Abstract
Precise measurements of the proton electromagnetic form factor ratio R=μ pGEp/GMp 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 Q2 for Q2 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 Q2 values in the range 3.5GeV2≤Q2≤5.6GeV2. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q2 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-Q2 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.
| Original language | English (US) |
|---|---|
| Article number | 045203 |
| Journal | Physical Review C - Nuclear Physics |
| Volume | 85 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 11 2012 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Nuclear and High Energy Physics
Cite this
Final analysis of proton form factor ratio data at Q2=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.; Benmokhtar, F.; Bertozzi, W.; Bimbot, L.; Calarco, J. R.; Cavata, C.; Chai, Z.; Chang, C. C.; Chang, T.; Chen, J. P.; Chudakov, E.; De Leo, R.; Dieterich, Sonja; Endres, R.; Epstein, M. B.; Escoffier, S.; Fissum, K. G.; Fonvieille, H.; Frullani, S.; Gao, J.; Garibaldi, F.; Gilad, S.; Gilman, R.; Glamazdin, A.; Glashausser, C.; Gomez, J.; Hansen, J. O.; Higinbotham, D.; Huber, G. M.; Iodice, M.; De Jager, C. W.; Jiang, X.; Khandaker, M.; Kozlov, S.; Kramer, K. M.; Kumbartzki, G.; Lerose, J. J.; Lhuillier, D.; Lindgren, R. A.; Liyanage, N.; Lolos, G. J.; Margaziotis, D. J.; Marie, F.; Markowitz, P.; McCormick, K.; Michaels, R.; Milbrath, B. D.; Nanda, S. K.; Neyret, D.; Piskunov, N. M.; Ransome, R. D.; Raue, B. A.; Roché, R.; Rvachev, M.; Salgado, C.; Sirca, S.; Sitnik, I.; Strauch, S.; Todor, L.; Tomasi-Gustafsson, E.; Urciuoli, G. M.; Voskanyan, H.; Wijesooriya, K.; Wojtsekhowski, B. B.; Zheng, X.; Zhu, L.
In: Physical Review C - Nuclear Physics, Vol. 85, No. 4, 045203, 11.04.2012.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Final analysis of proton form factor ratio data at Q2=4.0, 4.8, and 5.6 GeV2
AU - Puckett, A. J R
AU - Brash, E. J.
AU - Gayou, O.
AU - Jones, M. K.
AU - Pentchev, L.
AU - Perdrisat, C. F.
AU - Punjabi, V.
AU - Aniol, K. A.
AU - Averett, T.
AU - Benmokhtar, F.
AU - Bertozzi, W.
AU - Bimbot, L.
AU - Calarco, J. R.
AU - Cavata, C.
AU - Chai, Z.
AU - Chang, C. C.
AU - Chang, T.
AU - Chen, J. P.
AU - Chudakov, E.
AU - De Leo, R.
AU - Dieterich, Sonja
AU - Endres, R.
AU - Epstein, M. B.
AU - Escoffier, S.
AU - Fissum, K. G.
AU - Fonvieille, H.
AU - Frullani, S.
AU - Gao, J.
AU - Garibaldi, F.
AU - Gilad, S.
AU - Gilman, R.
AU - Glamazdin, A.
AU - Glashausser, C.
AU - Gomez, J.
AU - Hansen, J. O.
AU - Higinbotham, D.
AU - Huber, G. M.
AU - Iodice, M.
AU - De Jager, C. W.
AU - Jiang, X.
AU - Khandaker, M.
AU - Kozlov, S.
AU - Kramer, K. M.
AU - Kumbartzki, G.
AU - Lerose, J. J.
AU - Lhuillier, D.
AU - Lindgren, R. A.
AU - Liyanage, N.
AU - Lolos, G. J.
AU - Margaziotis, D. J.
AU - Marie, F.
AU - Markowitz, P.
AU - McCormick, K.
AU - Michaels, R.
AU - Milbrath, B. D.
AU - Nanda, S. K.
AU - Neyret, D.
AU - Piskunov, N. M.
AU - Ransome, R. D.
AU - Raue, B. A.
AU - Roché, R.
AU - Rvachev, M.
AU - Salgado, C.
AU - Sirca, S.
AU - Sitnik, I.
AU - Strauch, S.
AU - Todor, L.
AU - Tomasi-Gustafsson, E.
AU - Urciuoli, G. M.
AU - Voskanyan, H.
AU - Wijesooriya, K.
AU - Wojtsekhowski, B. B.
AU - Zheng, X.
AU - Zhu, L.
PY - 2012/4/11
Y1 - 2012/4/11
N2 - Precise measurements of the proton electromagnetic form factor ratio R=μ pGEp/GMp 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 Q2 for Q2 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 Q2 values in the range 3.5GeV2≤Q2≤5.6GeV2. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q2 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-Q2 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.
AB - Precise measurements of the proton electromagnetic form factor ratio R=μ pGEp/GMp 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 Q2 for Q2 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 Q2 values in the range 3.5GeV2≤Q2≤5.6GeV2. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q2 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-Q2 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.
UR - http://www.scopus.com/inward/record.url?scp=84860126886&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84860126886&partnerID=8YFLogxK
U2 - 10.1103/PhysRevC.85.045203
DO - 10.1103/PhysRevC.85.045203
M3 - Article
AN - SCOPUS:84860126886
VL - 85
JO - Physical Review C - Nuclear Physics
JF - Physical Review C - Nuclear Physics
SN - 0556-2813
IS - 4
M1 - 045203
ER -