The reaction ${\pi }^{-}+p\to {\pi }^{-}+{\pi }^{+}+n$ is studied in the Lawrence Radiation Laboratory's 72-in. hydrogen bubble chamber. Events are located by scanning the pictures for ${\pi }^{+}$ tracks. Cross sections, Dalitz plots, and ${\pi }^{+}{\pi }^{-}$ and ${\pi }^{\pm }n$ mass spectra are given at 360-, 430-, 460-, 480-, 555-, 605-, 673-, and 780-MeV beam energies. No clear evidence is found for ${\pi }^{+}{\pi }^{-}$ resonances between threshold and 680 MeV. However, there is a strong preference for high ${\pi }^{+}{\pi }^{-}$ effective masses, especially at the lowest beam energies. Arguments are given to ascrib this anomaly to the $I=0\mathrm{}$ state of the $\pi -\pi$ system. The ${N_{\frac{3}{2}}}^{*}\mathrm{}\left(1238\right)\mathrm{}$ isobar is observed in its negative charge state. The angular distribution of its production is discussed.

• Received 14 February 1963

DOI:https://doi.org/10.1103/PhysRev.130.2481