6533b831fe1ef96bd12990a8

RESEARCH PRODUCT

Measurement ofD0−D¯0mixing using the ratio of lifetimes for the decaysD0→K−π+andK+K−

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description

We present a measurement of ${D}^{0}\mathrm{\text{\ensuremath{-}}}{\overline{D}}^{0}$ mixing and $CP$ violation using the ratio of lifetimes simultaneously extracted from a sample of ${D}^{0}$ mesons produced through the flavor-tagged process ${D}^{*+}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\pi}}^{+}$, where ${D}^{0}$ decays to ${K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}^{\ensuremath{-}}{K}^{+}$, or ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$, along with the untagged decays ${D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and ${D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}^{+}$. The lifetimes of the $CP$-even, Cabibbo-suppressed modes ${K}^{\ensuremath{-}}{K}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ are compared to that of the $CP$-mixed mode ${K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ in order to measure ${y}_{CP}$ and $\ensuremath{\Delta}Y$. We obtain ${y}_{CP}=[0.72\ifmmode\pm\else\textpm\fi{}0.18(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.12(\mathrm{syst})]%$ and $\ensuremath{\Delta}Y=[0.09\ifmmode\pm\else\textpm\fi{}0.26(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{syst})]%$, where $\ensuremath{\Delta}Y$ constrains possible $CP$ violation. The ${y}_{CP}$ result excludes the null mixing hypothesis at $3.3\ensuremath{\sigma}$ significance. This analysis is based on an integrated luminosity of $468\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected with the BABAR detector at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider.