Measurement of the branching fraction and $\it CP$-violating asymmetry of the decay $B^{0} \rightarrow \pi^{0} \pi^{0}$ using $387$ million bottom-antibottom meson pairs in Belle II data

Abstract We measure the branching fraction and $\it CP$-violating flavor-dependent rate asymmetry of $B^{0} \to \pi^{0} \pi^{0}$ decays reconstructed using the Belle II detector in an electron-positron collision sample containing $387 \times 10^{6}$$B\overline{B}$ pairs. Using an optimized event selection, we find $126\pm 20$ signal decays in a fit to background-discriminating and flavor-sensitive distributions. The resulting branching fraction is $(1.25 \pm 0.23)\times 10^{-6}$ and the $CP$-violating asymmetry is $0.03 \pm 0.30$.
Tags
Working group B Hadronic
Principal authors @  Mirco Dorigo, Sebastiano Raiz, Diego Tonelli
Reference Phys. Rev. D 111, L071102 (2025), DOI: 10.1103/PhysRevD.111.L071102
Document BELLE2-PUB-PH-2026-002
Links arXiv:2412.14260, Inspire, PRD
Bibtex 
@article{Belle-II:2024baw,
    author = "Adachi, Ichiro and others",
    collaboration = "Belle-II",
    title = "{Measurement of the branching fraction and CP-violating asymmetry of the decay B0{\textrightarrow}{\ensuremath{\pi}}0{\ensuremath{\pi}}0 using 387 million {\Upsilon}(4S) decays in Belle II data}",
    eprint = "2412.14260",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2024-032, KEK Preprint 2024-34",
    doi = "10.1103/PhysRevD.111.L071102",
    journal = "Phys. Rev. D",
    volume = "111",
    number = "7",
    pages = "L071102",
    year = "2025"
}