Current status and prospects of surface detector of the TAx4 experiment

Abstract

Telescope Array (TA) is the largest ultrahigh energy cosmic-ray (UHECR) observatory in the Northern Hemisphere. A surface detector (SD) array covers approximately 700 km 2 , and the SD array is surrounded by three fluorescence detector (FD) stations. TA has found evidence for a cluster of cosmic rays with energies greater than 57 EeV from the TA SD data. In order to confirm this evidence with more data, we started the TAx4 experiment which expands the detection area using new SDs and FDs. We started construction of new SDs which are arranged in a square grid with 2.08 km spacing at the north east and south east of the TA SD array. More than half of the new SDs are already deployed and running. We present the current status of the TAx4 SD, trigger efficiency and exposure prospects for the highest energy part of the cosmic ray spectrum.

Constraining ultra-high-energy cosmic ray composition through cross-correlations

“…Our results imply that already with current data significant quantitative statements about the composition of UHECRs at the highest energies can be made. Moreover, in the near future with the completion of the expansions of both the Telescope Array detector TAx4 [36], and in the longer term with the advent of next-generation detectors such as GRAND [37] and POEMMA [38], the larger available data sets would quickly improve the sensitivity of our method and allow to determine (or exclude) with more precision several composition models.…”

Status of the K-EUSO Orbital Detector of Ultra-high Energy Cosmic Rays

“…We expect that the optics performance will meet the requirements. 3 https://www.shibaura-machine.co.jp/en/product/nano/lineup/utd/shiyo.html (accessed on 13 December 2021).…”

“…For example, the array of surface detectors of the world's largest cosmic ray observatory, the Pierre Auger Observatory (Auger), extends over an area of 3000 km 2 [2]. Surface detectors of the second largest experiment, the Telescope Array (TA), occupy an area around 700 km 2 , and the array is being expanded to cover an area approximately equal to that of Auger [3]. Both experiments employ a so-called hybrid technique for registering cosmic rays, complementing surface detectors with stations of fluorescence telescopes that observe ultraviolet emission of extensive air showers (EASs) developing in the nocturnal atmosphere.…”

Cosmic Ray Indirect Rapporteur Report (37th ICRC )

“…The main drivers for the upgrades were increased statistics at the highest energies, e.g. TAx4 [30], lowering the energy-reach of the detectors, e.g. Auger's SD-433 [31], TALE-infill [32], or improving the quality of collected data by adding new detection channels.…”