# Measurement of time-dependent $CP$ violation in ${B}^{0}\to {K}_{S}^{0}{\pi }^{0}{\pi }^{0}$ decays

21 January 2019

Abstract: We report a measurement of time-dependent $CP$ violation in ${B}^{0}\to {K}_{S}^{0}{\pi }^{0}{\pi }^{0}$ decays using a data sample of $772×{10}^{6}\text{}\text{}B\overline{B}$ pairs collected by the Belle experiment running at the $\Upsilon \left(4S\right)$ resonance at the KEKB ${e}^{+}{e}^{-}$ collider. This decay proceeds mainly via a $b\to sd\overline{d}$ “penguin” amplitude. The results are $\mathrm{sin}2{\varphi }_{1}^{\text{eff}}=0.9{2}_{-0.31}^{+0.27}$ (stat.) $±0.11$ (syst.) and $A=0.28±0.21$ (stat.) $±0.04$ (syst.), which are the most precise measurements of $CP$ violation in this decay mode to date. The value for the $CP$-violating parameter $\mathrm{sin}2{\varphi }_{1}^{\text{eff}}$ is consistent with that obtained using decay modes proceeding via a $b\to c\overline{c}s$ “tree” amplitude.

Published in: Physical Review D 99 (2019)