From LUXE to Future Colliders: Probing Strong-Field QED and Beyond

TL;DR

The paper addresses the experimental exploration of non-perturbative strong-field QED near the Schwinger field $E_S$, leveraging Lorentz boosts with $ ext{order} \\sim 10^4$ to access extreme fields in the lab. It outlines the LUXE approach—colliding 16.5 GeV electrons with a high-intensity laser to study non-linear Compton scattering and non-linear Breit–Wheeler pair production, with a staged laser and a downstream dipole magnet to reconstruct final states—and discusses how this setup benchmarks SFQED predictions and informs future colliders. It further introduces photon-beam NP searches, notably LUXE-NPOD, which use high-energy photons from SFQED in beam-dump configurations to probe axion-like particles and related weakly coupled states, with sensitivity projections across multiple accelerator environments. Overall, the work establishes a concrete experimental pathway for precision SFQED tests in current and next-generation accelerator facilities and links these tests to potential photon-based new-physics discoveries that extend beyond present constraints.

Abstract

Strong-field quantum electrodynamics offers a unique window into non-perturbative phenomena such as vacuum pair production, in which electron--positron pairs are created from the vacuum in the presence of intense electromagnetic fields. The LUXE experiment at DESY is designed to probe this regime using collisions between a high-intensity laser and the 16.5 GeV electron beam of the European XFEL. Future accelerator infrastructures, such as linear colliders, could extend these studies to even higher intensity and energy scales. Additionally, high-energy photons produced in such interactions can be used in beam-dump experiments to search for new physics.

Figures (2)

• Figure 1: Overview of strong-field QED regimes relevant to non-linear Breit--Wheeler pair production accessible in different experimental environments as a function of the relevant interaction parameters. The figure highlights the parameter space that can be probed using electron–laser interactions, aligned crystals, and beam–beam effects. Future high-energy collider facilities extend the reach toward higher energies and intensities, building on the experimental program established by LUXE. Figure adapted from Ref. Fedotov:2022ely.
• Figure 2: Projected sensitivity estimates at 95% C.L. of photon-beam-dump searches for axion-like particles coupling to photons at different accelerator facilities, assuming one year of operation ($10^7$ seconds) in a background-free configuration. The projections are based on photon spectra and geometric acceptances characteristic of the considered setups and are intended to demonstrate the relative scaling with photon energy and flux. A detailed description of the underlying simulation framework and assumptions is given in Ref. Schulthess:2025tct.