Auger@TA: Current Status of the independent Pierre Auger Observatory SD micro-array at the Telescope Array Project

The Pierre Auger Observatory (Auger), in the southern hemisphere in Malargüe, Mendoza, Argentina, and the Telescope Array (TA), in the northern hemisphere in Delta, Utah, are the largest ultra-high-energy cosmic ray (UHECR) observatories currently in operation. In order to increase our statistical understanding of UHECR, efforts to compare findings between the two arrays have been ongoing to achieve full sky coverage. When compared, discrepancies are apparent in the spectrum of UHECR observed by Auger and TA, possibly suggesting an astrophysical difference in the Northern and Southern skies. However, the two observatories utilize different surface detection techniques, which may lead to a systematic difference in energy reconstructions and, thereby, a bias in the UHECR spectrum. The Auger@TA project aims to address this possibility by cross-validating the two detection methods.

The Auger@TA group is deploying and operating a micro-array of Auger Surface Detector stations within TA to cross-calibrate the detector response of both observatories in-situ using the same cosmic ray showers. This micro-array is self-triggering and consists of eight Auger stations, seven of which use a 1-PMT prototype configuration, referred to as an Auger@TA station, and form a single hexagon with a traditional 1.5 km Auger spacing. A standard Auger tank with two photomultiplier tubes, which will have the same instrumentation behavior as an Auger standard station, is located in the center of the array in a triplet configuration with an Auger@TA station and a TA station, allowing for a three-way comparison. Each Auger station will also be outfitted with an AugerPrime Surface Scintillator Detector. This setup allows for comparisons on both a station-to-station and an event-to-event level. The array has been deployed and is starting operations. An update on the status of the array will be given, including expected performance and data.