Journal of High Energy Physics (2020-11-01)

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

  • 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,
  • P. Rubin

DOI
https://doi.org/10.1007/JHEP11(2020)042
Journal volume & issue
Vol. 2020, no. 11
pp. 1 – 57

Abstract

Read online

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.

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