Enhancing the cosmic-ray mass sensitivity of air-shower arrays by combining radio and muon detectors

Abstract

The muonic and electromagnetic components of air showers induced by cosmic-ray particles are sensitive to their mass. The sizes of the components can be measured with particle detectors on ground, and the electromagnetic component in addition indirectly via its radio emission in the atmosphere. The electromagnetic particles do not reach the ground for very inclined showers. On the contrary, the atmosphere is transparent for the radio emission and its footprint on ground increases with the zenith angle. Therefore, the radio technique offers a reliable detection over the full range of zenith angles, and in particular for inclined showers. In this work, the mass sensitivity of a combination of the radio emission with the muons is investigated in a case study for the site of the Pierre Auger Observatory using CORSIKA Monte Carlo simulations of showers in the EeV energy range. It is shown, that the radio-muon combination features superior mass separation power in particular for inclined showers, when compared to established mass observables such as a combination of muons and electrons or the shower maximum X max . Accurate measurements of the energy-dependent mass composition of ultra-high energy cosmic rays are essential to understand their still unknown origin. Thus, the combination of muon and radio detectors can enhance the scientific performance of future air-shower arrays and offers a promising upgrade option for existing arrays.

Targeting ultra-high energy neutrinos with the ARIANNA experiment

“…These events will provide an exceptional amount of information and will be important for cross-calibration purposes. In addition, the radio signal is only sensitive to the electromagnetic air-shower component whereas IceTop and especially IceCube provides a complementary measurement of the hadronic shower component which allows for a measurement of the cosmic-ray mass (Holt et al, 2019). This is facilitated by a newly developed technique to determine the air-shower energy from a single radio detector station (Welling et al, 2019).…”

Refractive displacement of the radio-emission footprint of inclined air showers simulated with CoREAS

“…The thickness of each layer is set to 1 m assuring a high accuracy of the calculation. 3 To predict the magnitude of a symmetry center displacement by refraction, we simulate the propagation of an electromagnetic wave along a bent trajectory with an initial direction aligned to the MC axis for a shower with a given zenith angle, towards the ground plane. The intersection between the bent trajectory and the ground plane is compared to the intersection between the ground plane and the MC axis.…”

“…Combined with a measurement of the muonic shower component, e.g. by a particle detector, measurements of inclined air showers also provide a high mass-composition sensitivity [3], which will be in particular a target of the large-scale radio detector of the upcoming upgrade of the Pierre Auger Observatory [4]. Therefore, inclined air showers have a high relevance and a detailed understanding of the signal distribution of their radio emission is crucial to accurately reconstruct the cosmic-ray properties of interest.…”

The GRANDProto300 experiment: a pathfinder with rich astroparticle and radio-astronomy science case

“…For inclined air showers, the only particles reaching the ground are muons [21]. With the complementary particle detector array, a separate measurement of the shower components will be made [22]. A comparison of the muon component, measured with the particle array, and the electromagnetic (EM) energy in the shower, measured with radio, will shed light on the enhanced muon content observed in ultra-high-energy air showers [23,24].…”