Browsing by Autor "Y. Hayashi"

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    ALPACA experiment: A new air shower array to explore the sub-PeV gamma-ray sky in the southern hemisphere
    (2022) T. Sako; M. Anzorena; A. Gomi; Y. Hayashi; K. Hibino; N. Hotta; A Jimenez-Meza; Y. Katayose; C. Kato; S. Kato
    In the last few years, gamma-ray astronomy opens a new window in the sub-PeV to PeV range inaugurated by the Tibet AS𝛾 collaboration followed by the HAWC and LHAASO collaborations. The successful three experiments are located in the northern hemisphere and they are not able to study the southern sky where potential interesting objects are known to exist. Andes Large area PArticle detector for Cosmic ray physics and Astronomy (ALPACA) is a project to cover the southern sub-PeV to PeV sky using a new air shower array at the plateau of the Chacaltaya mountain at the altitude of 4,740 m in Bolivia. The prime target of ALPACA is to reveal PeV cosmic-ray accelerators presumably existing in the galactic plane, including the galactic center. A prototype array ALPAQUITA consisting of 97 surface counters and 900 m$^2$ muon detectors is now under construction and planned to partly start data taking in 2022. The extension to the 401 counters and 3,700 m$^2$ muon detectors is scheduled in 2024. In this contribution, a general introduction to ALPACA, the current status of ALPAQUITA, and an extension plan after 2023 are presented.
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    $$\gamma $$/hadron discrimination by analysis of the muon lateral distribution and the ALPAQUITA array
    (Springer Science+Business Media, 2025) M. Anzorena; E. De la Fuente; K. Fujita; R. Murillo Garcia; Kenta Goto; Y. Hayashi; K. Hibino; N. Hotta; G. Imaizumi; A. Jiménez-Meza
    Abstract A new method using the muon lateral distribution and an underground muon detector to achieve high discrimination power against hadrons is presented. The method is designed to be applied in the Andes Large-area PArticle detector for Cosmic-ray physics and Astronomy (ALPACA) experiment in Bolivia. This new observatory in the Southern hemisphere has the goal of detecting &gt;100 TeV $$\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> </mml:math> rays in search for the origins of Galactic cosmic rays. The method uses the weighted sum of the lateral distribution of the muons detected by underground detectors to separate between air showers initiated by cosmic rays and $$\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> </mml:math> rays. We evaluate the performance of the method through Monte Carlo simulations with CORSIKA and Geant4 and apply the analysis to the prototype of ALPACA, ALPAQUITA. With the application of this method in ALPAQUITA, we achieve an improvement of about 18 % in the energy range from 60 to 100 TeV over the estimated sensitivity using only the total number of muons.