Measurements of ep→e′π+n at 1.6<W<2.0 GeV and extraction of nucleon resonance electrocouplings at CLAS MEASUREMENTS of ep→e′π+n ⋯ K. PARK et al.

K. Park, I. G. Aznauryan, V. D. Burkert, K. P. Adhikari, M. J. Amaryan, S. Anefalos Pereira, H. Avakian, M. Battaglieri, R. Badui, I. Bedlinskiy, A. S. Biselli, J. Bono, W. J. Briscoe, W. K. Brooks, D. S. Carman, A. Celentano, S. Chandavar, G. Charles, L. Colaneri, P. L. ColeM. Contalbrigo, O. Cortes, V. Crede, A. D'Angelo, N. Dashyan, R. De Vita, E. De Sanctis, A. Deur, C. Djalali, D. Doughty, R. Dupre, H. Egiyan, A. El Alaoui, L. Elouadrhiri, L. El Fassi, P. Eugenio, G. Fedotov, S. Fegan, R. Fersch, A. Filippi, J. A. Fleming, B. Garillon, M. Garçon, N. Gevorgyan, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, H. S. Joo, J. T. Goetz, E. Golovatch, R. W. Gothe, K. A. Griffioen, B. Guegan, M. Guidal, L. Guo, H. Hakobyan, C. Hanretty, M. Hattawy, K. Hicks, M. Holtrop, S. M. Hughes, C. E. Hyde, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, D. Jenkins, H. Jiang, H. S. Jo, K. Joo, S. Joosten, D. Keller, M. Khandaker, A. Kim, W. Kim, A. Klein, F. J. Klein, V. Kubarovsky, S. E. Kuhn, S. V. Kuleshov, P. Lenisa, K. Livingston, H. Y. Lu, I. J.D. Macgregor, N. Markov, D. Martinez, B. McKinnon, V. Mokeev, R. A. Montgomery, H. Moutarde, C. Munoz Camacho, P. Nadel-Turonski, S. Niccolai, G. Niculescu, I. Niculescu, M. Osipenko, A. I. Ostrovidov, M. Paolone, E. Pasyuk, P. Peng, W. Phelps, J. J. Phillips, S. Pisano, O. Pogorelko, J. W. Price, S. Procureur, Y. Prok, D. Protopopescu, A. J.R. Puckett, B. A. Raue, M. Ripani, A. Rizzo, G. Rosner, P. Rossi, P. Roy, F. Sabatié, C. Salgado, D. Schott, R. A. Schumacher, E. Seder, Y. G. Sharabian, A. Simonyan, Iu Skorodumina, E. S. Smith, G. D. Smith, N. Sparveris, P. Stoler, I. I. Strakovsky, S. Strauch, V. Sytnik, M. Taiuti, W. Tang, C. E. Taylor, Ye Tian, A. Trivedi, M. Ungaro, H. Voskanyan, E. Voutier, N. K. Walford, D. P. Watts, X. Wei, L. B. Weinstein, M. H. Wood, N. Zachariou, L. Zana, J. Zhang, Z. W. Zhao, I. Zonta

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35 Scopus citations

Abstract

Differential cross sections of the exclusive process ep→e′π+n were measured with good precision in the range of the photon virtuality Q2=1.8-4.5 GeV2 and the invariant mass range of the π+n final state W=1.6-2.0 GeV using the Continuous Electron Beam Accelerator Facility Large Acceptance Spectrometer. Data were collected with nearly complete coverage in the azimuthal and polar angles of the nπ+ center-of-mass system. More than 37000 cross-section points were measured. The contributions of the isospin I=12 resonances N(1675)52-,N(1680)52+, and N(1710)12+ were extracted at different values of Q2 using a single-channel, energy-dependent resonance amplitude analysis. Two different approaches, the unitary isobar model and the fixed-t dispersion relations, were employed in the analysis. We observe significant strength of the N(1675)52- in the A1/2 amplitude, which is in strong disagreement with quark models that predict both transverse amplitudes to be strongly suppressed. For the N(1680)52+ we observe a slow changeover from the dominance of the A3/2 amplitude at the real photon point (Q2=0) to a Q2 where A1/2 begins to dominate. The scalar amplitude S1/2 drops rapidly with Q2 consistent with quark model prediction. For the N(1710)12+ resonance our analysis shows significant strength for the A1/2 amplitude at Q2<2.5 GeV2.

Original languageEnglish (US)
Article number045203
JournalPhysical Review C - Nuclear Physics
Volume91
Issue number4
DOIs
StatePublished - Apr 13 2015
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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