Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction

I. G. Aznauryan; V. D. Burkert; A. S. Biselli; H. Egiyan; K. Joo; W. Kim; K. Park; L. C. Smith; M. Ungaro; K. P. Adhikari; M. Anghinolfi; H. Avakian; J. Ball; M. Battaglieri; V. Batourine; I. Bedlinskiy; M. Bellis; C. Bookwalter; D. Branford; W. J. Briscoe; W. K. Brooks; S. L. Careccia; D. S. Carman; P. L. Cole; P. Collins; V. Crede; A. D'Angelo; A. Daniel; R. De Vita; E. De Sanctis; A. Deur; B. Dey; S. Dhamija; R. Dickson; C. Djalali; D. Doughty; R. Dupre; A. El Alaoui; L. Elouadrhiri; P. Eugenio; G. Fedotov; S. Fegan; T. A. Forest; M. Y. Gabrielyan; G. P. Gilfoyle; K. L. Giovanetti; F. X. Girod; J. T. Goetz; W. Gohn; E. Golovatch; R. W. Gothe; M. Guidal; L. Guo; K. Hafidi; H. Hakobyan; C. Hanretty; N. Hassall; D. Heddle; K. Hicks; M. Holtrop; C. E. Hyde; Y. Ilieva; D. G. Ireland; B. S. Ishkhanov; E. L. Isupov; S. S. Jawalkar; H. S. Jo; J. R. Johnstone; D. Keller; M. Khandaker; P. Khetarpal; A. Klein; F. J. Klein; L. H. Kramer; V. Kubarovsky; S. E. Kuhn; S. V. Kuleshov; V. Kuznetsov; K. Livingston; H. Y. Lu; M. Mayer; J. McAndrew; M. E. McCracken; B. McKinnon; C. A. Meyer; T. Mineeva; M. Mirazita; V. Mokeev; B. Moreno; K. Moriya; B. Morrison; H. Moutarde; E. Munevar; P. Nadel-Turonski; R. Nasseripour; C. S. Nepali; S. Niccolai; G. Niculescu; I. Niculescu; M. R. Niroula; M. Osipenko; A. I. Ostrovidov; S. Park; E. Pasyuk; S. Anefalos Pereira; S. Pisano; O. Pogorelko; S. Pozdniakov; J. W. Price; S. Procureur; Y. Prok; D. Protopopescu; B. A. Raue; G. Ricco; M. Ripani; Barry Ritchie; G. Rosner; P. Rossi; F. Sabatié; M. S. Saini; J. Salamanca; R. A. Schumacher; H. Seraydaryan; N. V. Shvedunov; D. I. Sober; D. Sokhan; S. S. Stepanyan; P. Stoler; I. I. Strakovsky; S. Strauch; R. Suleiman; M. Taiuti; D. J. Tedeschi; S. Tkachenko; M. F. Vineyard; D. P. Watts; L. B. Weinstein; D. P. Weygand; M. Williams; M. H. Wood; L. Zana; J. Zhang; B. Zhao

