High Resolution Study of Pionic 0- State in 16O

The cross sections and analyzing powers of the ¹⁶O(p,p')¹⁶O(0^-,T = 1) scattering were measured at a bombarding energy of 295 MeV and an angular range of 14 ° ≤ θ_lab ≤ 30°. The isovector 0^- state at E_x = 12.80 MeV is clearly separated from the neighboring states with an energy resolution of ΔE ≃ 30 keV. The data have been compared with distorted wave impulse approximation (DWIA) calculations. The analyzing powers are sensitive to the effective nucleon-nucleon (NN) interaction used in DWIA calculations, and our data support the medium modification of the NN interaction in nuclei. The DWIA calculation employing a random phase approximation (RPA) response function predicts an enhancement of the cross sections around a momentum transfer of q ≃ 1.7 fm^-1, and it gives a reasonable agreement with the data.