Prospects of searches for invisible $B$-meson decays at FCC-ee

Abstract

We investigate the physics reach and potential for the study of $B$-meson decays to invisible final states at the Future Circular Collider running electron-positron collisions at the $Z$ pole (FCC-ee). Signal and background candidates are simulated for a proposed multipurpose detector, including inclusive contributions from $Z$ decays to leptons or quarks. Signal candidates are selected by a mixture of rectangular cuts and a multiclass boosted decision tree classifier. We determine that branching fractions above $7.6\times10^{-9}$ ($9.7\times10^{-9}$) would be excluded at 90% (95%) confidence level, and branching fractions above $3.0\times10^{-8}$ would be within discovery reach at FCC-ee if $6\times 10^{12}$ $Z$ bosons are produced.