000003861 001__ 3861
000003861 005__ 20230921155550.0
000003861 037__ $$aBELLE2-TALK-CONF-2023-131
000003861 041__ $$aeng
000003861 088__ $$aBELLE2-TALK-DRAFT-2023-124
000003861 100__ $$aRoberta Volpe
000003861 245__ $$aAnalysis of the rare B+ -> K+ nu nubar decay at Belle II
000003861 260__ $$aKEK IPNS Seminar on B+ -> Knunu$$c2023-08-24
000003861 300__ $$amult. p
000003861 520__ $$aWe search for the rare decay B+ -> K+ nu nubar in a 362 /fb sample of electron-positron collisions at the Upsilon(4S) resonance collected with the Belle II detector at the SuperKEKB collider.  The branching fraction is predicted with high accuracy in the standard model (SM) and is enhanced in several SM extensions.  We use the inclusive properties of the other \B meson in the Upsilon(4S) -> B Bbar events to suppress background from other B-meson decays and light-quark pair production. In addition, we validate the measurement with an auxiliary analysis based on a conventional hadronic reconstruction of the accompanying B meson. The signal-reconstruction efficiency and background suppression are validated using control channels. The branching fraction is extracted in a maximum likelihood fit. Our inclusive and hadronic analyses obtain consistent results. The accuracy is significantly improved compared to the previous Belle II analysis.  The results are combined and compared to the background-only hypothesis and to the SM expectations.
000003861 8560_ $$fdjaffe@bnl.gov
000003861 8564_ $$uhttps://docs.belle2.org/record/3861/files/BELLE2-TALK-CONF-2023-131.pdf