Polarization degrees of freedom in photoinduced two-nucleon knockout from finite nuclei

The polarization degrees of freedom in photoinduced two-nucleon knockout from finite nuclei are studied. It is pointed out that they open good perspectives to study the dynamics of dinucleons in the medium in detail. The (γ,pp) and (γ,pn) angular cross sections, photon asymmetries, and outgoing nucleon polarizations are calculated for the target nuclei ¹⁶O and ¹²C and photon energies ranging from 100 up to 500 MeV. It is investigated to which degree the two-nucleon emission reaction is dominated by photoabsorption on ³S₁(T=0) proton-neutron and ¹S₀(T=1) proton-proton pairs in the nuclear medium. The calculations demonstrate that dominance of S-wave photoabsorption in the (γ,pn) channel does not necessarily imply that the reaction mechanism is similar to what is observed in deuteron photodisintegration.