Thank you for sharing this. I knew that they were working towards this experiment for a few years now. I see that they are ionizing gold nuclei to do a near miss pass to created the virtual photons. It is a good workaround, since they cannot currently make a direct photon-photon interaction with high enough energy to get the pair production process to work right. The reverse process can be experimentally done if you happen to have the right anti-matter target handy. They often use positrons for this, as it is a natural decay product from certain radioactive isotopes. The resulting photons are in the high x-ray range.
Hopefully it will give clues to the inner workings of String Theory. I will be happy either way if it proves or disproves some of my theories on this subject. Either way, it will get us closer to how matter/anti-matter is formed.