First Measurement of the Double Spin Asymmetry in e→p→→e′π+n in the Resonance Region

De Vita, R.; Anghinolfi, M.; Burkert, V.; Dodge, G.; Minehart, R.; Taiuti, MAURO GINO; Weller, H.; Adams, G.; Amaryan, M.; Anciant, E.; Armstrong, D.; Asavapibhop, B.; Asryan, G.; Audit, G.; Auger, T.; Avakian, H.; Bagdasaryan, H.; Ball, J.; Barrow, S.; Battaglieri, M.; Beard, K.; Bektasoglu, M.; Bianchi, N.; Biselli, A.; Boiarinov, S.; Bonner, B.; Bosted, P.; Bouchigny, S.; Branford, D.; Brooks, W.; Bueltmann, S.; Calarco, J.; Capitani, G.; Carman, D.; Carnahan, B.; Cazes, A.; Ciciani, L.; Cole, P.; Coleman, A.; Connelly, J.; Cords, D.; Corvisiero, Pietro; Crabb, D.; Crannell, H.; Cummings, J.; De Sanctis, E.; Degtyarenko, P.; Demirchyan, R.; Denizli, H.; Dennis, L.; Dharmawardane, K.; Dhuga, K.; Djalali, C.; Doughty, D.; Dragovitsch, P.; Dugger, M.; Dytman, S.; Eckhause, M.; Egiyan, H.; Egiyan, K.; Elouadrhiri, L.; Empl, A.; Farhi, L.; Fatemi, R.; Feuerbach, R.; Ficenec, J.; Forest, T.; Frolov, V.; Funsten, H.; Gaff, S.; Gai, M.; Garçon, M.; Gavalian, G.; Gilad, S.; Gilfoyle, G.; Giovanetti, K.; Girard, P.; Golovatch, E.; Griffioen, K.; Guidal, M.; Guillo, M.; Gyurjyan, V.; Hadjidakis, C.; Hancock, D.; Hardie, J.; Heddle, D.; Heimberg, P.; Hersman, F.; Hicks, K.; Hicks, R.; Holtrop, M.; Hu, J.; Hyde Wright, C.; Ishkanov, B.; Ito, M.; Jenkins, D.; Joo, K.; Kelley, J.; Kellie, J.; Khandaker, M.; Kim, K.; Kim, K.; Kim, W.; Klein, A.; Klein, F.; Klusman, M.; Kossov, M.; Kramer, L.; Kuang, Y.; Kuhn, S.; Lachniet, J.; Laget, J.; Lawrence, D.; Li, Ji; Livingston, K.; Longhi, A.; Loukachine, K.; Lucas, M.; Major, W.; Manak, J.; Marchand, C.; Mcaleer, S.; Mccarthy, J.; Mcnabb, J.; Mecking, B.; Mestayer, M.; Meyer, C.; Mikhailov, K.; Mirazita, M.; Miskimen, R.; Mokeev, V.; Muccifora, V.; Mueller, J.; Mutchler, G.; Napolitano, J.; Nelson, S.; Niculescu, G.; Niculescu, I.; Niczyporuk, B.; Niyazov, R.; Opper, A.; O'Rielly, G.; Osipenko, M.; Park, K.; Pasyuk, E.; Peterson, G.; Philips, S.; Pivnyuk, N.; Pocanic, D.; Pogorelko, O.; Polli, E.; Pozdniakov, S.; Preedom, B.; Price, J.; Prok, Y.; Protopopescu, D.; Qin, L.; Raue, B.; Reolon, A.; Riccardi, G.; Ricco, Giovanni; Ripani, M.; Ritchie, B.; Rock, S.; Ronchetti, F.; Rossi, P.; Rowntree, D.; Rubin, P.; Sabatié, F.; Sabourov, K.; Salgado, C.; Sapunenko, V.; Sargsyan, M.; Schumacher, R.; Serov, V.; Shafi, A.; Sharabian, Y.; Shaw, J.; Skabelin, A.; Smith, E.; Smith, T.; Smith, L.; Sober, D.; Sorrell, L.; Spraker, M.; Stavinsky, A.; Stepanyan, S.; Stoler, P.; Strakovsky, I.; Taylor, S.; Tedeschi, D.; Thompson, R.; Todor, L.; Ungaro, M.; Vineyard, M.; Vlassov, A.; Wang, K.; Weinstein, L.; Weisberg, A.; Weygand, D.; Whisnant, C.; Wolin, E.; Yegneswaran, A.; Yun, J.; Zhang, B.; Zhao, J.; Zhou, Z.

doi:10.1103/PhysRevLett.88.082001

The double spin asymmetry in the e⃗p⃗→e′π+n reaction has been measured for the first time in the resonance region for four-momentum transfer Q2 = 0.35–1.5GeV2. Data were taken at Jefferson Lab with the CLAS detector using a 2.6 GeV polarized electron beam incident on a polarized solid NH3 target. Comparison with predictions of phenomenological models shows strong sensitivity to resonance contributions. Helicity- 1/2 transitions are found to be dominant in the second and third resonance regions. The measured asymmetry is consistent with a faster rise with Q2 of the helicity asymmetry A1 for the F15(1680) resonance than expected from the analysis of the unpolarized data.