{
  "annotation_id": "7729676a-32d9-4f59-9c06-38ea9b93a179",
  "date_created": "2026-02-17T05:53:15.098000Z",
  "date_modified": "2026-02-17T05:53:15.098000Z",
  "file_hash": "6cc35d455424982932967d7e583a962d404191b62b2e28aa6f919e751ed91261",
  "private": false,
  "record": {
    "abstract": "The Andes Large area PArticle detector for Cosmic ray and Astronomy (ALPACA) is a new air-shower array experiment under construction in the Bolivian Andes, and its prototype ALPAQUITA surface array has been operating since 2023 April. In addition to the traditional $\\ge$3-hit or $\\ge$4-hit coincidences to trigger recording air-shower events, ALPAQUITA records the counting rates of the $\\ge$1-hit and $\\ge$2-hit events (Any1 and Any2, respectively). We report a successful detection of a Forbush decrease occurred on 2024 May 10 caused by a passage of an interplanetary shock formed ahead of the Interplanetary Coronal Mass Ejection. The amplitude detected in the Any1 rate is 4.26$\\pm$0.33% at the median primary rigidity of 76GV which is consistent with the observations with the worldwide neutron monitor and muon detector networks. Under the assumption of a power-law rigidity spectrum, we renormalized the errors of the observed amplitude ($A_{obs}$) and fitted them as a function of the median primary rigidity ($R_{m}$) of each detector and observational method. The result $A_{obs} = (10.9\\% \\pm 0.9\\%) \\times (R_{m}/10\\,GV)^{-0.55 \\pm 0.07}$ exhibits a hard nature of this event. Our non-detection in the Any2 rate decrease constrains the amplitude with a 2$\\sigma$ upper limit to be 0.95% at 960GV. This marginally suggests an existence of a spectral softening between 100GV and 1000GV as also suggested by the Misato underground muon detector at 145GV. Although a strong geomagnetic storm was observed during this period, we conclude it does not impact our results. Our novel technique realizes a unique coverage to study the behavior of the Forbush decreases at the highest rigidity.",
    "arxiv_id": "2601.08154",
    "authors": [
      "M. Anzorena",
      "E. de la Fuente",
      "K. Fujita",
      "R. Garcia",
      "Y. Hayashi",
      "K. Hibino",
      "N. Hotta",
      "G. Imaizumi",
      "Y. Katayose",
      "C. Kato",
      "S. Kato",
      "T. Kawashima",
      "K. Kawata",
      "M. Kobayashi",
      "S. Kobayashi",
      "T. Koi",
      "H. Kojima",
      "P. Miranda",
      "S. Mitsuishi",
      "A. Mizuno",
      "K. Munakata",
      "Y. Nakamura",
      "M. Nishizawa",
      "Y. Noguchi",
      "S. Ogio",
      "M. Ohishi",
      "M. Ohnishi",
      "A. Oshima",
      "M. Raljevic",
      "H. Rivera",
      "T. Saito",
      "T. Sako",
      "T. K. Sako",
      "S. Shibata",
      "A. Shiomi",
      "M. Subieta",
      "F. Sugimoto",
      "N. Tajima",
      "W. Takano",
      "Y. Takeyama",
      "M. Takita",
      "N. Tamaki",
      "Y. Tameda",
      "K. Tanaka",
      "R. Ticona",
      "H. Tsuchiya",
      "Y. Tsunesada",
      "S. Udo",
      "G. Yamagishi",
      "Y. Yamanaka",
      "K. Yamazaki",
      "Y. Yokoe"
    ],
    "categories": [
      "astro-ph.HE",
      "astro-ph.SR"
    ],
    "license": "http://creativecommons.org/licenses/by/4.0/",
    "title": "Observation of the Forbush decrease on 2024 May 10, using the ALPAQUITA air-shower array at the 70-1000 GV rigidity range",
    "url": "https://arxiv.org/abs/2601.08154",
    "version": "v1"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "a3eab82f-ea8d-463e-8e51-f657e9d00dc5",
    "id": "arXiv Dataset",
    "type": "Model",
    "variant": "snapshot-2026-01-17",
    "version": "0.1.0"
  },
  "user_id": 1000002
}