Measurement of $A_{CP}$ in $D^0\to\pi^0\pi^0$ in Belle II data

Abstract We measure the time-integrated $CP$ asymmetry, $A_{CP}$, in $D^0\toπ^0π^0$ decays reconstructed in $e^+e^-\to c\bar{c}$ events collected by Belle II during 2019--2022. The data corresponds to an integrated luminosity of 428$\mathrm{fb}^{-1}$. The $D^0$ decays are required to originate from the flavor-conserving $D^{*+} \to D^0 π^+$ decay to determine the charm flavor at production time. Control samples of $D^0\to K^- π^+$ decays, with or without an associated pion from a $D^{*+}$ decay, are used to correct for detection asymmetries. The result, $A_{CP}(D^0\toπ^0π^0) = (0.30\pm 0.72\pm 0.20)\%$, where the first uncertainty is statistical and the second systematic, is consistent with $CP$ symmetry.
Tags Run 1
Working group Charm
Principal authors @  Michel Bertemes, Angelo Di Canto
Reference Phys.Rev.D 112, 012006 (2025), DOI: 10.1103/vg9c-xvdc
Document BELLE2-PUB-PH-2025-008
Links arXiv:2505.02912, Inspire, PRD
Bibtex 
@article{Belle-II:2025rmf,
    author = "Adachi, I. and others",
    collaboration = "Belle-II",
    title = "{Measurement of the time-integrated CP asymmetry in D0{\textrightarrow}{\ensuremath{\pi}}0{\ensuremath{\pi}}0 decays at Belle II}",
    eprint = "2505.02912",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2025-009, KEK Preprint 2025-7",
    doi = "10.1103/vg9c-xvdc",
    journal = "Phys. Rev. D",
    volume = "112",
    number = "1",
    pages = "012006",
    year = "2025"
}