THE FRAGMENT COALESCENCE MODEL

The extraction of source radii from heavy-ion collisions using coalesc ence models is explored. A new prescription is presented which conside rs nucleosynthesis via the coalescence of fragments which is, in parti cular, more appropriate for intermediate-energy collisions than the pr evious nucleon coalescence prescriptions. This fragment coalescence mo del provides an avenue for viewing the breakup stage of heavy-ion reac tions that yields valuable complimentary information to two-nucleon an d two-fragment correlation measurements. This model was applied to rec ent experimental data on central 55 and 115 MeV/nucleon Ar-40+Sc-45 co llisions studied at midrapidity. Source radii are presented versus the transverse velocity for six different coalescence channels leading to charge one, two, and three fragments. Particular attention is paid to the temperature input in the model, as the extracted radii depend sig nificantly on this parameter. A means of extracting the temperature fr om experimental data using the present model is described. Comparisons to the two temperature-dependent nucleon coalescence models will also be discussed.