Resonance decays and partial coherence in Bose-Einstein correlations

We investigate the influence of resonances on Bose-Einstein correlations (BEC) in the presence of coherence of the pion field. For this purpose a realistic description of resonance production via hydrodynamics is attempted by constraining the initial and freeze-out conditions so that the single inclusive rapidity and transverse momentum distributions are correctly reproduced. We find that even a totally coherent source of ''direct'' pions leads to an appreciable apparent chaoticity because of the important role played by resonances in distorting the correlation 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. Quantitative predictions of BEC in S+S reactions at 200 AGeV are made. (orig.)