl, Heinrich, Bizzeti, Andrea, Bucci, Francesca, Iacopini, Enrico, Latino, Giuseppe, Lenti, Massimo, Volpe, Roberta, Antonelli, Antonella, Gonnella, Francesco, Lamanna, Gianluca, Lanfranchi, Gaia, Mannocchi, Giampaolo, Martellotti, Silvia, Moulson, Matthew, Raggi, Mauro, Spadaro, Tommaso, Ambrosino, Fabio, Capussela, Tiziana, Corvino, Michele, Di Filippo, Domenico, Massarotti, Paolo, Mirra, Marco, Napolitano, Marco, Saracino, Giulio, Anzivino, Giuseppina, Imbergamo, Ermanno, Lollini, Riccardo, Santoni, Cristiano, Brizioli, Francesco, Barbanera, Mattia, Cenci, Patrizia, Checcucci, Bruno, Duk, Viacheslav, Lupi, Matteo, Pepe, Monica, Piccini, Mauro, Lubrano, Pasquale, Costantini, Flavio, Doble, Niels, Giorgi, Marcello, Giudici, Sergio, Pinzino, Jacopo, Pontisso, Luca, Sozzi, Marco, Di Lella, Luigi, Mannelli, Italo, Cerri, Claudio, Fantechi, Riccardo, Pedreschi, Elena, Piandani, Roberto, Spinella, Franco, Biagioni, Andrea, D Agostini, Giulio, Leonardi, Emanuele, Lonardo, Alessandro, Valente, Paolo, Vicini, Piero, Ammendola, Roberto, Bonaiuto, Vincenzo, Simone, Nicola, Federici, Luca, Fucci, Adolfo, Salamon, Andrea, Sargeni, Fausto, Arcidiacono, Roberta, Biino, Cristina, Bloch-Devaux, Brigitte, Boretto, Marco, Filippi, Alessandra, Iacobuzio, Lorenza, Marchetto, Flavio, Menichetti, Ezio, Migliore, Ernesto, Soldi, Dario, Engelfried, Jürgen, Estrada-Tristan, Nora, Bragadireanu, Alexandru Mario, Ghinescu, Stefan Alexandru, Hutanu, Ovidiu Emanuel, Temur Enik, Falaleev, Valeri, Kekelidze, Vladimir, Korotkova, Anna, Madigozhin, Dmitry, Misheva, Milena, Molokanova, Natalia, Movchan, Sergei, Polenkevich, Irina, Potrebenikov, Yuri, Shkarovskiy, Sergey, Zinchenko, Alexander, Fedotov, Sergei, Khotyantsev, Alexey, Gushchin, Evgeny, Kleimenova, Alina, Kudenko, Yury, Kurochka, Viktoriia, Medvedeva, Mariia, Mefodev, Aleksandr, Shaikhiev, Artur, Kholodenko, Sergey, Kurshetsov, Viktor, Obraztsov, Vladimir, Ostankov, Aleksandr, Semenov, Vitali, Sugonyaev, Valentin, Yushchenko, Oleg, Bician, Lubos, Blazek, Tomas, Cerny, Vladimir, Koval, Michal, Kucerova, Zuzana, Ceccucci, Augusto, Danielsson, Hans, Döbrich, Babette, Duval, Francois, Gatignon, Lau, Guida, Roberto, Hahn, Ferdinand, Jenninger, Berthold, Laycock, Paul, Lehmann Miotto, Giovanna, Lichard, Peter, Mapelli, Alessandro, Noy, Matthew, Palladino, Vito, Perrin-Terrin, Mathieu, Ruggiero, Giuseppe, Ryjov, Vladimir, Venditti, Stefano, Brunetti, Maria Brigida, Goudzovski, Evgueni, Lazzeroni, Cristina, Fascianelli, Valeria, Lurkin, Nicolas, Newson, Francis, Parkinson, Christopher, Romano, Angela, Sergi, Antonino, Sturgess, Andrew, Swallow, Joel, Heath, Helen, Page, Ryan, Trilov, Stoyan, Angelucci, Bruno, Britton, David, Protopopescu, Dan, Graham, Connor, Dainton, John Bourke, Fry, John Richard, Fulton, Liam, Hutchcroft, David, Massri, Karim, Maurice, Emilie, Wrona, Bozydar, Conovaloff, Adam, Cooper, Peter, Coward, David, Rubin, Philip David, Centre de Physique des Particules de Marseille (CPPM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Aix Marseille Université (AMU), NA62, and Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
background, neutrino: pair production, branching ratio: upper limit, measurement methods, CERN SPS, sensitivity, NA62, S010.20, High Energy Physics - Experiment, S010:Desig=20, K+: semileptonic decay, +pi%2B+neutrino+antineutrino%22">K+ --> pi+ neutrino antineutrino, K+: branching ratio, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], K+: secondary beam, experimental results
Abstract

The NA62 experiment at the CERN SPS reports the first search for $K^+ \rightarrow \pi^+ \nu \bar{\nu}$ using the decay-in-flight technique, based on a sample of $1.21\times10^{11}$ $K^+$ decays collected in 2016. The single event sensitivity is $3.15\times 10^{-10}$, corresponding to 0.267 Standard Model events. One signal candidate is observed while the expected background is 0.152 events. This leads to an upper limit of $14 \times 10^{-10}$ on the $K^+ \rightarrow \pi^+ \nu \bar{\nu}$ branching ratio at 95\% CL., Comment: 18 pages, 13 figures

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