PubDB | BELLE2-PUB-PH-2025-022

Abstract	KEK-PREPRINT-2025-17 We measure the time- and phase-space-integrated $C\!P$ asymmetry $A_{C\!P}$ in $D^0\to\pi^+\pi^-\pi^0$ decays reconstructed in $e^+e^-\to c\bar c$ events collected by the Belle II experiment from 2019 to 2022. This sample corresponds to an integrated luminosity of 428 fb$^{-1}$. We require $D^0$ mesons to be produced in flavor-conserving $D^{*+}\to D^0\pi^+$ decays to determine their flavor at production. Control samples of $D^0\to K^-\pi^+$ decays are used to correct for reconstruction-induced asymmetries. The result, $A_{C\!P}(D^0\to\pi^+\pi^-\pi^0)=(0.29\pm0.27\pm0.13)\%$, where the first uncertainty is statistical and the second systematic, is consistent with conservation of $C\!P$ symmetry and is the most precise determination to date.
Tags	Run 1
Working group	Charm
Principal authors	@ Giulia Casarosa, Ludovico Massaccesi
Reference	submitted to PRD
Links	arXiv:2510.21224,

Abstract

KEK-PREPRINT-2025-17 We measure the time- and phase-space-integrated $C\!P$ asymmetry $A_{C\!P}$ in $D^0\to\pi^+\pi^-\pi^0$ decays reconstructed in $e^+e^-\to c\bar c$ events collected by the Belle II experiment from 2019 to 2022. This sample corresponds to an integrated luminosity of 428 fb$^{-1}$. We require $D^0$ mesons to be produced in flavor-conserving $D^{*+}\to D^0\pi^+$ decays to determine their flavor at production. Control samples of $D^0\to K^-\pi^+$ decays are used to correct for reconstruction-induced asymmetries. The result, $A_{C\!P}(D^0\to\pi^+\pi^-\pi^0)=(0.29\pm0.27\pm0.13)\%$, where the first uncertainty is statistical and the second systematic, is consistent with conservation of $C\!P$ symmetry and is the most precise determination to date.

Measurement of CP Asymmetry in $D^0 \to \pi^+ \pi^− \pi^0$ decays