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Measurement of $CP$ violation in $B^{0}\rightarrow D^{\mp}\pi^{\pm}$ decays

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Abstract

A measurement of the $CP$ asymmetries $S_{f}$ and $S_{\bar{f}}$ in $B^0\to D^{\mp}\pi^{\pm}$ decays is reported. The decays are reconstructed in a dataset collected with the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV and corresponding to an integrated luminosity of $3.0 \rm{ fb}^{-1}$. The $CP$ asymmetries are measured to be $S_{f} = 0.058 \pm 0.020 (\rm{stat}) \pm 0.011(\rm{syst})$ and $S_{\bar{f}} = 0.038\pm 0.020 (\text{stat})\pm 0.007 (\text{syst})$. These results are in agreement with, and more precise than, previous determinations. They are used to constrain $|\sin\left(2\beta+\gamma\right)|$ and $\gamma$ to intervals that are consistent with the current world-average values.

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Invariant mass distributions of the (left) pion-like and (right) kaon-like samples with fit projections overlaid. The simultaneous fit of the two distributions is described in the text and yields a $\chi^2$ per degree of freedom of 1.18. The $B\rightarrow D ^\mp \rho$ component includes both $ B ^0 \rightarrow D ^\mp \rho^\pm$ and $ B ^\mp \rightarrow D ^\mp \rho^0$ decays.

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Measured mistag fraction $\omega$ versus predicted mistag probability $\eta$ of the combination of (left) OS and (right) SS taggers as determined in signal decays with the fit described in Sect. 6. The black histograms are the distributions of the mistag probabilities in arbitrary units. The shaded areas correspond to the 68% and 95% confidence-level regions of the calibration functions and do not include systematic uncertainties on the parameters. The calibration functions and the distributions of mistag probabilities are shown summing over candidates tagged as either $ B ^0$ or $\overline{ B }{} {}^0$ .

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Background-subtracted decay-time distribution for tagged candidates. The solid blue curve is the projection of the signal PDF. The red dotted curve indicates the efficiency function $\varepsilon\left(t\right)$ in arbitrary units.

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Decay-time-dependent signal-yield asymmetries for (left) the favoured and (right) the suppressed decays. The signal-yield asymmetries are defined in Eq. 12 and Eq. 13. The blue solid curve is the projection of the signal PDF, the red dotted curve indicates the projection of the fit when $ C\!P$ conservation is imposed.

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1--CL as a function of $|\sin(2\beta+\gamma)|$.

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(Left) 1--CL as a function of $\gamma$ and (right) confidence regions for $\gamma$ and $\delta$. The confidence regions hold the $39\%$ and $87\%$ CL. Points denote the preferred values.

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Tables and captions

Systematic uncertainties on the $ C\!P$ asymmetries $S_{f}$ and $S_{\bar f}$. The total uncertainty is the sum in quadrature of the individual contributions.

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Supplementary Material [file]

Supplementary material full pdf

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This ZIP file contains supplemetary material for the publication LHCb-PAPER-2018-009. The files are: Supplementary.pdf : An overview of the extra figures *.C, *.pdf, *.png, *.eps : The figures in various formats *.tex: The tables as tex code

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