Precision Measurement of $${\mu G_{E}^{p}/G_{M}^p}$$ at Low Q 2

Abstract

Precision measurements are presented of the proton electric to magnetic form-factors ratios at Q 2 = 0.3 - 0.8 (GeV/c)2, obtained by polarization-transfer in Hall A of the Jefferson Laboratory. The measured ratios are significantly lower than published values. New global fits to the individual form factors indicate a lower electric form factor and a slightly higher magnetic form factor. The proton charge radius extracted from the new results is somewhat smaller but consistent with previous values obtained from electron–proton scattering, and is in significant disagreement with the recent value obtained from muonic hydrogen. The effects of the new results on other quantities are briefly discussed.