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158 results on '"NA62 Collaboration"'

1. First search for $K^+\to\pi^0\pi\mu e$ decays

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

The first search for the lepton number violating decay $K^+\to\pi^0\pi^-\mu^+e^+$ and lepton flavour violating decays $K^+\to\pi^0\pi^+\mu^-e^+$, $K^+\to\pi^0\pi^+\mu^+e^-$ has been performed using a dataset collected by the NA62 experiment at CERN in 2016-2018. Upper limits of $2.9\times 10^{-10}$, $3.1\times 10^{-10}$ and $5.0\times 10^{-10}$, respectively, are obtained at 90% CL for the branching ratios of the three decays on the assumption of uniform phase-space distributions., Comment: Updated version, accepted for publication in Physics Letters B

Published
2024

2. Development of a new CEDAR for kaon identification at the NA62 experiment at CERN

Author

The NA62 Collaboration

Subjects
High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract

The NA62 experiment at CERN utilises a differential Cherenkov counter with achromatic ring focus (CEDAR) for tagging kaons within an unseparated monochromatic beam of charged hadrons. The CEDAR-H detector was developed to minimise the amount of material in the path of the beam by using hydrogen gas as the radiator medium. The detector was shown to satisfy the kaon tagging requirements in a test-beam before installation and commissioning at the experiment. The CEDAR-H performance was measured using NA62 data collected in 2023., Comment: To be submitted to JINST

Published
2023

3. Search for Leptonic Decays of Dark Photons at NA62

Author

The NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

The NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of $1.4\times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV$/c^2$ and coupling values in the range $10^{-6}$ to $4\times10^{-5}$. An interpretation of the $e^+ e^-$ search result in terms of the emission and decay of an axion-like particle is also presented.

Published
2023
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4. Measurement of the $K^+\to\pi^+\gamma\gamma$ decay

Author

The NA62 Collaboration

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

A sample of 3984 candidates of the $K^+\to\pi^+\gamma\gamma$ decay, with an estimated background of $291\pm14$ 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 $(9.61\pm0.17)\times10^{-7}$. The first search for production and prompt decay of an axion-like particle with gluon coupling in the process $K^+\to\pi^+a$, $a\to\gamma\gamma$ is also reported., Comment: Revised version, accepted for publication in Physics Letters B

Published
2023
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5. Search for $K^+$ decays into the $\pi^+e^+e^-e^+e^-$ final state

Author

NA62 collaboration

Subjects
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 $K^+\to\pi^+S$, $S\to A^\prime A^\prime$, $A^\prime\to e^+e^-$., Comment: Revised version, accepted for publication in Physics Letters B

Published
2023

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

Author

The NA62 Collaboration

Subjects
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.

Published
2023
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7. Improved calorimetric particle identification in NA62 using machine learning techniques

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment, Physics - Instrumentation and Detectors
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

8. Search for dark photon decays to $\mu^+\mu^-$ at NA62

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment
Abstract

The NA62 experiment at CERN, designed to study the ultra-rare decay $K^+ \to \pi^+\nu\overline{\nu}$, has also collected data in beam-dump mode. In this configuration, dark photons may be produced by protons dumped on an absorber and reach a decay volume beginning 80 m downstream. A search for dark photons decaying in flight to $\mu^+\mu^-$ pairs is reported, based on a sample of $1.4 \times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. A region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon masses between 215 and 550 MeV$/c^2$., Comment: 23 pages, 16 figures, final version, accepted for publication in JHEP

Published
2023

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

Author

NA62 collaboration

Subjects
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, published in Physics Letters B

Published
2022
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10. A measurement of the $K^{+} \to \pi^{+} \mu^{+} \mu^{-}$ decay

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment
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
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11. Performance of the NA62 trigger system

Author

The NA62 Collaboration

Subjects
High Energy Physics - Experiment, Physics - Instrumentation and Detectors
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

Published
2022

12. Searches for lepton number violating $K^+\to\pi^-(\pi^0)e^+e^+$ decays

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

Searches for lepton number violating $K^+\to\pi^-e^+e^+$ and $K^+\to\pi^-\pi^0e^+e^+$ decays have been performed using the complete dataset collected by the NA62 experiment at CERN in 2016-2018. Upper limits of $5.3\times 10^{-11}$ and $8.5\times 10^{-10}$ are obtained on the decay branching fractions at 90% confidence level. The former result improves by a factor of four over the previous best limit, while the latter result represents the first limit on the $K^+\to\pi^-\pi^0e^+e^+$ decay rate., Comment: Updated version (8 May 2022) accepted for publication in Physics Letters B

Published
2022
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13. Improved calorimetric particle identification in NA62 using machine learning techniques

Author

The NA62 collaboration, E. Cortina Gil, A. Kleimenova, E. Minucci, S. Padolski, P. Petrov, A. Shaikhiev, R. Volpe, W. Fedorko, T. Numao, Y. Petrov, B. Velghe, V. W. S. Wong, M. Yu, D. Bryman, J. Fu, Z. Hives, T. Husek, J. Jerhot, K. Kampf, M. Zamkovsky, B. De Martino, M. Perrin-Terrin, A. T. Akmete, R. Aliberti, G. Khoriauli, J. Kunze, D. Lomidze, L. Peruzzo, M. Vormstein, R. Wanke, P. Dalpiaz, M. Fiorini, A. Mazzolari, I. Neri, A. Norton, F. Petrucci, M. Soldani, H. Wahl, L. Bandiera, A. Cotta Ramusino, A. Gianoli, M. Romagnoni, A. Sytov, E. Iacopini, G. Latino, M. Lenti, P. Lo Chiatto, I. Panichi, A. Parenti, A. Bizzeti, F. Bucci, A. Antonelli, G. Georgiev, V. Kozhuharov, G. Lanfranchi, S. Martellotti, M. Moulson, T. Spadaro, G. Tinti, F. Ambrosino, T. Capussela, M. Corvino, M. D’Errico, D. Di Filippo, R. Fiorenza, R. Giordano, P. Massarotti, M. Mirra, M. Napolitano, I. Rosa, G. Saracino, G. Anzivino, F. Brizioli, E. Imbergamo, R. Lollini, R. Piandani, C. Santoni, M. Barbanera, P. Cenci, B. Checcucci, P. Lubrano, M. Lupi, M. Pepe, M. Piccini, F. Costantini, L. Di Lella, N. Doble, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, M. Sozzi, C. Cerri, R. Fantechi, L. Pontisso, F. Spinella, I. Mannelli, G. D’Agostini, M. Raggi, A. Biagioni, P. Cretaro, O. Frezza, E. Leonardi, A. Lonardo, M. Turisini, P. Valente, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, M. Boretto, E. Menichetti, E. Migliore, D. Soldi, C. Biino, A. Filippi, F. Marchetto, A. Briano Olvera, J. Engelfried, N. Estrada-Tristan, M. A. Reyes Santos, P. Boboc, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, L. Bician, T. Blazek, V. Cerny, Z. Kucerova, J. Bernhard, A. Ceccucci, M. Ceoletta, H. Danielsson, N. De Simone, F. Duval, B. Döbrich, L. Federici, E. Gamberini, L. Gatignon, R. Guida, F. Hahn, E. B. Holzer, B. Jenninger, M. Koval, P. Laycock, G. Lehmann Miotto, P. Lichard, A. Mapelli, R. Marchevski, K. Massri, M. Noy, V. Palladino, J. Pinzino, V. Ryjov, S. Schuchmann, S. Venditti, T. Bache, M. B. Brunetti, V. Duk, V. Fascianelli, J. R. Fry, F. Gonnella, E. Goudzovski, J. Henshaw, L. Iacobuzio, C. Kenworthy, C. Lazzeroni, N. Lurkin, F. Newson, C. Parkinson, A. Romano, J. Sanders, A. Sergi, A. Sturgess, J. Swallow, A. Tomczak, H. Heath, R. Page, S. Trilov, B. Angelucci, D. Britton, C. Graham, D. Protopopescu, J. Carmignani, J. B. Dainton, R. W. L. Jones, G. Ruggiero, L. Fulton, D. Hutchcroft, E. Maurice, B. Wrona, A. Conovaloff, P. Cooper, D. Coward, P. Rubin, A. Baeva, D. Baigarashev, D. Emelyanov, T. Enik, V. Falaleev, S. Fedotov, K. Gorshanov, E. Gushchin, V. Kekelidze, D. Kereibay, S. Kholodenko, A. Khotyantsev, A. Korotkova, Y. Kudenko, V. Kurochka, V. Kurshetsov, L. Litov, D. Madigozhin, M. Medvedeva, A. Mefodev, M. Misheva, N. Molokanova, S. Movchan, V. Obraztsov, A. Okhotnikov, A. Ostankov, I. Polenkevich, Yu. Potrebenikov, A. Sadovskiy, V. Semenov, S. Shkarovskiy, V. Sugonyaev, O. Yushchenko, and A. Zinchenko

