Trident pair creation by a train of laser pulses: Resonance, threshold, and carrier envelope phase effects

TL;DR

This paper develops a general quantum electrodynamics framework for pair creation in laser pulse trains, revealing resonance phenomena and threshold effects, and demonstrates how carrier envelope phase tuning isolates and characterizes these resonances.

Contribution

It introduces a formalism for analyzing resonances in strong-field QED processes with laser pulse trains, applicable to various phenomena including pair creation, and shows how phase control isolates resonances.

Findings

Resonances originate from poles of the photon propagator.

Carrier envelope phase tuning isolates and characterizes resonances.

Probability distributions exhibit threshold singularities.

Abstract

General formulation in the realm of strong-field quantum electrodynamics is provided for a process that occurs in the presence of a train of laser pulses and, in the tree level, is represented by a two-vertex Feynman diagram with exchange of a virtual photon. A scheme of retrieving resonances in the corresponding probability distributions is also formulated in these general settings. While the presented formalism is applicable to a variety of processes like electron-positron pair creation and annihilation, M\"oller scattering, Bhabha scattering, etc., we illustrate it for a trident process. Specifically, we consider electron-positron pair creation in the muon--laser-field collisions. We demonstrate that the probability distributions exhibit integrable singularities close to the threshold of pair creation. Also, a variety of resonances is observed that originate from the poles of the Feynman photon propagator. While those resonances are, in general, obscured by strong quantum interferences, we show that they can be isolated by changing the carrier envelope phase of the driving laser pulses. In that case, while transformed into the Lorentz-Breit-Wigner shape profile, the resonance position and width can be determined.