Evidence for Narrow Baryon Resonances in InelasticppScattering

The reaction $\mathrm{pp}\to p{\pi }^{+}N$ has been studied at three energies ( $T_p=1520\mathrm{}$, 1805, and 2100 MeV) and six angles from 0° up to 17° (laboratory). Several narrow states have been observed in missing mass spectra at 1004, 1044, and 1094 MeV. Their widths are typically 1 order of magnitude smaller than the widths of $N^{*}$ or $\Delta$. Possible biases are discussed. These masses are in good agreement with those calculated within a simple phenomenological mass formula based on color magnetic interaction between two colored quark clusters.