Subjects
Fixed Target Experiments, Branching fraction, Rare Decay, Flavour Physics, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract Measurement of the ultra-rare K + → π + ν ν ¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ 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 × 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.

Published
2023
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14. Search for dark photon decays to μ + μ − at NA62

Author

The NA62 collaboration, E. Cortina Gil, J. Jerhot, A. Kleimenova, N. Lurkin, M. Zamkovsky, T. Numao, B. Velghe, V. W. S. Wong, D. Bryman, Z. Hives, T. Husek, K. Kampf, M. Koval, B. De Martino, M. Perrin-Terrin, A. T. Akmete, R. Aliberti, L. Di Lella, N. Doble, L. Peruzzo, S. Schuchmann, H. Wahl, R. Wanke, P. Dalpiaz, A. Mazzolari, I. Neri, F. Petrucci, M. Soldani, L. Bandiera, A. Cotta Ramusino, A. Gianoli, M. Romagnoni, A. Sytov, M. Lenti, P. Lo Chiatto, R. Marchevski, I. Panichi, G. Ruggiero, A. Bizzeti, F. Bucci, A. Antonelli, V. Kozhuharov, G. Lanfranchi, S. Martellotti, M. Moulson, T. Spadaro, G. Tinti, F. Ambrosino, M. D’Errico, R. Fiorenza, R. Giordano, P. Massarotti, M. Mirra, M. Napolitano, I. Rosa, G. Saracino, G. Anzivino, F. Brizioli, P. Cenci, V. Duk, R. Lollini, P. Lubrano, M. Pepe, M. Piccini, F. Costantini, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, J. Pinzino, M. Sozzi, R. Fantechi, F. Spinella, I. Mannelli, M. Raggi, A. Biagioni, P. Cretaro, O. Frezza, A. Lonardo, M. Turisini, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, E. Menichetti, E. Migliore, C. Biino, A. Filippi, F. Marchetto, D. Soldi, A. Briano Olvera, J. Engelfried, N. Estrada-Tristan, R. Piandani, M. A. Reyes Santos, P. Boboc, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, T. Blazek, V. Cerny, Z. Kucerova, R. Volpe, J. Bernhard, L. Bician, M. Boretto, A. Ceccucci, M. Ceoletta, M. Corvino, H. Danielsson, F. Duval, B. Döbrich, L. Federici, E. Gamberini, R. Guida, E. B. Holzer, B. Jenninger, G. Lehmann Miotto, P. Lichard, K. Massri, E. Minucci, M. Noy, V. Ryjov, J. Swallow, J. R. Fry, F. Gonnella, E. Goudzovski, J. Henshaw, C. Kenworthy, C. Lazzeroni, C. Parkinson, A. Romano, J. Sanders, A. Sergi, A. Shaikhiev, A. Tomczak, H. Heath, D. Britton, A. Norton, D. Protopopescu, J. B. Dainton, L. Gatignon, R. W. L. Jones, P. Cooper, D. Coward, P. Rubin, A. Baeva, D. Baigarashev, D. Emelyanov, T. Enik, V. Falaleev, S. Fedotov, K. Gorshanov, E. Gushchin, V. Kekelidze, D. Kereibay, S. Kholodenko, A. Khotyantsev, A. Korotkova, Y. Kudenko, V. Kurochka, V. Kurshetsov, L. Litov, D. Madigozhin, A. Mefodev, M. Misheva, N. Molokanova, V. Obraztsov, A. Okhotnikov, I. Polenkevich, Yu. Potrebenikov, A. Sadovskiy, S. Shkarovskiy, V. Sugonyaev, and O. Yushchenko

Subjects
Beyond Standard Model, Exotics, Fixed Target Experiments, Dark Matter, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract The NA62 experiment at CERN, designed to study the ultra-rare decay K + → π + ν ν ¯ $$ \nu \overline{\nu} $$ , has also collected data in beam-dump mode. In this configuration, dark photons may be produced by protons dumped on an absorber and reach a decay volume beginning 80 m downstream. A search for dark photons decaying in flight to μ + μ − pairs is reported, based on a sample of 1.4 × 1017 protons on dump collected in 2021. No evidence for a dark photon signal is observed. A region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon masses between 215 and 550 MeV/c 2.

Published
2023
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15. Search for lepton number and flavour violation in $K^{+}$ and $\pi^{0}$ decays

Author

NA62 Collaboration

Subjects
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: $\mathcal{B}(K^{+}\rightarrow\pi^{-}\mu^{+}e^{+})<4.2\times 10^{-11}$, $\mathcal{B}(K^{+}\rightarrow\pi^{+}\mu^{-}e^{+})<6.6\times10^{-11}$ and $\mathcal{B}(\pi^{0}\rightarrow\mu^{-}e^{+})<3.2\times 10^{-10}$. These results improve by one order of magnitude over previous results for these decay modes., Comment: 8 pages, 4 figures

Published
2021
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16. Measurement of the very rare $K^+\rightarrow\pi^+\nu\bar{\nu}$ decay

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment
Abstract

The NA62 experiment reports the branching ratio measurement BR$(K^+ \rightarrow \pi^+ \nu\bar{\nu}) = (10.6^{+4.0}_{-3.4} |_{\rm stat} \pm 0.9_{\rm syst}) \times 10 ^{-11}$ at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016-2018. This provides evidence for the very rare $K^+ \rightarrow \pi^+ \nu\bar{\nu}$ decay, observed with a significance of 3.4$\sigma$. The experiment achieves a single event sensitivity of $(0.839\pm 0.054)\times 10^{-11}$, corresponding to 10.0 events assuming the Standard Model branching ratio of $(8.4\pm1.0)\times10^{-11}$. This measurement is also used to set limits on BR($K^+ \to \pi^+ X$), where $X$ is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.

