The effect of virtual states on the saturation properties of nuclear matter is studied within the framework of lowest-order Brueckner theory. The is treated as a stable elementary particle. Transitions from the nucleon-nucleon () channel to the nucleon- channel are caused by a nonrelativistic potential obtained from the static limit of meson theory. The coupled-channel potentials are constrained to fit the phase shifts. Saturation curves are calculated for the couplings and , and the effects of other couplings to nucleon-nucleon and waves are estimated. Calculations are done using both the Reid soft-core and Ueda-Green potentials for partial waves not coupled to the channel. The coupling does not change the usual tendency of the calculated saturation points to lie in a narrow band in the energy-density plane that does not contain the empirical saturation point. This result is illuminated by a rough approximation to the Pauli and dispersion effects. We have also used this approximation to estimate the loss of binding due to coupling in those channels not treated by detailed calculation. Combining all our results, we find that at the empirical density (1) the inclusion of coupling in nucleon-nucleon , , and waves reduced the binding energy by about 3.3, 3.2, and 0.8 MeV, respectively, and (2) each particle spends about 3.7% of its time as a . All these figures vary roughly quadratically with the coupling constant and increase rapidly with density. The size of the shift in energy depends strongly on the suppression of the short-range part of the two-body wave function, but our approximate formulas indicate that the tendency of the calculated saturation points to remain in a narrow band is independent of the short-range behavior of the two-body interaction, i.e., it is model-independent.
NUCLEAR STRUCTURE Effect of on saturation of nuclear matter studied in lowest-order Brueckner-Bethe-Goldstone theory.
- Received 22 December 1975
- Published in the issue dated April 1976
© 1976 The American Physical Society