Hard photodisintegration of a proton pair

We present a study of high energy photodisintegration of proton-pairs through the γ+He3→p+p+n channel. Photon energies, Eγ, from 0.8 to 4.7 GeV were used in kinematics corresponding to a proton pair with high relative momentum and a neutron nearly at rest. The s−11 scaling of the cross section, as predicted by the constituent counting rule for two nucleon photodisintegration, was observed for the first time. The onset of the scaling is at a higher energy and the cross section is significantly lower than for deuteron (pn pair) photodisintegration. For Eγ below the scaling region, the scaled cross section was found to present a strong energy-dependent structure not observed in deuteron photodisintegration.