Does the delta quench Gamow-Teller strength in (p,n)- and (p vector,p vector')-reactions

Microscopic analyses of complete forward angle intermediate energy (p,n)-, (3He,t)- and (p vector,p vector')-spin-flip spectra are presented for the reactions 90Zr(p,n), 90Zr(3He,t) and 90Zr(p vector,p vector'). It is shown that the whole spectra up to high excitation energies (EX∝50 MeV) are the result of correlated one-particle-one-hole (1p1h) spin-isospin transitions only. The spectra reflect, therefore, the linear spin-isospin response of the target nucleus to the probing external hadronic fields. Our results suggest that the measured (p,n)-, (3He,t)- and (p vector,p vector')-cross sections are compatible with the transition strength predictions as obtained from random phase approximation (RPA) calculations. This means that the Δ isobar quenching mechanism is likely to be rather small. (orig.)