In this work, we study the $B^+\to K^+ E_{ \mathrm{ miss}}$, $B^0\to K^{ *0} E_{ \mathrm{ miss}}$, and $\Lambda_b^0\to \Lambda^0 E_{ \mathrm{ miss}}$ decays under three different new physics hypotheses: the heavy new particles, the light neutral vector particles, and the axion-like particles. We find that all three hypotheses can resolve the Belle-II excess, and they can be clearly distinguished by the longitudinal polarization fraction of $K^*$. Furthermore, we discover that the longitudinal polarization fraction of $\Lambda$ can be used to distinguish the chirality of the effective operators.
Categories: hep-ph