Three-Body Charmful Baryonic B Decays $\bar B\to D(D^*)N\bar N$

We study the charmful three-body baryonic B decays $\bar B\to D^{(*)}N\bar N$: the color-allowed modes $\bar B^0\to D^{(*)+}n\bar p$ and the color-suppressed ones $\bar B^0\to D^{(*)0}p\bar p$. While the $D^{*+}/D^+$ production ratio is predicted to be of order 3, it is found that $D^0p\bar p$ has a similar rate as $D^{*0}p\bar p$. It is pointed out that $\bar B^0\to D(D^*)N\bar N$ are dominated by the nucleon vector current or by vector meson intermediate states, whereas $\bar B^0\to D^0p\bar p$ proceeds mainly via the exchange of the axial-vector intermediate state $a_1(1260)$. The study of the $N\bar N$ invariant mass distribution in general indicates a threshold baryon pair production; that is, a recoil charmed meson accompanied by a low mass baryon pair except that the spectrum of $D^0p\bar p$ has a hump at large $p\bar p$ invariant mass $m_{p\bar p}\sim 3.0$ GeV.