1. Exclusive photoproduction of <math><msup><mi>π</mi><mn>0</mn></msup></math> up to large values of Mandelstam variables <math><mrow><mi>s</mi><mo>,</mo><mspace width='0.16em'></mspace><mi>t</mi><mo>,</mo></mrow></math> and <math><mi>u</mi></math> with CLAS
- Author
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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., Brooks, W.K., 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 Alaoui, A., 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., Hakobyan, H., 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., Mineeva, T., Mokeev, V., Montgomery, R.A., Movsisyan, A., Munoz Camacho, C., Nadel-Turonski, P., Niccolai, S., Niculescu, G., Osipenko, M., Ostrovidov, A.I., Paolone, M., Park, K., Pasyuk, E., Payette, D., Phelps, W., Pogorelko, O., Poudel, J., Price, J.W., Procureur, S., Prok, Y., Protopopescu, D., Ripani, M., Ritchie, B.G., Rizzo, A., Rosner, G., Roy, A., Sabatié, F., Salgado, C., Schadmand, S., Schumacher, R.A., Sharabian, Y.G., Skorodumina, Iu., Stepanyan, S., Sokhan, D., Sober, D.I., Sparveris, N., Strauch, S., Taiuti, M., Tan, J.A., Ungaro, M., Voskanyan, H., Voutier, E., Watts, D.P., Weinstein, L., Wei, X., Weygand, D.P., Zachariou, N., Zhang, J., and Zhao, Z.W.
- 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.
- Published
- 2018