Title

Exclusive photoproduction of π0 up to large values of Mandelstam variables s, t, and u with CLAS

Authors

M. C. Kunkel, Forschungszentrum Jülich (FZJ)
M. J. Amaryan, Old Dominion University
I. I. Strakovsky, The George Washington University
J. Ritman, Ruhr-Universitat Bochum
G. R. Goldstein, Tufts University
K. P. Adhikari, Mississippi State University
S. Adhikari, Florida International University
H. Avakian, Thomas Jefferson National Accelerator Facility
J. Ball, Institut de Recherche sur les Lois Fondamentales de l'Univers
I. Balossino, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara
L. Barion, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara
M. Battaglieri, Istituto Nazionale di Fisica Nucleare, Sezione di Genova
V. Batourine, Kyungpook National University
I. Bedlinskiy, Alikhanov Institute for Theoretical and Experimental Physics
A. S. Biselli, Carnegie Mellon University
S. Boiarinov, Thomas Jefferson National Accelerator Facility
W. J. Briscoe, The George Washington University
W. K. Brooks, Thomas Jefferson National Accelerator Facility
S. Bültmann, Old Dominion University
V. D. Burkert, Thomas Jefferson National Accelerator Facility
F. Cao, University of Connecticut
D. S. Carman, Thomas Jefferson National Accelerator Facility
A. Celentano, Istituto Nazionale di Fisica Nucleare, Sezione di Genova
G. Charles, Old Dominion University
T. Chetry, Ohio University
G. Ciullo, University of Ferrara
L. Clark, University of Glasgow
P. L. Cole, Idaho State University
M. Contalbrigo, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara
O. Cortes, Idaho State University
G. Fedotov, Ohio University
K. Hicks, Ohio University

Document Type

Article

Publication Date

7-25-2018

Abstract

© 2018 authors. Published by the American Physical Society. 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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