Abstract
Telescope Array (TA) is the largest ultrahigh energy cosmic-ray (UHECR) observatory in the Northern Hemisphere. It explores the origin of UHECRs by measuring their energy spectrum, arrival-direction distribution, and mass composition using a surface detector (SD) array covering approximately 700 km2 and fluorescence detector (FD) stations. TA has found evidence for a cluster of cosmic rays with energies greater than 57 EeV. In order to confirm this evidence with more data, it is necessary to increase the data collection rate. We have begun building an expansion of TA that we call TAx4. In this paper, we explain the motivation, design, technical features, and expected performance of the TAx4 SD. We also present TAx4’s current status and examples of the data that have already been collected.
Highlights
Telescope Array (TA) is the largest cosmic-ray observatory in the Northern Hemisphere [1]
The performance of the TAx4 surface detector (SD) array was estimated using Monte Carlo (MC) simulations of air showers and of detectors, similar to those already done for the TA SDs [16]
The mean of the core distances of the saturated TAx4 SDs is between 210 m and 340 m when the primary energies are greater than 10 EeV, whereas the mean of the core distances of the saturated TA SDs is expected to be between 260 m and 400 m under the same conditions
Summary
Telescope Array (TA) is the largest cosmic-ray observatory in the Northern Hemisphere [1]. In previous work using TA SD data collected over five years, we found that 19 out of 72 observed cosmic rays with energies above 57 EeV were concentrated within a single 20◦-radius circle (the “hotspot”) [5]. Correlation of arrival directions with energies was reported in [9]; the post-trial significance of the correlation in this case was estimated to be 4.2σ. These results were obtained using seven to eleven years of observations with the TA SD. The SD array of the TAx4 experiment is designed expressly to study cosmic rays with energies above 57 EeV.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
