{
  "abstract": "Electroweak penguin $B$ decays with neutrinos or $τ$ leptons in the final state are sensitive probes of physics beyond the Standard Model. Using the full Belle and Run 1 Belle II datasets, the first search for $B^0 \\to K^0_Sτ^+τ^-$ sets the upper limit on the branching fraction to $\\mathcal{B} < 8.3 \\times 10^{-4}$, the search for $B^+ \\to K^+τ^+τ^-$ sets $\\mathcal{B} < 5.6 \\times 10^{-4}$, and their isospin combination gives $\\mathcal{B}(B \\to Kτ^+τ^-) < 5.4 \\times 10^{-4}$, all at 90% confidence level (CL$_s$). The first search for inclusive $B \\to X_sν\\barν$ decays at Belle II sets $\\mathcal{B} < 3.3 \\times 10^{-4}$. Finally, the Belle II $B^+ \\to K^+ν\\barν$ result is reinterpreted in the Weak Effective Theory using its published likelihood. The data prefer an enhanced vector contribution and mildly favour a nonzero tensor contribution.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.37146",
  "author_total": 1,
  "authors": [
    {
      "name": "Lorenz Gärtner"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ay97ce9d333wj.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.37146",
  "fulltext_url": null,
  "id": "ay97ce9d333wj",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.37146",
  "language": null,
  "licence": "CC-BY-NC-ND-4.0",
  "licence_label": "CC BY-NC-ND 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "hep-ex"
    ],
    [
      "arxiv",
      "hep-ph"
    ],
    [
      "openalex",
      "3106|Particle physics theoretical and experimental studies"
    ]
  ],
  "openalex": "W7214936217",
  "pdf_url": "https://arxiv.org/pdf/2609.37146",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ay97ce9d333wj.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:31Z",
      "native_id": "2609.37146",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.37146"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:hep-ex",
      "subfield": "high-energy"
    }
  ],
  "title": "Measurements of electroweak penguin $B$ decays with missing energy at Belle and Belle II",
  "title_text": "Measurements of electroweak penguin B decays with missing energy at Belle and Belle II",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:31Z",
  "url": "https://research.draconitic.com/paper/ay97ce9d333wj",
  "venue": "arXiv",
  "versions": []
}