Search for narrow structures in $p\overline{p}{\pi }^{+}$ and $\Lambda \overline{p}{\pi }^{\pm }$ systems

We have performed a high-statistics search for narrow meson states ($\Gamma <~30$ MeV) produced in ${\pi }^{-}p$ interactions at 16 GeV/c and decaying into $p\overline{p}{\pi }^{+}$ or $\Lambda \overline{p}{\pi }^{\pm }$. This is the first systematic search in channels requiring exchange of exotic mesons. The cross section for production of such states is ruled out at the 95% confidence level with upper limits ranging from ∼10 nb at 2.3 GeV to ∼40 nb at 2.8 GeV.