000003233 001__ 3233
000003233 005__ 20220919085821.0
000003233 037__ $$aBELLE2-PTHESIS-2022-010
000003233 041__ $$aeng
000003233 100__ $$aCyrille Praz
000003233 245__ $$aSearch for B→Kνν decays with a machine learning method at the Belle II experiment
000003233 260__ $$aHamburg (Germany)$$bDESY$$c2022
000003233 300__ $$a165
000003233 500__ $$aPresented on 23 08 2022
000003233 502__ $$aPhD$$bHamburg (Germany), Hamburg University$$c2022
000003233 520__ $$aThis thesis documents a search for the rare decay of a B meson into a K meson and a pair of neutrinos at the Belle II experiment, which is located along the SuperKEKB energy-asymmetric electron-positron collider. This decay has never been observed, its branching fraction is predicted with accuracy in the standard model of particle physics, and is a good probe of physics beyond the standard model. A novel method to search for this decay, the inclusive tagging, is developed on a data sample corresponding to an integrated luminosity of 189 fb−1 collected at the Υ(4S) resonance, and a complementary sample of 18 fb−1 collected 60 MeV below the resonance. For this integrated luminosity, the expected upper limits on the branching fraction of B+→K+νν and B0→KS0νν are determined from simulation to be 1.0×10−5 and 1.8×10−5 at the 90% confidence level, respectively. When the method is applied to data samples of 63 fb−1 collected at the Υ(4S) resonance and 9 fb−1 collected 60 MeV below the resonance, no significant signal is observed, and an upper limit on the branching fraction of B+→K+νν is determined to be 4.1×10−5 at the 90% confidence level.
000003233 700__ $$aAlexander Glazov$$edir.
000003233 8560_ $$fprazcyri@mail.desy.de
000003233 8564_ $$uhttps://docs.belle2.org/record/3233/files/BELLE2-PTHESIS-2022-010.pdf
000003233 980__ $$aTHESIS