PreprintCC BY-NC-ND 4.0arXiv
Measurements of electroweak penguin B decays with missing energy at Belle and Belle II
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 B0 → K0Sτ+τ- sets the upper limit on the branching fraction to ℬ < 8.3 × 10−4, the search for B+ → K+τ+τ- sets ℬ < 5.6 × 10−4, and their isospin combination gives ℬ(B → Kτ+τ-) < 5.4 × 10−4, all at 90% confidence level (CLs). The first search for inclusive B → Xsνν̅ decays at Belle II sets ℬ < 3.3 × 10−4. Finally, the Belle II B+ → K+νν̅ 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.
Related
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BibTeX
@misc{gartner2026measurements,
title = {{Measurements of electroweak penguin $B$ decays with missing energy at Belle and Belle II}},
author = {Lorenz Gärtner},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37146},
eprint = {2609.37146},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37146},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Measurements of electroweak penguin B decays with missing energy at Belle and Belle II
AU - Lorenz Gärtner
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37146
UR - https://arxiv.org/abs/2609.37146
AB - 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 → K^0_Sτ^+τ^- sets the upper limit on the branching fraction to ℬ < 8.3 × 10^−4, the search for B^+ → K^+τ^+τ^- sets ℬ < 5.6 × 10^−4, and their isospin combination gives ℬ(B → Kτ^+τ^-) < 5.4 × 10^−4, all at 90% confidence level (CL_s). The first search for inclusive B → X_sνν̅ decays at Belle II sets ℬ < 3.3 × 10^−4. Finally, the Belle II B^+ → K^+νν̅ 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.
ER -