Φ-measure of pions in high energy heavy-ion collisions

Event-by-event fluctuations for high energy heavy-ion collisions are investigated. The Φ-measures are calculated for pions. It is found that multiparticle symmetrization correlation has great influence on the value of Φ if the phase space density is high. Previous derivation of Φ-measure has neglected multiparticle quantum correlation. So the explanation of Φ-measure as a measure of dynamical correlation is reasonable only when multiparticles quantum correlation effects are smaller. We argue that the Φ-measure might be applicable at the SPS energy where the pion phase space density is much less than one.