DEUTERON FORMATION IN EXPANDING NUCLEAR-MATTER FROM A STRONG-COUPLINGBCS APPROACH

The process of deuteron formation in intermediate heavy ion reactions is approached within the strong coupling BCS theory assuming that the final stage of the reaction can be described as an adiabatic expansion of a piece of nuclear matter. Since the gap equation in the S-3(1)-D- 3(1) channel goes over into the deuteron Schrodinger equation in the l ow density limit, a smooth transition from the superfluid Cooper pair phase to a Bose deuteron gas is found. For a fixed entropy ranging fro m 0.5 to 2 units per particle the deuteron fraction, the chemical pote ntial and temperature are reported as a function of density. For densi ties down to rho = 0.1 fm(-3) and lower, the deuteron-to-nucleon ratio rapidly increases from a density threshold strongly depending on the entropy. Decreasing further the density this ratio tends logarithmical ly to one. The possible relevance of these results for heavy ion colli sions and the shortcomings of the present approach are briefly discuss ed.