Making most of Belle II’s decays with invisible signatures

by Slavomira Stefkova (Bonn U.)

Tuesday 10 Dec 2024, 16:15 → 17:15 Europe/Berlin

ENC-D308

The decay $B^+ \to K^+ \nu \bar{\nu}$ is a rare process mediated by a flavor-changing neutral current, providing a powerful probe for New Physics (NP) beyond the Standard Model (SM). The SM predicts a branching fraction of approximately $6\times 10^{−6}$, while various NP scenarios, including those involving dark matter candidates, anticipate significant enhancements. A recent Belle II measurement observed a 4.6-fold enhancement of the rate with respect to SM with compatibility of  ‘only’ $2.7\sigma$.

In this seminar, I will present key aspects of this experimentally challenging measurement, highlighting the innovative techniques developed to suppress background and enhance signal efficiency. Additionally, I will introduce a novel approach to responsibly reinterpret such measurements under varying kinematic assumptions for the signal. Finally, I will discuss the future prospects of this "golden channel" and explore other opportunities in B-meson decays with similar invisible signatures.