Published
2021
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17. Search for $K^+$ decays to a muon and invisible particles

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

The NA62 experiment at CERN reports searches for $K^+\to\mu^+N$ and $K^+\to\mu^+\nu X$ decays, where $N$ and $X$ are massive invisible particles, using the 2016-2018 data set. The $N$ particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of ${\cal O}(10^{-8})$ of the neutrino mixing parameter $|U_{\mu4}|^2$ for $N$ masses in the range 200-384 MeV/$c^2$ and lifetime exceeding 50 ns. The $X$ particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for $X$ masses in the range 10-370 MeV/$c^2$ are reported for the first time, ranging from ${\cal O}(10^{-5})$ to ${\cal O}(10^{-7})$. An improved upper limit of $1.0\times 10^{-6}$ is established at 90% CL on the $K^+\to\mu^+\nu\nu\bar\nu$ branching fraction., Comment: Updated version published as Phys.Lett. B816 (2021) 136259

Published
2021
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18. Addendum to: A measurement of the K + → π + μ + μ − decay

Author

The NA62 collaboration, E. Cortina Gil, A. Kleimenova, E. Minucci, S. Padolski, P. Petrov, A. Shaikhiev, R. Volpe, T. Numao, Y. Petrov, B. Velghe, V. W. S. Wong, D. Bryman, J. Fu, T. Husek, J. Jerhot, K. Kampf, M. Zamkovsky, R. Aliberti, G. Khoriauli, J. Kunze, D. Lomidze, L. Peruzzo, M. Vormstein, R. Wanke, P. Dalpiaz, M. Fiorini, I. Neri, A. Norton, F. Petrucci, H. Wahl, A. Cotta Ramusino, A. Gianoli, E. Iacopini, G. Latino, M. Lenti, A. Parenti, A. Bizzeti, F. Bucci, A. Antonelli, G. Georgiev, V. Kozhuharov, G. Lanfranchi, S. Martellotti, M. Moulson, T. Spadaro, G. Tinti, F. Ambrosino, T. Capussela, M. Corvino, D. Di Filippo, R. Fiorenza, P. Massarotti, M. Mirra, M. Napolitano, G. Saracino, G. Anzivino, F. Brizioli, E. Imbergamo, R. Lollini, R. Piandani, C. Santoni, M. Barbanera, P. Cenci, B. Checcucci, P. Lubrano, M. Lupi, M. Pepe, M. Piccini, F. Costantini, L. Di Lella, N. Doble, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, M. Sozzi, C. Cerri, R. Fantechi, L. Pontisso, F. Spinella, I. Mannelli, G. D’Agostini, M. Raggi, A. Biagioni, P. Cretaro, O. Frezza, E. Leonardi, A. Lonardo, M. Turisini, P. Valente, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, M. Boretto, E. Menichetti, E. Migliore, D. Soldi, C. Biino, A. Filippi, F. Marchetto, J. Engelfried, N. Estrada-Tristan, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, A. Baeva, D. Baigarashev, D. Emelyanov, T. Enik, V. Falaleev, V. Kekelidze, A. Korotkova, L. Litov, D. Madigozhin, M. Misheva, N. Molokanova, S. Movchan, I. Polenkevich, Yu. Potrebenikov, S. Shkarovskiy, A. Zinchenko, S. Fedotov, E. Gushchin, A. Khotyantsev, Y. Kudenko, V. Kurochka, M. Medvedeva, A. Mefodev, S. Kholodenko, V. Kurshetsov, V. Obraztsov, A. Ostankov, V. Semenov, V. Sugonyaev, O. Yushchenko, L. Bician, T. Blazek, V. Cerny, Z. Kucerova, J. Bernhard, A. Ceccucci, H. Danielsson, N. De Simone, F. Duval, B. Döbrich, L. Federici, E. Gamberini, L. Gatignon, R. Guida, F. Hahn, E. B. Holzer, B. Jenninger, M. Koval, P. Laycock, G. Lehmann Miotto, P. Lichard, A. Mapelli, R. Marchevski, K. Massri, M. Noy, V. Palladino, M. Perrin-Terrin, J. Pinzino, V. Ryjov, S. Schuchmann, S. Venditti, T. Bache, M. B. Brunetti, V. Duk, V. Fascianelli, J. R. Fry, F. Gonnella, E. Goudzovski, J. Henshaw, L. Iacobuzio, C. Lazzeroni, N. Lurkin, F. Newson, C. Parkinson, A. Romano, A. Sergi, A. Sturgess, J. Swallow, A. Tomczak, H. Heath, R. Page, S. Trilov, B. Angelucci, D. Britton, C. Graham, D. Protopopescu, J. Carmignani, J. B. Dainton, R. W. L. Jones, G. Ruggiero, L. Fulton, D. Hutchcroft, E. Maurice, B. Wrona, A. Conovaloff, P. Cooper, D. Coward, and P. Rubin

Subjects
Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Published
2023
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19. Search for a feebly interacting particle $X$ in the decay $K^{+}\rightarrow\pi^{+}X$

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment
Abstract

A search for the $K^{+}\rightarrow\pi^{+}X$ decay, where $X$ is a long-lived feebly interacting particle, is performed through an interpretation of the $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ analysis of data collected in 2017 by the NA62 experiment at CERN. Two ranges of $X$ masses, $0$-$110\,\text{MeV}/c^{2}$ and $154$-$260\,\text{MeV}/c^{2}$, and lifetimes above $100\,\text{ps}$ are considered. The limits set on the branching ratio, $\text{BR}(K^{+}\rightarrow\pi^{+}X)$, are competitive with previously reported searches in the first mass range, and improve on current limits in the second mass range by more than an order of magnitude., Comment: 14 pages, 6 figures, accepted for publication by JHEP

Published
2020

20. Search for $\pi^0$ decays to invisible particles

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment
Abstract

The NA62 experiment at the CERN SPS reports a study of a sample of $4 \times10^{9}$ tagged $\pi^0$ mesons from $K^+ \to \pi^+ \pi^0 (\gamma)$, searching for the decay of the $\pi^0$ to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of $4.4 \times10^{-9}$ is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model-independent upper limit on the branching ratio for the decay $K^+ \to \pi^+ X$, where $X$ is a particle escaping detection with mass in the range 0.110-0.155 GeV$/c^2$ and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming $X$ to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson., Comment: 23 pages, 8 figures, to be submitted to JHEP

Published
2020
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21. Rare decays at the CERN high-intensity kaon beam facility

Author

NA62 Collaboration and KLEVER Collaboration

Subjects
High Energy Physics - Experiment
Abstract

Precision measurements of the branching ratios (BRs) for rare kaon decays can provide unique constraints on CKM unitarity and may reveal the existence of new physics. The BRs for two of these decays, $K^+\to\pi^+\nu\bar{\nu}$ and $K_L\to\pi^0\nu\bar{\nu}$, are strongly suppressed in the Standard Model, while their rates can be calculated with very small theoretical uncertainties.These decays are potentially sensitive to high mass scales, and several models of new physics predict large deviations from the Standard Model. Much progress has been made recently in the measurement of the $K\to\pi\nu\bar{\nu}$ BRs. Following upon NA62's successful application of the in-flight technique to measure ${\rm BR}(K^+\to\pi^+\nu\bar{\nu})$, we envision a comprehensive program for the study of the rare decay modes of both $K^+$ and $K_L$ mesons, to be carried out with high-intensity kaon beams from the CERN SPS in multiple phases, including both an experiment to measure ${\rm BR}(K^+\to\pi^+\nu\bar{\nu})$ at the 5% level and an experiment to measure ${\rm BR}(K_L\to\pi^0\nu\bar{\nu})$ at the 20% level. The detectors could also be reconfigured to allow measurements of $K_L$ decays with charged particles, such as $K_L\to\pi^0\ell^+\ell^-$., Comment: Letter of Interest for Snowmass 2021. Corresponding authors: C.Lazzeroni (cristina.lazzeroni@cern.ch) and M. Moulson (Matthew.Moulson@cern.ch)

Published
2020

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

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment
Abstract

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
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23. Search for heavy neutral lepton production in $K^+$ decays to positrons

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

A search for heavy neutral lepton ($N$) production in $K^+\to e^+N$ 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/$c^2$., Comment: Version accepted for publication in Physics Letters B (28 June 2020)

Published
2020
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24. Performance of the NA62 trigger system

