The interaction of photons with relativistic electrons constitutes a fundamental electromagnetic process whose polarization transfer mechanics remain incompletely characterized. We report the first systematic measurement of spatial polarization distribution for $\gamma$-rays generated via \SI{ 45}{ \degree} slant inverse Compton scattering (ICS) between linearly polarized \SI{ 0.117}{ \eV} photons and \SI{ 3.5}{ \GeV} electrons, performing full 2D mapping of intensity, polarization angle (AOP), and degree of polarization (DOP). Measurements reveal an asymmetric beam profile along the laser's polarization direction that resembles \SI{ 180}{ \degree} backward ICS observations. The central beam region exhibits DOP $\approx$ 1.0 with AOP rigidly aligned at \SI{ 45}{ \degree}, while peripheral regions display complex non-uniform polarization distributions. These findings confirm quantum electrodynamics predictions of near-complete polarization transfer along the beam axis in slant geometries, thus establishing slant scattering as a viable alternative to head-on configurations for generating high DOP $\gamma$-rays.
Categories: nucl-ex physics.class-ph