Angular asymmetries in $B\to\Lambda\bar p M$ decays

The forward-backward angular asymmetry (${\cal A}_{FB}$) for $\bar B^0\to \Lambda\bar p\pi^+$ measured by Belle has presented an experimental value in the range of $-30\%$ to $-50\%$. In our study, we find that ${\cal A}_{FB}[\bar B^0\to\Lambda\bar p \pi^+(B^-\to \Lambda\bar p\pi^0)]$ can be as large as $(-14.6^{+0.9}_{-1.5}\pm 6.9)\%$. In addition, we present ${\cal A}_{FB}[\bar B^0\to\Lambda\bar p \rho^+(B^-\to \Lambda\bar p\rho^0)] =(4.1^{+2.8}_{-0.7}\pm 2.0)\%$ as the first prediction involving a vector meson in the charmless $B\to{\bf B\bar B'}M$ decays. While ${\cal A}_{FB}(B\to\Lambda\bar p M)$ indicates an angular correlation caused by the rarely studied baryonic form factors in the timelike region, LHCb and Belle~II are capable of performing experimental examinations.