Author

The NA62 collaboration, E. Cortina Gil, A. Kleimenova, E. Minucci, S. Padolski, P. Petrov, A. Shaikhiev, R. Volpe, T. Numao, Y. Petrov, B. Velghe, V. W. S. Wong, D. Bryman, J. Fu, T. Husek, J. Jerhot, K. Kampf, M. Zamkovsky, R. Aliberti, G. Khoriauli, J. Kunze, D. Lomidze, L. Peruzzo, M. Vormstein, R. Wanke, P. Dalpiaz, M. Fiorini, I. Neri, A. Norton, F. Petrucci, H. Wahl, A. Cotta Ramusino, A. Gianoli, E. Iacopini, G. Latino, M. Lenti, A. Parenti, A. Bizzeti, F. Bucci, A. Antonelli, G. Georgiev, V. Kozhuharov, G. Lanfranchi, S. Martellotti, M. Moulson, T. Spadaro, G. Tinti, F. Ambrosino, T. Capussela, M. Corvino, D. Di Filippo, R. Fiorenza, P. Massarotti, M. Mirra, M. Napolitano, G. Saracino, G. Anzivino, F. Brizioli, E. Imbergamo, R. Lollini, R. Piandani, C. Santoni, M. Barbanera, P. Cenci, B. Checcucci, P. Lubrano, M. Lupi, M. Pepe, M. Piccini, F. Costantini, L. Di Lella, N. Doble, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, M. Sozzi, C. Cerri, R. Fantechi, L. Pontisso, F. Spinella, I. Mannelli, G. D’Agostini, M. Raggi, A. Biagioni, P. Cretaro, O. Frezza, E. Leonardi, A. Lonardo, M. Turisini, P. Valente, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, M. Boretto, E. Menichetti, E. Migliore, D. Soldi, C. Biino, A. Filippi, F. Marchetto, J. Engelfried, N. Estrada-Tristan, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, A. Baeva, D. Baigarashev, D. Emelyanov, T. Enik, V. Falaleev, V. Kekelidze, A. Korotkova, L. Litov, D. Madigozhin, M. Misheva, N. Molokanova, S. Movchan, I. Polenkevich, Yu. Potrebenikov, S. Shkarovskiy, A. Zinchenko, S. Fedotov, E. Gushchin, A. Khotyantsev, Y. Kudenko, V. Kurochka, M. Medvedeva, A. Mefodev, S. Kholodenko, V. Kurshetsov, V. Obraztsov, A. Ostankov, V. Semenov, V. Sugonyaev, O. Yushchenko, L. Bician, T. Blazek, V. Cerny, Z. Kucerova, J. Bernhard, A. Ceccucci, H. Danielsson, N. De Simone, F. Duval, B. Döbrich, L. Federici, E. Gamberini, L. Gatignon, R. Guida, F. Hahn, E. B. Holzer, B. Jenninger, M. Koval, P. Laycock, G. Lehmann Miotto, P. Lichard, A. Mapelli, R. Marchevski, K. Massri, M. Noy, V. Palladino, M. Perrin-Terrin, J. Pinzino, V. Ryjov, S. Schuchmann, S. Venditti, T. Bache, M. B. Brunetti, V. Duk, V. Fascianelli, J. R. Fry, F. Gonnella, E. Goudzovski, J. Henshaw, L. Iacobuzio, C. Lazzeroni, N. Lurkin, F. Newson, C. Parkinson, A. Romano, A. Sergi, A. Sturgess, J. Swallow, A. Tomczak, H. Heath, R. Page, S. Trilov, B. Angelucci, D. Britton, C. Graham, D. Protopopescu, J. Carmignani, J. B. Dainton, R. W. L. Jones, G. Ruggiero, L. Fulton, D. Hutchcroft, E. Maurice, B. Wrona, A. Conovaloff, P. Cooper, D. Coward, and P. Rubin

Subjects
Fixed Target Experiments, Flavour Physics, Flavour Changing Neutral Currents, Rare Decay, Trigger, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract The NA62 experiment at CERN targets the measurement of the ultra-rare K + → π + ν ν ¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ 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.

Published
2023
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25. Searches for lepton number violating $K^+$ decays

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

The NA62 experiment at CERN reports a search for the lepton number violating decays $K^+\to\pi^-e^+e^+$ and $K^+\to\pi^-\mu^+\mu^+$ using a data sample collected in 2017. No signals are observed, and upper limits on the branching fractions of these decays of $2.2\times 10^{-10}$ and $4.2\times 10^{-11}$ are obtained, respectively, at 90% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively., Comment: Revised version accepted for publication in Physics Letters B

Published
2019
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26. Search for production of an invisible dark photon in $\pi^0$ decays

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

The results of a search for $\pi^0$ decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported. From a total of $4.12\times10^8$ tagged $\pi^0$ mesons, no signal is observed. Assuming a kinetic-mixing interaction, limits are set on the dark photon coupling to the ordinary photon as a function of the dark photon mass, improving on previous searches in the mass range 60--110 MeV/$c^2$. The present results are interpreted in terms of an upper limit of the branching ratio of the electro-weak decay $\pi^0 \to \gamma \nu \overline{\nu}$, improving the current limit by more than three orders of magnitude.

Published
2019
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27. A measurement of the K + → π + μ + μ − decay

Author

The NA62 collaboration, E. Cortina Gil, A. Kleimenova, E. Minucci, S. Padolski, P. Petrov, A. Shaikhiev, R. Volpe, T. Numao, Y. Petrov, B. Velghe, V. W. S. Wong, D. Bryman, J. Fu, T. Husek, J. Jerhot, K. Kampf, M. Zamkovsky, R. Aliberti, G. Khoriauli, J. Kunze, D. Lomidze, L. Peruzzo, M. Vormstein, R. Wanke, P. Dalpiaz, M. Fiorini, I. Neri, A. Norton, F. Petrucci, H. Wahl, A. Cotta Ramusino, A. Gianoli, E. Iacopini, G. Latino, M. Lenti, A. Parenti, A. Bizzeti, F. Bucci, A. Antonelli, G. Georgiev, V. Kozhuharov, G. Lanfranchi, S. Martellotti, M. Moulson, T. Spadaro, G. Tinti, F. Ambrosino, T. Capussela, M. Corvino, D. Di Filippo, R. Fiorenza, P. Massarotti, M. Mirra, M. Napolitano, G. Saracino, G. Anzivino, F. Brizioli, E. Imbergamo, R. Lollini, R. Piandani, C. Santoni, M. Barbanera, P. Cenci, B. Checcucci, P. Lubrano, M. Lupi, M. Pepe, M. Piccini, F. Costantini, L. Di Lella, N. Doble, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, M. Sozzi, C. Cerri, R. Fantechi, L. Pontisso, F. Spinella, I. Mannelli, G. D’Agostini, M. Raggi, A. Biagioni, P. Cretaro, O. Frezza, E. Leonardi, A. Lonardo, M. Turisini, P. Valente, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, M. Boretto, E. Menichetti, E. Migliore, D. Soldi, C. Biino, A. Filippi, F. Marchetto, J. Engelfried, N. Estrada-Tristan, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, A. Baeva, D. Baigarashev, D. Emelyanov, T. Enik, V. Falaleev, V. Kekelidze, A. Korotkova, L. Litov, D. Madigozhin, M. Misheva, N. Molokanova, S. Movchan, I. Polenkevich, Yu. Potrebenikov, S. Shkarovskiy, A. Zinchenko, S. Fedotov, E. Gushchin, A. Khotyantsev, Y. Kudenko, V. Kurochka, M. Medvedeva, A. Mefodev, S. Kholodenko, V. Kurshetsov, V. Obraztsov, A. Ostankov, V. Semenov, V. Sugonyaev, O. Yushchenko, L. Bician, T. Blazek, V. Cerny, Z. Kucerova, J. Bernhard, A. Ceccucci, H. Danielsson, N. De Simone, F. Duval, B. Döbrich, L. Federici, E. Gamberini, L. Gatignon, R. Guida, F. Hahn, E. B. Holzer, B. Jenninger, M. Koval, P. Laycock, G. Lehmann Miotto, P. Lichard, A. Mapelli, R. Marchevski, K. Massri, M. Noy, V. Palladino, M. Perrin-Terrin, J. Pinzino, V. Ryjov, S. Schuchmann, S. Venditti, T. Bache, M. B. Brunetti, V. Duk, V. Fascianelli, J. R. Fry, F. Gonnella, E. Goudzovski, J. Henshaw, L. Iacobuzio, C. Lazzeroni, N. Lurkin, F. Newson, C. Parkinson, A. Romano, A. Sergi, A. Sturgess, J. Swallow, A. Tomczak, H. Heath, R. Page, S. Trilov, B. Angelucci, D. Britton, C. Graham, D. Protopopescu, J. Carmignani, J. B. Dainton, R. W. L. Jones, G. Ruggiero, L. Fulton, D. Hutchcroft, E. Maurice, B. Wrona, A. Conovaloff, P. Cooper, D. Coward, and P. Rubin

Subjects
Branching fraction, Fixed Target Experiments, Flavour Changing Neutral Currents, Rare Decay, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract A sample of 2.8 × 104 K + → π + μ + μ − 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 ± 0.08) × 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 O $$ \mathcal{O} $$ (p 6).

