Observation of $D^0-{\bar{D}}^0$ Mixing in $e^{+}{e}^{-}$ Collisions

Abstract

We observe $D^0-{\bar{D}}^0$ mixing in the decay $D^0\to K^{+}\ddot{I}{€}^{-}$ 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 ${x^{\prime }}^2=(0.09\pm 0.22)\times 10^{-3}$ and $y^{\prime }=(4.6\pm 3.4)\times 10^{-3}$ and the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates $R_D=(3.53\pm 0.13)\times 10^{-3}$, where the uncertainties are statistical and systematic combined. Our measurement excludes the no-mixing hypothesis at the 5.1 standard deviation level.

6 pages, 4 figures