Measurement of the CP asymmetry in $D^+\to\pi^+\pi^0$ decays using Belle II Run 1 data

Abstract We measure the CP asymmetry in $D^+ \to π^+ π^0$ decays reconstructed in $e^+ e^-$ collisions at the Belle II experiment using a data set corresponding to an integrated luminosity of 428 fb$^{-1}$. A control sample of $D^+ \to π^+ K_{S}$ decays is used to correct for detection and production asymmetries. The result, $A_{CP}(D^+ \to π^+π^0) =(-1.8 \pm 0.9 \pm 0.1)\%$, where the first uncertainty is statistical and the second systematic, is the most precise determination to date. It agrees with the prediction of CP symmetry from the standard model, and with results of previous measurements.
Tags Run 1
Working group Charm
Principal authors @  Angelo Di Canto, Yifan Jin
Reference Phys.Rev.D 112, L031101 (2025), DOI: 10.1103/3kqk-ldm4
Document BELLE2-PUB-PH-2025-011
Links arXiv:2506.07879, Inspire, PRL
Bibtex 
@article{Belle-II:2025wsy,
    author = "Adachi, Ichiro and others",
    collaboration = "Belle-II",
    title = "{Measurement of the CP asymmetry in D+{\textrightarrow}{\ensuremath{\pi}}+{\ensuremath{\pi}}0 decays at Belle II}",
    eprint = "2506.07879",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2025-012, KEK Preprint 2025-10",
    doi = "10.1103/3kqk-ldm4",
    journal = "Phys. Rev. D",
    volume = "112",
    number = "3",
    pages = "L031101",
    year = "2025"
}