Generation of polarization-tunable hybrid cylindrical vector $gamma$ rays from rotating electron beams

Cylindrical vector (CV) γ rays can introduce spatially structured polarization as a new degree of freedom for fundamental research and practical applications. However, their generation and control remain largely unexplored. Here, we put forward a novel method to generate CV γ rays with tunable hybrid polarization via a rotating electron beam interacting with a solid foil. In this process, the beam generates a coherent transition radiation field and subsequently emits γ rays through nonlinear Compton scattering. By manipulating the initial azimuthal momentum of the beam, the polarization angle of γ rays relative to the transverse momentum can be controlled, yielding tunable hybrid CV polarization states. Three-dimensional spin-resolved particle-in-cell simulations demonstrate continuous tuning of the polarization angle across (-90°, 90°) with a high polarization degree exceeding 60%. Our work contributes to the development of structured γ rays, potentially opening up new avenues in high-energy physics, nuclear science and laboratory astrophysics.