SPIN-ISOSPIN RESPONSE FUNCTIONS AND THE EFFECTS OF THE DELTA-HOLE CONFIGURATIONS IN FINITE NUCLEI

Effects of the delta-isobar (Δ) mixing on the spin-isospin response functions in finite nuclei are studied in the quasielastic region. A method to calculate the response function for a finite system composed of nucleon (N) and Δ is formulated in a ring approximation. It is designed to treat the Δ-related Landau-Migdal parameters gNΔ′, gΔΔ′ and the nucleon parameter gNN′, independently, so that the universality ansatz, gNN′=gNΔ′=gΔΔ′, is removed. We calculated the isovector spin-longitudinal and -transverse response functions, RL and RT, with and without the Δ mixing. Inclusion of Δ enhances RL but reduces RT for ordinary interactions. Dependence of RL,T on gNN′ and gNΔ′ is investigated. Decomposition into the process-decomposed response functions, R[NN], R[NΔ], and R[ΔΔ], is very elucidative to see the Δ effects, which are found to be mainly governed by R[NΔ] and sensitive to gNΔ′. The isovector spin-transverse response function RT(e,e′) obtained by (e,e′) is calculated by various effective interactions and compared to each other as well as experimental data. © 1995 The American Physical Society.