Measurement of the $B^{+}\to p\overline{p}{K}^{+}$ branching fraction and study of the decay dynamics

With a sample of $232\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ events collected with the BABAR detector, we study the decay $B^{+}\to p\overline{p}{K}^{+}$ excluding charmonium decays to $p\overline{p}$. We measure a branching fraction $\mathcal{B}(B^{+}\to p\overline{p}{K}^{+})=(6.7\pm 0.5\pm 0.4)\times {10}^{-6}$. An enhancement at low $p\overline{p}$ mass is observed and the Dalitz plot asymmetry suggests dominance of the penguin amplitude in this $B$ decay. We search for a pentaquark candidate ${\Theta }^{*++}$ decaying into $p{K}^{+}$ in the mass range 1.43 to $2.00\mathrm{GeV}/c^2$ and set limits on $\mathcal{B}(B^{+}\to {\Theta }^{*++}\overline{p})\times \mathcal{B}({\Theta }^{*++}\to p{K}^{+})$ at the ${10}^{-7}$ level.

Figure 1

The main Feynman diagrams for the nonresonant $B^{+}\to p\overline{p}{K}^{+}$ decay: (a) leading penguin diagram, (b) leading tree diagram (external $W^{+}$-emission), (c) Okubo-Zweig-Iizuka-suppressed penguin diagram.

Figure 2

Distribution of $\Delta E$ versus $m_{ES}$ for the $p\overline{p}{K}^{+}$ candidates in data. The solid (dashed) lines define the wide (narrow) signal and sideband regions.

Figure 3

Sample $\Delta E$ distributions for the $p\overline{p}{K}^{+}$ candidates in data for (a) $m_{p\overline{p}}<2.05\mathrm{GeV}/c^2$ and (b) $2.45<m_{p\overline{p}}<2.65\mathrm{GeV}/c^2$ regions.

Figure 4

The $m_{p\overline{p}}$ distribution for data in the wide signal (points) and sideband (shade) regions. The sideband histogram is scaled to the expected number of the combinatorial background events in the signal region.

Figure 5

Efficiency-corrected yield of $B^{+}\to p\overline{p}{K}^{+}$ events as a function of $m_{p\overline{p}}$ in data (points) and in three-body phase-space signal MC (histogram). Errors shown are statistical only.

Figure 6

Dalitz plot of data in the narrow signal region, and sideband region (inset). These distributions are not efficiency-corrected. The lines show the positions of the prominent charmonium backgrounds, from left to right ${\psi }^{\prime },{\chi }_{c2,1,0},J/\psi ,{\eta }_c$. The sideband contains about 8 times more combinatorial background events than the signal region.

Figure 7

Efficiency-corrected distributions in the narrow signal (points) and rescaled sideband (shade) regions: (a) $m_{p{K}^{+}}$ (for $m_{p{K}^{+}}>m_{\overline{p}{K}^{+}}$), (b) $m_{\overline{p}{K}^{+}}$ (for $m_{p{K}^{+}}<m_{\overline{p}{K}^{+}}$), and (c) difference between (a) and (b). Errors shown are statistical only.

Figure 8

(a) The $m_{\overline{p}{K}^{+}}$ distribution for data events in $\Lambda (1520)$ mass region; (b) The $m_{p{K}^{+}}$ distributions for data events in the signal region outside (dashed) or inside (solid) the $2.85<m_{p\overline{p}}<3.15\mathrm{GeV}/c^2$ region. Distributions are not efficiency corrected.