Thermodynamics of Distinguishable Particles: A Key to High-Energy Strong Interactions?

Abstract

A new kind of thermodynamical model for strong interactions at high energies is proposed. We start from the fact that strong interactions produce so many possible particle states (from \(\uppi\) over its resonances to nucleons, strange particles and their resonances, up to highly excited ‘fireballs’) that in an actual process each of these states practically never occurs more than once. We use this in order to treat the very first instant of a high-energy collision by statistical thermodynamics of a system of an illimited number of distinguishable particles. The model shows surprising properties: there exists a universal highest possible temperature T0 of the order of 150–200 MeV (corresponding to ≈ 1012 K) which governs all high-energy processes of strongly interacting particles, independently of the actual energy and independently of the particle number, from cosmic ray jets down to elastic scattering. If a Lorentz contracted volume is introduced, the transverse momentum distribution in jets as well as in elastic scattering is described in agreement with experimental results. Paradoxically, this distribution is independent of whether or not ‘thermal equilibrium’ is reached. If it is not reached—in the majority of cases it is not reached—then the jet structure for production processes is the consequence. If the model turns out to be as good as present experiments indicated, then the existence of a highest temperature is very likely; it implies that, from higher and higher energy experiments, not much new can be learnt about the structure of strong interactions, since the mode of excitation (which depends on the dynamical details we would like to know) has no influence on what is finally observed. The situation would then be similar to that in ordinary thermodynamics, where no experiment could possibly reveal how a certain system was brought into its thermodynamical state. In astrophysics, the method of thermodynamics of distinguishable particles may have important consequences for the treatment of the highly compressed interior of heavy stars (‘neutron stars’) where Fermi statistics would have to be replaced by the one used here.