Measurement of single- and double-polarization observables in the photoproduction of π+π− meson pairs off the proton using CLAS at Jefferson Laboratory

Roy, P.; Cao, S.; Crede, V.; Klempt, E.; Nikonov, V. A.; Sarantsev, A. V.; Burkert, V. D.; Mokeev, V.; Achenbach, P.; Alvarado, J. S.; Armstrong, W. R.; Atac, H.; Avakian, H.; Baltzell, N. A.; Barion, L.; Bashkanov, M.; Battaglieri, M.; Benmokhtar, F.; Bianconi, A.; Biselli, A. S.; Bondi, M.; Bossu, F.; Boiarinov, S.; Brinkmann, K. -T.; Briscoe, W. J.; Brooks, W. K.; Cao, T.; Capobianco, R.; Carman, D. S.; Chatagnon, P.; Ciullo, G.; Cole, P. L.; Contalbrigo, M.; D'Angelo, A.; Dashyan, N.; De Vita, R.; Defurne, M.; Deur, A.; Diehl, S.; Djalali, C.; Dugger, M.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Eugenio, P.; Fegan, S.; Fernando, I. P.; Filippi, A.; Gavalian, G.; Gothe, R. W.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hattawy, M.; Hayward, T. B.; Heddle, D.; Hobart, A.; Holtrop, M.; Ilieva, Y.; Ireland, D. G.; Isupov, E. L.; Jenkins, D.; Jiang, H.; H. S., Jo; Joo, K.; Joosten, S.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Klimenko, V.; Kripko, A.; Kubarovsky, V.; Lanza, L.; Lenisa, P.; Li, X.; Livingston, K.; Macgregor, I. J. D.; Marchand, D.; Martiryan, D.; Mascagna, V.; Matamoros, D.; Mccracken, M. E.; Mckinnon, B.; Mineeva, T.; Camacho, C. M.; Nadel-Turonski, P.; Neupane, K.; Nguyen, D.; Niculescu, G.; Osipenko, M.; Ostrovidov, A. I.; Ouillon, M.; Pandey, P.; Paolone, M.; Pappalardo, L. L.; Paremuzyan, R.; Pasyuk, E.; Paul, S. J.; Phelps, W.; Pilleux, N.; Rafael, S. P.; Price, J.; Prok, Y.; Protopopescu, D.; Richards, J.; Ripani, M.; Ritchie, B.; Ritman, J.; Rosner, G.; Rossi, P.; Rusova, A. A.; Salgado, C.; Schadmand, S.; Schmidt, A.; Schumacher, R. A.; Sharabian, Y. G.; Shirokov, E. V.; Shrestha, S.; Sokhan, D.; Sparveris, N.; Spreafico, M.; Strakovsky, I. I.; Strauch, S.; Tan, J. A.; Tenorio, M.; Trotta, N.; Tyson, R.; Ungaro, M.; Vallarino, S.; Venturelli, L.; Vittorini, T.; Voskanyan, H.; Voutier, E.; Watts, D. P.; Weerasinghe, U.; Wei, X.; Wood, M. H.; Xu, L.; Zachariou, N.; Zhao, Z. W.; Zurek, M.

doi:10.1103/bddq-9qlq

The photoproduction of π+π− meson pairs off the proton has been studied in the reaction γ p→ pπ+π− using the CEBAF Large Acceptance Spectrometer (CLAS) and the frozen-spin target (FROST) in Hall B at the Thomas Jefferson National Accelerator Facility. For the first time, the beam and target asymmetries, Is,c and Px,y have been measured along with the beam-target double-polarization observables, Ps,cx,y using a transversely polarized target with center-of-mass energies ranging from 1.51 GeV up to 2.04 GeV. These data and additional ππ photoproduction observables from CLAS and experiments elsewhere were included in a partial-wave analysis within the Bonn-Gatchina framework. Significant contributions from s-channel resonance production are observed in addition to t-channel exchange processes. The data indicate significant contributions from N* and Δ* resonances in the third and fourth resonance regions.