Measurements of the decays $B^0\to {\overline{D}}^{0}p\overline{p}$, $B^0\to {\overline{D}}^{*0}p\overline{p}$, $B^0\to D^{-}p\overline{p}{\pi }^{+}$, and $B^0\to D^{*-}p\overline{p}{\pi }^{+}$

We present measurements of branching fractions of $B^0$ decays to multibody final states containing protons, based on $232\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy $B$ factory. We measure the branching fractions $\mathcal{B}(B^0\to {\overline{D}}^{0}p\overline{p})=(1.13\pm 0.06\pm 0.08)\times {10}^{-4}$, $\mathcal{B}(B^0\to {\overline{D}}^{*0}p\overline{p})=(1.01\pm 0.10\pm 0.09)\times {10}^{-4}$, $\mathcal{B}(B^0\to D^{-}p\overline{p}{\pi }^{+})=(3.38\pm 0.14\pm 0.29)\times {10}^{-4}$, and $\mathcal{B}(B^0\to D^{*-}p\overline{p}{\pi }^{+})=(4.81\pm 0.22\pm 0.44)\times {10}^{-4}$ where the first error is statistical and the second systematic. We present a search for the charmed pentaquark state, ${\Theta }_c(3100)$ observed by H1 and put limits on the branching fraction $\mathcal{B}(B^0\to {\Theta }_c\overline{p}{\pi }^{+})\times \mathcal{B}({\Theta }_c\to D^{*-}p)<14\times {10}^{-6}$ and $\mathcal{B}(B^0\to {\Theta }_c\overline{p}{\pi }^{+})\times \mathcal{B}({\Theta }_c\to D^{-}p)<9\times {10}^{-6}$. Upon investigation of the decay structure of the above four $B^0$ decay modes, we see an enhancement at low $p\overline{p}$ mass and deviations from phase-space in the $\overline{D}\overline{p}$ and $\overline{D}p$ invariant mass spectra.

Figure 1

Fit projections of $m_{ES}$ for (clockwise from top-left) $B^0\to {\overline{D}}^{0}p\overline{p}({\overline{D}}^0\to K^{+}{\pi }^{-}$), $B^0\to {\overline{D}}^{*0}p\overline{p}({\overline{D}}^0\to K^{+}{\pi }^{-}$), $B^0\to D^{*-}p\overline{p}{\pi }^{+}({\overline{D}}^0\to K^{+}{\pi }^{-}$), and $B^0\to D^{-}p\overline{p}{\pi }^{+}(D^{-}\to K^{+}{\pi }^{-}{\pi }^{-})$. The dashed line is the background contribution and the solid line is the background plus signal.

Figure 2

The distributions of the branching fractions (in units of ${10}^{-6}/\mathrm{GeV}/c^2$) for $B^0\to {\overline{D}}^{0}p\overline{p}$ (top row, left), $B^0\to {\overline{D}}^{*0}p\overline{p}$ (top row, right), $B^0\to D^{-}p\overline{p}{\pi }^{+}$ (middle row), and $B^0\to D^{*-}p\overline{p}{\pi }^{+}$ (bottom row) projected over two invariant mass dimensions.

Figure 3

The branching fraction (B, in units of ${10}^{-6}/\mathrm{GeV}/c^2$) distributions versus $p\overline{p}$ (top), nonexotic (i.e $\overline{D}\overline{p}$) (middle), exotic (i.e $\overline{D}p$) (bottom) invariant mass for (from left) $B^0\to {\overline{D}}^{0}p\overline{p}$, $B^0\to {\overline{D}}^{*0}p\overline{p}$, $B^0\to D^{-}p\overline{p}{\pi }^{+}$, and $B^0\to D^{*-}p\overline{p}{\pi }^{+}$ with all $D$ decay modes combined. The solid lines are the distributions expected from a purely phase-space decay.

Figure 4

Left: The phase-space corrected $p\overline{p}$ invariant mass distributions for all four decay modes: $B^0\to {\overline{D}}^{0}p\overline{p}$ (triangles), $B^0\to {\overline{D}}^{*0}p\overline{p}$ (open circles), $B^0\to D^{-}p\overline{p}{\pi }^{+}$ (squares), and $B^0\to D^{*-}p\overline{p}{\pi }^{+}$ (closed circles). Right: The $p\overline{p}$ distributions from the present analysis averaged over the four decay modes (closed circles) compared to the distributions obtained in $e^{+}{e}^{-}\to p\overline{p}\gamma$ (open squares) and $B^{+}\to p\overline{p}{K}^{+}$ (open circles).