Simulation study of the detected and expected events for the EUSO-TA fluorescence detector

Abstract

EUSO-TA is a ground-based cosmic ray fluorescence detector, pathfinder of the JEM-EUSO experiment, installed in 2013 at the Telescope Array (TA) site, in front of a TA fluorescence detector station at the Black Rock Mesa site (TA-FD), and completed with the focal surface detector in 2015, when it started to be operational. The data acquisition works in coincidence with TA-FD. This guarantees an easy identification of the cosmic ray events detected by EUSO-TA with reliability of the TA-FD event detection and reconstruction methods. Up to now, a few cosmic ray events have been identified. Two simulation software are developed for the JEM-EUSO detectors: ESAF and Off line . ESAF is the software package that has been developed in the efforts of the EUSO and JEM-EUSO projects; Off line was originally developed and successfully tested for years by the Auger Collaboration, and it has recently been adapted for the JEM-EUSO detectors. Thanks to the first events detected by EUSO-TA, ESAF and Off line have been improved in order to have a good comparison between data and simulations. This made the evaluation of the EUSO-TA detection threshold possible, with an Off line study based on the simulated air showers according to TA reconstruction. In parallel, an independent simulation to estimate the number of detectable events by EUSO-TA has been conducted using ESAF code. The simulation methods are described in this work, as well as the comparison between the number of actual detected events and the number of expected ones.

The EUSO program to study UHECR from space: status and perspectives.

“…So far we have observed several events with E ∼ 10 18 eV: due to the proximity of the event the track is going through the whole FOV in a single GTU (one frame of 2.5 µs), as shown in Figure 2 (right). The parameters were derived from TAFD which, thanks to a larger FOV and higher time-resolution, could see the shower evolution [19].…”