Monocular and Hybrid Analysis for TA×4 Fluorescence Detectors

Abstract

The TA×4 project is an extension of the Telescope Array (TA) experiment, aimed at clarifying the origin of the highest energy cosmic rays. It has deployed 4 fluorescence detectors (FDs) and 130 surface detectors (SDs) at the northeast lobe of the original TA array and 8 FDs and 127 SDs at the southeast lobe of the original TA array, expanding the detection area about four times larger than the TA experiment. This expansion enables us to sample larger data. The TA×4 has been collecting data to obtain solid evidence of the excess of events in the arrival direction distribution, known as the TA hotspot, reported in 2014 by the TA experiment. The north and south observations began in 2018 and 2019, respectively, and are ongoing except for a hiatus from February to June 2020 due to the COVID-19 pandemic. In this presentation, we will report the details of TA×4 FD monocular analysis.