Multiple Photon Effects in Nonlinear Compton Scattering

Compton scattering between a photon and an electron is one of the most basic QED processes. Recent developments of lasers provide unique dense and coherent sources of photon. Electron scattering with strong lasers then becomes nonlinear Compton scattering which involves multiple photons. Present understanding on nonlinear Compton scattering includes several classical ideas such as forward emission, recoil reaction and spectrum cutoff. We investigated multiple photon effects in nonlinear Compton scattering in ultra intense lasers with strong field QED theory. New features of nonlinear Compton scattering induced by multiple photon effects including fixed emission angle, deflection of electron, and disappear of spectrum cutoff are deduced. Results show that nonlinear Compton scattering would be reshaped by involved coherent photons in ultra intense lasers and corresponding signal is measurable on $10$PW scale lasers.