We investigate degree of coherence of pion sources produced in relativistic heavy ion collisions using multi-particle interferometry. In order to obtain ''true'' chaoticity, lambdatrue from two-pion correlation functions measured in experiments, we make a correction for long-lived resonance decay contributions. Using this lambdatrue and the weight factor which are obtained from parameter fitted to two- and three-pion correlation function, we calculate a chaotic fraction e and the number of coherent sources alpha for different colliding energies. The result gives constraints on the source and shows an increase of the minimum number of alpha with multiplicity, although multiplicity independent chaoticity is not excluded.
Relativistic heavy ion collisions; Pion interferometry
