First systematic experimental 2D mapping of linearly polarized γ-ray polarimetric distribution in relativistic Compton scattering

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 γ-rays generated via {45}{°} slant inverse Compton scattering (ICS) between linearly polarized {0.117}{} photons and {3.5}{} 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 {180}{°} backward ICS observations. The central beam region exhibits DOP ≈ 1.0 with AOP rigidly aligned at {45}{°}, 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 γ-rays.