The electron mass shift in an intense plane wave

TL;DR

This paper derives a new, compact expression for the electron mass shift in arbitrary plane waves within strong-field QED, extending previous results and exploring the local and non-local aspects of the electron's anomalous magnetic moment.

Contribution

It introduces a new representation of the electron mass operator in momentum space and generalizes the electron mass shift to arbitrary plane waves, including spin-dependent effects.

Findings

Derived a more compact form of the electron mass operator.

Generalized the electron mass shift to arbitrary plane waves.

Connected the spin-dependent mass shift to the electron's anomalous magnetic moment.

Abstract

Upcoming experiments on the interaction of electrons with intense laser fields are envisaged to become more and more accurate, which calls for theoretical computations of rates and probabilities with correspondingly higher precision. In strong-field QED this requires the knowledge of radiative corrections to be added to leading-order results. Here, we first derive the mass operator in momentum space of an off-shell electron in the presence of an arbitrary plane wave. By taking the average of the mass operator in momentum space over an on-shell electron state, we obtain a new representation, equivalent to but more compact than the known one computed in [Sov. Phys. JETP \textbf{42}, 400 (1975)]. Moreover, we use the obtained mass operator to determine the electron mass shift in an arbitrary plane wave, which generalizes the already known expression in a constant crossed field. The spin-dependent part of the electron mass shift can be related to the anomalous magnetic moment of the electron in the plane wave. We show that within the locally constant field approximation it is possible to conveniently define a local expression of the electron anomalous magnetic moment, which reduces to the known expression in a constant crossed field. Beyond the locally constant field approximation, however, the interaction between the electron and the plane wave is non-local such that it is not possible to conveniently introduce an electron anomalous magnetic moment.