Study of $p{\pi }^{+}{\pi }^{-}$ Isobars Produced in the $\mathrm{pp}{\pi }^{+}{\pi }^{-}$ Final State by $\mathrm{pp}$ Interactions at 16 GeV/c

We have observed enhancements at around 1450 and 1700 MeV in the $p{\pi }^{+}{\pi }^{-}$ mass spectrum for the $\mathrm{pp}{\pi }^{+}{\pi }^{-}$ final state produced in $\mathrm{pp}$ interactions at 16 GeV/c. Our results show that the 1700-MeV effect does not have a dominant ${\Delta }^{++}{\pi }^{-}$ decay mode. An attempt has been made to determine the spin assignments. We favor $J=\frac{1}{2}$ for the 1450-MeV enhancement, assuming that this decays via the uncorrelated $p{\pi }^{+}{\pi }^{-}$ mode. For the 1700-MeV enhancement, we require contributions from one or more of the spin-parity series ${\frac{3}{2}}^{-}$, ${\frac{5}{2}}^{+}$, ${\frac{7}{2}}^{-}$ in accord with the proposed Gribov-Morrison parity rule.