Angular correlation of e'+ e'- pair production in QED

We study the angular correlation of monoenergetic e'+e'- pairs produced by gamma gamma collisions in QED to lowest order in the fine-structure constant. This is done by computing, in the process, the gamma gamma-polarization-momentum averaged, the e'+e'- spin averaged conditional probability density that the e'+e'-emerge, upon their production, making certain angles between their outgoing momenta. The conditional probability density is non-zero for separation angles greater than as well as less than pi/2. The angular correlation is defined as the average of the cosine of the angle of separation. In particular, we learn that the angular correlation is negative for all energies indicating that the e'+e'- tend to travel in opposing directions in a statistical sense. (Author) 6 refs