Yinghui GUAN

14 January 2018

Abstract: The Belle II experiment at the SuperKEKB collider is a major upgrade of the KEK ``B factory'' facility in Tsukuba, Japan. The machine is designed for an instantaneous luminosity of $8\times10^{35} \rm cm^{-2}s^{-1}$, and the experiment is expected to accumulate a data sample of about 50 ab$^{-1}$. With this amount of data, decays sensitive to physics beyond the Standard Model can be studied with unprecedented precision. One promising set of modes are physics processes with missing energy such as $B^+ \rightarrow \tau^+ \nu$, $B \rightarrow D^{(*)} \tau \nu$, and $B \rightarrow K^{(*)} \nu \bar{\nu}$ decays. The $B \rightarrow K^{(*)} \nu \bar{\nu}$ decay provides one of the cleanest experimental probes of the flavour-changing neutral current process $b \rightarrow s \nu \bar{\nu}$, which is sensitive to physics beyond the Standard Model. However, the missing energies of the neutrinos in the final state makes the measurement challenging and requires full reconstruction of the spectator $B$ meson in $e^+ e^- \rightarrow \Upsilon(4S) \rightarrow B\bar{B}$ events. This report discusses the expected sensitivities of Belle II for these rare decays.