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Search for $CP$ violation using $T$-odd correlations in $D^0 to K^+K^-pi^+pi^-$ decays

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 Added by Maurizio Martinelli
 Publication date 2014
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and research's language is English




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A search for $CP$ violation using $T$-odd correlations is performed using the four-body $D^0 to K^+K^-pi^+pi^-$ decay, selected from semileptonic $B$ decays. The data sample corresponds to integrated luminosities of $1.0,text{fb}^{-1}$ and $2.0,text{fb}^{-1}$ recorded at the centre-of-mass energies of 7 TeV and 8 TeV, respectively. The $CP$-violating asymmetry $a_{CP}^{Ttext{-odd}}$ is measured to be $(0.18pm 0.29text{(stat)}pm 0.04text{(syst)})%$. Searches for $CP$ violation in different regions of phase space of the four-body decay, and as a function of the $D^0$ decay time, are also presented. No significant deviation from the $CP$ conservation hypothesis is found.



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A search for time-dependent violation of the charge-parity symmetry in $D^0 to K^+ K^-$ and $D^0 to pi^+ pi^-$ decays is performed at the LHCb experiment using proton-proton collision data recorded from 2015 to 2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb$^{-1}$. The $D^0$ meson is required to originate from a $D^*(2010)^+ to D^0 pi^+$ decay, such that its flavour at production is identified by the charge of the accompanying pion. The slope of the time-dependent asymmetry of the decay rates of $D^0$ and $bar{D}^0$ mesons into the final states under consideration is measured to be $Delta Y_{K^+ K^-} = (-2.3 pm 1.5 pm 0.3) times 10^{-4}$, $Delta Y_{pi^+ pi^-} = (-4.0 pm 2.8 pm 0.4)times 10^{-4}$, where the first uncertainties are statistical and the second are systematic. These results are compatible with the conservation of the $CP$ symmetry at the level of 2 standard deviations and improve the precision by nearly a factor of two.
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