Perturbative QCD predictions for γγ → Β bar Β

While it is evident that perturbative QCD should not be expected to account for γγ → p bar p and γγ → Δ++bar Δ++ at the presently accessible energies of Wγγ ∼ 2.4GeV or less, since it should apply only to processes with large momentum transfer, it is inevitable that physicists are tempted to compare perturbative QCD predictions with the data. The previous study made the first such predictions for the reaction γγ → π+ π-, and data is in quite reasonable agreement. The expected scaling behavior is also observed. However γγ → p bar p is observed to be much larger than the predictions. Moreover it is observed that γγ → Δ++ bar Δ++ is less than 3 times as large as γγ → p bar p. This paper addresses the question of using that latter bound as a clue in understanding better the physics of these reactions