Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment

The Telescope Array is the largest cosmic-ray detector in the northern hemisphere. It

consists of a scintillator surface detector (SD) array (Abu-Zayyad et al. 2012a) and three

fluorescence detector (FD) stations (Tokuno et al. 2012). The observatory has been in full

operation in Millard Country, Utah, USA (39. ◦ 30N, 112. ◦ 91W; about 1,400 m above sea level)

since 2008. The TA SD array consists of 507 plastic scintillation detectors each 3 m 2 in

area and located on a 1.2 km square grid. The array has an area of ∼700 km 2 . The TA

SD array observes cosmic ray induced extensive air showers with E >∼1 EeV, regardless

of weather conditions with a duty cycle near 100% and a wide field of view (FoV). These

capabilities ensure a very stable and large geometrical exposure over the northern sky survey

in comparison with FD observations that have a duty cycle of ∼10%.

arXiv