Published
2022
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28. First search for $K^+\rightarrow\pi^+\nu\bar{\nu}$ using the decay-in-flight technique

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
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

Published
2018
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29. Search for $K^{+}\rightarrow\pi^{+}\nu\overline{\nu}$ at NA62

Author

NA62 Collaboration, Rinella, G. Aglieri, Aliberti, R., Ambrosino, F., Ammendola, R., Angelucci, B., Antonelli, A., Anzivino, G., Arcidiacono, R., Azhinenko, I., Balev, S., Barbanera, M., Bendotti, J., Biagioni, A., Bician, L., Biino, C., Bizzeti, A., Blazek, T., Blik, A., Bloch-Devaux, B., Bolotov, V., Bonaiuto, V., Boretto, M., Bragadireanu, M., Britton, D., Britvich, G., Brunetti, M. B., Bryman, D., Bucci, F., Butin, F., Calvo, J., Capitolo, E., Capoccia, C., Capussela, T., Cassese, A., Catinaccio, A., Cecchetti, A., Ceccucci, A., Cenci, P., Cerny, V., Cerri, C., Checcucci, B., Chikilev, O., Chiozzi, S., Ciaranfi, R., Collazuol, G., Conovaloff, A., Cooke, P., Cooper, P., Corradi, G., Gil, E. Cortina, Costantini, F., Cotorobai, F., Ramusino, A. Cotta, Coward, D., D'Agostini, G., Dainton, J., Dalpiaz, P., Danielsson, H., Degrange, J., De Simone, N., Di Filippo, D., Di Lella, L., Di Lorenzo, S., Dixon, N., Doble, N., Dobrich, B., Duk, V., Elsha, V., Engelfried, J., Enik, T., Estrada, N., Falaleev, V., Fantechi, R., Fascianelli, V., Federici, L., Fedotov, S., Filippi, A., Fiorini, M., Fry, J., Fu, J., Fucci, A., Fulton, L., Gallorini, S., Galeotti, S., Gamberini, E., Gatignon, L., Georgiev, G., Ghinescu, S., Gianoli, A., Giorgi, M., Giudici, S., Glonti, L., Martins, A. Goncalves, Gonnella, F., Goudzovski, E., Guida, R., Gushchin, E., Hahn, F., Hallgren, B., Heath, H., Herman, F., Husek, T., Hutanu, O., Hutchcroft, D., Iacobuzio, L., Iacopini, E., Imbergamo, E., Jamet, O., Jarron, P., Jones, E., Kampf, T. Jones K., Kaplon, J., Kekelidze, V., Kholodenko, S., Khoriauli, G., Khotyantsev, A., Khudyakov, A., Kiryushin, Yu., Kleimenova, A., Kleinknecht, K., Kluge, A., Koval, M., Kozhuharov, V., Krivda, M., Kucerova, Z., Kudenko, Yu., Kunze, J., Lamanna, G., Latino, G., Lazzeroni, C., Lehmann-Miotto, G., Lenci, R., Lenti, M., Leonardi, E., Lichard, P., Lietava, R., Likhacheva, V., Litov, L., Lollini, R., Lomidze, D., Lonardo, A., Lupi, M., Lurkin, N., McCormick, K., Madigozhin, D., Maire, G., Mandeiro, C., Mannelli, I., Mannocchi, G., Mapelli, A., Marchetto, F., Marchevski, R., Martellotti, S., Massarotti, P., Massri, K., Matak, P., Maurice, E., Medvedeva, M., Mefodev, A., Menichetti, E., Migliore, E., Minucci, E., Mirra, M., Misheva, M., Molokanova, N., Morant, J., Morel, M., Moulson, M., Movchan, S., Munday, D., Napolitano, M., Neri, I., Newson, F., Noël, J., Norton, A., Noy, M., Nuessle, G., Numao, T., Obraztsov, V., Ostankov, A., Padolski, S., Page, R., Palladino, V., Paoluzzi, G., Parkinson, C., Pedreschi, E., Pepe, M., Gomez, F. Perez, Perrin-Terrin, M., Peruzzo, L., Petrov, P., Petrucci, F., Piandani, R., Piccini, M., Pietreanu, D., Pinzino, J., Polenkevich, I., Pontisso, L., Potrebenikov, Yu., Protopopescu, D., Raffaelli, F., Raggi, M., Riedler, P., Romano, A., Rubin, P., Ruggiero, G., Russo, V., Ryjov, V., Salamon, A., Salina, G., Samsonov, V., Santoni, C., Saracino, G., Sargeni, F., Semenov, V., Sergi, A., Serra, M., Shaikhiev, A., Shkarovskiy, S., Skillicorn, I., Soldi, D., Sotnikov, A., Sugonyaev, V., Sozzi, M., Spadaro, T., Spinella, F., Staley, R., Sturgess, A., Sutcliffe, P., Szilasi, N., Tagnani, D., Trilov, S., Valdata-Nappi, M., Valente, P., Vasile, M., Vassilieva, T., Velghe, B., Veltri, M., Venditti, S., Vicini, P., Volpe, R., Vormstein, M., Wahl, H., Wanke, R., Wertelaers, P., Winhart, A., Winston, R., Wrona, B., Yushchenko, O., Zamkovsky, M., and Zinchenko, A.

Subjects
High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract

$K^{+}\rightarrow\pi^{+}\nu\overline{\nu}$ is one of the theoretically cleanest meson decay where to look for indirect effects of new physics complementary to LHC searches. The NA62 experiment at CERN SPS is designed to measure the branching ratio of this decay with 10\% precision. NA62 took data in pilot runs in 2014 and 2015 reaching the final designed beam intensity. The quality of 2015 data acquired, in view of the final measurement, will be presented., Comment: proceeding of the conference New Trends in High-Energy Physics 2016

Published
2018

30. Search for heavy neutral lepton production in $K^+$ decays

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

A search for heavy neutral lepton production in $K^+$ decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the $10^{-7}$ to $10^{-6}$ level are established on the elements of the extended neutrino mixing matrix $|U_{\ell 4}|^2$ ($\ell=e,\mu$) for heavy neutral lepton mass in the range $170-448~{\rm MeV}/c^2$. This improves on the results from previous production searches in $K^+$ decays, setting more stringent limits and extending the mass range., Comment: Version accepted for publication in Phys.Lett.B (12/01/2018)

Published
2017
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31. Search for Heavy Neutrinos in $K^+ \rightarrow \mu^+ \nu_{\mu}$ Decays

Author

The NA62 Collaboration

Subjects
High Energy Physics - Experiment
Abstract

The NA62 experiment recorded a large sample of $K^+ \rightarrow \mu^+ \nu_{\mu}$ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range $2 \times 10^{-6}$ to $10^{-5}$ have been set on the squared mixing matrix element $|U_{\mu4} |^2$ between muon and heavy neutrino states, for heavy neutrino masses in the range 300-375 MeV/$c^2$. The result extends the range of masses for which upper limits have been set on the value of $|U_{\mu4} |^2$ in previous production search experiments., Comment: 12 pages, 8 figures. Published in Physics Letters B

