EUSO-SPB1: Flight data classification and Air Shower Search Results

TL;DR

The paper reports on the flight data from EUSO-SPB1, classifying detected events and searching for ultra-high-energy cosmic ray air showers, but finds no candidate air showers during the mission.

Contribution

It provides the first classification of events from EUSO-SPB1 flight data and details the search for air showers using a balloon-borne UV telescope.

Findings

Majority of triggered events are direct cosmic ray hits.

No air shower candidates were identified.

Data collected over 12 moonless nights.

Abstract

The Extreme Universe Space Observatory on a Super Pressure Balloon (EUSO-SPB1) is the second balloon pathfinder of the JEM-EUSO collaboration. It is a nadir pointing UV telescope which aims at observing Ultra High Energy Cosmic Rays (UHECR) air showers through their fluorescence emission. It was launched the 24th of April, 2017, from the NASA balloon launch site in Wanaka, New Zealand. During its flight, EUSO-SPB1 took data during 12 moonless nights until the termination of the mission. In this paper we present events found in triggered data while searching for air showers. We classify these events into different populations whose characteristics and origins we discuss. We show that the majority of our triggered events are direct Cosmic Ray hits on the detector. No air shower candidate have been found in this analysis.