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内容記述 |
With the development of intense laser technology, nonlinear Compton scattering (NCS) experiments, in which multiple laser photons are absorbed and a single high-energy photon is emitted, have been actively performed to study the behavior of electrons and photons in strong fields [1]. Recently, experiments have begun to generate photon vortices, i.e. photons with orbital angular momentum (OAM) in the gamma-ray energy range, using circularly polarized and spatially structured laser beams in NCS setups [2]. These advances have led to the need for theoretical calculations to support and guide the interpretation of experimental results.In such experiments, where relatively moderate laser intensities are used to count individual absorbed photons, it is important to go beyond the typical high-intensity approximation. We therefore perform calculations using the Feynman diagram approach, assuming cylindrical wave functions for both the electrons and the photons [3]. While many previous theoretical studies rely on the local constant field approximation (LCFA), which treats the laser as a classical background field and is suitable for ultra-intense regimes [4], our method is more appropriate for moderate intensities, where discrete multiphoton effects become prominent.We study the photon vortex production using the Feynman approach, assuming cylindrical wavefunctions for both the electrons and the photons. In this framework, we perform calculations suitable for relatively weak laser intensities, where the number of absorbed photons can be treated discretely.This approach not only clarifies the underlying mechanism of vortex photon generation in the NCS, but also provides detailed, testable predictions for upcoming experiments using structured light fields. Our results may provide a practical guide for the design of experiments aimed at controlling or diagnosing the OAM content of high-energy photons.[1] A.Di Piazza et al., Rev.Mod.Phys. (2012).[2] Y.Taira, T. Hayakawa, M. Katoh, Sci. Rep. 7, 5018 (2017).[3] T. Maruyama et al., Phys. Rev. D 111, 016016 (2024). |
