cern.ch

Measurement of $CP$ observables in $B^\pm \to D^{(*)} K^\pm$ and $B^\pm \to D^{(*)} \pi^\pm$ decays

[to restricted-access page]

Abstract

Measurements of $CP$ observables in $B^\pm \rightarrow D^{(*)} K^\pm$ and $B^\pm \rightarrow D^{(*)} \pi^\pm$ decays are presented, where $D^{(*)}$ indicates a neutral $D$ or $D^*$ meson that is an admixture of $D^{(*)0}$ and $\bar{D}^{(*)0}$ states. Decays of the $D^*$ meson to the $D\pi^0$ and $D\gamma$ final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the $B$ candidate invariant mass distribution. Decays of the $D$ meson are fully reconstructed in the $K^\pm \pi^\mp$, $K^+ K^-$ and $\pi^+ \pi^-$ final states. The analysis uses a sample of charged $B$ mesons produced in $pp$ collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb$^{-1}$ taken at centre-of-mass energies of $\sqrt{s}$ = 7, 8 and 13 TeV, respectively. The study of $B^{\pm} \to D^{*} K^{\pm}$ and $B^{\pm} \to D^{*} \pi^{\pm}$ decays using a partial reconstruction method is the first of its kind, while the measurement of $B^{\pm} \to D K^{\pm}$ and $B^{\pm} \to D \pi^{\pm}$ decays is an update of previous LHCb measurements. The $B^{\pm} \to D K^{\pm}$ results are the most precise to date.

Figures and captions

Invariant mass distributions of selected $ B ^\pm \rightarrow [ K ^\pm \pi ^\mp ]_{D}h^{\pm}$ candidates, separated by charge, with $ B ^- {\rm(} B ^+ {\rm)}$ candidates on the left (right). The top panels contain the $ B ^\pm \rightarrow D^{(*)0}K^{\pm}$ candidate samples, as defined by a PID requirement on the companion particle. The remaining candidates are placed in the bottom panels, reconstructed with a pion hypothesis for the companion. The result of the fit is shown by the thin solid black line, and each component is listed in the legend. The component referred to as `Part. reco. mis-ID' is the total contribution from all partially reconstructed and misidentified decays.

Fig1a.eps [95 KiB]
HiDef png [201 KiB]
Thumbnail [29 KiB]
*.C file
Fig1a.eps
Fig1b.eps [403 KiB]
HiDef png [145 KiB]
Thumbnail [57 KiB] *.C file
Fig1b.eps
Fig1c.eps [402 KiB]
HiDef png [118 KiB]
Thumbnail [39 KiB] *.C file
Fig1c.eps

Invariant mass distributions of selected $ B ^\pm \rightarrow [ K ^+ K ^- ]_{D}h^{\pm}$ candidates, separated by charge. See Fig. 1 for details of each component.

Fig2.eps [114 KiB]
HiDef png [224 KiB]
Thumbnail [30 KiB]
*.C file
Fig2.eps

Invariant mass distributions of selected $ B ^\pm \rightarrow [\pi ^+ \pi ^- ]_{D}h^{\pm}$ candidates, separated by charge. See Fig. 1 for details of each component.

Fig3.eps [115 KiB]
HiDef png [223 KiB]
Thumbnail [31 KiB]
*.C file
Fig3.eps

$1\sigma$, $2\sigma$ and $3\sigma$ profile likelihood contours for $r_{B}^{D^{*}\!K}$, $\delta_{B}^{D^{*}\!K}$ and $\gamma$, corresponding to 68.3%, 95.5% and 99.7% confidence level (CL), respectively. The contours are measured using $ B ^- \rightarrow ( D \pi ^0 )_{ D ^* } K ^- $ and $ B ^- \rightarrow ( D \gamma)_{ D ^* } K ^- $ decays. The colour scale represents $1-\text{CL}$.

Fig4a.eps [913 KiB]
HiDef png [1 MiB]
Thumbnail [119 KiB]
*.C file
Fig4a.eps
Fig4b.eps [904 KiB]
HiDef png [1 MiB]
Thumbnail [124 KiB] *.C file
Fig4b.eps
Fig4c.eps [884 KiB]
HiDef png [996 KiB]
Thumbnail [114 KiB] *.C file
Fig4c.eps

Animated gif made out of all figures.

