Low-energy isoscalar quadrupole strength in 40Ca and 48Ca from (p,p′x) reactions

A decomposition of giant multipole strength in 40Ca and 48Ca is performed from angular correlations and emission angle-integrated angular distributions of the reactions 40Ca(p, p′α0)36Ar, 40Ca(p, p′p0)39K and 48Ca(p, p′n0)47Ca. The deduced B(E2) strength distributions agree reasonably well in shape and magnitude with the results of electron-induced experiments. Previous suggestions of a systematic discrepancy of the total E2 strengths in the α0 channel derived from hadronic and electromagnetic probes are shown to be unfounded. In 48Ca, for the first time evidence for sizable isoscalar E2 strength at low excitation energies, similar to 40Ca, could be established.