Study of Threshold Enhancements in ${\rho }^0{\pi }^{-}$ and $f^0{\pi }^{-}$ Systems from the Reaction ${\pi }^{-}p\to p{\pi }^{+}{\pi }^{-}{\pi }^{-}$ AT 6 GeV/c

We have observed, in a high-statistics experiment, well-defined threshold enhancements in the ${\rho }^0{\pi }^{-}$ and $f^0{\pi }^{-}$ systems at 1120 and 1645 MeV, respectively. We have searched for other dominant decay modes of these enhancements and found none. The question of whether these objects are threshold enhancements of kinematic origin or resonances is examined.