doi:10.1103/PhysRevC.80.055203

Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction

I. G. Aznauryan, V. D. Burkert, A. S. Biselli, H. Egiyan, K. Joo, W. Kim, K. Park, L. C. Smith, M. Ungaro, K. P. Adhikari, M. Anghinolfi, H. Avakian, J. Ball, M. Battaglieri, V. Batourine, I. Bedlinskiy, M. Bellis, C. Bookwalter, D. Branford, W. J. BriscoeW. K. Brooks, S. L. Careccia, D. S. Carman, P. L. Cole, P. Collins, V. Crede, A. D'Angelo, A. Daniel, R. De Vita, E. De Sanctis, A. Deur, B. Dey, S. Dhamija, R. Dickson, C. Djalali, D. Doughty, R. Dupre, A. El Alaoui, L. Elouadrhiri, P. Eugenio, G. Fedotov, S. Fegan, T. A. Forest, M. Y. Gabrielyan, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, J. T. Goetz, W. Gohn, E. Golovatch, R. W. Gothe, M. Guidal, L. Guo, K. Hafidi, H. Hakobyan, C. Hanretty, N. Hassall, D. Heddle, K. Hicks, M. Holtrop, C. E. Hyde, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, S. S. Jawalkar, H. S. Jo, J. R. Johnstone, D. Keller, M. Khandaker, P. Khetarpal, A. Klein, F. J. Klein, L. H. Kramer, V. Kubarovsky, S. E. Kuhn, S. V. Kuleshov, V. Kuznetsov, K. Livingston, H. Y. Lu, M. Mayer, J. McAndrew, M. E. McCracken, B. McKinnon, C. A. Meyer, T. Mineeva, M. Mirazita, V. Mokeev, B. Moreno, K. Moriya, B. Morrison, H. Moutarde, E. Munevar, P. Nadel-Turonski, R. Nasseripour, C. S. Nepali, S. Niccolai, G. Niculescu, I. Niculescu, M. R. Niroula, M. Osipenko, A. I. Ostrovidov, S. Park, E. Pasyuk, S. Anefalos Pereira, S. Pisano, O. Pogorelko, S. Pozdniakov, J. W. Price, S. Procureur, Y. Prok, D. Protopopescu, B. A. Raue, G. Ricco, M. Ripani, Barry Ritchie, G. Rosner, P. Rossi, F. Sabatié, M. S. Saini, J. Salamanca, R. A. Schumacher, H. Seraydaryan, N. V. Shvedunov, D. I. Sober, D. Sokhan, S. S. Stepanyan, P. Stoler, I. I. Strakovsky, S. Strauch, R. Suleiman, M. Taiuti, D. J. Tedeschi, S. Tkachenko, M. F. Vineyard, D. P. Watts, L. B. Weinstein, D. P. Weygand, M. Williams, M. H. Wood, L. Zana, J. Zhang, B. Zhao

Research output: Contribution to journal › Article › peer-review

252 Scopus citations

Abstract

We present results on the electroexcitation of the low mass resonances Δ(1232)P33, N(1440)P11, N(1520)D13, and N(1535)S11 in a wide range of Q2. The results were obtained in the comprehensive analysis of data from the Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for π electroproduction off the proton. The data were analyzed using two conceptually different approaches-fixed-t dispersion relations and a unitary isobar model-allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the Δ(1232)P33 show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for Q2 □6 GeV2. For the Roper resonance, N(1440)P11, the data provide strong evidence that this state is a predominantly radial excitation of a three-quark (3q) ground state. Measured in pion electroproduction, the transverse helicity amplitude for the N(1535)S11 allowed us to obtain the branching ratios of this state to the πN and ηN channels via comparison with the results extracted from η electroproduction. The extensive CLAS data also enabled the extraction of the γ*p→N(1520)D13 and N(1535)S11 longitudinal helicity amplitudes with good precision. For the N(1535)S11, these results became a challenge for quark models and may be indicative of large meson-cloud contributions or of representations of this state that differ from a 3q excitation. The transverse amplitudes for the N(1520)D13 clearly show the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2 > 1 GeV2, confirming a long-standing prediction of the constituent quark model.

Original language	English (US)
Article number	055203
Journal	Physical Review C - Nuclear Physics
Volume	80
Issue number	5
DOIs	https://doi.org/10.1103/PhysRevC.80.055203
State	Published - Nov 10 2009

ASJC Scopus subject areas

Nuclear and High Energy Physics

Access to Document

10.1103/PhysRevC.80.055203

Cite this

Aznauryan, I. G., Burkert, V. D., Biselli, A. S., Egiyan, H., Joo, K., Kim, W., Park, K., Smith, L. C., Ungaro, M., Adhikari, K. P., Anghinolfi, M., Avakian, H., Ball, J., Battaglieri, M., Batourine, V., Bedlinskiy, I., Bellis, M., Bookwalter, C., Branford, D., ... Zhao, B. (2009). Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction. Physical Review C - Nuclear Physics, 80(5), Article 055203. https://doi.org/10.1103/PhysRevC.80.055203

