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

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 $B^0\to K^{\ast 0}\nu \bar{\nu }$, $B_s^0\to \varphi \nu \bar{\nu }$, $B^0\to K_S^0\nu \bar{\nu }$ 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.