Search for Strange-Pentaquark Production in $e^{+}{e}^{-}$ Annihilation at $\sqrt{s}=10.58\mathrm{GeV}$

We search for strange-pentaquark states that have been previously reported by other experiments—the $\Theta (1540{)}^{+}$, ${\Xi }_5(1860{)}^{--}$, and ${\Xi }_5(1860{)}^0$—in $123{\mathrm{fb}}^{-1}$ of data recorded with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ storage ring. We find no evidence for these states and set 95% confidence level upper limits on the number of $\Theta (1540{)}^{+}$ and ${\Xi }_5(1860{)}^{--}$ pentaquarks produced per $e^{+}{e}^{-}$ annihilation into $q\overline{q}$ and per ${\rm Y}(4S)$ decay. For $q\overline{q}$ events the $\Theta (1540{)}^{+}$ [${\Xi }_5(1860{)}^{--}$] limit is about 8 [4] times lower than the rates measured for ordinary baryons of similar mass.

Figure 1

Distribution of the $p{K}_S^0$ invariant mass for combinations satisfying the criteria described in the text. The same data are plotted for the full kinematically allowed $p{K}_S^0$ mass range and, in the inset, with statistical uncertainties and a suppressed zero on the vertical scale, for the mass range in which the $\Theta (1540{)}^{+}$ has been reported.

Figure 2

The measured differential production cross sections (symbols) and corresponding 95% CL upper limits (lines) for ${\Theta }^{+}$ (top panel) and ${\Xi }_5^{--}$ (bottom panel), assuming natural widths of $\Gamma =1\mathrm{MeV}/c^2$ (solid lines) and at the current experimental upper limit on $\Gamma$ (open symbols and dashed lines), as functions of c.m. momentum.

Figure 3

${\Xi }^{-}{\pi }^{+}$ (black) and ${\Xi }^{-}{\pi }^{-}$ (gray) invariant-mass distributions. The same data are plotted for the full kinematically allowed ${\Xi }^{-}{\pi }^{\pm }$ mass range and, in the inset, with statistical uncertainties and a suppressed zero on the vertical scale, for the mass range in which the ${\Xi }_5(1860{)}^{--}$ and ${\Xi }_5(1860{)}^0$ have been reported.