Measurement ofπ+/π−cross section ratio for the giant quadrupole resonance inPb208

Cross sections have been measured for ${\pi }^{+}$ and ${\pi }^{\mathrm{-}}$ scattering to the giant resonance region of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ with 162-MeV pions. The value of R=σ(${\pi }^{\mathrm{-}}$)/σ(${\pi }^{+}$) measured for the giant quadrupole resonance is 2.72. A distorted wave impulse approximation analysis of these data using collective model form factors gives the ratio of neutron to proton matrix elements to be 3.8. This is much larger than expected from the hydrodynamical model which predicts a value of N/Z of 1.54.