A bstract 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 × 10 − 9 (9 . 7 × 10 − 9 ) would be excluded at 90% (95%) confidence level, and branching fractions above 3 . 0 × 10 − 8 would be within discovery reach at FCC-ee if 6 × 10 12 Z bosons are produced.
Cartelle et al. (2026) studied this question.