Nonlinear pair production in scattering of photons on ultra-short laser pulses at high energy

TL;DR

This paper analyzes how ultra-short laser pulses at high energy induce nonlinear electron-positron pair production, showing saturation effects at high intensities due to multi-photon interactions, with implications for experimental verification.

Contribution

It derives the total cross section for pair production considering all multi-photon interactions and identifies the saturation intensity lower than Schwinger's critical value.

Findings

Total cross section saturates at high intensities due to multi-photon effects.

Saturation intensity is significantly lower than Schwinger's critical value.

The interaction remains coherent over the entire pulse length.

Abstract

We consider scattering of a photon on a short intense laser pulse at high energy. We argue that for ultra-short laser pulses the interaction is coherent over the entire length of the pulse. At low pulse intensity $I$ the total cross section for electron-positron pair production is proportional to $I$. However, at pulse intensities higher than the characteristic value $I_s$, the total cross section saturates -- it becomes proportional to the logarithm of intensity. This nonlinear effect is due to multi-photon interactions. We derive the total cross section for pair production at high energies by resuming the multi-photon amplitudes to all orders in intensity. We calculate the saturation intensity $I_s$ and show that it is significantly lower than the Schwinger's critical value. We discuss possible experimental tests.