Published
2017
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32. The Beam and detector of the NA62 experiment at CERN

Author

NA62 collaboration

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

NA62 is a fixed-target experiment at the CERN SPS dedicated to measurements of rare kaon decays. Such measurements, like the branching fraction of the $K^{+} \rightarrow \pi^{+} \nu \bar\nu$ decay, have the potential to bring significant insights into new physics processes when comparison is made with precise theoretical predictions. For this purpose, innovative techniques have been developed, in particular, in the domain of low-mass tracking devices. Detector construction spanned several years from 2009 to 2014. The collaboration started detector commissioning in 2014 and will collect data until the end of 2018. The beam line and detector components are described together with their early performance obtained from 2014 and 2015 data., Comment: Accepted by JINST, few typos fixed, authors.xml file added, 121 pages, 77 figures

Published
2017
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33. Measurement of the $\pi^0$ electromagnetic transition form factor slope

Author

The NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

The NA62 experiment collected a large sample of charged kaon decays in 2007 with a highly efficient trigger for decays into electrons. A measurement of the $\pi^0$ electromagnetic transition form factor slope parameter from $1.11\times10^{6}$ fully reconstructed $K^\pm \to \pi^\pm \pi^0_D, \pi^0_D \to e^+ e^-\gamma$ events is reported. The measured value $a = (3.68 \pm 0.57)\times10^{-2}$ is in good agreement with theoretical expectations and previous measurements, and represents the most precise experimental determination of the slope in the time-like momentum transfer region., Comment: 12 pages, 7 figures; Revised version accepted for publication in Physics Letters B

Published
2016
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34. Measurement of the very rare K + → π + ν ν ¯ $$ {\pi}^{+}\nu \overline{\nu} $$ decay

Author

The NA62 collaboration, E. Cortina Gil, A. Kleimenova, E. Minucci, S. Padolski, P. Petrov, A. Shaikhiev, R. Volpe, T. Numao, Y. Petrov, B. Velghe, D. Bryman, J. Fu, T. Husek, J. Jerhot, K. Kampf, M. Zamkovsky, R. Aliberti, G. Khoriauli, J. Kunze, D. Lomidze, L. Peruzzo, M. Vormstein, R. Wanke, P. Dalpiaz, M. Fiorini, I. Neri, A. Norton, F. Petrucci, H. Wahl, A. Cotta Ramusino, A. Gianoli, E. Iacopini, G. Latino, M. Lenti, A. Parenti, A. Bizzeti, F. Bucci, A. Antonelli, G. Georgiev, V. Kozhuharov, G. Lanfranchi, S. Martellotti, M. Moulson, T. Spadaro, F. Ambrosino, T. Capussela, M. Corvino, D. Di Filippo, P. Massarotti, M. Mirra, M. Napolitano, G. Saracino, G. Anzivino, F. Brizioli, E. Imbergamo, R. Lollini, R. Piandani, C. Santoni, M. Barbanera, P. Cenci, B. Checcucci, P. Lubrano, M. Lupi, M. Pepe, M. Piccini, F. Costantini, L. Di Lella, N. Doble, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, M. Sozzi, C. Cerri, R. Fantechi, L. Pontisso, F. Spinella, I. Mannelli, G. D’Agostini, M. Raggi, A. Biagioni, E. Leonardi, A. Lonardo, P. Valente, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, M. Boretto, E. Menichetti, E. Migliore, D. Soldi, C. Biino, A. Filippi, F. Marchetto, J. Engelfried, N. Estrada-Tristan, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, A. Baeva, D. Baigarashev, D. Emelyanov, T. Enik, V. Falaleev, V. Kekelidze, A. Korotkova, L. Litov, D. Madigozhin, M. Misheva, N. Molokanova, S. Movchan, I. Polenkevich, Yu. Potrebenikov, S. Shkarovskiy, A. Zinchenko, S. Fedotov, E. Gushchin, A. Khotyantsev, Y. Kudenko, V. Kurochka, M. Medvedeva, A. Mefodev, S. Kholodenko, V. Kurshetsov, V. Obraztsov, A. Ostankov, V. Semenov, V. Sugonyaev, O. Yushchenko, L. Bician, T. Blazek, V. Cerny, Z. Kucerova, J. Bernhard, A. Ceccucci, H. Danielsson, N. De Simone, F. Duval, B. Döbrich, L. Federici, E. Gamberini, L. Gatignon, R. Guida, F. Hahn, E. B. Holzer, B. Jenninger, M. Koval, P. Laycock, G. Lehmann Miotto, P. Lichard, A. Mapelli, R. Marchevski, K. Massri, M. Noy, V. Palladino, M. Perrin-Terrin, J. Pinzino, V. Ryjov, S. Schuchmann, S. Venditti, T. Bache, M. B. Brunetti, V. Duk, V. Fascianelli, J. R. Fry, F. Gonnella, E. Goudzovski, J. Henshaw, L. Iacobuzio, C. Lazzeroni, N. Lurkin, F. Newson, C. Parkinson, A. Romano, A. Sergi, A. Sturgess, J. Swallow, H. Heath, R. Page, S. Trilov, B. Angelucci, D. Britton, C. Graham, D. Protopopescu, J. Carmignani, J. B. Dainton, R. W. L. Jones, G. Ruggiero, L. Fulton, D. Hutchcroft, E. Maurice, B. Wrona, A. Conovaloff, P. Cooper, D. Coward, and P. Rubin

Subjects
FCNC Interaction, Flavour Changing Neutral Currents, Rare decay, Fixed target experiments, Flavor physics, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract The NA62 experiment reports the branching ratio measurement BR K + → π + ν ν ¯ = 10.6 − 3.4 + 4.0 stat ± 0.9 syst × 10 − 11 $$ \mathrm{BR}\left({K}^{+}\to {\pi}^{+}\nu \overline{\nu}\right)=\left({10.6}_{-3.4}^{+4.0}\left|{}_{\mathrm{stat}}\right.\pm {0.9}_{\mathrm{syst}}\right)\times {10}^{-11} $$ at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016–2018. This provides evidence for the very rare K + → π + ν ν ¯ $$ {\pi}^{+}\nu \overline{\nu} $$ decay, observed with a significance of 3.4σ. The experiment achieves a single event sensitivity of (0.839 ± 0.054) × 10 −11, corresponding to 10.0 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10 −11. This measurement is also used to set limits on BR(K + → π + X), where X is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.

Published
2021
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35. Search for a feebly interacting particle X in the decay K + → π + X

