Phi-measure of event-by-event fluctuations

by Stanislaw Mrowczynski (Warsaw)

Monday 27 Mar 2000, 14:00 → 14:15 Europe/Zurich

CERN

Event-by-event fluctuations can be used as a source of information on the dynamics of heavy-ion collisions. However, there is a problem how to disentangle the 'dynamical' fluctuations of interest from the 'trivial' geometrical ones due to the impact parameter variation. The problem is solved in a specific way by using the measure of fluctuations or correlation's which is called Phi. It equals zero when the correlations are entirely absent. On the other hand, Phi is constructed in such a way that it is exactly the same for nucleon-nucleon and nucelus-nucelus collisions if the latter one is a simple superposition of the former. Phi-measure has been successfully applied to the NA49 experimental data and the fluctuations of transverse momentum, which are observed in nucleon-nucleon collisions, have been found to be significantly reduced in the central Pb-Pb collisions at 158 GeV per nucleon. The Phi-measure is applicable not only to the fluctuations of kinematical quantities such as p_T but to the azimuthal and chemical fluctuations as well. We discuss in detail how the quantum statistics, secondary interactions, and collective flow influence Phi.

Organiser(s): Yiota Foka and Ulrich Heinz

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