Exclusive photoproduction of π 0 up to large values of Mandelstam variables s, t, and u with CLAS.

Document Type

Article

Publication Date

2018

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.

Comments

Copyright 2018 American Physical Society

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

Publication Title

Physical Review C

Published Citation

Kunkel, M. C., M. J. Amaryan, I. I. Strakovsky, J. Ritman, G. R. Goldstein, K. P. Adhikari, S. Adhikari, Biselli, A. et al [CLAS Collaboration]. "Exclusive photoproduction of π 0 up to large values of Mandelstam variables s, t, and u with CLAS." Physical Review C 98, no. 1 (2018): 015207. DOI:https://doi.org/10.1103/PhysRevC.98.015207

DOI

10.1103/PhysRevC.98.015207

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