Search for $CP$ violation in $D^0\to \pi^-\pi^+\pi^0$ decays with the energy test

Information

LHCb-PAPER-2014-054
CERN-PH-EP-2014-251
arXiv:1410.4170 [PDF]

(Submitted on 15 Oct 2014)
Phys. Lett. B740 (2015) 158
Inspire 1322386

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Abstract

A search for time-integrated CP violation in the Cabibbo-suppressed decay $D^0\to\pi^-\pi^+\pi^0$ is performed using for the first time an unbinned model-independent technique known as the energy test. Using proton-proton collision data, corresponding to an integrated luminosity of 2.0 fb$^{-1}$ collected by the LHCb detector at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV, the world's best sensitivity to CP violation in this decay is obtained. The data are found to be consistent with the hypothesis of CP symmetry with a p-value of (2.6 +/- 0.5).

Figures and captions

Distribution of $\Delta{}m$ with fit overlaid for the selected data set with (a) resolved and (b) merged $\pi ^0$ candidates. The lines show the fit results for total signal (dot-dashed red), widest Gaussian signal component (dotted red), background (dashed green), and total (solid blue).	DeltaM[..].pdf [23 KiB] HiDef png [305 KiB] Thumbnail [203 KiB] *.C file
	DeltaM[..].pdf [23 KiB] HiDef png [301 KiB] Thumbnail [196 KiB] *.C file
Dalitz plot of the (a) resolved, (b) merged and (c) combined $ D ^0 \rightarrow \pi ^- \pi ^+ \pi ^0 $ data sample. Enhanced event densities in the phase-space corners originate from the $\rho(770)$ resonances.	Fig2a_.png [113 KiB] HiDef png [476 KiB] Thumbnail [197 KiB] *.C file
	Fig2b_.png [99 KiB] HiDef png [543 KiB] Thumbnail [219 KiB] *.C file
	Fig2c_.png [132 KiB] HiDef png [480 KiB] Thumbnail [189 KiB] *.C file
Distribution of permutation $T$ values fitted with a GEV function for the simulated sample and showing the nominal $T$ value as a vertical line for (a) $2\%$ $ C P$ violation in the amplitude and (b) $1^\circ$ phase $ C P$ violation of the $\rho^+$ resonance.	Fig3_sub1a.pdf [28 KiB] HiDef png [143 KiB] Thumbnail [123 KiB] *.C file
	Fig3_sub1b.pdf [28 KiB] HiDef png [147 KiB] Thumbnail [120 KiB] *.C file
(a,c) $T_i$ value distributions, and (b,d) local asymmetry significances for (top) $2\%$ $ C P$ violation in the amplitude and (bottom) $1^\circ$ phase $ C P$ violation of the $\rho^+$ resonance.	Fig3_sub2a.png [60 KiB] HiDef png [407 KiB] Thumbnail [188 KiB] *.C file
	Fig3_sub2b.png [47 KiB] HiDef png [300 KiB] Thumbnail [171 KiB] *.C file
	Fig3_sub2c.png [58 KiB] HiDef png [395 KiB] Thumbnail [188 KiB] *.C file
	Fig3_sub2d.png [46 KiB] HiDef png [301 KiB] Thumbnail [171 KiB] *.C file
The selection efficiency as a function of $m(\pi ^+ \pi ^- )$. The efficiency for the combined sample is fitted with a straight line.	acceptance.pdf [17 KiB] HiDef png [190 KiB] Thumbnail [191 KiB] *.C file
(a) Permutation $T$ value distribution showing the fit function and the measured $T$ value as a red line. (b) Visualisation of local asymmetry significances. The positive (negative) asymmetry significance is set for the $ D ^0$ candidates having positive (negative) contribution to the measured $T$ value, respectively (see Sec.4).	Fig5a_.pdf [29 KiB] HiDef png [173 KiB] Thumbnail [143 KiB] *.C file
	SigLev[..].png [38 KiB] HiDef png [304 KiB] Thumbnail [179 KiB] *.C file
Animated gif made out of all figures.	PAPER-2014-054.gif Thumbnail

Tables and captions

Overview of sensitivities to various $ C P$ violation scenarios. $\Delta A$ and $\Delta \phi$ denote, respectively, change in amplitude and phase of the resonance $R$.	Table_1.pdf [53 KiB] HiDef png [108 KiB] Thumbnail [52 KiB] tex code
Results for various metric parameter values. The $ p$ -values are obtained with the counting method.	Table_2.pdf [42 KiB] HiDef png [65 KiB] Thumbnail [30 KiB] tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [880 KiB]
This archive contains the supplementary material to LHCb-PAPER-2014-054. This is figures 6-9 as well as one table. The figure caption and table source is given in supplementary-app.tex. All information is comiled in supplementary.pdf.	Fig6.pdf [14 KiB] HiDef png [103 KiB] Thumbnail [99 KiB] *C file
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