Small-scale Cosmic-Ray Anisotropy Observed by the GRAPES-3 Experiment at TeV Energies

GRAPES-3 is a mid-altitude (2200 m) and near-equatorial (11.degrees 4N) air shower array, overlapping in its field of view for cosmic-ray observations with experiments that are located in the Northern and Southern Hemispheres. We analyze a sample of 3.7 x 10(9) cosmic-ray events collected by the GRAPES-3 experiment between 2013 January 1 and 2016 December 31 with a median energy of similar to 16 TeV for study of small-scale (<60 degrees) angular-scale anisotropies. We observed two structures, labeled A and B, that deviate from the expected isotropic distribution of cosmic rays in a statistically significant manner. Structure A spans 50 degrees-80 degrees in R.A. and from -15 degrees to 30 degrees in decl. The relative excess observed in structure A is at the level of (6.5 +/- 1.3) x 10(-4) with a statistical significance of 6.8 standard deviations. Structure B is observed in the R.A. range 110 degrees-140 degrees and at decl. from -10 degrees to 30 degrees. The relative excess observed in this region is at the level of (4.9 +/- 1.4) x 10(-4) with a statistical significance of 4.7 standard deviations. These structures are consistent with those reported by Milagro, ARGO-YBJ, and HAWC. These observations could provide a better understanding of the sources of cosmic rays, their propagation, and the magnetic structures in our Galaxy.