PAPER-2017-021.gif
Thumbnail
thumbnail_PAPER-2017-021.gif

Tables and captions

Table_1.pdf [128 KiB]
HiDef png [37 KiB]
Thumbnail [4 KiB]
tex code
Table_1.pdf

Table_2.pdf [60 KiB]
HiDef png [8 KiB]
Thumbnail [1 KiB]
tex code
Table_2.pdf

Systematic uncertainties for the $ C\!P$ observables measured in a partially reconstructed manner, quoted as a percentage of the statistical uncertainty on the observable.

Table_3.pdf [46 KiB]
HiDef png [40 KiB]
Thumbnail [6 KiB]
tex code
Table_3.pdf

Systematic uncertainties for the $ C\!P$ observables measured in a fully reconstructed manner, quoted as a percentage of the statistical uncertainty on the observable. The Sim uncertainty on $R_{K/\pi}^{K\pi}$ is due to the limited size of the simulated samples used to determine the relative efficiency for reconstructing and selecting $ B ^- \rightarrow D \pi ^- $ and $ B ^- \rightarrow D K ^- $ decays.

Table_4.pdf [40 KiB]
HiDef png [73 KiB]
Thumbnail [11 KiB]
tex code
Table_4.pdf

Systematic uncertainties for the branching fraction measurements, quoted as a percentage of the statistical uncertainty on the observable.

Table_5.pdf [54 KiB]
HiDef png [68 KiB]
Thumbnail [10 KiB]
tex code
Table_5.pdf

Statistical correlation matrix for the $ C\!P$ observables measured using partially reconstructed decays.

Table_6.pdf [40 KiB]
HiDef png [69 KiB]
Thumbnail [10 KiB]
tex code
Table_6.pdf

Statistical correlation matrix for the $ C\!P$ observables measured using fully reconstructed decays.

Table_7.pdf [32 KiB]
HiDef png [69 KiB]
Thumbnail [10 KiB]
tex code
Table_7.pdf

Systematic uncertainty correlation matrix for the $ C\!P$ observables measured using partially reconstructed decays.

Table_8.pdf [41 KiB]
HiDef png [70 KiB]
Thumbnail [10 KiB]
tex code
Table_8.pdf

Systematic uncertainty correlation matrix for the $ C\!P$ observables measured using fully reconstructed decays.

Table_9.pdf [32 KiB]
HiDef png [67 KiB]
Thumbnail [10 KiB]
tex code
Table_9.pdf

Supplementary Material [file]

Supplementary material full pdf

supple[..].pdf [1 MiB]
supplementary.pdf
Fig1a.pdf [1 MiB]
HiDef png [719 KiB]
Thumbnail [86 KiB]
*C file
Fig1a.pdf
Fig1b.pdf [1 MiB]
HiDef png [760 KiB]
Thumbnail [91 KiB]
*C file
Fig1b.pdf
Fig1c.pdf [1 MiB]
HiDef png [442 KiB]
Thumbnail [67 KiB]
*C file
Fig1c.pdf
Fig2a.pdf [208 KiB]
HiDef png [294 KiB]
Thumbnail [63 KiB]
*C file
Fig2a.pdf
Fig2b.pdf [441 KiB]
HiDef png [65 KiB]
Thumbnail [23 KiB]
*C file
Fig2b.pdf
Fig3.pdf [226 KiB]
HiDef png [337 KiB]
Thumbnail [67 KiB]
*C file
Fig3.pdf
Fig4.pdf [226 KiB]
HiDef png [342 KiB]
Thumbnail [70 KiB]
*C file
Fig4.pdf
Fig5a.pdf [55 KiB]
HiDef png [238 KiB]
Thumbnail [62 KiB]
*C file
Fig5a.pdf
Fig5b.pdf [53 KiB]
HiDef png [192 KiB]
Thumbnail [67 KiB]
*C file
Fig5b.pdf

Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.