SEPARABLE NN POTENTIALS FROM INVERSE SCATTERING FOR NUCLEAR MATTER STUDIES

Low-rank separable potentials greatly simplify perturbation-theory bas ed many-body computations and are especially useful in finite temperat ure and nonequilibrium nuclear matter studies. With local potentials s uch calculations become very lengthy. In this paper, we present a firs t version of a separable potential constructed directly from available empirical nucleon-nucleon phase shifts (E-lab<1.6 GeV), and establish ed deuteron properties, via nonrelativistic inverse scattering. In our approach, the on-shell and off-shell properties of the potential can be independently varied: the on-shell scattering data are exactly fitt ed by construction while physically motivated off-shell features can b e systematically included. This advantage is illustrated by the applic ation of the procedure in the S-3(1)-D-3(1) channel, where the deutero n wave function serves as off-shell input at the binding energy. The: simplest potential thus constructed in this channel has rank il. The d euteron wave function is nevertheless empirically undetermined at high momenta, prompting us to adopt as well as construct several model wav e functions that all fit the low momentum deuteron data while allowing variations at high momenta. The effects of these off-shell variations on predicted nuclear matter properties are discussed. No off-shell in formation is included in the other channels, leading to potentials of rank either I or 2. With this simple model potential we perform standa rd Brueckner nuclear matter ground state calculations and compare the results with Machleidt's using Bonn OBEP. The agreement is good in the S channels and in the singlet D-2 channel. Other channels show larger discrepancies, the most significant of which coming from the P-3(1) a nd D-3(1) channels. These results are explained by the off-shell behav ior of our model potential as compared to the Bonn OBEP. Further off-s hell input, empirical and/or theoretical, will be explored in future i mproved versions of the model.