Measurements of electroweak penguin and lepton-flavor violating B decays to final states with missing energy at Belle and Belle II

TL;DR

This paper reports on measurements of rare electroweak penguin and lepton-flavor-violating B decays with missing energy using data from Belle and Belle II, providing insights into potential new physics beyond the Standard Model.

Contribution

It presents the first results from Belle and Belle II on these rare B decays, including searches for processes with neutrinos and lepton flavor violation, expanding the experimental understanding of these phenomena.

Findings

Results on $b o s uar{ u}$ processes

Searches for $B o K^{*0} au^+ au^-$ decays

Limits on lepton-flavor-violating $B$ decays

Abstract

The Belle and Belle II experiments have collected a 1.2 ab$^{-1}$ sample of collisions at a center-of-mass energy corresponding to the $\Upsilon(4S)$ resonance. These datasets, with low particle multiplicity and constrained initial state kinematics, are an ideal environment to search for rare electroweak penguin $B$ decays and lepton-flavor-violating $B$ decays to final states with missing energy from neutrinos. Results from $b \to s\nu\bar{\nu}$ processes and their interpretation are presented. In addition, we provide an overview of the search for the $B \to K^{*0}\tau^+\tau^-$ decays and the lepton-flavor violating decays $B^0 \to K^{(*)0}\tau^\pm\ell^\mp$, where $\ell$ is an electron or a muon.