Proton elastic form factor ratios to Q2=3.5 GeV2 by polarization transfer -: art. no. 055202

The ratio of the proton elastic electromagnetic form factors, G(Ep)/G(Mp), was obtained by measuring P-t and P-l, the transverse and longitudinal recoil proton polarization components, respectively, for the elastic e(->)p -> ep(->)reaction in the four-momentum transfer squared range of 0.5 to 3.5 GeV2. In the single-photon exchange approximation, G(Ep)/G(Mp) is directly proportional to P-t/P-l. The simultaneous measurement of P-t and P-l in a polarimeter reduces systematic uncertainties. The results for G(Ep)/G(Mp) show a systematic decrease with increasing Q(2), indicating for the first time a definite difference in the distribution of charge and magnetization in the proton. The data have been reanalyzed and their systematic uncertainties have become significantly smaller than those reported previously.