A novel approach for air shower profile reconstruction with dense radio antenna arrays using Information Field Theory

Reconstructing the longitudinal profile of extensive air showers, generated from the interaction of cosmic rays in the Earth's atmosphere, is crucial to understand their mass composition, which in turn provides valuable insight on their possible source of origin. Furthermore, the substructures within the profile allow us to probe the intricate particle interactions that occur within these air showers. Dense radio antenna arrays such as the LOw Frequency ARray (LOFAR) telescope as well as the upcoming Square Kilometre Array (SKA) are ideal instruments to explore the potential of air shower profile reconstruction, as its high antenna density allows cosmic ray observations with unprecedented accuracy. However, current frameworks can only recover parametrisations of the shower and rely heavily on computationally expensive simulations. As such, it is ever more so crucial to develop new analysis approaches that can perform a full air shower profile reconstruction.

In this work, we develop a novel framework to reconstruct the longitudinal profile of air showers using measurements from radio detectors with Information Field Theory (IFT), a state-of-the-art reconstruction framework based on Bayesian inference. ... mehrThrough IFT, we are able to exploit all available information in the signal (amplitude, phase, and pulse shape) at each antenna position simultaneously for reconstructing the profile. Furthermore, we explicitly utilise shower parameters that are motivated through our current understanding of air shower physics to model the profile. We leverage on a novel fast-forward model for the radio emission based on template synthesis which generates traces in the antennas using scaling relations. We apply our framework on simulated datasets based on LOFAR and SKA where we incorporate realistic antenna and noise models. Using our framework, we can not only reconstruct the air shower profile with uncertainties in each bin but also recover the reconstructed trace at each antenna position. We demonstrate that radio measurements from dense antenna layouts such as LOFAR and SKA have the capability to go beyond reconstruction of standard shower parameters which will undoubtedly further our understanding of cosmic ray air showers.