Are the new particles heavy or light in $b\to s{E}_{\mathrm{miss}}$?

Abstract

In this work, we study the $B^{+}\to K^{+}{E}_{\mathrm{miss}}$, $B^0\to K^{\ast 0}{E}_{\mathrm{miss}}$, 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 $K^{\ast }$. Furthermore, we discover that the longitudinal polarization fraction of $\Lambda$ can be used to distinguish the chirality of the effective operators.

arXiv comment8 pages, 2 figures, 1 table. Minor alterations. Accepted for publication in EPJC