Exclusive production of proton-antiproton pairs in two-photon collisions

We report cross sections for the process ..gamma gamma -->..pp-bar at center-of-mass energies W from 2.0 to 2.8 GeV. These results have been extracted from measurements of e/sup +/e/sup -/..-->..e/sup +/e/sup -/pp-bar at an overall center-of-mass energy of 29 GeV, using the TPC/Two-Gamma facility at the SLAC storage ring PEP. Cross sections for the untagged mode (both photons nearly real) are shown to lie well above QCD predictions. Results are also presented for the single-tagged mode (one photon in the range 0.16