Delta-hole Interaction in Nuclei and the Gamow-teller Strength In

The recently obtained experimental result for the quenching of the GT sum rule in the reaction 90Zr(p,n)90Nb is used to extract the value of the Landau-Migdal parameter g N∆, taking into account also the effect of the finite range meson exchange interactions. The extracted value is compared to the one obtained in the π + ρ exchange model by explicitly taking into account the effects of antisymmetrization and short range correlations. Although the π+ρ exchange model tends to give a somewhat stronger quenching than observed experimentally, the results are consistent within the experimental error bars if the quark model value for the parameter f∆/fπ is used. PACS: 21.30.Fe; 21.60.Ev; 24.30.Cz; 25.40.Kv; 27.60.+j Keywords; Landau-Migdal parameters; Quenching of Gamow-Teller strength; ∆-hole interaction The study of the renormalization of Gamow-Teller (GT) matrix elements in nuclei has revealed valuable information on nuclear structure effects and non-nucleonic degrees of freedom like mesons and delta-isobars [1, 2]. If one considers only the low energy part of the GT strength function, as provided by the GT β-decay matrix elements or the charge exchange reactions at low excitation energies, one cannot decide a priori whether the experimentally observed quenchings originate from nuclear structure effects, like configuration mixing and core polarization, or from non-nucleonic degrees of freedom. Although theoretical calculations with realistic interactions have shown that a considerable amount of strength is shifted to the higher energy region due to the admixture of 2p− 2h components in even-even nuclei[3], the observed quenchings have also been attributed to the admixture of ∆-hole components by assuming a large value of the Landau-Migdal parameter g N∆ characterizing the strength of the NN → N∆ transition potential [4]. In order to E-mail addresses: [email protected] (W. Bentz), [email protected] (Toshio Suzuki), [email protected] (Toshio Suzuki)