학술논문
Exclusive photoproduction of $\pi^0$ up to large values of Mandelstam variables $s, t$ and $u$ with CLAS
Document Type
Working Paper
Author
Kunkel, M. C.; Amaryan, 18 M. J.; Strakovsky, I. I.; Ritman, 16 J.; Goldstein, 18 G. R.; Adhikari, 43 K. P.; Adhikari, 28 S; Avakian, 13 H.; Ball, 39 J.; Balossino, 7 I.; Barion, 19 L.; Battaglieri, 19 M.; Batourine, 21 V.; Bedlinskiy, 27 I.; Biselli, 25 A. S.; Boiarinov, 5 S.; Briscoe, 39 W. J.; Brooks, 16 W. K.; Bueltmann, 39 S.; Burkert, 32 V. D.; Cao, 39 F.; Carman, 9 D. S.; Celentano, 39 A.; Charles, 21 G.; Chetry, 32 T.; Ciullo, 31 G.; Clark, 12 L.; Cole, 42 P. L.; Contalbrigo, 17 M.; Cortes, 19 O.; Crede, 17 V.; DAngelo, 14 A.; Dashyan, 35 N.; De Vita, 47 R.; De Sanctis, 21 E.; Degtyarenko, 20 P. V.; Defurne, 39 M.; Deur, 7 A.; Djalali, 39 C.; Dugger, 37 M.; Dupre, 2 R.; Egiyan, 24 H.; Alaoui, 39 A. El; Fassi, 40 L. El; Elouadrhiri, 28 L.; Eugenio, 39 P.; Fedotov, 14 G.; Fersch, 31 R.; Filippi, 46 A.; Fradi, 23 A.; Gavalian, 24 G.; Ghandilyan, 29 Y.; Ghosh, 47 S.; Gilfoyle, 10 G. P.; Giovanetti, 34 K. L.; Girod, 26 F. X.; Glazier, 39 D. I.; Gohn, 42 W.; Golovatch, E.; Gothe, 36 R. W.; Griffioen, 37 K. A.; Guo, 46 L.; Guidal, 39 M.; Hafidi, 24 K.; Hakobyan, 1 H.; Harrison, 47 N.; Hattawy, 39 M.; Hicks, 1 K.; Holtrop, 31 M.; Hyde, 29 C. E.; Ireland, 32 D. G.; Ishkhanov, 42 B. S.; Isupov, 36 E. L.; Jenkins, 36 D.; Joo, 44 K.; Kabir, 9 M. L.; Keller, 28 D.; Khachatryan, 45 G.; Khachatryan, 47 M.; Khandaker, 32 M.; Kim, A.; Kim, 9 W.; Klein, 27 A.; Klein, 32 F.; Kubarovsky, 16 V.; Kuhn, 39 S. E.; Laget, 32 J. M.; Lanza, 7 L.; Lenisa, 35 P.; Lersch, 19 D.; Livingston, 18 K.; MacGregor, 42 I . J . D.; Markov, 42 N.; Mbianda, 9 G.; McKinnon, 32 B.; Mineeva, 42 T.; Mokeev, 9 V.; Montgomery, 36 R. A.; Movsisyan, 42 A; Camacho, 19 C. Munoz; Nadel-Turonski, 24 P.; Niccolai, 39 S.; Niculescu, 24 G.; Osipenko, 26 M.; Ostrovidov, 21 A. I.; Paolone, 14 M.; Park, 38 K.; Pasyuk, 37 E.; Payette, 39 D.; Phelps, 32 W.; Pogorelko, 16 O.; Poudel, 25 J.; Price, 32 J. W.; Procureur, 4 S.; Prok, 7 Y.; Protopopescu, 45 D.; Ripani, 42 M.; Ritchie, 21 B. G.; Rizzo, 2 A.; Rosner, 35 G.; Roy, 42 A.; Sabatie, 10 F.; Salgado, 7 C.; Schadmand, 30 S.; Schumacher, 18 R. A.; Sharabian, 5 Y. G.; Skorodumina, 39 Iu.; Ireland, 36 D. G.; Sokhan, 42 D.; Sober, 42 D. I.; Sparveris, 6 N.; Strauch, 38 S.; Taiuti, 16 M.; Tan, 15 J. A.; Ungaro, 27 M.; Voskanyan, 33 H.; Voutier, 47 E.; Watts, 24 D. P.; Weinstein, 41 L.; Wei, 32 X.; Weygand, 39 D. P.; Zachariou, 8 N.; Zhang, 41 J.; Zhao32, Z. W.
Source
Phys. Rev. C 98, 015207 (2018)
Subject
Language
Abstract
Exclusive photoproduction cross sections have been measured for the process $\gamma p \rightarrow p\pi^0(e^+e^-(\gamma))$ with the Dalitz decay final state using tagged photon energies in the range of $E_{\gamma} = 1.275-5.425$ GeV. The complete angular distribution of the final state $\pi^0$, 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 $d\sigma/dt$, at mid to large angles, decreases with energy as $s^{-6.89\pm 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 $\pi^0$ photoproduction are more consistent with experimental data.
Comment: 7 pages, 6 figures
Comment: 7 pages, 6 figures