RELATIVISTIC CALCULATION OF PAIR-PRODUCTION POLARIZATION CORRELATIONS FOR PHOTONS OF ENERGIES NEAR-THRESHOLD ON ATOMS

We calculated numerically in a relativistic partial-wave formulation the pair-production polarization correlations between incident photon and emitted positron in the field of atoms with atomic number Z = 1,6,13 and 82 for photons of energies near threshold, k = 2.001, 2.01, and 2.10m(e)c(2). It is shown that pair production can be used as a polarizer of positrons, a transmitter of polarization from photons to positrons, or an analyzer of polarized photons. In this low-photon-energy region, our partial-wave results indicate that the Horn approximation prediction is good only for the cases when the Coulomb parameter is quite small compared with unity. However, all these correlations can be large for the cases with high Z at suitable positron angles. Also, our partial-wave results show that the polarization correlations are almost independent of the atomic-electron screening. This suggests again that the screening be primarily a normalization effect.