Measurements ofep→e′π+nat1.6<W<2.0 GeV and extraction of nucleon resonance electrocouplings at CLAS

Park, K. et al. (2015) Measurements ofep→e′π+nat1.6<W<2.0 GeV and extraction of nucleon resonance electrocouplings at CLAS. Physical Review C, 91, 045203. (doi: 10.1103/PhysRevC.91.045203)

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 37 000 cross-section points were measured. The contributions of the isospin I = 1 2 resonances N(1675) 5 2 − , N(1680) 5 2 + , and N(1710) 1 2 + 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) 5 2 − 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) 5 2 + 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) 1 2 + resonance our analysis shows significant strength for the A1/2 amplitude at Q2 < 2.5 GeV2 .

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: McKinnon, Dr Bryan and Livingston, Dr Kenneth and Protopopescu, Dr Dan and Ireland, Professor David and MacGregor, Professor Douglas and Rosner, Professor Guenther
• Authors: Park, K., Aznauryan, I. G., Burkert, V. D., Adhikari, K. P., Amaryan, M. J., Pereira, S. A., Avakian, H., Battaglieri, M., Badui, R., Bedlinskiy, I., Biselli, A. S., Bono, J., Briscoe, W. J., Brooks, W. K., Carman, D. S., Celentano, A., Chandavar, S., Charles, G., Colaneri, L., Cole, P. L., Contalbrigo, M., Cortes, O., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Doughty, D., Dupre, R., Egiyan, H., Alaoui, A. E., Elouadrhiri, L., Fassi, L. E., Eugenio, P., Fedotov, G., Fegan, S., Fersch, R., Filippi, A., Fleming, J. A., Garillon, B., Garçon, M., Gevorgyan, N., Gilfoyle, G. P., Giovanetti, K. L., Girod, F. X., Joo, H. S., Goetz, J. T., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guegan, B., Guidal, M., Guo, L., Hakobyan, H., Hanretty, C., Hattawy, M., Hicks, K., Holtrop, M., Hughes, S. M., Hyde, C. E., Ilieva, Y., Ireland, D.G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Jiang, H., Jo, H. S., Joo, K., Joosten, S., Keller, D., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F. J., Kubarovsky, V., Kuhn, S. E., Kuleshov, S. V., Lenisa, P., Livingston, K., Lu, H. Y., MacGregor, I.J.D., Markov, N., Martinez, D., McKinnon, B., Mokeev, V., Montgomery, R. A., Moutarde, H., Camacho, C. M., Nadel-Turonski, P., Niccolai, S., Niculescu, G., Niculescu, I., Osipenko, M., Ostrovidov, A. I., Paolone, M., Pasyuk, E., Peng, P., Phelps, W., Phillips, J.J., Pisano, S., Pogorelko, O., Price, J. W., Procureur, S., Prok, Y., Protopopescu, D., Puckett, A. J. R., Raue, B. A., Ripani, M., Rizzo, A., Rosner, G., Rossi, P., Roy, P., Sabatié, F., Salgado, C., Schott, D., Schumacher, R. A., Seder, E., Sharabian, Y. G., Simonyan, A., Skorodumina, I., Smith, E. S., Smith, G. D., Sparveris, N., Stoler, P., Strakovsky, I. I., Strauch, S., Sytnik, V., Taiuti, M., Tang, W., Taylor, C. E., Tian, Y., Trivedi, A., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N. K., Watts, D. P., Wei, X., Weinstein, L. B., Wood, M. H., Zachariou, N., Zana, L., Zhang, J., Zhao, Z. W., and Zonta, I.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physical Review C
• Publisher: American Physical Society
• ISSN: 0556-2813
• ISSN (Online): 1089-490X