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

Information

LHCb-PAPER-2014-046
CERN-PH-EP-2014-194
arXiv:1408.1299 [PDF]

(Submitted on 06 Aug 2014)
JHEP 10 (2014) 005
Inspire 1310000

Tools

Abstract

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 $a_{CP}^{T\text{-odd}}$ is measured to be $(0.18\pm 0.29\text{(stat)}\pm 0.04\text{(syst)})\%$. 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.

Figures and captions

Distributions of the $ K ^+ K ^- \pi ^+ \pi ^- $ invariant mass in the four samples defined by $ D ^0$ ( $\overline{ D }{} {}^0$ ) flavour and the sign of $ C_{T}$ ( $\overline{C}_{T}$ ). The results of the fit are overlaid as a solid line, and a dashed line is used for representing the background. The normalised residuals (pulls) of the difference between the fit results and the data points, divided by their uncertainties, are shown on top of each distribution.	Fig1a.pdf [29 KiB] HiDef png [255 KiB] Thumbnail [246 KiB] *.C file
	Fig1b.pdf [29 KiB] HiDef png [259 KiB] Thumbnail [248 KiB] *.C file
	Fig1c.pdf [28 KiB] HiDef png [254 KiB] Thumbnail [246 KiB] *.C file
	Fig1d.pdf [29 KiB] HiDef png [261 KiB] Thumbnail [249 KiB] *.C file
Sideband-subtracted distributions of $ D ^0$ ( $\overline{ D }{} {}^0$ ) candidates in variables of (a, b) $m_{\pi ^+ \pi ^- }$ and (c, d) $m_{ K ^+ K ^- }$ for different values of $ C_{T}$ ( $\overline{C}_{T}$ ). The veto for $ D ^0 \rightarrow K ^0_{\rm\scriptscriptstyle S} K ^+ K ^- $ decays is visible in the $m_{\pi ^+ \pi ^- }$ distribution.	Fig2ab.pdf [28 KiB] HiDef png [144 KiB] Thumbnail [74 KiB] *.C file
	Fig2cd.pdf [23 KiB] HiDef png [145 KiB] Thumbnail [75 KiB] *.C file
Sideband-subtracted distributions of $ D ^0$ ( $\overline{ D }{} {}^0$ ) candidates in variables of (a, b) $\cos(\theta_{ K ^+ })$, (c, d) $\cos(\theta_{\pi ^+ })$, and (e, f) $\Phi$ for different values of $ C_{T}$ ( $\overline{C}_{T}$ ). The asymmetric distributions with respect to 0 for $\cos(\theta_{ K ^+ })$ and $\cos(\theta_{\pi ^+ })$ variables, and with respect to $\pi/2$ for the $\Phi$ variable, are due to the dynamics of the four-body decay.	Fig3ab.pdf [28 KiB] HiDef png [166 KiB] Thumbnail [84 KiB] *.C file
	Fig3cd.pdf [29 KiB] HiDef png [164 KiB] Thumbnail [83 KiB] *.C file
	Fig3ef.pdf [30 KiB] HiDef png [167 KiB] Thumbnail [84 KiB] *.C file
Distributions of the asymmetry parameters (a) $ A_{T}$ , (b) $\overline{A}_{T}$ and (c) $ a_{ C P }^{\text{ T -odd}}$ in 32 regions of the phase space.	Fig4a.pdf [16 KiB] HiDef png [113 KiB] Thumbnail [69 KiB] *.C file
	Fig4b.pdf [16 KiB] HiDef png [113 KiB] Thumbnail [69 KiB] *.C file
	Fig4c.pdf [16 KiB] HiDef png [136 KiB] Thumbnail [79 KiB] *.C file
Distributions of the asymmetry parameters (a) $ A_{T}$ , (b) $\overline{A}_{T}$ and (c) $ a_{ C P }^{\text{ T -odd}}$ as a function of the $ D ^0$ decay time. For $ a_{ C P }^{\text{ T -odd}}$ , the value of the $\chi^2/\mathrm{ndf}$ for the $ C P$ conservation hypothesis, represented by a dashed line, is also quoted. The scale is broken for the first and last bin.	Fig5a.pdf [16 KiB] HiDef png [98 KiB] Thumbnail [52 KiB] *.C file
	Fig5b.pdf [16 KiB] HiDef png [98 KiB] Thumbnail [52 KiB] *.C file
	Fig5c.pdf [15 KiB] HiDef png [116 KiB] Thumbnail [62 KiB] *.C file
Animated gif made out of all figures.	PAPER-2014-046.gif Thumbnail

Tables and captions

Number of signal decays obtained from the fit to data for each of the four samples defined by the $ D ^0$ / $\overline{ D }{} {}^0$ flavour and the sign of $ C_{T}$ or $\overline{C}_{T}$ .	Table_1.pdf [43 KiB] HiDef png [69 KiB] Thumbnail [30 KiB] tex code
Considered sources of systematic uncertainty and their relative contributions to the total uncertainty.	Table_2.pdf [46 KiB] HiDef png [54 KiB] Thumbnail [24 KiB] tex code
Definition of the 32 regions of the five-dimensional phase space of the four-body $ D ^0 \rightarrow K ^+ K ^- \pi ^+ \pi ^- $ decay.	Table_3.pdf [58 KiB] HiDef png [248 KiB] Thumbnail [105 KiB] tex code
Measurements of $ a_{ C P }^{\text{ T -odd}}$ , $ A_{T}$ and $\overline{A}_{T}$ in each region of phase space. The uncertainties are statistical only. A common systematic uncertainty of 0.13%, 0.12% and 0.04% should be added to the asymmetries $ A_{T}$ , $\overline{A}_{T}$ and $ a_{ C P }^{\text{ T -odd}}$ , respectively. This uncertainty is considered fully correlated among the bins.	Table_4.pdf [45 KiB] HiDef png [211 KiB] Thumbnail [92 KiB] tex code
Measurements of $ a_{ C P }^{\text{ T -odd}}$ , $ A_{T}$ and $\overline{A}_{T}$ in different intervals of $ D ^0$ decay time, $t$, expressed in $ {\rm ps}$ . The uncertainties are statistical only. A common systematic uncertainty of 0.13%, 0.12% and 0.04% should be added to the asymmetries $ A_{T}$ , $\overline{A}_{T}$ and $ a_{ C P }^{\text{ T -odd}}$ , respectively. This uncertainty is considered fully correlated among the bins.	Table_5.pdf [43 KiB] HiDef png [38 KiB] Thumbnail [17 KiB] tex code