Prospects for searches of $b \to s \nu \bar{\nu}$ decays at FCC-ee

TL;DR

This paper assesses the potential of FCC-ee to study rare $b o s u ar{ u}$ decays, evaluating sensitivities, detector design impacts, and implications for Standard Model and new physics parameters.

Contribution

It provides the first detailed sensitivity projections for $b o s u ar{ u}$ decays at FCC-ee, including detector optimization effects and phenomenological implications.

Findings

Expected sensitivities of 0.53% to 9.86% for various decay modes.

Detector design choices significantly affect measurement precision.

Potential to constrain Standard Model and new physics parameters.

Abstract

We investigate the physics reach and potential for the study of various decays involving a $b \to s \nu \bar{\nu}$ transition at the Future Circular Collider running electron-positron collisions at the $Z$-pole (FCC-ee). Signal and background candidates, which involve inclusive $Z$ contributions from $b\bar{b}$, $c\bar{c}$ and $uds$ final states, are simulated for a proposed multi-purpose detector. Signal candidates are selected using two Boosted Decision Tree algorithms. We determine expected relative sensitivities of $0.53\%$, $1.20\%$, $3.37\%$ and $9.86\%$ for the branching fractions of the $B^{0} \to K^{*0} \nu \bar{\nu}$, $B^{0}_{s} \to \phi \nu \bar{\nu}$, $B^{0} \to K^{0}_{S} \nu \bar{\nu}$ and $\Lambda_{b}^{0} \to \Lambda^{0} \nu \bar{\nu}$ decays, respectively. In addition, we investigate the impact of detector design choices related to particle-identification and vertex resolution. The phenomenological impact of such measurements on the extraction of Standard Model and new physics parameters is also studied.