PoS - Proceedings of Science
Volume 395 - 37th International Cosmic Ray Conference (ICRC2021) - GAD - Gamma Ray Direct
Observation of sub-GeV atmospheric gamma rays on GRAINE 2018 balloon experiment and comparison with HKKM calculation
H. Rokujo*, S. Aoki, A. Iyono, A. Karasuno, K. Kodama, R. Komatani, M. Komatsu, M. Komiyama, K. Kuretsubo, T. Marushima, S. Matsuda, K. Morishima, M. Morishita, N. Naganawa, M. Nakamura, M. Nakamura, T. Nakamura, Y. Nakamura, N. Nakano, T. Nakano, A. Nishio, M. Oda, O. Sato, K. Sugimura, A. Suzuki, S. Takahashi, M. Torii, S. Yamamoto and M. Yoshimotoet al. (click to show)
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Pre-published on: July 28, 2021
Published on: March 18, 2022
We report a precise measurement of the sub-GeV atmospheric gamma-ray spectrum at balloon altitude on GRAINE 2018 experiment, and comparisons with the predictions calculated by the latest HKKM, which is widely known as a model for atmospheric neutrino flux calculation.
Understanding the interactions between cosmic rays and atmospheric nuclei is important for accurate atmospheric neutrino flux calculations. Observation data of sub-GeV atmospheric gamma rays at balloon altitudes are useful for verifying such hadronic interaction models and pion productions in the low energy region.
In April 2018, we conducted a balloon experiment (GRAINE 2018) in Australia with the aim of detecting and imaging the celestial gamma-ray sources with the nuclear emulsion telescope. Following flight data analysis, we derived an atmospheric gamma-ray spectrum in 0.1--1 GeV region at altitudes of ~36 km (residual depth ~4 g / cm^2). The flux around the 1 GeV region is in good agreement with the HKKM prediction and smoothly connects to the multi-GeV observations of past balloon experiments. On the other hand, the flux around 0.1 GeV shows a discrepancy with the prediction.
In this presentation, the balloon experiment, flight data analysis, and observation results are described.
DOI: https://doi.org/10.22323/1.395.0638
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