Isobar Production inp+p→p+p+π++π−AT 6.6 GeV/c

At 6.6 GeV/c, the reaction $p+p\to p+{\pi }^{+}+p+{\pi }^{-}$ proceeds dominantly through the $N^{*++}p{\pi }^{-}$ channel. When peripheral $N^{*++}\text{'}\mathrm{s}$ are selected, the $p{\pi }^{-}$ angular distribution reproduces the angular distributions of free ${\pi }^{-}p$ scattering in the c.m. energy range from threshold to 2.0 GeV. The diffraction scattering at the upper end of this energy band can account for the 1.4-GeV $N^{*}$ deduced in recoil-proton spectrum studies.