Estimating the sensitivity of the expanded OVRO-LWA array to cosmic-ray primary composition

Abstract

In this study we investigate the capability of the planned expansion of the Owens Valley Long Wavelength Array (OVRO-LWA) to perform radio based composition studies of the cosmic-ray flux between 50 PeV and 1 EeV. We use ZHAIRES simulations in conjunction with a method similar to the one developed by the LOFAR experiment, but that only uses radio data between 30 and 80 MHz, to reconstruct the depth of shower maximum X max. We found that the lower antenna densities away from the central core of the array lead to a decrease in the effective area for quality X max reconstructions of low zenith angle events, and that the asymmetry of the array layout creates the need for quality cuts that depend on arrival direction. We also investigate the dependence of X max uncertainties on shower energy and arrival direction and show that at 500 PeV it is possible to obtain X max uncertainties lower than 20 g/cm 2 for the majority of arrival directions by using a set of simple cuts. For energies below 10 17 eV, alternative reconstruction methods, such as the use of hierarchical beamforming to increase SNR or the use of arrival time measurements on the ground may be needed to maintain X max resolution at a desirable level.

A continuously-operating standalone radio cosmic ray detection system at the OVRO-LWA

“…We plan to estimate energy and 𝑋 max for each air shower, in order to search for features in the composition spectrum across the Galactic to extragalactic transition. Simulations [4] suggest that we will be able to estimate 𝑋 max with precision better than 20 g/cm 2 . When fully commissioned, the OVRO-LWA is expected to detect thousands of cosmic rays per year from 10 17 -10 18 eV.…”

Radio Simulations of Upgoing Extensive Air Showers Observed from Low-Earth Orbit

“…The ZHAireS simulation [7] package integrates the ZHS radio emission modeling in the frequency [8] and time domain [9] with the AIRES [10] extensive air shower simulations. This simulation package has been used for ground-based observatories, such as the Owens Valley Radio Observatory Long Wavelength Array [11] among other applications, and has been adapted to simulate upgoing air showers for the analysis of the ANITA air shower tau neutrino channel [12] at ∼37 km altitude and the BEACON high-elevation observatory concept [13] at 1-4 km altitudes. In this work, we apply the ZHAireS simulation package to provide predictions of the radio emission from upgoing extensive air showers for an observatory at the low-Earth orbit altitude of 525 km (Figure 1).…”