Mass sensitivity in the radio lateral distribution function

TL;DR

This paper investigates how the slope of the radio lateral distribution function can serve as an indicator of cosmic ray mass composition, using simulations and LOPES data to explore potential signatures of protons versus iron nuclei.

Contribution

It demonstrates the feasibility of using the radio lateral distribution slope as a composition signature in cosmic ray air showers, supported by simulations aligned with LOPES observations.

Findings

Radio lateral distribution slope correlates with primary particle type.

Simulations show distinguishable slopes for proton and iron showers.

Analysis suggests potential mass composition signatures in LOPES data.

Abstract

Measuring the mass composition of ultra-high energy cosmic rays is one of the main tasks in the cosmic rays field. Here we are exploring the composition signature in the coherent electromagnetic emission from extensive air showers, detected in the MHz frequency range. One of the experiments that successfully detects radio events in the frequency band of 40-80 MHz is the LOPES experiment at KIT. It is a digital interferometric antenna array and has the important advantage of taking data in coincidence with the particle detector array KASCADE-Grande. A possible method to look at the composition signature in the radio data, predicted by simulations, concerns the radio lateral distribution function, since its slope is strongly correlated with Xmax. Recent comparison between REAS3 simulations and LOPES data showed a significantly improved agreement in the lateral distribution function and for this reason an analysis on a possible LOPES mass signature through the slope method is promising. Trying to reproduce a realistic case, proton and iron showers are simulated with REAS3 using the LOPES selection information as input parameters. The obtained radio lateral distribution slope is analyzed in detail. The lateral slope method to look at the composition signature in the radio data is shown here and a possible signature of mass composition in the LOPES data is discussed.