“…T h e interpretation of the small structure, observed by Barepre et al (1964) in aT(.r-p) at a laboratory momentum of 0.5 Gevlc, as due to the presence of a pionnucleon isobar, has been discussed for some time. A bump at the corresponding centre-of-momentum energy (about 1400 hIev) has been observed in the energy spectrum of protons scattered inelastically off protons (Belletini et al 1965a, ,Inderson et al 1966, Blair et al 1966, and evidence for an isobar in this mass range also comes from phase-shift analysis in pion-nucleon scattering. We may conclude, then, that the structure observed by Bareyre et al can be accounted for by the presence of this isobar with I = J = 4, of mass 1410 k 15 Vel7 (Blair et al 1969).…”