Measurements of charm mixing parameters from the decay-time-dependent ratio of $D^0\to K^{+}{\pi }^{-}$ to $D^0\to K^{-}{\pi }^{+}$ rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to $3{\mathrm{fb}}^{-1}$ of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity ($CP$ ) symmetry, the mixing parameters are determined to be $x^{\prime 2}=(5.5\pm 4.9)\times {10}^{-5}$, $y^{\prime }=(4.8\pm 1.0)\times {10}^{-3}$, and $R_D=(3.568\pm 0.066)\times {10}^{-3}$. Allowing for $CP$ violation, the measurement is performed separately for $D^0$ and ${\overline{D}}^0$ mesons yielding $A_D=(-0.7\pm 1.9)\%$, for the direct $CP$-violating asymmetry, and $0.75<|q/p|<1.24$ at the 68.3% confidence level, for the parameter describing $CP$ violation in mixing. This is the most precise determination of these parameters from a single experiment and shows no evidence for $CP$ violation.

• Received 25 September 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.251801

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© 2013 CERN, for the LHCb Collaboration