A search for direct CP violation in D0 > h h+ (where h=K or pi) is presented using data corresponding to an integrated luminosity of 1.0 fb^1 collected in 2011 by LHCb in pp collisions at a centreofmass energy of 7 TeV. The analysis uses D0 mesons produced in inclusive semileptonic bhadron decays to the D0 mu X final state, where the charge of the accompanying muon is used to tag the flavour of the D0 meson. The difference in the CPviolating asymmetries between the two decay channels is measured to be Delta A_CP = A_CP(KK+)  A_CP(pipi+) = (0.49 + 0.30 (stat) + 0.14 (syst)) % . This result does not confirm the evidence for direct CP violation in the charm sector reported in other analyses.
Invariant mass distributions for (a, c) $ D ^0 \!\rightarrow K ^ K ^+ $ and (b, d) $ D ^0 \!\rightarrow \pi ^ \pi ^+ $ muontagged candidates for the two magnet polarities. The result of the fit is overlaid, showing the contribution from signal, combinatorial background and $ D ^0 \!\rightarrow K ^ \pi ^+ $ reflection. Underneath each plot the pull in each mass bin is shown. 
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Kinematic distributions of the (a, c) $ D ^0$ meson and (b, d) muon for $ D ^0 \!\rightarrow \pi ^ \pi ^+ $ (black circles) and $ D ^0 \!\rightarrow K ^ K ^+ $ (red squares) candidates normalised to unit area. The histograms show the distributions of signal candidates, after background subtraction. Underneath each plot the ratio of the two distributions is shown. 
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Kinematic distributions of the (a, c) $ D ^0$ meson and (b, d) muon for $ D ^0 \!\rightarrow \pi ^ \pi ^+ $ (black circles) and $ D ^0 \!\rightarrow K ^ K ^+ $ (red squares) candidates normalised to unit area after the weighting procedure. The histograms show the distributions of signal candidates, after background subtraction. Underneath each plot the ratio of the two distributions is shown. 
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Decay time distribution for signal candidates (solid points) with the result from the fit overlaid for (a) $ D ^0 \!\rightarrow K ^ K ^+ $ and (b) $ D ^0 \!\rightarrow \pi ^ \pi ^+ $ decays. The distribution for background candidates scaled to a $\pm34 {\mathrm{\,MeV\!/}c^2} $ window around the nominal $ D ^0$ mass is shown in the shaded (green) region. The distributions for signal and background candidates are obtained using the sPlot method. 
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Raw asymmetries and $\Delta A_{\mathcal{C}_{P} }$ as a function of (a) $p_{\rm T}$ and (b) $\eta$ of the $ D ^0$ meson. No weighting is applied. 
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Animated gif made out of all figures. 
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Unweighted raw asymmetries (in %) for the $ D ^0 \!\rightarrow \pi ^ \pi ^+ $ , $ D ^0 \!\rightarrow K ^ K ^+ $ and $ D ^0 \!\rightarrow K ^ \pi ^+ $ decays for the two magnet polarities. The mean value is the arithmetic average over the two polarities. The uncertainties are statistical only. 
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Weighted raw asymmetries (in %) for the $ D ^0 \!\rightarrow \pi ^ \pi ^+ $ and $ D ^0 \!\rightarrow K ^ K ^+ $ decays for the two magnet polarities. The mean value is the arithmetic average over the two polarities. The uncertainties are statistical only. 
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Contributions to the systematic uncertainty of $\Delta A_{\mathcal{C}_{P} }$ . 
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Created on 16 February 2019.Citation count from INSPIRE on 21 February 2019.