Robust signatures of quantum radiation reaction with an electron beam in a focused laser pulse

摘要

Several signatures of quantum radiation reaction are investigated in the interaction of an electron beam with superstrong focused laser pulses in the radiation dominated regime. Analytic expressions for the electromagnetic fields of an ultrashort, tightly focused, laser pulse in vacuum are derived from scalar and vector potentials, using on equal footing two small parameters connected with the waist size of the laser beam and its duration. Due to the combined effect of the laser focusing and radiation reaction the angular spread of the main photon-emission region has a prominent maximum at an intermediate pulse duration and decreases along the further increase of the pulse duration, and the spectral bandwidth monotonically decreases with rising pulse duration. Those signatures can be used to distinguish the quantum radiation reaction with the classic radiation reaction and are measurable with currently available laser systems.