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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.
Journal
Physical Review C - Nuclear Physics
Date Issued
2015-04-13
Author(s)
Park, K.
Aznauryan, I. G.
Burkert, V. D.
Adhikari, K. P.
Amaryan, M. J.
Pereira, S. Anefalos
Avakian, H.
Battaglieri, M.
Badui, R.
Bedlinskiy, I.
Biselli, A. S.
Bono, J.
Briscoe, W. J.
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.
Elouadrhiri, L.
Fassi, L. El
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.
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.
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. Munoz
Nadel-Turonski, P.
Niccolai, S.
Niculescu, G.
Niculescu, I.
Osipenko, M.
Ostrovidov, A. I.
Paolone, M.
Pasyuk, E.
Peng, P.
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.
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.
Subjects
