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Measurement of $CP$ observables in $B^{\pm} \rightarrow D K^{*\pm}$ decays using two- and four-body $D$ final states

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Abstract

Measurements of $CP$ observables in $B^{\pm} \rightarrow D K^{*\pm}$ decays are presented, where $D$ denotes a superposition of $D^0$ and $\overline{D^0}$ meson states. Decays of the $D$ meson to $K^{-}\pi^{+}$, $K^{-}K^{+}$, $\pi^{-}\pi^{+}$, $K^{-}\pi^{+}\pi^{-}\pi^{+}$ and $\pi^{-}\pi^{+}\pi^{-}\pi^{+}$ are used and the $K^{*\pm}$ meson is reconstructed in the $K^{0}_{\mathrm{S}}\pi^{\pm}$ final state. This analysis uses a data sample of $pp$ collisions collected with the LHCb experiment, corresponding to integrated luminosities of 1 $\mathrm{fb}^{-1}$, 2 $\mathrm{fb}^{-1}$ and 1.8 $\mathrm{fb}^{-1}$ at centre-of-mass energies $\sqrt{s} = $ 7 TeV, 8 TeV and 13 TeV, respectively. The sensitivity of the results to the CKM angle $\gamma$ is discussed.

Figures and captions

Invariant mass distribution with the fit result superimposed for the favoured $ B ^- \rightarrow D ( K ^- \pi ^+ ) K ^{*-} $ decay mode (top), and $ B ^- \rightarrow D ( K ^- \pi ^+ \pi ^- \pi ^+ ) K ^{*-} $ decay mode (bottom), using Run 1 and Run 2 data combined. The labels 0 and $\pm$1 correspond to the helicity state of the $ D ^*$ meson.

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massFitDD_allyears_KPi.pdf
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massFitDD_allyears_KPiPiPi.pdf

Result of fits to data for the two-body decay modes with Run 1, Run 2, long and downstream categories summed for presentation. The signal is represented by the red shaded area, the combinatorial background by the dotted blue line and the partially reconstructed background by the solid green line. In the $ D ^0 \rightarrow K ^+ K ^- $ fits the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c K ^{*-} $ background is represented by the dashed purple line. The total fit is given by the black line. The residuals, shown below each plot, are defined as the difference between the data and the fit value in each bin, normalised by the uncertainty.

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canvas_d2kk.pdf
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canvas_d2pipi.pdf
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canvas_d2pik.pdf

Result of fits to data for the four-body decay modes with Run 1, Run 2, long and downstream categories summed for presentation. The signal is represented by the red shaded area, the combinatorial background by the dotted blue line and the partially reconstructed background by the solid green line. The total fit is given by the black line. The residuals are shown below each plot.\vspace{75pt}

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canvas_d2kpipipi.pdf
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canvas_d2pipipipi.pdf
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canvas_d2pikpipi.pdf

Contour plots showing 2D scans of physics parameters $\gamma$ versus $r_B$ (left) and $\gamma$ versus $\delta_B$ (right). The dashed lines represent the $\Delta \chi^2 = 2.30,\ 6.18,\ 11.8$ contours, corresponding to 68.3%, 95.5%, 99.7% confidence levels (CL), respectively. The colour scale represents $1-\text{CL}$.

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rBu_dkstar_gamma_2Dscan_nomixing.pdf
deltaB[..].pdf [43 KiB]
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deltaBu_dkstar_gamma_2Dscan_nomixing.pdf

Animated gif made out of all figures.

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Tables and captions

Fitted yields in each of the $ B $ decay modes. The uncertainties are statistical only.

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Summary of systematic uncertainties. Uncertainties are not shown if they are more than two orders of magnitude smaller than the statistical uncertainty.

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Correlation matrix of the statistical uncertainties for the twelve physics observables from the simultaneous fit to data. Only half of the symmetric matrix is shown.

 Table_3.pdf [46 KiB]
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Correlation matrix of the systematic uncertainties for the twelve physics observables from the simultaneous fit to data. Only half of the symmetric matrix is shown.

 Table_4.pdf [47 KiB]
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Created on 02 May 2024.