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

TL;DR

This study systematically maps the 2D polarization distribution of gamma rays produced by relativistic inverse Compton scattering, revealing asymmetric polarization profiles and confirming quantum electrodynamics predictions.

Contribution

It provides the first detailed 2D polarization mapping of gamma rays in slant ICS, demonstrating high polarization transfer and complex spatial polarization patterns.

Findings

Central beam has DOP ≈ 1.0 with AOP at 45°

Peripheral regions show complex polarization distributions

Results confirm QED predictions of polarization transfer

Abstract

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.