First measurement of direct photoproduction of the a2(1320)0 meson on the proton

Celentano, A.; Battaglieri, M.; De Vita, R.; Marsicano, L.; Mathieu, V.; Pilloni, A.; Szczepaniak, A.; Adhikari, K. P.; Adhikari, S.; Amaryan, M. J.; Angelini, G.; Atac, H.; Barion, L.; Bedlinskiy, I.; Benmokhtar, F.; Bianconi, A.; Biselli, A. S.; Bossu, F.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Bulumulla, D.; Burkert, V. D.; Carman, D. S.; Carvajal, J. C.; Chatagnon, P.; Chetry, T.; Ciullo, G.; Clark, L.; Cole, P. L.; Contalbrigo, M.; Cortes, O.; Crede, V.; Cruz-Torres, R.; D'Angelo, A.; Dashyan, N.; Defurne, M.; Deur, A.; Diehl, S.; Djalali, C.; Dugger, M.; Dupre, R.; Egiyan, H.; Ehrhart, M.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fersch, R.; Filippi, A.; Gavalian, G.; Gevorgyan, N.; Girod, F. X.; Glazier, D. I.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Hafidi, K.; Hakobyan, H.; Harrison, N.; Hattawy, M.; Hauenstein, F.; Hayward, T. B.; Heddle, D.; Hicks, K.; Hobart, A.; Holtrop, M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jenkins, D.; H. S., Jo; Joo, K.; Joosten, S.; Keller, D.; Khachatryan, M.; Khanal, A.; Khandaker, M.; Kim, A.; Kim, C. W.; Kim, W.; Klein, F. J.; Kubarovsky, V.; Lanza, L.; Leali, M.; Lenisa, P.; Livingston, K.; Lucherini, V.; Macgregor, I. J. D.; Marchand, D.; Markov, N.; Mascagna, V.; Mccracken, M. E.; Mckinnon, B.; Meziani, Z. -E.; Mirazita, M.; Mokeev, V.; Movsisyan, A.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Neupane, K.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A. I.; Paolone, M.; Pappalardo, L. L.; Paremuzyan, R.; Pasyuk, E.; Phelps, W.; Pogorelko, O.; Price, J. W.; Prok, Y.; Ripani, M.; Ritman, J.; Rizzo, A.; Rosner, G.; Rowley, J.; Sabatie, F.; Salgado, C.; Schmidt, A.; Schumacher, R. A.; Shrestha, U.; Sokan, D.; Soto, O.; Sparveris, N.; Stepanyan, S.; Strakovsky, I. I.; Strauch, S.; Tan, J. A.; Tyler, N.; Ungaro, M.; Venturelli, L.; Voskanyan, H.; Voutier, E.; Watts, D.; Wei, X.; Wood, M. H.; Zachariou, N.; Zhang, J.; Zhao, Z. W.

doi:10.1103/PhysRevC.102.032201

We present the first measurement of the reaction γp→a2(1320)0p in the photon energy range 3.5-5.5GeV and four-momentum transfer squared 0.2<-t<2.0GeV2. Data were collected with the CEBAF Large Acceptance Spectrometer detector at the Thomas Jefferson National Accelerator Facility. The a2 resonance was detected by measuring the reaction γp→π0ηp and reconstructing the π0η invariant mass. The most prominent feature of the differential cross section is a dip at-t≈0.55GeV2. This can be described in the framework of Regge phenomenology, where the exchange degeneracy hypothesis predicts a zero in the reaction amplitude for this value of the four-momentum transfer.