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Constraints on the CKM angle $\gamma$ from $B^\pm\rightarrow Dh^\pm$ decays using $D\rightarrow h^\pm h^{\prime\mp}\pi^0$ final states

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Abstract

A data sample collected with the LHCb detector corresponding to an integrated luminosity of 9 fb$^{-1}$ is used to measure eleven $CP$ violation observables in $B^\pm\to Dh^\pm$ decays, where $h$ is either a kaon or a pion. The neutral $D$ meson decay is reconstructed in the three-body final states: $K^\pm\pi^\mp\pi^0$}; $\pi^+\pi^-\pi^0$; $K^+K^-\pi^0$ and the suppressed $\pi^\pm K^\mp\pi^0$ combination. The mode where a large $CP$ asymmetry is expected, $B^\pm\to [\pi^\pm K^\mp\pi^0]_DK^\pm$, is observed with a significance greater than seven standard deviations. The ratio of the partial width of this mode relative to that of the favoured mode, $B^\pm\to [K^\pm\pi^\mp\pi^0]_D K^\pm$, is $R_{{\rm ADS}(K)} = (1.27\pm0.16\pm0.02)\times 10^{-2}$. Evidence for a large $CP$ asymmetry is also seen: $A_{{\rm ADS}(K)} = -0.38\pm0.12\pm0.02$. Constraints on the CKM angle $\gamma$ are calculated from the eleven reported observables.

Figures and captions

Mass distributions of $ B ^\mp \rightarrow [ K ^\mp \pi ^\pm \pi ^0 ]_D K ^\mp $ (top) and $ B ^\mp \rightarrow [ K ^\mp \pi ^\pm \pi ^0 ]_D\pi ^\mp $ (bottom) candidates, separated by charge.

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Mass distributions of $ B ^\mp \rightarrow [\pi ^\mp K ^\pm \pi ^0 ]_D K ^\mp $ (top) and $ B ^\mp \rightarrow [\pi ^\mp K ^\pm \pi ^0 ]_D\pi ^\mp $ (bottom) candidates, separated by charge.

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Mass distributions of $ B ^\mp \rightarrow [\pi ^\pm \pi ^\mp \pi ^0 ]_D K ^\mp $ (top) and $ B ^\mp \rightarrow [\pi ^\pm \pi ^\mp \pi ^0 ]_D\pi ^\mp $ (bottom) candidates, separated by charge.

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Mass distributions of $ B ^\mp \rightarrow [ K ^\pm K ^\mp \pi ^0 ]_D K ^\mp $ (top) and $ B ^\mp \rightarrow [ K ^\pm K ^\mp \pi ^0 ]_D\pi ^\mp $ (bottom) candidates, separated by charge.

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Confidence regions of the strong phase, $\delta_B$ versus the unitarity triangle angle, $\gamma $ shows (left) two solutions, one of which is shown (right) to be consistent with the 2021 $\gamma $ combination result [33] whose confidence intervals are superimposed.

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Animated gif made out of all figures.

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Tables and captions

Signal yields for each decay mode. The uncertainties quoted are statistical only.

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Systematic uncertainties on the observables, multiplied by $10^4$. PID refers to the fixed PID efficiencies of the companion tracks. PDFs refers to the uncertainties in fixing parameters in the fit PDF. Sim refers to the use of simulation to calculate relative efficiencies between the $ B ^- \rightarrow D K ^- $ and $ B ^- \rightarrow D \pi ^- $ modes. $A_{\rm instr}$ refers to the interaction and detection asymmetries. $ D $ decay refers to the effect of assuming that the distribution of candidates in the $ D $ meson decay phase-space is not sculpted by the selection. The Total column corresponds to the quadrature sum over the five categories.

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Correlation matrix for statistical uncertainties.

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Correlation matrix for systematic uncertainties.

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Created on 02 May 2024.