Measurements of indirect CP asymmetries in $D^0\to K^-K^+$ and $D^0\to\pi^-\pi^+$ decays

Information

LHCb-PAPER-2013-054
CERN-PH-EP-2013-180
arXiv:1310.7201 [PDF]

(Submitted on 27 Oct 2013)
Phys. Rev. Lett. 112 (2014) 041801
Inspire 1262317

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Abstract

A study of indirect CP violation in $D^0$ mesons through the determination of the parameter $A_\Gamma$ is presented using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected with the LHCb detector and recorded at the centre-of-mass energy of 7 TeV at the LHC. The parameter $A_\Gamma$ is the asymmetry of the effective lifetimes measured in decays of $D^0$ and $\bar{D}^0$ mesons to the CP eigenstates $K^-K^+$ and $\pi^-\pi^+$. Fits to the data sample yield $A_\Gamma(KK)=(-0.35\pm0.62\pm0.12)\times 10^{-3}$ and $A_\Gamma(\pi\pi)=(0.33\pm1.06\pm0.14)\times 10^{-3}$, where the first uncertainties are statistical and the second systematic. The results represent the world's best measurements of these quantities. They show no difference in $A_\Gamma$ between the two final states and no indication of CP violation.

Figures and captions

Fit of $\Delta m$ for one of the eight subsets, containing the $\overline{ D }{} ^0 \rightarrow K ^- K ^+ $ candidates with magnet polarity down for the earlier run period.	Deltam[..].pdf [72 KiB] HiDef png [230 KiB] Thumbnail [169 KiB] *.C file
(Top) Fit of decay time to $\overline{ D }{} ^0 \rightarrow K ^- K ^+ $ and corresponding pull plot for candidates with magnet polarity down for the earlier run period, where pull is defined as $({\rm data}-{\rm model})/{\rm uncertainty}$, and (middle and bottom) ratio of $\overline{ D }{} ^0$ to $ D ^0$ data and fit model for decays to $ K ^- K ^+ $ and $\pi ^- \pi ^+ $ for all data, respectively.	Timefi[..].pdf [59 KiB] HiDef png [364 KiB] Thumbnail [275 KiB] *.C file
	ratio-[..].pdf [43 KiB] HiDef png [93 KiB] Thumbnail [83 KiB] *.C file
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Fits of $\ln(\chi^2_{\rm IP} )$ for $\overline{ D }{} ^0 \rightarrow K ^- K ^+ $ candidates for decay-time bins (left to right) $0.25-0.37 {\rm ps} $, $0.74-0.78 {\rm ps} $, and $1.55-1.80 {\rm ps} $.	KK_Dow[..].pdf [29 KiB] HiDef png [232 KiB] Thumbnail [167 KiB] *.C file
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Animated gif made out of all figures.	PAPER-2013-054.gif Thumbnail

Tables and captions

Systematic uncertainties, given as multiples of $10^{-3}$. The first column for each final state refers to the unbinned fit method and the second column to the binned fit method.

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Supplementary Material [file]

Supplementary material full pdf	Supple[..].pdf [1 MiB]
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