Search For Structure In Nucleon Isobar Mass Spectrum From 1100 To 1800 Mev

A new high-resolution (\ifmmode\pm\else\textpm\fi{}5 MeV) missing-mass spectrometer was used to search for minor peaks and structure in the ${N}^{*}$ spectrum with \ensuremath{\sim}${10}^{5}$ events per 2-MeV mass bin. All the widths were found to be narrower than widths obtained from $\ensuremath{\pi}p$ phase-shift analyses. For example, our result for ${N}^{*}(1512)$ is $\ensuremath{\Gamma}=88\ifmmode\pm\else\textpm\fi{}2$ MeV as compared with the "table value" of 105-155 MeV. No narrow structure greater than 5% of the cross section for the known peaks was observed.