Quark loops and open channels in hadron mass-spectrum dynamics

Chew-s S-matrix theory program has, from the beginning, attempted to exploit to the fullest constraints arising from certain general principles governing open hadronic-channel amplitudes. Its most extreme expression is the bootstrap theory, where these are assumed to be sufficient to determine the complete hadronic spectrum. On the other hand, in a ''confined'' theory like QCD, ''closed'' channels like qq-bar also contribute. In fact, these are often assumed to dominate. Since there is accumulating evidence to the contrary we have embarked on a program in which the closed-channel-only spectrum is taken as the input but in which non-perturbative methods are then used to build up the contributions of the open hadronic channels. Unlike earlier attempts to ''unitarize'' the quark model, the authors' approach does not exclude the possibility of formally switching off all the closed channels, thereby allowing the data itself to eventually decide how important the latter should be. The preliminary results are so far very promising