ALPACA project to observe sub-PeV gamma-ray sky in the southern hemisphere
T. Sako*, M. Anzorena, E. de la Fuente, K. Fujita, R. Garcia, K. Goto, Y. Hayashi, K. Hibino, N. Hotta, G. Imaizumi, A. Jimenez-Meza, Y. Katayose, C. Kato, S. Kato, T. Kawashima, K. Kawata, T. Koi, H. Kojima, T. Makishima, Y. Masuda, S. Matsuhashi, M. Matsumoto, R. Mayta, P. Miranda, A. Mizuno, K. Munakata, Y. Nakamura, M. Nishizawa, Y. Noguchi, S. Ogio, M. Ohnishi, S. Okukawa, A. Oshima, M. Raljevich, H. Rivera, T. Saito, T.K. Sako, T. Shibasaki, S. Shibata, A. Shiomi, M. Subieta, F. Sugimoto, N. Tajima, W. Takano, M. Takita, Y. Tameda, K. Tanaka, R. Ticona, I. Toledano-Juarez, H. Tsuchiya, Y. Tsunesada, S. Udo, R. Usui, G. Yamagishi, K. Yamazaki and Y. Yokoeet al. (click to show)
*: corresponding author
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Pre-published on: March 21, 2025
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Abstract
Though the maximum energy of the charged cosmic ray observations exceeds 100 EeV, the energy frontier of the gamma-ray observations is PeV. In the past years, Tibet AS𝛾, HAWC and LHAASO opened a new window of astronomy in the sub-PeV to PeV range, which is important to unveil yet unknown PeV cosmic accelerators in our galaxy. As these 3 experiments are all located in the northern hemisphere, observations in the southern hemisphere have been awaited. Andes Large area PArticle detector for Cosmic ray physics and Astronomy (ALPACA) is a new air shower array experiment under construction in the Bolivian Andes to explore the southern gamma-ray sky for the first time in this energy range. In this paper, we will provide an overview of the ALPACA project, including the initial observational results from a quarter-sized array named ALPAQUITA, which has been operating since 2023. A successful detection of the shadow of the moon, for example, validates the designed performance of the array. We will also outline the plan for the full-scale construction of ALPACA.
DOI: https://doi.org/10.22323/1.484.0112
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