QUARK-MODEL CALCULATIONS OF CURRENT CORRELATORS IN THE NONPERTURBATIVE DOMAIN

We study the vector-isovector current correlator in this work, making use of a generalized Nambu-Jona-Lasinio (NJL) model. In our work, the original NJL model is extended to describe the coupling of the quark-antiquark states to the two-pion continuum. Further, a model for confinement is introduced that is seen to remove the nonphysical cuts that appear in various amplitudes when the quark and antiquark go on mass shell. Quite satisfactory results are obtained for the correlator. We also use the correlator to define a T-matrix for confined quarks and discuss a rho-dominance model for that T-matrix. It is also seen that the Bethe-Salpeter equation that determines the rho mass (in the absence of the coupling to the two-pion continuum) has more satisfactory behavior in the generalized model than in the model without confinement. That improved behavior is here related to the absence of the q (q) over bar cut in the basic quark-loop integral of the generalized model. In our model, it is seen how one may work with both quark and hadron degrees of freedom, with only the hadrons appearing as physical particles. (C) 1995 Academic Press, Inc.