Aznauryan, IG, Burkert, VD, Biselli, AS, Egiyan, H, Joo, K, Kim, W, Park, K, Smith, LC, Ungaro, M, Adhikari, KP, Anghinolfi, M, Avakian, H, Ball, J, Battaglieri, M, Batourine, V, Bedlinskiy, I, Bellis, M, Bookwalter, C, Branford, D, Briscoe, WJ, Brooks, WK, Careccia, SL, Carman, DS, Cole, PL, Collins, P, Crede, V, D'Angelo, A, Daniel, A, Vita, RD, Sanctis, ED, Deur, A, Dey, B, Dhamija, S, Dickson, R, Djalali, C, Doughty, D, Dupre, R, Alaoui, AE, Elouadrhiri, L, Eugenio, P, Fedotov, G, Fegan, S, Forest, TA, Gabrielyan, MY, Gilfoyle, GP, Giovanetti, KL, Girod, FX, Goetz, JT, Gohn, W, Golovatch, E, Gothe, RW, Guidal, M, Guo, L, Hafidi, K, Hakobyan, H, Hanretty, C, Hassall, N, Heddle, D, Hicks, K, Holtrop, M, Hyde, CE, Ilieva, Y, Ireland, DG, Ishkhanov, BS, Isupov, EL, Jawalkar, SS, Jo, HS, Johnstone, JR, Keller, D, Khandaker, M, Khetarpal, P, Klein, A, Klein, FJ, Kramer, LH, Kubarovsky, V, Kuhn, SE, Kuleshov, SV, Kuznetsov, V, Livingston, K, Lu, HY, Mayer, M, McAndrew, J, McCracken, ME, McKinnon, B, Meyer, CA, Mineeva, T, Mirazita, M, Mokeev, V, Moreno, B, Moriya, K, Morrison, B, Moutarde, H, Munevar, E, Nadel-Turonski, P, Nasseripour, R, Nepali, CS, Niccolai, S, Niculescu, G, Niculescu, I, Niroula, MR, Osipenko, M, Ostrovidov, AI, Park, S, Pasyuk, E, Pereira, SA, Pisano, S, Pogorelko, O, Pozdniakov, S, Price, JW, Procureur, S, Prok, Y, Protopopescu, D, Raue, BA, Ricco, G, Ripani, M, Ritchie, B, Rosner, G, Rossi, P, Sabatié, F, Saini, MS, Salamanca, J, Schumacher, RA, Seraydaryan, H, Shvedunov, NV, Sober, DI, Sokhan, D, Stepanyan, SS, Stoler, P, Strakovsky, II, Strauch, S, Suleiman, R, Taiuti, M, Tedeschi, DJ, Tkachenko, S, Vineyard, MF, Watts, DP, Weinstein, LB, Weygand, DP, Williams, M, Wood, MH, Zana, L, Zhang, J & Zhao, B 2009, 'Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction', Physical Review C - Nuclear Physics, vol. 80, no. 5, 055203. https://doi.org/10.1103/PhysRevC.80.055203

@article{92a1e780496e4611a501fb3e4ad706bc,

title = "Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction",

abstract = "We present results on the electroexcitation of the low mass resonances Δ(1232)P33, N(1440)P11, N(1520)D13, and N(1535)S11 in a wide range of Q2. The results were obtained in the comprehensive analysis of data from the Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for π electroproduction off the proton. The data were analyzed using two conceptually different approaches-fixed-t dispersion relations and a unitary isobar model-allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the Δ(1232)P33 show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for Q2 □6 GeV2. For the Roper resonance, N(1440)P11, the data provide strong evidence that this state is a predominantly radial excitation of a three-quark (3q) ground state. Measured in pion electroproduction, the transverse helicity amplitude for the N(1535)S11 allowed us to obtain the branching ratios of this state to the πN and ηN channels via comparison with the results extracted from η electroproduction. The extensive CLAS data also enabled the extraction of the γ*p→N(1520)D13 and N(1535)S11 longitudinal helicity amplitudes with good precision. For the N(1535)S11, these results became a challenge for quark models and may be indicative of large meson-cloud contributions or of representations of this state that differ from a 3q excitation. The transverse amplitudes for the N(1520)D13 clearly show the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2 > 1 GeV2, confirming a long-standing prediction of the constituent quark model.",

