Measurement of the very rare K⁺ ⁺ ()over-bar decay at the NA62 experiment

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

INTERNATIONAL CONFERENCE ON KAON PHYSICS, KAON 2022（2023）

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Abstract

The K+ -> pi(+) nu(nu) over bar decay, with a very precisely predicted branching ratio of less than 10(-10), is among the best processes to reveal indirect effects of new physics. The NA62 experiment reports the branching ratio measurement BR(K+ -> pi(+) nu(nu) over bar) = (1.06(-0.34)(+0.40)vertical bar(stat) +/- 0.09 vertical bar syst) . 10(-10) 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+ -> pi(+)nu(nu) over bar decay, observed with a significance of 3.4 sigma. This measurement is also used to set limits on BR(K+ -> pi(+) X), where X is a new feebly interacting scalar or pseudo-scalar particle, foreseen in several new physics scenarios.

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Measurement of the very rare K+ + ()over-bar decay at the NA62 experiment

Measurement of the very rare K⁺ ⁺ ()over-bar decay at the NA62 experiment