# EPS-HEP2021 conference

26-30 July 2021
Zoom
Europe/Berlin timezone

## Search for rare electroweak decay $B^{+} \to K^{+}νν$ in early Belle II dataset

29 Jul 2021, 10:15
15m
Zoom

#### Zoom

Parallel session talk Flavour Physics and CP Violation

### Speaker

Simon Kurz (BELLE (BELLE II Experiment))

### Description

In the recent years, several measurements of $B$-decays with flavor changing neutral currents (FCNC), i.e. $b\to s \ell \ell$ transitions, hint at deviations from the Standard Model (SM) predictions.

A search for the flavor-changing neutral current decay $B^{+}→K^{+}\nu\bar{\nu}$ 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 $B^{+}→K^{+}\nu\bar{\nu}$ = $4.1 \times 10^{−5}$ is set at the 90% confidence level. We will talk about this novel analysis technique and the result.

Email libby@iitm.ac.in Belle II Jim Libby