Search for a long-lived spin-0 mediator in $b \to s$ transitions at the Belle II experiment

Abstract Additional spin-0 particles appear in many extensions of the standard model. We search for long-lived spin-0 particles $S$ in $B$-meson decays mediated by a $b\to s$ quark transition in $e^+e^-$ collisions at the $\Upsilon(4S)$ resonance at the Belle II experiment. Based on a sample corresponding to an integrated luminosity of $189 \mathrm{\,fb}^{-1}$, we observe no evidence for signal. We set model-independent upper limits on the product of branching fractions $\mathrm{Br}(B^0\to K^*(892)^0(\to K^+\pi^-)S)\times \mathrm{Br}(S\to x^+x^-)$ and $\mathrm{Br}(B^+\to K^+S)\times \mathrm{Br}(S\to x^+x^-)$, where $x^+x^-$ indicates $e^+e^-, \mu^+\mu^-, \pi^+\pi^-$, or $K^+K^-$, as functions of $S$ mass and lifetime at the level of $10^{-7}$.
Tags
Working group Dark Sector and Low Multiplicity
Principal authors @  Sascha Dreyer, Torben Ferber
Reference Phys.Rev.D 108, L111104 (2023), DOI: 10.1103/PhysRevD.108.L111104
Document BELLE2-PUB-PH-2023-020
Links arXiv:2306.02830, Inspire, PRD
Bibtex 
@article{Belle-II:2023ueh,
    author = "Adachi, I. and others",
    collaboration = "Belle-II",
    title = "{Search for a long-lived spin-0 mediator in b{\textrightarrow}s transitions at the Belle II experiment}",
    eprint = "2306.02830",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2023-009, KEK Preprint 2023-7",
    doi = "10.1103/PhysRevD.108.L111104",
    journal = "Phys. Rev. D",
    volume = "108",
    number = "11",
    pages = "L111104",
    year = "2023"
}