Final Analysis of Proton Form Factor Ratio Data at $\mathbf{Q^2 = 4.0}$, 4.8 and 5.6 GeV$\mathbf{^2}$
Creators: name: Puckett, A. J. R.
name: Brash, E. J.
name: Gayou, O.
name: Jones, M. K.
name: Pentchev, L.
name: Perdrisat, C. F.
name: Punjabi, V.
name: Aniol, K. A.
name: Averett, T.
name: Benmokhtar, F.
name: Bertozzi, W.
name: Bimbot, L.
name: Calarco, J. R.
name: Cavata, C.
name: Chai, Z.
name: Chang, C. -C.
name: Chang, T.
name: Chen, J. P.
name: Chudakov, E.
name: De Leo, R.
name: Dieterich, S.
name: Endres, R.
name: Epstein, M. B.
name: Escoffier, S.
name: Fonvieille, K. G. Fissum. H.
name: Frullani, S.
name: Gao, J.
name: Garibaldi, F.
name: Gilad, S.
name: Gilman, R.
name: Glamazdin, A.
name: Glashausser, C.
name: Gomez, J.
name: Hansen, J. -O.
name: Higinbotham, D.
name: Huber, G. M.
name: Iodice, M.
name: de Jager, C. W.
name: Jiang, X.
name: Khandaker, M.
name: Kozlov, S.
name: Kramer, K. M.
name: Kumbartzki, G.
name: LeRose, J. J.
name: Lhuillier, D.
name: Lindgren, R. A.
name: Liyanage, N.
name: Lolos, G. J.
name: Margaziotis, D. J.
name: Marie, F.
name: Markowitz, P.
name: McCormick, K.
name: Michaels, R.
name: Milbrath, B. D.
name: Nanda, S. K.
name: Neyret, D.
name: Piskunov, N. M.
name: Ransome, R. D.
name: Raue, B. A.
name: Roché, R.
name: Rvachev, M.
name: Saha, A.
name: Salgado, C.
name: Sirca, S.
name: Sitnik, I.
name: Strauch, S.
name: Todor, L.
name: Tomasi-Gustafsson, E.
name: Urciuoli, G. M.
name: Voskanyan, H.
name: Wijesooriya, K.
name: Wojtsekhowski, B. B.
name: Zheng, X.
name: Zhu, L.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Precise measurements of the proton electromagnetic form factor ratio $R = μ_p G_E^p/G_M^p$ 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 $Q^2 \gtrsim 1$ GeV$^2$, 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 GeV$^2 \le Q^2 \le 5.6$ GeV$^2$. 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.
description: 30 pages, 17 figures, 4 tables. Final version to appear in Phys. Rev. C