Polarization transfer in hard x-ray Rayleigh scattering for non-coplanar geometry

We present an experimental study of the Rayleigh scattering of highly linearly polarized hard x rays. For thisstudy, photons produced by a synchrotron source with an energy of 175 keV are scattered by a thin gold foiltarget. While the linear polarization in terms of degree of polarization and its orientation of the incident photonbeam are well known, the outgoing scattered photons are analyzed by means of Compton polarimetry. For this,a polarimeter detector is positioned at different observation angles with respect to the incident photon beam. Forthe first time the polarization of elastically scattered photons outside of the polarization plane of the incidentradiation is investigated, enabling novel access to a so-far untested component of the polarization transfer. Theexperimental findings are compared to predictions of two theoretical models. It is found that, when leaving thepolarization plane of the incident photon beam, a strong deviation from the form factor approximation is evident,while calculations of the Rayleigh scattering in the S-matrix approach agree with the experimental results.Furthermore, this study is a foundation for future experiments dedicated to a polarization-resolved analysis ofDelbrück scattering.