Search for effects beyond the Born approximation in polarization transfer observables in $\vec{e}p$ elastic scattering

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton form factor ratio $G_{Ep}/G_{Mp}$ obtained from cross section and polarization measurements. One possible explanation for this difference is a two-photon-exchange contribution. We report the results of the JLab Hall C $GEp2\gamma$ experiment, which measured the kinematical dependence of polarization transfer observables in elastic electron-proton scattering at $Q^2=2.5$ GeV$^2$, in search of effects beyond the Born approximation. For a wide range of values of the kinematic factor $\epsilon$ ($\epsilon=$0.15, 0.63, and 0.77), the proton polarization component ratio and the longitudinal polarization transfer component were measured with statistical uncertainties of $\pm$0.01 and $\pm$0.006 and systematic uncertainties of 0.013 and 0.01, respectively.