Interplay between experimental and theoretical physics

This paper reports on two periods in the scientific career of Leon Van Hove that demonstrate how progress in a very complex field can be reached by means of a very close interplay between phenomenological analysis of sufficiently accurate experiments, mainly in terms of various tentative models, and application of the few general theoretical principles which seem to be well established. These periods are an earlier one ranging from Longitudinal Phase Space to Analytical Multichannel Analysis and a recent one from Negative Binomial Multiplicity Distributions to Globs of Cold Quark-Gluon Plasma and beyond. The experimental applications are historical by necessity, but the basic ideas also apply to future experiments, wherever physics has to be extracted from the bulk of background