SPIN-ISOSPIN MODES IN HEAVY-ION COLLISIONS .1. NUCLEAR-MATTER AT FINITE TEMPERATURES

With a view toward implementation in microscopic transport simulations of heavy-ion collisions, the properties of spin-isospin modes are stu died in nuclear matter consisting of nucleons and Delta isobars that i nteract by the exchange of pi and p mesons. For a standard p-wave inte raction and an effective g' short-range interaction, the dispersion re lations for the spin-isospin modes, and the associated amplitudes, are calculated at various nuclear densities and temperatures within the r andom-phase approximation. Quantities of physical interest are then ex tracted, including the total and partial Delta decay widths and the De lta cross sections in the nuclear medium. The self-consistent inclusio n of the Delta width has a strong effect on the Delta cross sections a t twice the normal nuclear density, as compared with the result of ign oring the width. Generally, the obtained quantities exhibit a strong d ensity dependence, but are Fairly insensitive to the temperature, at l east up to T=25 MeV. Finally, it is described how these in-medium effe cts may be consistently included in microscopic transport simulations of nuclear collisions, and the improvements over previous approaches a re discussed. (C) 1995 Academic Press. Inc.