author = "Aznauryan, {I. G.} and Burkert, {V. D.} and Biselli, {A. S.} and H. Egiyan and K. Joo and W. Kim and K. Park and Smith, {L. C.} and M. Ungaro and Adhikari, {K. P.} and M. Anghinolfi and H. Avakian and J. Ball and M. Battaglieri and V. Batourine and I. Bedlinskiy and M. Bellis and C. Bookwalter and D. Branford and Briscoe, {W. J.} and Brooks, {W. K.} and Careccia, {S. L.} and Carman, {D. S.} and Cole, {P. L.} and P. Collins and V. Crede and A. D'Angelo and A. Daniel and Vita, {R. De} and Sanctis, {E. De} and A. Deur and B. Dey and S. Dhamija and R. Dickson and C. Djalali and D. Doughty and R. Dupre and Alaoui, {A. El} and L. Elouadrhiri and P. Eugenio and G. Fedotov and S. Fegan and Forest, {T. A.} and Gabrielyan, {M. Y.} and Gilfoyle, {G. P.} and Giovanetti, {K. L.} and Girod, {F. X.} and Goetz, {J. T.} and W. Gohn and E. Golovatch and Gothe, {R. W.} and M. Guidal and L. Guo and K. Hafidi and H. Hakobyan and C. Hanretty and N. Hassall and D. Heddle and K. Hicks and M. Holtrop and Hyde, {C. E.} and Y. Ilieva and Ireland, {D. G.} and Ishkhanov, {B. S.} and Isupov, {E. L.} and Jawalkar, {S. S.} and Jo, {H. S.} and Johnstone, {J. R.} and D. Keller and M. Khandaker and P. Khetarpal and A. Klein and Klein, {F. J.} and Kramer, {L. H.} and V. Kubarovsky and Kuhn, {S. E.} and Kuleshov, {S. V.} and V. Kuznetsov and K. Livingston and Lu, {H. Y.} and M. Mayer and J. McAndrew and McCracken, {M. E.} and B. McKinnon and Meyer, {C. A.} and T. Mineeva and M. Mirazita and V. Mokeev and B. Moreno and K. Moriya and B. Morrison and H. Moutarde and E. Munevar and P. Nadel-Turonski and R. Nasseripour and Nepali, {C. S.} and S. Niccolai and G. Niculescu and I. Niculescu and Niroula, {M. R.} and M. Osipenko and Ostrovidov, {A. I.} and S. Park and E. Pasyuk and Pereira, {S. Anefalos} and S. Pisano and O. Pogorelko and S. Pozdniakov and Price, {J. W.} and S. Procureur and Y. Prok and D. Protopopescu and Raue, {B. A.} and G. Ricco and M. Ripani and Barry Ritchie and G. Rosner and P. Rossi and F. Sabati{\'e} and Saini, {M. S.} and J. Salamanca and Schumacher, {R. A.} and H. Seraydaryan and Shvedunov, {N. V.} and Sober, {D. I.} and D. Sokhan and Stepanyan, {S. S.} and P. Stoler and Strakovsky, {I. I.} and S. Strauch and R. Suleiman and M. Taiuti and Tedeschi, {D. J.} and S. Tkachenko and Vineyard, {M. F.} and Watts, {D. P.} and Weinstein, {L. B.} and Weygand, {D. P.} and M. Williams and Wood, {M. H.} and L. Zana and J. Zhang and B. Zhao",

note = "Funding Information: Du Min, Liu Min, Liu Jue Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China Corresponding author: Liu Jue, Email: jueliu@bjmu.edu.cn 【Abstract】 SARS-CoV-2 Delta variant has the characteristics of stronger infectivity, higher viral load, and shorter incubation period, posing new challenges to the prevention and control of COVID-19 pandemic. SARS-CoV-2 Delta variant was first discovered in India, then quickly spread in many countries and has gradually become one of the main epidemic strains worldwide. Local epidemics caused by SARS-CoV-2 Delta variant also occurred in several provinces in China. This article summarizes the progress in research of etiological characteristics, transmission characteristics or possible mechanism and epidemiological characteristics of SARS-CoV-2 Delta variant, and the protective effects of vaccines and control measures against SARS-CoV-2 Delta variant in order to provide references for the effective prevention and control of COVID-19 epidemic caused by SARS-CoV-2 Delta variant. 【Key words】 SARS-CoV-2; Delta variants of concern; Epidemiology; Review Fund program: National Natural Science Foundation of China (72122001, 71934002); National Key Research and Development Project of China (2020YFC0846300, 2020YFC0849500)",

year = "2009",

month = nov,

day = "10",

doi = "10.1103/PhysRevC.80.055203",

language = "English (US)",

volume = "80",

journal = "Physical Review C - Nuclear Physics",

issn = "0556-2813",

publisher = "American Physical Society",

number = "5",

}

TY - JOUR

T1 - Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction

AU - Aznauryan, I. G.