Author

The NA62 collaboration, E. Cortina Gil, A. Kleimenova, E. Minucci, S. Padolski, P. Petrov, A. Shaikhiev, R. Volpe, T. Numao, B. Velghe, D. Bryman, J. Fu, T. Husek, J. Jerhot, K. Kampf, M. Zamkovsky, R. Aliberti, G. Khoriauli, J. Kunze, D. Lomidze, R. Marchevski, L. Peruzzo, M. Vormstein, R. Wanke, P. Dalpiaz, M. Fiorini, I. Neri, A. Norton, F. Petrucci, H. Wahl, A. Cotta Ramusino, A. Gianoli, E. Iacopini, G. Latino, M. Lenti, A. Parenti, A. Bizzeti, F. Bucci, A. Antonelli, G. Georgiev, V. Kozhuharov, G. Lanfranchi, S. Martellotti, M. Moulson, T. Spadaro, F. Ambrosino, T. Capussela, M. Corvino, D. Di Filippo, P. Massarotti, M. Mirra, M. Napolitano, G. Saracino, G. Anzivino, F. Brizioli, E. Imbergamo, R. Lollini, R. Piandani, C. Santoni, M. Barbanera, P. Cenci, B. Checcucci, P. Lubrano, M. Lupi, M. Pepe, M. Piccini, F. Costantini, L. Di Lella, N. Doble, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, M. Sozzi, C. Cerri, R. Fantechi, L. Pontisso, F. Spinella, I. Mannelli, G. D’Agostini, M. Raggi, A. Biagioni, E. Leonardi, A. Lonardo, P. Valente, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, M. Boretto, E. Menichetti, E. Migliore, D. Soldi, C. Biino, A. Filippi, F. Marchetto, J. Engelfried, N. Estrada-Tristan, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, A. Baeva, D. Baigarashev, D. Emelyanov, T. Enik, V. Falaleev, V. Kekelidze, A. Korotkova, L. Litov, D. Madigozhin, M. Misheva, N. Molokanova, S. Movchan, I. Polenkevich, Yu. Potrebenikov, S. Shkarovskiy, A. Zinchenko, S. Fedotov, E. Gushchin, A. Khotyantsev, Y. Kudenko, V. Kurochka, M. Medvedeva, A. Mefodev, S. Kholodenko, V. Kurshetsov, V. Obraztsov, A. Ostankov, V. Semenov, V. Sugonyaev, O. Yushchenko, L. Bician, T. Blazek, V. Cerny, Z. Kucerova, J. Bernhard, A. Ceccucci, H. Danielsson, N. De Simone, F. Duval, B. Döbrich, L. Federici, E. Gamberini, L. Gatignon, R. Guida, F. Hahn, E. B. Holzer, B. Jenninger, M. Koval, P. Laycock, G. Lehmann Miotto, P. Lichard, A. Mapelli, K. Massri, M. Noy, V. Palladino, M. Perrin-Terrin, J. Pinzino, V. Ryjov, S. Schuchmann, S. Venditti, T. Bache, M. B. Brunetti, V. Duk, V. Fascianelli, J. R. Fry, F. Gonnella, E. Goudzovski, L. Iacobuzio, C. Lazzeroni, N. Lurkin, F. Newson, C. Parkinson, A. Romano, A. Sergi, A. Sturgess, J. Swallow, H. Heath, R. Page, S. Trilov, B. Angelucci, D. Britton, C. Graham, D. Protopopescu, J. Carmignani, J. B. Dainton, R. W. L. Jones, G. Ruggiero, L. Fulton, D. Hutchcroft, E. Maurice, B. Wrona, A. Conovaloff, P. Cooper, D. Coward, and P. Rubin

Subjects
Beyond Standard Model, Exotics, Fixed target experiments, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract A search for the K + → π + X decay, where X is a long-lived feebly interacting particle, is performed through an interpretation of the K + → π + ν ν ¯ $$ {\pi}^{+}\nu \overline{\nu} $$ analysis of data collected in 2017 by the NA62 experiment at CERN. Two ranges of X masses, 0–110 MeV/c 2 and 154–260 MeV/c 2, and lifetimes above 100 ps are considered. The limits set on the branching ratio, BR(K + → π + X), are competitive with previously reported searches in the first mass range, and improve on current limits in the second mass range by more than an order of magnitude.

Published
2021
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36. Study of the $K^\pm\to\pi^\pm\gamma\gamma$ decay by the NA62 experiment

Author

NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

A study of the dynamics of the rare decay $K^\pm\to\pi^\pm\gamma\gamma$ has been performed on a sample of 232 decay candidates, with an estimated background of $17.4\pm1.1$ 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 ${\cal B}_{\rm MI}(z>0.2) = (0.965 \pm 0.063) \times 10^{-6}$, and the combined branching ratio in the full kinematic range assuming a Chiral Perturbation Theory description is ${\cal B}(K_{\pi\gamma\gamma}) = (1.003 \pm 0.056) \times 10^{-6}$. A detailed comparison of the results with the previous measurements is performed., Comment: A revised version accepted for publication in Physics Letters B

Published
2014

37. An investigation of the very rare K + → π + ν ν ¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ decay

Author

The NA62 collaboration, E. Cortina Gil, A. Kleimenova, E. Minucci, S. Padolski, P. Petrov, A. Shaikhiev, R. Volpe, T. Numao, B. Velghe, D. Bryman, J. Fu, T. Husek, J. Jerhot, K. Kampf, M. Zamkovsky, R. Aliberti, G. Khoriauli, J. Kunze, D. Lomidze, R. Marchevski, L. Peruzzo, M. Vormstein, R. Wanke, P. Dalpiaz, M. Fiorini, I. Neri, A. Norton, F. Petrucci, H. Wahl, A. Cotta Ramusino, A. Gianoli, E. Iacopini, G. Latino, M. Lenti, A. Parenti, A. Bizzeti, F. Bucci, A. Antonelli, G. Georgiev, V. Kozhuharov, G. Lanfranchi, S. Martellotti, M. Moulson, T. Spadaro, F. Ambrosino, T. Capussela, M. Corvino, D. Di Filippo, P. Massarotti, M. Mirra, M. Napolitano, G. Saracino, G. Anzivino, F. Brizioli, E. Imbergamo, R. Lollini, R. Piandani, C. Santoni, M. Barbanera, P. Cenci, B. Checcucci, P. Lubrano, M. Lupi, M. Pepe, M. Piccini, F. Costantini, L. Di Lella, N. Doble, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, M. Sozzi, C. Cerri, R. Fantechi, L. Pontisso, F. Spinella, I. Mannelli, G. D’Agostini, M. Raggi, A. Biagioni, E. Leonardi, A. Lonardo, P. Valente, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, M. Boretto, E. Menichetti, E. Migliore, D. Soldi, C. Biino, A. Filippi, F. Marchetto, J. Engelfried, N. Estrada-Tristan, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, A. Baeva, D. Baigarashev, D. Emelyanov, T. Enik, V. Falaleev, V. Kekelidze, A. Korotkova, L. Litov, D. Madigozhin, M. Misheva, N. Molokanova, S. Movchan, I. Polenkevich, Yu. Potrebenikov, S. Shkarovskiy, A. Zinchenko, S. Fedotov, E. Gushchin, A. Khotyantsev, Y. Kudenko, V. Kurochka, M. Medvedeva, A. Mefodev, S. Kholodenko, V. Kurshetsov, V. Obraztsov, A. Ostankov, V. Semenov, V. Sugonyaev, O. Yushchenko, L. Bician, T. Blazek, V. Cerny, Z. Kucerova, J. Bernhard, A. Ceccucci, H. Danielsson, N. De Simone, F. Duval, B. Döbrich, L. Federici, E. Gamberini, L. Gatignon, R. Guida, F. Hahn, E. B. Holzer, B. Jenninger, M. Koval, P. Laycock, G. Lehmann Miotto, P. Lichard, A. Mapelli, K. Massri, M. Noy, V. Palladino, M. Perrin-Terrin, J. Pinzino, V. Ryjov, S. Schuchmann, S. Venditti, T. Bache, M. B. Brunetti, V. Duk, V. Fascianelli, J. R. Fry, F. Gonnella, E. Goudzovski, L. Iacobuzio, C. Lazzeroni, N. Lurkin, F. Newson, C. Parkinson, A. Romano, A. Sergi, A. Sturgess, J. Swallow, H. Heath, R. Page, S. Trilov, B. Angelucci, D. Britton, C. Graham, D. Protopopescu, J. Carmignani, J. B. Dainton, R. W. L. Jones, G. Ruggiero, L. Fulton, D. Hutchcroft, E. Maurice, B. Wrona, A. Conovaloff, P. Cooper, D. Coward, and P. Rubin

Subjects
Fixed target experiments, Flavor physics, Flavour Changing Neutral Currents, Rare decay, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract The NA62 experiment reports an investigation of the K + → π + ν ν ¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ 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 + → π + ν ν ¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of ( 0.48 − 0.48 + 0.72 $$ {0.48}_{-0.48}^{+0.72} $$ ) × 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.

