Can quark models explain electroproduction of the L = 1 supermultiplet?

Abstract

A review of the application of quark models to photo- and electroproduction of the [70, 1-] nucleon resonances is presented. Also since there is no dynamically complete theory of the quarks in hadrons, we decompose a wide class of algebra-preserving quark models for electroproduction into three elements: the electromagnetic current, the quark wavefunctions, and the hadronic boost prescription. All quark models have made choices, often implicit, for these three ingredients although they are not independent in a complete theory. In focussing attention on these ingredients, we highlight the wide range of choices which may be made in empirical quark model applications. Several resulting models are examined and compared with both the proton magnetic form factor and the electroproduction data; some of these models compare more favourably with the data than others. In particular we find that popular models using free quark spinors cannot simultaneously fit the photoproduction data and the behaviour of the reduced matrix elements in the electroproduction region. However, with spinors derived from a Dirac equation with a potential all the elements present in the data may be reproduced.