Measurement of the cross-section for the process γγ→pp¯ at √see=183−189GeV at LEP

The exclusive production of proton-antiproton pairs in the collisions of two quasi-real photons has been studied using data taken at √see = 183 GeV and 189 GeV with the OPAL detector at LEP. Results are presented for pp¯ invariant masses, W, in the range 2.15 <W < 3.95 GeV. The cross-section measurements are compared with previous data and with recent analytic calculations based on the quark-diquark model