20.500.12556/DiRROS-29042 Evidence for ▫$B^+ \to K^+ \nu \bar{\nu}$▫ decays We search for the rare decay �+ →�+⁢�⁢ ¯ � in a 362  fb−1 sample of electron-positron collisions at the ϒ⁡(4⁢�) resonance collected with the Belle II detector at the SuperKEKB collider. We use the inclusive properties of the accompanying � meson in ϒ⁡(4⁢�)→�⁢ ¯ � events to suppress background from other decays of the signal � candidate and light-quark pair production. We validate the measurement with an auxiliary analysis based on a conventional hadronic reconstruction of the accompanying � meson. For background suppression, we exploit distinct signal features using machine learning methods tuned with simulated data. The signal-reconstruction efficiency and background suppression are validated through various control channels. The branching fraction is extracted in a maximum likelihood fit. Our inclusive and hadronic analyses yield consistent results for the �+ →�+⁢�⁢ ¯ � branching fraction of [2.7±0.5⁢(stat)±0.5⁢(syst)] ×10−5 and [1.1+0.9 −0.8⁢(stat)+0.8 −0.5⁢(syst)] ×10−5, respectively. Combining the results, we determine the branching fraction of the decay �+ →�+⁢�⁢ ¯ � to be [2.3±0.5⁢(stat)+0.5 −0.4⁢(syst)] ×10−5, providing the first evidence for this decay at 3.5 standard deviations. The combined result is 2.7 standard deviations above the standard model expectation. Belle experiment magnetic spectrometer eksperiment Belle true false true American Physical Society ZDA Angleški jezik Slovenski jezik Neznano 2026-04-20 08:42:00 2026-04-20 08:42:00 2026-04-21 04:15:20 0000-00-00 00:00:00 2024 0 0 Nasl. z nasl. zaslona; Opis vira z dne 10. 10. 2025; soavtorji iz slovenije: Adamczyk Karol, Borah Jyotirmoi, Bračko Marko, Korpar Samo, Križan Peter, Lozar Andrej, Mrvar Manca, Pestotnik Rok, Podobnik Tomaž, Rizzuto Leonardo B., Starič Marko, Šantelj Luka, Zhukova Valentina I., Feichtinger Paul, Ganiev Eldar; str. 112006-1-112006-29 Vol. 109, 112006 Jun. 2024 0000-00-00 Zaloznikova Objavljeno NiDoloceno 2023-11-27 2024-02-28 2024-06-06 539.1 2470-0029 10.1103/PhysRevD.109.112006 252623363 https://journals.aps.org/prd/abstract/10.1103/PhysRevD.109.112006 1 0d223c8a-3c84-11f1-b8c8-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=43365 RAZ_Adachi_Ichiro_2024.pdf RAZ_Adachi_Ichiro_2024.pdf 1 B30DCC65AA675413FE1DA957205499B8 9c26b9a5c2752797f0be98097738c494fd1494b73b720510bdaee719d3aeec2b 94211739-3c84-11f1-b8c8-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=43366 Institut Jožef Stefan 0 0 0