The Study of a Cosmic Ray Candidate Detected by the Askaryan Radio Array

TL;DR

This paper reports on a candidate cosmic ray event detected by the Askaryan Radio Array, analyzing its features and using simulations to understand its origin as a cosmic-ray induced air shower.

Contribution

It presents the first detailed analysis of a cosmic-ray candidate event detected by ARA, combining simulations and data to interpret the signals as a CR-induced air shower.

Findings

Detection of a candidate cosmic-ray event with characteristic double pulses.

Successful simulation of the event using combined CR shower and detector models.

Insights into the event topology and signal timing consistent with a CR air shower.

Abstract

Experiments designed to detect ultra-high energy (UHE) neutrinos using radio techniques are also capable of detecting the radio signals from cosmic-ray (CR) induced air showers. These CR signals are important both as a background and as a tool for calibrating the detector. The Askaryan Radio Array (ARA), a radio detector array, is designed to detect UHE neutrinos. The array currently comprises five independent stations, each instrumented with antennas deployed at depths of up to 200 meters within the ice at the South Pole. In this study, we focus on a candidate event recorded by ARA Station 2 (A2) that shows features consistent with a downward-going CR-induced air shower. This includes distinctive double-pulse signals in multiple channels, interpreted as geomagnetic and Askaryan radio emissions arriving at the antennas in sequence. To investigate this event, we use detailed simulations that combine a modern ice-impacting CR shower simulation framework, FAERIE, with a realistic detector simulation package, AraSim. We will present results for an optimization of the event topology, identified through simulated CR showers, comparing the vertex reconstruction of both the geomagnetic and Askaryan signals of the event, as well as the observed time delays between the two signals in each antenna.