Published
2020
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38. Precision Measurement of the Ratio of the Charged Kaon Leptonic Decay Rates

Author

The NA62 collaboration

Subjects
High Energy Physics - Experiment
Abstract

A precision measurement of the ratio RK of the rates of kaon leptonic decays K+- --> e nu and K+- --> mu nu with the full data sample collected by the NA62 experiment at CERN in 2007-2008 is reported. The result, obtained by analysing ~150000 reconstructed K+- --> e nu candidates with 11% background contamination, is RK = (2.488+-0.010)*10^{-5}, in agreement with the Standard Model expectation., Comment: Accepted for publication in Physics Letters B (18 January 2013). 18 pages, 6 figures

Published
2012

39. Search for production of an invisible dark photon in π 0 decays

Author

The NA62 collaboration, E. Cortina Gil, A. Kleimenova, E. Minucci, S. Padolski, P. Petrov, A. Shaikhiev, R. Volpe, G. Georgiev, V. Kozhuharov, L. Litov, T. Numao, Y. Petrov, B. Velghe, D. Bryman, J. Fu, T. Husek, J. Jerhot, K. Kampf, M. Zamkovsky, R. Aliberti, G. Khoriauli, J. Kunze, D. Lomidze, L. Peruzzo, M. Vormstein, R. Wanke, P. Dalpiaz, M. Fiorini, I. Neri, A. Norton, F. Petrucci, H. Wahl, A. Cotta Ramusino, A. Gianoli, E. Iacopini, G. Latino, M. Lenti, A. Parenti, A. Bizzeti, F. Bucci, A. Antonelli, G. Lanfranchi, G. Mannocchi, S. Martellotti, M. Moulson, T. Spadaro, F. Ambrosino, T. Capussela, M. Corvino, D. Di Filippo, P. Massarotti, M. Mirra, M. Napolitano, G. Saracino, G. Anzivino, F. Brizioli, E. Imbergamo, R. Lollini, R. Piandani, C. Santoni, M. Barbanera, P. Cenci, B. Checcucci, P. Lubrano, M. Lupi, M. Pepe, M. Piccini, F. Costantini, L. Di Lella, N. Doble, M. Giorgi, S. Giudici, G. Lamanna, E. Lari, E. Pedreschi, M. Sozzi, C. Cerri, R. Fantechi, L. Pontisso, F. Spinella, I. Mannelli, G. D’Agostini, M. Raggi, A. Biagioni, E. Leonardi, A. Lonardo, P. Valente, P. Vicini, R. Ammendola, V. Bonaiuto, A. Fucci, A. Salamon, F. Sargeni, R. Arcidiacono, B. Bloch-Devaux, M. Boretto, E. Menichetti, E. Migliore, D. Soldi, C. Biino, A. Filippi, F. Marchetto, J. Engelfried, N. Estrada-Tristan, A. M. Bragadireanu, S. A. Ghinescu, O. E. Hutanu, T. Enik, V. Falaleev, V. Kekelidze, A. Korotkova, D. Madigozhin, M. Misheva, N. Molokanova, S. Movchan, I. Polenkevich, Yu. Potrebenikov, S. Shkarovskiy, A. Zinchenko, S. Fedotov, E. Gushchin, A. Khotyantsev, Y. Kudenko, V. Kurochka, M. Medvedeva, A. Mefodev, S. Kholodenko, V. Kurshetsov, V. Obraztsov, A. Ostankov, V. Semenov, V. Sugonyaev, O. Yushchenko, L. Bician, T. Blazek, V. Cerny, Z. Kucerova, J. Bernhard, A. Ceccucci, H. Danielsson, N. De Simone, F. Duval, B. Döbrich, L. Federici, E. Gamberini, L. Gatignon, R. Guida, F. Hahn, E. B. Holzer, B. Jenninger, M. Koval, P. Laycock, G. Lehmann Miotto, P. Lichard, A. Mapelli, R. Marchevski, K. Massri, M. Noy, V. Palladino, M. Perrin-Terrin, J. Pinzino, V. Ryjov, S. Schuchmann, S. Venditti, T. Bache, M. B. Brunetti, V. Duk, V. Fascianelli, J. R. Fry, F. Gonnella, E. Goudzovski, L. Iacobuzio, C. Lazzeroni, N. Lurkin, F. Newson, C. Parkinson, A. Romano, A. Sergi, A. Sturgess, J. Swallow, H. Heath, R. Page, S. Trilov, B. Angelucci, D. Britton, C. Graham, D. Protopopescu, J. Carmignani, J. B. Dainton, R. W. L. Jones, G. Ruggiero, L. Fulton, D. Hutchcroft, E. Maurice, B. Wrona, A. Conovaloff, P. Cooper, D. Coward, and P. Rubin

Subjects
Beyond Standard Model, Exotics, Fixed target experiments, Rare decay, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract The results of a search for π 0 decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported. From a total of 4.12 × 108 tagged π 0 mesons, no signal is observed. Assuming a kinetic-mixing interaction, limits are set on the dark photon coupling to the ordinary photon as a function of the dark photon mass, improving on previous searches in the mass range 60–110 MeV/c 2. The present results are interpreted in terms of an upper limit of the branching ratio of the electro-weak decay π 0 → γ ν ν ¯ $$ {\pi}^0\to \gamma \nu \overline{\nu} $$ , improving the current limit by more than three orders of magnitude.

Published
2019
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40. Performance of the NA62 trigger system

Author

UCL - SST/IRMP - Institut de recherche en mathématique et physique, Cortina Gil, Eduardo, Lurkin, Nicolas, Kleimenova, Alina, Jerhot, Jan, NA62 Collaboration, UCL - SST/IRMP - Institut de recherche en mathématique et physique, Cortina Gil, Eduardo, Lurkin, Nicolas, Kleimenova, Alina, Jerhot, Jan, and NA62 Collaboration

Published
2023

41. Search for leptonic decays of the dark photon at NA62

Author

The NA62 collaboration and The NA62 collaboration

Abstract

The NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of $1.4\times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV$/c^2$ and coupling values in the range $10^{-6}$ to $4\times10^{-5}$. An interpretation of the $e^+ e^-$ search result in terms of the emission and decay of an axion-like particle is also presented.

Published
2023

42. 2023 NA62 Status Report to the CERN SPSC

Author

NA62, Collaboration

Subjects
Detectors and Experimental Techniques
Abstract

The status of the NA62 experiment is reported. The current status of detectors and hardware is summarised, together with our experience of the 2022 data taking and plans for the 2023 data taking. The status of the $K^+\to\pi^+\nu\bar{\nu}$ analysis is presented, and highlights of rare and forbidden decay analyses and searches for exotic processes are discussed.

Published
2023

43. Performance of the NA62 trigger system

Author

Cortina Gil, Eduardo, Lurkin, Nicolas, Kleimenova, Alina, Jerhot, Jan, NA62 Collaboration, and UCL - SST/IRMP - Institut de recherche en mathématique et physique

Published
2023

44. A study of the $K^+ \to π^0 e^+ νγ$ decay

Author

The NA62 Collaboration

Subjects
High Energy Physics - Experiment (hep-ex), FOS: Physical sciences
Abstract

A sample of $1.3 \times 10^5$ $K^+ \to π^0 e^+ νγ$ 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
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49. A search for the $K^+\toμ^-νe^+e^+$ decay

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment (hep-ex), FOS: Physical sciences
Abstract

A search for the $K^+\toμ^-νe^+e^+$ 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., Final version, accepted for publication in Physics Letters B

Published
2022
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50. A measurement of the $K^{+} \to π^{+} μ^{+} μ^{-}$ decay

Author

NA62 Collaboration

Subjects
High Energy Physics - Experiment (hep-ex), FOS: Physical sciences
Abstract

A sample of $2.8 \times 10^4$ $K^{+} \to π^{+} μ^{+} μ^{-}$ 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 $\mathcal{O}(p^6)$., 17 pages, 5 figures. Updated version (6 October 2022) accepted for publication in JHEP

Published
2022
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