Measurement of ${D^{0}}$-${\overline{D}{}^{0}}$ Mixing and Search for   Indirect $CP$ Violation Using ${D^0\to K_S^0\pi^+\pi^-}$ Decays
  We report a measurement of ${D^{0}}$-${\overline{D}{}^{0}}$ mixing parameters and a search for indirect $CP$ violation through a time-dependent   amplitude analysis of ${D^0\to K_S^0\pi^+\pi^-}$ decays. The results are based on 921~fb$^{-1}$ of data accumulated with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Assuming $CP$ conservation, we measure the mixing parameters $x=(0.56\pm0.19^{+0.03}_{-0.09}{^{+0.06}_{-0.09}})\%$ and $y=(0.30\pm0.15^{+0.04}_{-0.05}{^{+0.03}_{-0.06})}\%$, where the errors are statistical, experimental systematic, and systematic due to the amplitude model, respectively. With $CP$ violation allowed, the parameters $|q/p|=0.90^{+0.16}_{-0.15}{^{+0.05}_{-0.04}}{^{+0.06}_{-0.05}}$ and $\arg(q/p)=(-6\pm11{\pm3}{^{+3}_{-4}})^{\circ}$ are found to be consistent with conservation of $CP$ symmetry in mixing and in the interference between mixing and decay, respectively. 
Belle Collaboration: A. Abdesselam, I. Adachi, H. Aihara, K.   Arinstein, D. M. Asner, V. Aulchenko, T. Aushev, R. Ayad, A. ...
hep-ex