Proton elastic form factor ratios to Q2=3.5GeV2 by polarization transfer

Le résumé fourni par la source

The ratio of the proton elastic electromagnetic form factors, ${G}_{\mathit{Ep}}/{G}_{\mathit{Mp}}$, was obtained by measuring ${P}_{t}$ and ${P}_{\ensuremath{\ell}}$, the transverse and longitudinal recoil proton polarization components, respectively, for the elastic $\stackrel{\ensuremath{\rightarrow}}{e}p\ensuremath{\rightarrow}e\stackrel{\ensuremath{\rightarrow}}{p}$reaction in the four-momentum transfer squared range of 0.5 to $3.5\phantom{\rule{0.3em}{0ex}}\text{GeV}{}^{2}$. In the single-photon exchange approximation, ${G}_{\mathit{Ep}}/{G}_{\mathit{Mp}}$ is directly proportional to ${P}_{t}/{P}_{\ensuremath{\ell}}$. The simultaneous measurement of ${P}_{t}$ and ${P}_{\ensuremath{\ell}}$ in a polarimeter reduces systematic uncertainties. The results for ${G}_{\mathit{Ep}}/{G}_{\mathit{Mp}}$ 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.

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