Observation of $D^0-\bar{D}^0$ Mixing in $e^+e^-$ Collisions
  We observe $D^0-\bar{D}^0$ mixing in the decay $D^0\rightarrow K^+\pi^-$ using a data sample of integrated luminosity 976 fb$^{-1}$ collected with the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. We measure the mixing parameters ${x'}^2 = (0.09\pm0.22)\times 10^{-3}$ and $y' = (4.6\pm3.4)\times 10^{-3}$ and the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates $R_D = (3.53\pm0.13)\times 10^{-3}$, where the uncertainties are statistical and systematic combined. Our measurement excludes the no-mixing hypothesis at the 5.1 standard deviation level. 
B. R. Ko, E. Won, I. Adachi, H. Aihara, K. Arinstein, D. M. Asner, V.   Aulchenko, T. Aushev, A. Bala, V. Bhardwaj, B. Bhuya...
hep-ex