Source chaoticity in relativistic heavy ion collisions at SPS and RHIC

Abstract

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

Effects of source opacity and expansion on two-pion Bose-Einstein correlations

“…The value of two-pion correlation function at the zero relative momentum is less than two after the final-state interaction is removed in the case of chaotic sources. The result suggests that the sources are partially coherent due to the collective action of a large group of nucleons in addition to the chaoticity coming from isolated nucleon-nucleon collisions in the pion field [2,4, [7][8][9][10][11][12][13][14]. A more detailed investigation on partially coherent pion field can reveal the kinematic information on pion-emitting mechanism.…”