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Exclusive photoproduction of π0 up to large values of Mandelstam variables s, t, and u with CLAS
Journal
Physical Review C
Date Issued
2018-07-25
Author(s)
Kunkel, M. C.
Amaryan, M. J.
Strakovsky, I. I.
Ritman, J.
Goldstein, G. R.
Adhikari, K. P.
Adhikari, S.
Avakian, H.
Ball, J.
Balossino, I.
Barion, L.
Battaglieri, M.
Batourine, V.
Bedlinskiy, I.
Biselli, A. S.
Boiarinov, S.
Briscoe, W. J.
Bültmann, S.
Burkert, V. D.
Cao, F.
Carman, D. S.
Celentano, A.
Charles, G.
Chetry, T.
Ciullo, G.
Clark, L.
Cole, P. L.
Contalbrigo, M.
Cortes, O.
Crede, V.
D'Angelo, A.
Dashyan, N.
De Vita, R.
De Sanctis, E.
Degtyarenko, P. V.
Defurne, M.
Deur, A.
Djalali, C.
Dugger, M.
Dupre, R.
Egiyan, H.
El Fassi, L.
Elouadrhiri, L.
Eugenio, P.
Fedotov, G.
Fersch, R.
Filippi, A.
Fradi, A.
Gavalian, G.
Ghandilyan, Y.
Ghosh, S.
Gilfoyle, G. P.
Giovanetti, K. L.
Girod, F. X.
Glazier, D. I.
Gohn, W.
Golovatch, E.
Gothe, R. W.
Griffioen, K. A.
Guo, L.
Guidal, M.
Hafidi, K.
Harrison, N.
Hattawy, M.
Hicks, K.
Holtrop, M.
Hyde, C. E.
Ireland, D. G.
Ishkhanov, B. S.
Isupov, E. L.
Jenkins, D.
Joo, K.
Kabir, M. L.
Keller, D.
Khachatryan, G.
Khachatryan, M.
Khandaker, M.
Kim, A.
Kim, W.
Klein, A.
Klein, F.
Kubarovsky, V.
Kuhn, S. E.
Laget, J. M.
Lanza, L.
Lenisa, P.
Lersch, D.
Livingston, K.
Macgregor, I. J.D.
Markov, N.
Mbianda Njencheu, G.
McKinnon, B.
Mokeev, V.
Montgomery, R. A.
Movsisyan, A.
Munoz Camacho, C.
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 = 11 GeV2
. At
the same time, the Regge-exchange-based models for π0 photoproduction are more consistent with experimental
data.
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 = 11 GeV2
. At
the same time, the Regge-exchange-based models for π0 photoproduction are more consistent with experimental
data.
Subjects
