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Observation of $D^0 - \overline{D}^0$ oscillations

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Abstract

We report a measurement of the time-dependent ratio of D0->K+pi- to D0->K-pi+ decay rates in D*+-tagged events using 1.0 fb^{-1} of integrated luminosity recorded by the LHCb experiment. We measure the mixing parameters x'2=(-0.9+-1.3)x10^{-4}, y'=(7.2+-2.4)x10^{-3} and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates R_D=(3.52+-0.15)x10^{-3}, where the uncertainties include statistical and systematic sources. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of D0-D0bar oscillations from a single measurement.

Figures and captions

Time-integrated $ D ^0 \pi_{\rm s} ^+$ mass distributions for the selected RS $ D ^0 \rightarrow K^-\pi^+$ (left) and WS $ D ^0 \rightarrow K^+\pi^-$ (right) candidates with fit projections overlaid. The bottom plots show the normalized residuals between the data points and the fits.

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Decay-time evolution of the ratio, $R$, of WS $ D ^0 \rightarrow K^+\pi^-$ to RS $ D ^0 \rightarrow K^-\pi^+$ yields (points) with the projection of the mixing allowed (solid line) and no-mixing (dashed line) fits overlaid.

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Estimated confidence-level (CL) regions in the $(x'^2,y')$ plane for $1-\text{CL}=0.317$ ($1\sigma$), $2.7\times10^{-3}$ ($3\sigma$) and $5.73\times10^{-7}$ ($5\sigma$). Systematic uncertainties are included. The cross indicates the no-mixing point.

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Tables and captions

Results of the time-dependent fit to the data. The uncertainties include statistical and systematic sources; ndf indicates the number of degrees of freedom.

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Supplementary Material [file]

Supplementary material full pdf

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This archive contains extra figures related to LHCb-PAPER-2012-038 supplementary.pdf - A PDF file with all figures and captions Fig*.pdf - Figures in PDF format Fig*.eps - Figures in EPS format Fig*.png - Figures in PNG format

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Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.