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Exclusive photoproduction of π0 up to large values of Mandelstam variables s,t, and u with CLAS
- Source :
- Physical Review C. 98
- Publication Year :
- 2018
- Publisher :
- American Physical Society (APS), 2018.
-
Abstract
- Exclusive photoproduction cross sections have been measured for the process γ p → p π 0 [ e + e − ( γ ) ] with the Dalitz decay final state using tagged photon energies in the range of E γ = 1.275 – 5.425 GeV. The complete angular distribution of the final state π 0 , 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 d σ / d t , 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 = 11 GeV 2 . At the same time, the Regge-exchange-based models for π 0 photoproduction are more consistent with experimental data.
Details
- ISSN :
- 24699993 and 24699985
- Volume :
- 98
- Database :
- OpenAIRE
- Journal :
- Physical Review C
- Accession number :
- edsair.doi...........1a4e19728e49360ee149ee5baf0be7f9