Coalescence and flow in ultrarelativistic heavy ion collisions

Using a density matrix approach to describe the process of coalescence, we calculate the coalescence probabilities and invariant momentum spectra for deuterons and antideuterons. We evaluate our expressions with a hydrodynami cally motivated parametrization for the source at freeze-out which implemen ts rapid collective expansion of the collision zone formed in heavy ion col lisions. We find that the coalescence process is governed by the same lengt hs of homogeneity which can be extracted from Hanbury Brown-Twiss (HBT) int erferometry. They appear in the absolute cluster yield via an effective vol ume factor as well as in a quantum mechanical correction factor which accou nts for the internal structure of the deuteron cluster. Our analysis provid es a new interpretation for the parameters in the popular phenomenological coalescence model and for the effective overlap volume in Hagedorn's model for cluster production in pp collisions. Using source parameters extracted from a recent HBT analysis of two-pion correlations, we successfully descri be deuteron and antideuteron production data from Pb + Pb collisions at the CERN PS as measured by the NA44 and NA52 Collaborations. We also confirm t he recent finding by Polleri et al. that the different measured slopes of n ucleon and deuteron transverse mass spectra require a transverse density pr ofile of the source which is closer to a box than to a Gaussian shape. [S05 56-2813(99)06102-6].