A search for feebly-interacting particles in $B$ decays with missing energy at Belle

Sumitted to PubDB: 2024-05-02

Category: Physics / performance paper

Tags: Belle

Principal Authors Daniel Marcantonio, Phillip Urquijo
Date 2026-07-20
Working group Dark Sector and Low Multiplicity
Belle II Number BELLE2-PUB-DRAFT-2024-007
Abstract We present a search for an invisible hidden-sector particle $ X_{\rm{inv}}$, produced in $B^0 \to \bar{D}^0 X_{\rm{inv}}$ and $B^\pm\to h X_{\rm{inv}}$ decays, where $h = \pi^\pm$, $K^\pm$, $D_{s}^\pm$, $p^\pm$. The search is performed using $e^+ e^-$ collision data recorded with the Belle detector, corresponding to 711~fb$^{-1}$. No significant signal is observed. We set 90\% confidence level upper limits ranging between $10^{-4}$ and $10^{-6}$ on the branching fraction $\mathcal{B}(B \to h X_{\rm{inv}})$ as a function of $m_{ X_{\rm{inv}}}$. Corresponding limits are set on $\mathcal{B}(B \to hX)\times\mathcal{B}(X\to\gamma\gamma)$ for lifetimes $c\tau_X$ between 10~$\mu$m and 10~m. Many of these limits are the first direct constraints on their respective decays. Our results provide the most stringent exclusion limits to date on the branching fractions for all search channels, and exclude previously unexplored regions of parameter space relevant to several new physics models.
ArXiv https://arxiv.org/abs/2601.07104
Inspire https://inspirehep.net/literature/3103099
Bibtex 
@article{Belle-II:2026tyb,
    author = "Abumusabh, M. and others",
    collaboration = "Belle-II, Belle",
    title = "{A search for feebly-interacting particles in $B$ decays with missing energy at Belle}",
    eprint = "2601.07104",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint: 2025-029 KEK Preprint: 2025-36",
    month = "1",
    year = "2026"
}
Journal Phys.Rev.Lett.
Preprint Number 2025-029

Files