Onset of asymptotic scaling in deuteron photodisintegration

We investigate the transition from the nucleon-meson to the quark-gluon description of the strong interaction using the photon energy dependence of the d ( γ , p ) n differential cross section for photon energies above 0.5 GeV and center-of-mass proton angles between 30° and 150°. A possible signature for this transition is the onset of cross-section s ^-11 scaling with the total energy squared, s , at some proton transverse momentum P _T . The results show that the scaling has been reached for proton transverse momentum above about 1.1  GeV/ c . This may indicate that the quark-gluon regime is reached above this momentum.