Measurements of the elastic electromagnetic form factor ratio ${\mu }_p{G}_{\mathrm{Ep}}{/G}_{\mathrm{Mp}}$ via polarization transfer

We present measurements of the ratio of the proton elastic electromagnetic form factors, ${\mu }_p{G}_{\mathrm{Ep}}{/G}_{\mathrm{Mp}}.$ The Jefferson Lab Hall A Focal Plane Polarimeter was used to determine the longitudinal and transverse components of the recoil proton polarization in $\mathrm{ep}$ elastic scattering; the ratio of these polarization components is proportional to the ratio of the two form factors. These data reproduce the observation of Jones et al. [Phys. Rev. Lett. 84, 1398 (2000)], that the form factor ratio decreases significantly from unity above $Q^2=1\mathrm{}\hspace{0.5em}{\mathrm{GeV}}^2.$