Multiplicity fluctuations in high-energy nuclear collisions as signature of the temperature fluctuations

Abstract

The large number of produced secondaries observed in recent heavy ion experiments (and still larger multiplicities expected to come from the LHC experiments) allows to study different aspects of dynamics of hadronization process on event-by-event basis. Among them the experimentally measured multiplicity fluctuations are especially important as a potential source of information on the strongly interacting system formed in such collisions. Most of studies of such processes use a statistical approach based on the Boltzmann-Gibbs (BG) statistics. However, conditions for the use of BG approach are usually not fully met in such reactions and one encounters some inherent problems arising from the smallness of the collision system and from its rapid evolution (the spatial configuration of the system are far from uniform and global equilibrium is not established). Nevertheless, one can still use simple statistical approach provided it is based on the nonextensive extension of the BG statistics with a new additional nonextensivity parameter q. In this extension, usually called Tsallis statistics, parameter q accounts summarily for all dynamical factors resulting in violation of assumptions of BG statistics. It characterizes itself by power-law form of basic distribution (see [T.S. Biro (ed.), Eur. Phys. J. A 40(3)(2009)] for recent review on this subject; for q → 1 the usual BG approach with the usual exponential distributions is recovered). In this presentation we shortly review the most interesting results of our studies (done using nonextensive statistics) of the recently observed fluctuations of multiplicity in heavy ion collisions.