{
  "abstract": "The longitudinal evolution of second-harmonic anisotropy inherited from the first interaction in extensive air showers is investigated with CORSIKA simulations. Events with large initial anisotropy are selected. Second-harmonic observables are evaluated separately using the coordinate and momentum azimuths at several atmospheric depths and compared with their corresponding initial harmonic orientations. More than 84% of the initial second-harmonic signal is attenuated within the first 20 g cm$^{-2}$ of shower development. In coordinate space, the second-harmonic correlation with the initial orientation persists to ground level at approximately 0.09% of its initial magnitude. This residual is evaluated against a matched source-isotropized reference, constructed for each selected event by independently randomizing the azimuths of the first-interaction final-state particles and simulating the shower under identical atmospheric conditions. The positive coordinate-space ensemble-mean difference at ground level is statistically resolved, and the two samples show little event-level separation. In momentum space, a weak ensemble-level residual remains at 200 g cm$^{-2}$, and the original and source-isotropized signals become statistically indistinguishable by 300 g cm$^{-2}$ and remain so at ground level.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.12380",
  "author_total": 2,
  "authors": [
    {
      "name": "Hao Sun"
    },
    {
      "name": "Cunfeng Feng"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6aq0tfxgvdwz0.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.12380",
  "fulltext_url": null,
  "id": "6aq0tfxgvdwz0",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.12380",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "openalex",
      "3106|Astrophysics and Cosmic Phenomena"
    ]
  ],
  "openalex": "W7213119876",
  "pdf_url": "https://arxiv.org/pdf/2609.12380",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-11",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6aq0tfxgvdwz0.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:07Z",
      "native_id": "2609.12380",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.12380"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Evolution of first-interaction second-harmonic anisotropy in cosmic-ray air showers",
  "title_text": "Evolution of first-interaction second-harmonic anisotropy in cosmic-ray air showers",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:07Z",
  "url": "https://research.draconitic.com/paper/6aq0tfxgvdwz0",
  "venue": "arXiv",
  "versions": []
}