Average universal shower profile reconstruction using radio interferometry

Abstract: Radio detection of extensive air showers enables near-continuous observation and precise measurements of the shower geometry and the depth of shower maximum, $X_{\rm max}$. Beyond $X_{\rm max}$, the longitudinal shower development follows a Universal Shower Profile (USP), whose shape parameters contain information on primary mass composition and hadronic interaction models. While previous studies have focused on event-by-event reconstruction of profile parameters, in this work we investigate the reconstruction of the average USP using radio interferometric techniques. Using Monte Carlo simulations, we reconstruct the average longitudinal profile directly from radio data and extract the Gaisser-Hillas shape parameters $(R,L)$. We find that the radio-derived average profiles provide enhanced separation between primary masses and hadronic interaction models compared to that obtained from fluorescence-equivalent longitudinal profiles. These results demonstrate that radio interferometry can access higher-order information on the longitudinal shower development and that the use of the average USP significantly improves the sensitivity to composition and hadronic interaction studies at ultra-high energies.