Nonperturbative signatures of nonlinear Compton scattering

Abstract

The probabilities of various elementary laser-photon-electron/positron interactions display in selected phase space and parameter regions typical nonperturbative dependencies such as Pexp{-aEcrit/E}, where P is a preexponential factor, Ecrit denotes the critical Sauter-Schwinger field strength, and E characterizes the (laser) field strength. While the Schwinger process with a=aSπ and the nonlinear Breit-Wheeler process in the tunneling regime with a=anℓBW4m/3ω′ (with ω′ the probe photon energy and m the electron/positron mass) are famous results, we point out here that also the nonlinear Compton scattering exhibits a similar behavior when focusing on high harmonics. Using a suitable cutoff c>0, the factor a becomes a=anℓC23cm/(p0+p02-m2). This opens the avenue toward a new signature of the boiling point of the vacuum even for field strengths E below Ecrit by employing a high electron beam-energy p0 to counter balance the large ratio Ecrit/E by a small factor a to achieve E/a→Ecrit. In the weak-field regime, the cutoff facilitates a threshold leading to multiphoton signatures showing up in the total cross section at subthreshold energies.