Simon Kurz

26 July 2021
EPS-HEP 2021

Abstract: In the recent years, several measurements of 𝐵-decays with flavor changing neutral currents (FCNC), i.e. 𝑏→𝑠ℓℓ transitions, hint at deviations from the Standard Model (SM) predictions.A search for the flavor-changing neutral current decay 𝐵+→𝐾+𝜈𝜈¯ is performed with data sample corresponding to 63 𝑓𝑏−1 collected at the Υ(4S) resonance by the Belle II experiment. A novel measurement method is developed, which exploits topological properties of the decay that differ from both generic B-meson decays and light-quark pair-production. This inclusive tagging approach has the benefit of a higher signal efficiency compared to previous searches for this rare decay. As no significant signal is observed, an upper limit on the branching fraction of 𝐵+→𝐾+𝜈𝜈¯ = 4.1×10−5 is set at the 90% confidence level. We will talk about this novel analysis technique and the result.