Analysis of theN*(1500)andN*(1700)Baryon Resonances Produced via Diffraction Dissociation

We report on evidence in the $\pi \pi N$ mass spectrum for the production of two nucleon isobars, the $N^{*}\mathrm{}\left(1500\right)\mathrm{}$ and $N^{*}\mathrm{}\left(1700\right)\mathrm{}$. They appear to be produced very peripherally, and have the same production cross section at both 7.0 and 25.0 $\frac{\mathrm{GeV}}{c}$, indicating that a nuclear diffraction-dissociation process is dominant. The $N^{*}\mathrm{}\left(1500\right)\mathrm{}$ seems to be $J^P={\frac{1}{2}}^{+}$ and decays principally via $p\sigma$ and not ${\Delta }^{++}{\pi }^{-}$ as previously suggested. The $N^{*}\mathrm{}\left(1700\right)\mathrm{}$ could be the $N^{*}\mathrm{}\left(1688\right)\mathrm{}{\frac{5}{2}}^{+}$ decaying partially into ${\Delta }^{++}{\pi }^{-}$, or it could be the $N^{*}\mathrm{}\left(1700\right)\mathrm{}{\frac{1}{2}}^{-}$ decaying in a non-${\Delta }^{++}{\pi }^{-}$ mode riding on a large ${\Delta }^{++}{\pi }^{-}{\frac{5}{2}}^{+}$ nonresonant Deck-type background. Finally the $\Lambda K$ decay of the $N^{*}\mathrm{}\left(1700\right)\mathrm{}$ is observed and evidence presented for it being a $J=\frac{1}{2}$ object. Production of this ${\mathrm{½}}^{-}$ isobar should be forbidden by the Morrison $\Delta P={\mathrm{}(-1\mathrm{})\mathrm{}}^{\Delta J}$ rule.