An investigation of the very rare K + → π + ν ν ¯ $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ decay Cortina Gil E. , Kleimenova A. , CERN, European Organization for Nuclear Research , Brookhaven National Laboratory , Petrov P. , Institute for Nuclear Research of the Russian Academy of Sciences , Comenius University , Numao T. , Velghe B. , University of British Columbia , UCLA Physics and Biology in Medicine , IFIC, Universitat de València — CSIC , Charles University , Kampf K. , Zamkovsky M. , Aliberti R. , Universität Würzburg , Kunze J. , Universität Hamburg , CERN, European Organization for Nuclear Research , Peruzzo L. , Vormstein M. , Wanke R. , Dalpiaz P. , Fiorini M. , Neri I. , Norton A. , Petrucci F. , Wahl H. , Cotta Ramusino A. , Gianoli A. , Iacopini E. , Latino G. , Lenti M. , Parenti A. , Università di Modena e Reggio Emilia , Bucci F. , Antonelli A. , University of Sofia , University of Sofia , Lanfranchi G. , Martellotti S. , Moulson M. , Spadaro T. , Ambrosino F. , Capussela T. , CERN, European Organization for Nuclear Research , Di Filippo D. , Massarotti P. , Mirra M. , Napolitano M. , Saracino G. , Anzivino G. , Brizioli F. , Imbergamo E. , Lollini R. , Institut für Experimentelle Teilchenphysik (KIT) , Santoni C. , INFN, Sezione di Pisa , Cenci P. , Checcucci B. , Lubrano P. , Goethe Universität , Pepe M. , Piccini M. , Costantini F. , Di Lella L. , Doble N. , Giorgi M. , Giudici S. , Lamanna G. , Lari E. , Pedreschi E. , Sozzi M. , Cerri C. , Fantechi R. , Pontisso L. , Spinella F. , Mannelli I. , D’Agostini G. , Raggi M. , Biagioni A. , Leonardi E. , Lonardo A. , Valente P. , Vicini P. , Ammendola R. , University of Roma Tor Vergata , Fucci A. , Salamon A. , University of Roma Tor Vergata , Università degli Studi del Piemonte Orientale , Bloch-Devaux B. , CERN, European Organization for Nuclear Research , Menichetti E. , Migliore E. , Soldi D. , Biino C. , Filippi A. , Marchetto F. , Engelfried J. , Universidad de Guanajuato , Bragadireanu A. M. , Ghinescu S. A. , Hutanu O. E. , Baeva A. , Baigarashev D. , Emelyanov D. , Enik T. , Falaleev V. , Kekelidze V. , Korotkova A. , University of Sofia , Madigozhin D. , Institute of Nuclear Research and Nuclear Energy of Bulgarian Academy of Science (INRNE-BAS) , Molokanova N. , Movchan S. , Polenkevich I. , Potrebenikov Yu. , Shkarovskiy S. , Zinchenko A. , Fedotov S. , Gushchin E. , Khotyantsev A. , Moscow Institute of Physics and Technology , Kurochka V. , Medvedeva M. , Mefodev A. , Kholodenko S. , Kurshetsov V. , Obraztsov V. , Ostankov A. , Semenov V. , Sugonyaev V. , Yushchenko O. , CERN, European Organization for Nuclear Research , Blazek T. , Cerny V. , Kucerova Z. , Bernhard J. , Ceccucci A. , Danielsson H. , DESY , Duval F. , Döbrich B. , Federici L. , Gamberini E. , Gatignon L. , Guida R. , Hahn F. , Holzer E. B. , Jenninger B. , CERN, European Organization for Nuclear Research , Brookhaven National Laboratory , Lehmann Miotto G. , Lichard P. , Mapelli A. , Massri K. , Noy M. , Imperial College London , Aix Marseille University, CNRS/IN2P3, CPPM , University of Toronto , Ryjov V. , CERN, European Organization for Nuclear Research , Venditti S. , Bache T. , University of Warwick , University of Birmingham , Università di Roma La Sapienza , Fry J. R. , Gonnella F. , Goudzovski E. , Iacobuzio L. , Lazzeroni C. , University of Birmingham , Newson F. , University of Birmingham , Romano A. , Sergi A. , Sturgess A. , Swallow J. , Heath H. , Page R. , Trilov S. , Angelucci B. , Britton D. , Graham C. , Protopopescu D. , Carmignani J. , Dainton J. B. , Jones R. W. L. , Ruggiero G. , Fulton L. , Hutchcroft D. , Laboratoire Leprince Ringuet , Wrona B. , Conovaloff A. , Cooper P. , Stanford University , Rubin P. Journal of High Energy Physics（2020）
摘要
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.
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关键词
Fixed target experiments, Flavor physics, Flavour Changing Neutral Currents, Rare decay
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