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

Abstract

We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57~EeV in the northern sky using data collected over a 5 year period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20${}^{\circ }$-radius circles. The hotspot has a Li-Ma statistical significance of 5.1$\sigma$, and is centered at R.A.=146.7${}^{\circ }$, Dec.=43.2${}^{\circ }$. The position of the hotspot is about 19${}^{\circ }$ off of the supergalactic plane. The probability of a cluster of events of 5.1$\sigma$ significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7$\times$10${}^{-4}$ (3.4$\sigma$).

16 pages, 3 figures, accepted for publication in the ApJ Letters

References in corpus (2)

• The Cosmic Ray Energy Spectrum Observed with the Surface Detector of the Telescope Array Experiment
• Searching for a Correlation Between Cosmic-Ray Sources Above 10^{19} eV and Large-Scale Structure

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