Toward an actual account for the angular dependence of the Brueckner-Bethe-Goldstone propagator in nuclear matter

Abstract

Angular correlations arising from particle-particle (pp) propagation in symmetric nuclear matter are investigated. Their account follows a detailed treatment of the angular dependence of the energy denominator of the propagator in the Brueckner-Bethe-Goldstone (BBG) equation, in conjunction with the Pauli exclusion principle for intermediate states. As a result, taking a monopole approximation for the propagator, a correlation form factor emerges from the Cauchy principal-value integral of the pp propagator, while the imaginary part becomes structurally different from those in Lippmann-Schwinger-type equations. These features are investigated within the continuous choice of the single-particle potential considering the Argonne v18 and Paris two-nucleon potentials. We find that the behavior of the mass operator is affected, deepening slightly the saturation point of symmetric nuclear matter relative to those based on angle-averaged energy denominators. Implications of these angular correlations were also investigated in the context of proton-nucleus scattering, showing clear effects on scattering observables below 100 MeV.