Air shower interferometry to advance astroparticle physics

Introduction

The universe hosts a population of subatomic particles with astonishingly high kinetic energies, so-called cosmic rays. Where and how they obtain this energy is unknown. These particles initiate cascades of particles in the atmosphere called air showers. The particle interactions within air showers are not fully understood and probe a regime not easily accessible by particle accelerator experiments.

New Technique Development

I developed a new technique that applies interferometry on the radio emission from air showers. It improves the reconstruction accuracy of air shower properties and hence allows for better determination of the features of cosmic particles.

Facility Upgrades

The largest facility for ultra-high-energy cosmic ray detection, the Pierre Auger Observatory, is upgrading its infrastructure to include 1660 radio antennas. This CoG facilitates the interferometric technique for the upgrade by deploying an accurate synchronization system.

The Southern Wide-view Gamma-ray Observatory is a next-generation facility, starting construction in 2026. This CoG augments it with 800 antennas to perform interferometry on air showers.

Objectives

By improving the air shower reconstruction of these facilities, we aim to extend their capabilities to address major open questions in astroparticle physics. Specifically, the combination of particle detection and interferometry is used to reach these objectives:

1. Determine which particles contribute to the cosmic-ray flux at the highest energies, by measuring air shower depth.
2. Accurately measure the hadronic interactions in air showers, by simultaneously detailed observations of the muon and electromagnetic components of air showers. The same technique is applied over a wide cosmic-ray energy range.
3. Observe astrophysical photons with energies above 10^15 eV, to identify the most extreme particle accelerators in our galaxy.

Conclusion

This CoG pioneers the interferometric air shower reconstruction on a large scale and will pave the way for its use in future projects.