Angular distributions in three-body baryonic B decays

We study the angular distributions of the baryon-antibaryon low-mass enhancements in the three-body baryonic B decays of $B\to p\bar{p}M$ (M=K and $\pi$) in the framework of the perturbative QCD. By writing the most general forms for the transition form factors of $B\to p\bar{p}$, we find that the angular distribution asymmetry in $B^-\to p\bar{p}K^-$ measured by the Belle Collaboration can be explained. We give a quantitative description on the Dalitz plot asymmetry in $B^-\to p\bar{p}K^-$ shown by the BaBar Collaboration and demonstrate that it is equivalent to the angular asymmetry. In addition, we present our results on $\bar B^0\to p\bar{p}K_S$ and $B^-\to p\bar{p}\pi^-$ and we obtain that their angular asymmetries are $-0.35\pm0.11$ and $0.45\pm0.10$, respectively, which can be tested by the ongoing experiments at the B factories.