# 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. d2kskp[..].pdf [21 KiB] HiDef png [313 KiB] Thumbnail [97 KiB] *.C file d2kskp[..].pdf [19 KiB] HiDef png [255 KiB] Thumbnail [79 KiB] *.C file d2kskp[..].pdf [21 KiB] HiDef png [319 KiB] Thumbnail [99 KiB] *.C file d2kskp[..].pdf [19 KiB] HiDef png [254 KiB] Thumbnail [79 KiB] *.C file d2kspi[..].pdf [20 KiB] HiDef png [259 KiB] Thumbnail [85 KiB] *.C file d2kspi[..].pdf [19 KiB] HiDef png [222 KiB] Thumbnail [72 KiB] *.C file d2kspi[..].pdf [20 KiB] HiDef png [271 KiB] Thumbnail [87 KiB] *.C file d2kspi[..].pdf [19 KiB] HiDef png [223 KiB] Thumbnail [73 KiB] *.C file 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 ${\mathrm{\,MeV\!/}c^2}$ and 5317 ${\mathrm{\,MeV\!/}c^2}$ . 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] HiDef png [166 KiB] Thumbnail [61 KiB] *.C file Dalitz[..].pdf [102 KiB] HiDef png [263 KiB] Thumbnail [98 KiB] *.C file Dalitz acceptance determined using simulated events and normalised relative to the maximum efficiency. EffPlot.pdf [1 MiB] HiDef png [736 KiB] Thumbnail [94 KiB] *.C file 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 $2\sigma$. contou[..].pdf [297 KiB] HiDef png [2 MiB] Thumbnail [150 KiB] *.C file Animated gif made out of all figures. PAPER-2013-068.gif Thumbnail

## 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. Table_1.pdf [38 KiB] HiDef png [43 KiB] Thumbnail [7 KiB] tex code 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). Table_2.pdf [53 KiB] HiDef png [96 KiB] Thumbnail [14 KiB] tex code Absolute values of systematic uncertainties, in units of $10^{-2}$, for the fit to the whole Dalitz plot. Table_3.pdf [46 KiB] HiDef png [55 KiB] Thumbnail [8 KiB] tex code Absolute values of systematic uncertainties, in units of $10^{-2}$, for the fit in the restricted region. Table_4.pdf [46 KiB] HiDef png [55 KiB] Thumbnail [8 KiB] tex code

Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.