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Final analysis of proton form factor ratio data at Q(2)=4.0, 4.8, and 5.6 GeV2

Puckett, A. J. R.; Brash, E. J.; Gayou, O.; Jones, M. K.; Pentchev, L.; Perdrisat, C. F.; Punjabi, V.; Aniol, K. A.; Averett, T. and Benmokhtar, F., et al. (2012) In Physical Review C (Nuclear Physics) 85(4).
Abstract
Precise measurements of the proton electromagnetic form factor ratio R = mu(p)G(E)(p)/G(M)(p) using the polarization transfer method at Jefferson Lab have revolutionized the understanding of nucleon structure by revealing the strong decrease of R with momentum transfer Q(2) for Q(2) greater than or similar to 1 GeV2, in strong disagreement with previous extractions of R from cross-section measurements. In particular, the polarization transfer results have exposed the limits of applicability of the one-photon-exchange approximation and highlighted the role of quark orbital angular momentum in the nucleon structure. The GEp-II experiment in Jefferson Lab's Hall A measured R at four Q(2) values in the range 3.5 GeV2 <= Q(2) <= 5.6 GeV2.... (More)
Precise measurements of the proton electromagnetic form factor ratio R = mu(p)G(E)(p)/G(M)(p) using the polarization transfer method at Jefferson Lab have revolutionized the understanding of nucleon structure by revealing the strong decrease of R with momentum transfer Q(2) for Q(2) greater than or similar to 1 GeV2, in strong disagreement with previous extractions of R from cross-section measurements. In particular, the polarization transfer results have exposed the limits of applicability of the one-photon-exchange approximation and highlighted the role of quark orbital angular momentum in the nucleon structure. The GEp-II experiment in Jefferson Lab's Hall A measured R at four Q(2) values in the range 3.5 GeV2 <= Q(2) <= 5.6 GeV2. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q(2) motivated a new analysis of the GEp-II data. This article presents the final results of the GEp-II experiment, including details of the new analysis, an expanded description of the apparatus, and an overview of theoretical progress since the original publication. The key result of the final analysis is a systematic increase in the results for R, improving the consistency of the polarization transfer data in the high-Q(2) region. This increase is the result of an improved selection of elastic events which largely removes the systematic effect of the inelastic contamination, underestimated by the original analysis. (Less)
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Physical Review C (Nuclear Physics)
volume
85
issue
4
publisher
American Physical Society
external identifiers
  • wos:000302625500002
  • scopus:84860126886
ISSN
0556-2813
DOI
10.1103/PhysRevC.85.045203
language
English
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bdc40471-78ec-45c2-8ca6-5e3f1f28716f (old id 2571622)
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2012-06-04 11:31:16
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@article{bdc40471-78ec-45c2-8ca6-5e3f1f28716f,
  abstract     = {Precise measurements of the proton electromagnetic form factor ratio R = mu(p)G(E)(p)/G(M)(p) using the polarization transfer method at Jefferson Lab have revolutionized the understanding of nucleon structure by revealing the strong decrease of R with momentum transfer Q(2) for Q(2) greater than or similar to 1 GeV2, in strong disagreement with previous extractions of R from cross-section measurements. In particular, the polarization transfer results have exposed the limits of applicability of the one-photon-exchange approximation and highlighted the role of quark orbital angular momentum in the nucleon structure. The GEp-II experiment in Jefferson Lab's Hall A measured R at four Q(2) values in the range 3.5 GeV2 &lt;= Q(2) &lt;= 5.6 GeV2. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q(2) motivated a new analysis of the GEp-II data. This article presents the final results of the GEp-II experiment, including details of the new analysis, an expanded description of the apparatus, and an overview of theoretical progress since the original publication. The key result of the final analysis is a systematic increase in the results for R, improving the consistency of the polarization transfer data in the high-Q(2) region. This increase is the result of an improved selection of elastic events which largely removes the systematic effect of the inelastic contamination, underestimated by the original analysis.},
  author       = {Puckett, A. J. R. and Brash, E. J. and Gayou, O. and Jones, M. K. and Pentchev, L. and Perdrisat, C. F. and Punjabi, V. and Aniol, K. A. and Averett, T. and Benmokhtar, F. and Bertozzi, W. and Bimbot, L. and Calarco, J. R. and Cavata, C. and Chai, Z. and Chang, C. -C. and Chang, T. and Chen, J. P. and Chudakov, E. and De Leo, R. and Dieterich, S. and Endres, R. and Epstein, M. B. and Escoffier, S. and Fissum, Kevin and Fonvieille, H. and Frullani, S. and Gao, J. and Garibaldi, F. and Gilad, S. and Gilman, R. and Glamazdin, A. and Glashausser, C. and Gomez, J. and Hansen, J. -O. and Higinbotham, D. and Huber, G. M. and Iodice, M. and de Jager, C. W. and Jiang, X. and Khandaker, M. and Kozlov, S. and Kramer, K. M. and Kumbartzki, G. and LeRose, J. J. and Lhuillier, D. and Lindgren, R. A. and Liyanage, N. and Lolos, G. J. and Margaziotis, D. J. and Marie, F. and Markowitz, P. and McCormick, K. and Michaels, R. and Milbrath, B. D. and Nanda, S. K. and Neyret, D. and Piskunov, N. M. and Ransome, R. D. and Raue, B. A. and Roche, R. and Rvachev, M. and Salgado, C. and Sirca, S. and Sitnik, I. and Strauch, S. and Todor, L. and Tomasi-Gustafsson, E. and Urciuoli, G. M. and Voskanyan, H. and Wijesooriya, K. and Wojtsekhowski, B. B. and Zheng, X. and Zhu, L.},
  issn         = {0556-2813},
  language     = {eng},
  number       = {4},
  publisher    = {American Physical Society},
  series       = {Physical Review C (Nuclear Physics)},
  title        = {Final analysis of proton form factor ratio data at Q(2)=4.0, 4.8, and 5.6 GeV2},
  url          = {http://dx.doi.org/10.1103/PhysRevC.85.045203},
  volume       = {85},
  year         = {2012},
}