RESONANCE DECAYS AND PARTIAL COHERENCE IN BOSE-EINSTEIN CORRELATIONS

We investigate the influence of resonances on Bose-Einstein correlatio ns (BEC's) in the presence of coherence of the pion field. For this pu rpose a realistic description of resonance production via hydrodynamic s is attempted by constraining the initial and freeze-out conditions s o that the single inclusive rapidity and transverse momentum distribut ions are correctly reproduced. We find that even a totally coherent so urce of ''direct'' pions leads to an appreciable apparent chaoticity b ecause of the important role played by resonances in distorting the co rrelation function. On the other hand, kaons, being much less affected by resonance decays, seem to be ideal candidates for the experimental investigation of coherence in BEC's. Quantitative predictions of BEC' s in S + S reactions at 200 A GeV are made.