Measurement of $C P$ observables in $B^\pm \to D^{()} K^\pm$ and $B^\pm \to D^{()} \pi^\pm$ decays using two-body $D$ final states

Information

LHCb-PAPER-2020-036
CERN-EP-2020-225
arXiv:2012.09903 [PDF]

(Submitted on 17 Dec 2020)
JHEP 04 (2021) 081
Inspire 1838001

Tools

Abstract

Measurements of $C P$ 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 meson and anti-meson 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. Decays of the $D$ meson are 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 proton-proton collisions and collected with the LHCb experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7 fb$^{-1}$ taken at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The measurements of partially reconstructed $B^\pm \to D^* K^\pm$ and $B^\pm \to D^* \pi^\pm$ with $D \to K^\mp \pi^\pm$ decays are the first of their kind, and a first observation of the $B^\pm \to (D \pi^0)_{D^*} \pi^\pm$ decay is made with a significance of 6.1 standard deviations. All $C P$ observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle $\gamma$.

Figures and captions

Legend indicating the invariant-mass fit components shown in Figs. ???$-$???.	Fig1.pdf [232 KiB] HiDef png [121 KiB] Thumbnail [97 KiB] *.C file
Invariant-mass distribution of selected $ B ^\pm \rightarrow [ K ^\pm \pi ^\mp ]_{D}h^{\pm}$ candidates. The result of the fit is shown by the solid navy line, and each component is listed in a legend provided in Fig. ???.	Fig2a.pdf [410 KiB] HiDef png [218 KiB] Thumbnail [121 KiB] *.C file
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Invariant-mass distribution of $ B ^\pm \rightarrow [ K ^\mp \pi ^\pm ]_D h^\pm$ candidates with the fit result overlaid. A legend is provided in Fig. ???.	Fig3a.pdf [428 KiB] HiDef png [299 KiB] Thumbnail [168 KiB] *.C file
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Invariant-mass distribution of $ B ^\pm \rightarrow [ K ^+ K ^- ]_D h^\pm$ candidates with the fit result overlaid. A legend is provided in Fig. ???.	Fig4a.pdf [413 KiB] HiDef png [272 KiB] Thumbnail [139 KiB] *.C file
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Invariant-mass distribution of $ B ^\pm \rightarrow [\pi ^+ \pi ^- ]_D h^\pm$ candidates with the fit result overlaid. A legend is provided in Fig. ???.	Fig5a.pdf [419 KiB] HiDef png [278 KiB] Thumbnail [146 KiB] *.C file
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Confidence regions for the (top row) $ B ^- \rightarrow D K ^- $ , (second row) $ B ^- \rightarrow D \pi ^- $ , (third row) $ B ^- \rightarrow D^* K ^- $ , and (fourth row) $ B ^- \rightarrow D^* \pi ^- $ fundamental parameters. The $ B ^- \rightarrow D h^-$ with $D \rightarrow K ^0_{\mathrm{S}} h^+ h^-$ contours from Ref. \cite{LHCb-PAPER-2020-019} are also overlaid.	Fig6a.pdf [289 KiB] HiDef png [378 KiB] Thumbnail [200 KiB] *.C file
	Fig6b.pdf [268 KiB] HiDef png [553 KiB] Thumbnail [291 KiB] *.C file
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Animated gif made out of all figures.	PAPER-2020-036.gif Thumbnail

Tables and captions

The nine $ C P$ observables measured using $ B ^- \rightarrow D h^-$ decays, defined in terms of $B$ meson decay widths. Where indicated, $h^+h^-$ represents an average of the $D \rightarrow K ^+ K ^- $ and $D \rightarrow \pi ^+ \pi ^- $ modes. The $R$ observables represent partial width ratios and double ratios. The $A$ observables represent $ C P$ asymmetries.	Table_1.pdf [89 KiB] HiDef png [114 KiB] Thumbnail [61 KiB] tex code
The 19 $ C P$ observables measured using $ B ^- \rightarrow D^* h^-$ decays, defined in terms of $B$ meson decay widths. Where indicated, $h^+h^-$ represents an average of the $D \rightarrow K ^+ K ^- $ and $D \rightarrow \pi ^+ \pi ^- $ modes. The $R$ observables represent partial width ratios and double ratios. The $A$ observables represent $ C P$ asymmetries. The $R_{K/\pi}^{K\pi,\gamma /\pi ^0 }$ observable is an average over the $D^* \rightarrow D \pi ^0 $ and $D^* \rightarrow D\gamma $ modes.	Table_2.pdf [91 KiB] HiDef png [240 KiB] Thumbnail [124 KiB] tex code
Yields for the 24 signal modes.	Table_3.pdf [73 KiB] HiDef png [180 KiB] Thumbnail [88 KiB] tex code
	Table_4.pdf [91 KiB] HiDef png [51 KiB] Thumbnail [19 KiB] tex code
Statistical correlation matrix for $ B ^\pm \rightarrow D h^\pm$ observables.	Table_5.pdf [62 KiB] HiDef png [52 KiB] Thumbnail [24 KiB] tex code
Systematic correlation matrix for $ B ^\pm \rightarrow D h^\pm$ observables.	Table_6.pdf [63 KiB] HiDef png [52 KiB] Thumbnail [24 KiB] tex code
Statistical correlation matrix for $ B ^\pm \rightarrow D^* h^\pm$ observables.	Table_7.pdf [43 KiB] HiDef png [54 KiB] Thumbnail [20 KiB] tex code
Systematic correlation matrix for $ B ^\pm \rightarrow D^* h^\pm$ observables.	Table_8.pdf [44 KiB] HiDef png [55 KiB] Thumbnail [21 KiB] tex code