AU - Burkert, V. D.

AU - Biselli, A. S.

AU - Egiyan, H.

AU - Joo, K.

AU - Kim, W.

AU - Park, K.

AU - Smith, L. C.

AU - Ungaro, M.

AU - Adhikari, K. P.

AU - Anghinolfi, M.

AU - Avakian, H.

AU - Ball, J.

AU - Battaglieri, M.

AU - Batourine, V.

AU - Bedlinskiy, I.

AU - Bellis, M.

AU - Bookwalter, C.

AU - Branford, D.

AU - Briscoe, W. J.

AU - Brooks, W. K.

AU - Careccia, S. L.

AU - Carman, D. S.

AU - Cole, P. L.

AU - Collins, P.

AU - Crede, V.

AU - D'Angelo, A.

AU - Daniel, A.

AU - Vita, R. De

AU - Sanctis, E. De

AU - Deur, A.

AU - Dey, B.

AU - Dhamija, S.

AU - Dickson, R.

AU - Djalali, C.

AU - Doughty, D.

AU - Dupre, R.

AU - Alaoui, A. El

AU - Elouadrhiri, L.

AU - Eugenio, P.

AU - Fedotov, G.

AU - Fegan, S.

AU - Forest, T. A.

AU - Gabrielyan, M. Y.

AU - Gilfoyle, G. P.

AU - Giovanetti, K. L.

AU - Girod, F. X.

AU - Goetz, J. T.

AU - Gohn, W.

AU - Golovatch, E.

AU - Gothe, R. W.

AU - Guidal, M.

AU - Guo, L.

AU - Hafidi, K.

AU - Hakobyan, H.

AU - Hanretty, C.

AU - Hassall, N.

AU - Heddle, D.

AU - Hicks, K.

AU - Holtrop, M.

AU - Hyde, C. E.

AU - Ilieva, Y.

AU - Ireland, D. G.

AU - Ishkhanov, B. S.

AU - Isupov, E. L.

AU - Jawalkar, S. S.

AU - Jo, H. S.

AU - Johnstone, J. R.

AU - Keller, D.

AU - Khandaker, M.

AU - Khetarpal, P.

AU - Klein, A.

AU - Klein, F. J.

AU - Kramer, L. H.

AU - Kubarovsky, V.

AU - Kuhn, S. E.

AU - Kuleshov, S. V.

AU - Kuznetsov, V.

AU - Livingston, K.

AU - Lu, H. Y.

AU - Mayer, M.

AU - McAndrew, J.

AU - McCracken, M. E.

AU - McKinnon, B.

AU - Meyer, C. A.

AU - Mineeva, T.

AU - Mirazita, M.

AU - Mokeev, V.

AU - Moreno, B.

AU - Moriya, K.

AU - Morrison, B.

AU - Moutarde, H.

AU - Munevar, E.

AU - Nadel-Turonski, P.

AU - Nasseripour, R.

AU - Nepali, C. S.

AU - Niccolai, S.

AU - Niculescu, G.

AU - Niculescu, I.

AU - Niroula, M. R.

AU - Osipenko, M.

AU - Ostrovidov, A. I.

AU - Park, S.

AU - Pasyuk, E.

AU - Pereira, S. Anefalos

AU - Pisano, S.

AU - Pogorelko, O.

AU - Pozdniakov, S.

AU - Price, J. W.

AU - Procureur, S.

AU - Prok, Y.

AU - Protopopescu, D.

AU - Raue, B. A.

AU - Ricco, G.

AU - Ripani, M.

AU - Ritchie, Barry

AU - Rosner, G.

AU - Rossi, P.

AU - Sabatié, F.

AU - Saini, M. S.

AU - Salamanca, J.

AU - Schumacher, R. A.

AU - Seraydaryan, H.

AU - Shvedunov, N. V.

AU - Sober, D. I.

AU - Sokhan, D.

AU - Stepanyan, S. S.

AU - Stoler, P.

AU - Strakovsky, I. I.

AU - Strauch, S.

AU - Suleiman, R.

AU - Taiuti, M.

AU - Tedeschi, D. J.

AU - Tkachenko, S.

AU - Vineyard, M. F.

AU - Watts, D. P.

