EXCITATION OF NEGATIVE PARITY NUCLEON ISOBARS IN QUARK MODEL

We discuss recent measurements of excitation of higher nucleon isobars in both pp and πp collisions, together with speculations that have been made that their excitation is due to a diffraction dissociation process. We show how this mechanism can be related to recent models ascribing such high energy direct reactions to sums of quark-quark interactions, together with suggested assignments for higher isobars in the quark model: if these assumptions are valid, including the L-excitation assignments to the isobars, the quark-quark diffraaction scattering must then include a contribution involving spin-flip. This contribution has some consequences which can be used to check these models and the L = 1 assignments to the negative parity isobars. It is also noted how such a spin-flip contribution could be involved in other processes, including one, production of the A2 meson, in which its effects may already have been observed. © 1968.