Analogues of giant resonances and photoproduction of positive pions from ¹⁶O

Using a pure configuration shell model, differential and total cross sections have been evaluated for the photoproduction of positive pions from ¹⁶O leading to giant resonance states of various multipolarities in ¹⁶N. The two-particle-two-hole (2p-2h) ground state correlations in ¹⁶O are also taken into account. These 2p-2h correlations reduce the cross sections by about 30%. The total cross section for the 2⁺ giant quadrupole state is found to have a large peak near the first pion-nucleon resonance region, making it thereby possible to experimentally identify it from other multipole resonance states by varying the incident photon energy.