AU - Weinstein, L. B.

AU - Weygand, D. P.

AU - Williams, M.

AU - Wood, M. H.

AU - Zana, L.

AU - Zhang, J.

AU - Zhao, B.

N1 - Funding Information: Du Min, Liu Min, Liu Jue Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China Corresponding author: Liu Jue, Email: jueliu@bjmu.edu.cn 【Abstract】 SARS-CoV-2 Delta variant has the characteristics of stronger infectivity, higher viral load, and shorter incubation period, posing new challenges to the prevention and control of COVID-19 pandemic. SARS-CoV-2 Delta variant was first discovered in India, then quickly spread in many countries and has gradually become one of the main epidemic strains worldwide. Local epidemics caused by SARS-CoV-2 Delta variant also occurred in several provinces in China. This article summarizes the progress in research of etiological characteristics, transmission characteristics or possible mechanism and epidemiological characteristics of SARS-CoV-2 Delta variant, and the protective effects of vaccines and control measures against SARS-CoV-2 Delta variant in order to provide references for the effective prevention and control of COVID-19 epidemic caused by SARS-CoV-2 Delta variant. 【Key words】 SARS-CoV-2; Delta variants of concern; Epidemiology; Review Fund program: National Natural Science Foundation of China (72122001, 71934002); National Key Research and Development Project of China (2020YFC0846300, 2020YFC0849500)

PY - 2009/11/10

Y1 - 2009/11/10

N2 - We present results on the electroexcitation of the low mass resonances Δ(1232)P33, N(1440)P11, N(1520)D13, and N(1535)S11 in a wide range of Q2. The results were obtained in the comprehensive analysis of data from the Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for π electroproduction off the proton. The data were analyzed using two conceptually different approaches-fixed-t dispersion relations and a unitary isobar model-allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the Δ(1232)P33 show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for Q2 □6 GeV2. For the Roper resonance, N(1440)P11, the data provide strong evidence that this state is a predominantly radial excitation of a three-quark (3q) ground state. Measured in pion electroproduction, the transverse helicity amplitude for the N(1535)S11 allowed us to obtain the branching ratios of this state to the πN and ηN channels via comparison with the results extracted from η electroproduction. The extensive CLAS data also enabled the extraction of the γ*p→N(1520)D13 and N(1535)S11 longitudinal helicity amplitudes with good precision. For the N(1535)S11, these results became a challenge for quark models and may be indicative of large meson-cloud contributions or of representations of this state that differ from a 3q excitation. The transverse amplitudes for the N(1520)D13 clearly show the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2 > 1 GeV2, confirming a long-standing prediction of the constituent quark model.

AB - We present results on the electroexcitation of the low mass resonances Δ(1232)P33, N(1440)P11, N(1520)D13, and N(1535)S11 in a wide range of Q2. The results were obtained in the comprehensive analysis of data from the Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for π electroproduction off the proton. The data were analyzed using two conceptually different approaches-fixed-t dispersion relations and a unitary isobar model-allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the Δ(1232)P33 show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for Q2 □6 GeV2. For the Roper resonance, N(1440)P11, the data provide strong evidence that this state is a predominantly radial excitation of a three-quark (3q) ground state. Measured in pion electroproduction, the transverse helicity amplitude for the N(1535)S11 allowed us to obtain the branching ratios of this state to the πN and ηN channels via comparison with the results extracted from η electroproduction. The extensive CLAS data also enabled the extraction of the γ*p→N(1520)D13 and N(1535)S11 longitudinal helicity amplitudes with good precision. For the N(1535)S11, these results became a challenge for quark models and may be indicative of large meson-cloud contributions or of representations of this state that differ from a 3q excitation. The transverse amplitudes for the N(1520)D13 clearly show the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2 > 1 GeV2, confirming a long-standing prediction of the constituent quark model.

UR - http://www.scopus.com/inward/record.url?scp=70849103214&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=70849103214&partnerID=8YFLogxK

U2 - 10.1103/PhysRevC.80.055203

DO - 10.1103/PhysRevC.80.055203

M3 - Article

AN - SCOPUS:70849103214

SN - 0556-2813

VL - 80

JO - Physical Review C - Nuclear Physics

JF - Physical Review C - Nuclear Physics

IS - 5

M1 - 055203

ER -

Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction

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