Polarization measurements are allowing the electric to magnetic form factor ratio of the proton to be determined with unprecedented precision. Recent results indicate that there is a large deviation from unity in the proton form factor ratio around Q2 ≃ 0.35 GeV2. Furthermore, the deviation from unity is attributed to a deviation of the electric form factor from standard fits and calculations. A new, partially completed, experiment will significantly improve the existing data and will determine the presence, if any, of a narrow structure in the form factor ratio. The new measurement, combined with the expected high precision cross section measurements, will allow the extraction of individual form factors with unprecedented accuracy at low Q2.
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We would like to acknowledge the contribution of the Hall A LEDEX and E08-007 collaboration . In particular, we enjoyed the help of J. Arrington, S. Gilad, R. Gilman, D. Higinbotham, E. Piasetzky, A. Sarty and S. Strauch. We thank the JLab physics and accelerator divisions for their support. This work was supported by the U.S. Department of Energy, the U.S. National Science Foundation, the Israel Science Foundation, and the US-Israeli Bi-National Scientific Foundation and the Marcel Adams foundation of the Israeli academy for sciences and humanities.
- Jefferson Lab
- form factors