Home > Publications database > Exclusive photoproduction of π 0 up to large values of Mandelstam variables s , t , and u with CLAS |
Journal Article | FZJ-2018-04550 |
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2018
Inst.
Woodbury, NY
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Please use a persistent id in citations: http://hdl.handle.net/2128/19462 doi:10.1103/PhysRevC.98.015207
Abstract: 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±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.
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