A case study in intermittency: The Thermodynamic Model for intermediate energy heavy ion collisions

Abstract

The Thermodynamic Model for heavy ion collisions explains, at least semi-quantitatively, many, though not all, features of the experimental data at Bevalac energies. We use this model as a case study for intermittency. A composite with n nucleons and total momentum P will be registered at the detector as n nucleons each with momentum P/ n. We find that in this model the scaled factorial moments grow indefinitely with M where M is the number of divisions in the p z window. In so far as composites are droplets of various sizes (free nucleons constitute a gas), intermittency is seen to be linked to the existence of droplets. The role of resonances is examined by including excited “deuterons” whose mass determines the width of the momentum distribution of the decay nucleons. For nucleons and resonances only, the scaled factorial moments saturate with M when the bin size becomes smaller than the width. These results do not depend upon the size of the colliding systems thus the model cannot explain why, for example, e + e − shows stronger intermittency than the currently available heavy ion data.