Latest findings on large-scale cosmic ray anisotropy from the GRAPES-3 experiment

Cosmic ray anisotropy at various scales has been observed over the past decade by multiple experiments in both the Northern and Southern Hemispheres. The GRAPES-3 experiment, located at 11.4 degrees North, is well positioned to study a significant portion of both hemispheres, covering nearly 70 percent of the sky at TeV energies. Observing large-scale anisotropy is particularly challenging since the effect is extremely small, measuring less than 0.1%, while detector and atmospheric influences can reach up to 5% and must be carefully mitigated. Using one year of data collected by GRAPES-3 between January 1, 2013, and December 31, 2013, we apply the iterative maximum likelihood method to extract the large-scale anisotropy. The detection significance reaches 6 standard deviations. The results, along with a comparison to findings from other experiments, are described in this proceeding.

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Publication Details

Published
2025-09-23
DOI
https://doi.org/10.22323/1.501.0216
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
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Latest findings on large-scale cosmic ray anisotropy from the GRAPES-3 experiment

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Astrophysics and Cosmic Phenomena
article

Latest findings on large-scale cosmic ray anisotropy from the GRAPES-3 experiment

K. Ramesh, Y. Hayashi, Fahim Varsi, Medha Chakraborty, B. Hariharan, D. Pattanaik, M. Rameez, P. K. Mohanty, P.K. Nayak, Manish Talwar, Amit Kumar Jain, S. R. Dugad, S. Kawakami, S. K. Gupta, A. Oshima, P. Jagadeesan
article en

Abstract

Cosmic ray anisotropy at various scales has been observed over the past decade by multiple experiments in both the Northern and Southern Hemispheres. The GRAPES-3 experiment, located at 11.4 degrees North, is well positioned to study a significant portion of both hemispheres, covering nearly 70 percent of the sky at TeV energies. Observing large-scale anisotropy is particularly challenging since the effect is extremely small, measuring less than 0.1%, while detector and atmospheric influences can reach up to 5% and must be carefully mitigated. Using one year of data collected by GRAPES-3 between January 1, 2013, and December 31, 2013, we apply the iterative maximum likelihood method to extract the large-scale anisotropy. The detection significance reaches 6 standard deviations. The results, along with a comparison to findings from other experiments, are described in this proceeding.

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Astrophysics and Cosmic Phenomena
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