Identifying the quantum radiation reaction by using colliding ultraintense lasers in gases

Abstract

A scheme for identifying the quantum radiation reaction effect on relativistic electron motion in strong electromagnetic fields is proposed, where two ultraintense lasers are used to collide with each other in a tenuous gas. Different from the previous method by collision of an ultraintense laser with a high-energy electron beam, in which the radiation reaction effect is evidenced by the energy loss in the electron energy spectrum, here the transition between the classical and quantum radiation reaction regimes is distinguished from the angular distribution of the total electron radiations. With no need of additional relativistic electron beams, the scheme is more robust and easily achievable in experiments. Both theory and two-dimensional particle-in-cell simulations show that the classical radiation dominates in the transverse direction perpendicular to laser axis, forming a dipolelike pattern, while that in the quantum regime dominates at four diagonal directions, constituting a butterflylike structure.