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A study of CP violation in $B^\pm \to D K^\pm$ and $B^\pm \to D \pi^\pm$ decays with $D \to K^0_{\rm S} K^\pm \pi^\mp$ final states

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Abstract

A first study of CP violation in the decay modes $B^\pm\to [K^0_{\rm S} K^\pm \pi^\mp]_D h^\pm$ and $B^\pm\to [K^0_{\rm S} K^\mp \pi^\pm]_D h^\pm$, where $h$ labels a $K$ or $\pi$ meson and $D$ labels a $D^0$ or $\overline{D}^0$ meson, is performed. The analysis uses the LHCb data set collected in $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$. The analysis is sensitive to the CP-violating CKM phase $\gamma$ through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of $\gamma$ using other decay modes.

Figures and captions

Distributions of $ B ^\pm$ invariant mass of the SS and OS samples for the (a, c, e, g) $ B ^\pm \rightarrow D K ^\pm $ and (b, d, f, h) $ B ^\pm \rightarrow D\pi ^\pm $ candidates in the full data sample. The fits are shown for (a, b, e, f) $ B ^+ $ and (c, d, g, h) $ B ^- $ candidates. Fit PDFs are superimposed.

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d2kskpi_pass_plus.pdf
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d2kskp[..].pdf [21 KiB]
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d2kskpi_pass_minus.pdf
d2kskp[..].pdf [19 KiB]
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d2kskpi_fail_minus.pdf
d2kspi[..].pdf [20 KiB]
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d2kspik_pass_plus.pdf
d2kspi[..].pdf [19 KiB]
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d2kspik_fail_plus.pdf
d2kspi[..].pdf [20 KiB]
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d2kspik_pass_minus.pdf
d2kspi[..].pdf [19 KiB]
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d2kspik_fail_minus.pdf

Dalitz plot distribution of candidates selected in (a) the $ B ^\pm \rightarrow [ K ^0_{\rm\scriptscriptstyle S} K\pi]_D K ^\pm $ and (b) the $ B ^\pm \rightarrow [ K ^0_{\rm\scriptscriptstyle S} K\pi]_D\pi ^\pm $ decay modes, where the data in the SS and OS modes, and the two $ K ^0_{\rm\scriptscriptstyle S}$ categories, are combined. Candidates included are required to have a refitted $ B ^\pm $ mass in a nominal signal window between 5247 $ {\mathrm{ Me V /}c^2}$ and 5317 $ {\mathrm{ Me V /}c^2}$ . The kinematic boundary is added in blue, and the restricted region around the $K^*(892)^\pm$ resonance is indicated by horizontal red lines.

 Dalitz[..].pdf [76 KiB]
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Dalitz_both_B2DK_KSboth_both_graph.pdf
Dalitz[..].pdf [102 KiB]
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Dalitz_both_B2DPi_KSboth_both_graph.pdf

Dalitz acceptance determined using simulated events and normalised relative to the maximum efficiency.

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EffPlot.pdf

Scans of the $\chi^2$ probabilities over the $\gamma-r_B$ parameter space for (a) the whole Dalitz fit and (b) the fit inside the $K^*$ region (b). The contours are the usual $n\sigma$ profile likelihood contours, where $\Delta\chi^2 = n^2$ with $n = 1 \textrm{ (dark blue), } 2 \textrm{ (medium blue), and } 3 \textrm{ (light blue)}$. The $2\sigma$ contour encloses almost all of the parameter space shown, so a central value of $\gamma$ and relevant bounds are not extracted. The result is seen to be compatible with the current LHCb measurement of $\gamma$, indicated by the point at ($\gamma=72.0^\circ$ and $r_B=0.089$), at a level between 1 and $2\sigma$.

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contourPlot.pdf

Animated gif made out of all figures.

 PAPER-2013-068.gif
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Tables and captions

Signal yields and their statistical uncertainties derived from the fit to the whole Dalitz plot region, and in the restricted region of phase space around the $K^*(892)^\pm$ resonance.

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Results for the observables measured in the whole Dalitz plot region, and in the restricted region of phase space around the $K^*(892)^\pm$ resonance. The first uncertainty is statistical and the second is systematic. The corrections for production and detection asymmetries are applied, as is the efficiency correction defined in Eq. (5).

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Absolute values of systematic uncertainties, in units of $10^{-2}$, for the fit to the whole Dalitz plot.

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Absolute values of systematic uncertainties, in units of $10^{-2}$, for the fit in the restricted region.

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Created on 02 May 2024.