Final analysis of proton form factor ratio data at Q[superscript 2]=4.0, 4.8, and 5.6 GeV[superscript 2]
Name
Puckett-2012-Final analysis of proton form factor ratio.pdf
Size
1.17 MB
Format
Adobe PDF
Checksum (MD5)
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Author(s)
Bertozzi, William
Chai, Z.
Gao, J.
Gilad, Shalev
Higinbotham, D. W.
Rvachev, M.
Zhu, L.
Zheng, Xin, S. M. Massachusetts Institute of Technology
Date Issued
April 2012
Journal
Physical Review C
Publisher
American Physical Society
Citation
Puckett, A. J. et al. “Final analysis of proton form factor ratio data at Q[superscript 2]=4.0, 4.8, and 5.6 GeV[superscript 2].” Physical Review C 85.4 (2012). ©2012 American Physical Society
Version
Final published version
Abstract
Precise measurements of the proton electromagnetic form factor ratio R=μ[subscript p]G[subscript E][superscript p]/G[subscript M][superscript 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[superscript 2] for Q[superscript 2]≳1 GeV[superscript 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[superscript 2] values in the range 3.5 GeV[superscript 2]≤Q[superscript 2]≤5.6 GeV[superscript 2]. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q[superscript 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[superscript 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.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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DOI of Published Version
https://doi.org/10.1103/PhysRevC.85.045203
