Exclusive photoproduction of <math><msup><mi>π</mi><mn>0</mn></msup></math> up to large values of Mandelstam variables <math><mrow><mi>s</mi><mo>,</mo><mspace width='0.16em'></mspace><mi>t</mi><mo>,</mo></mrow></math> and <math><mi>u</mi></math> with CLAS

Exclusive photoproduction cross sections have been measured for the process γp→pπ0[e+e−(γ)] with the Dalitz decay final state using tagged photon energies in the range of Eγ=1.275–5.425 GeV. The complete angular distribution of the final state π0, for the entire photon energy range up to large values of t and u, has been measured for the first time. The data obtained show that the cross section dσ/dt, at mid to large angles, decreases with energy as s−6.89&#177;0.26. This is in agreement with the perturbative QCD quark counting rule prediction of s−7. Paradoxically, the size of angular distribution of measured cross sections is greatly underestimated by the QCD-based generalized parton distribution mechanism at highest available invariant energy s=11GeV2. At the same time, the Regge-exchange-based models for π0 photoproduction are more consistent with experimental data.