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First observation of the decay $B^0 \rightarrow D^0 \overline{D}{}^0 K^+ \pi^-$

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Abstract

The first observation of the decay $B^0 \rightarrow D^0 \overline{D}{}^0 K^+ \pi^-$ is reported using proton-proton collision data corresponding to an integrated luminosity of 4.7 $\mathrm{fb}^{-1}$ collected by the LHCb experiment in 2011, 2012 and 2016. The measurement is performed in the full kinematically allowed range of the decay outside of the $D^{*-}$ region. The ratio of the branching fraction relative to that of the control channel $B^0 \rightarrow D^{*-} D^0 K^+$ is measured to be $\mathcal{R} = (14.2 \pm 1.1 \pm 1.0)\%$, where the first uncertainty is statistical and the second is systematic. The absolute branching fraction of $B^0 \rightarrow D^0 \overline{D}{}^0 K^+ \pi^-$ decays is thus determined to be $\mathcal{B}(B^0 \rightarrow D^0 \overline{D}{}^0 K^+ \pi^-) = (3.50 \pm 0.27 \pm 0.26 \pm 0.30) \times 10^{-4}$, where the third uncertainty is due to the branching fraction of the control channel. This decay mode is expected to provide insights to spectroscopy and the charm-loop contributions in rare semileptonic decays.

Figures and captions

Feynman diagrams of the external (left) and internal (right) W emission contributing to $ B ^0 \rightarrow D ^0 \overline{ D } {}^0 K ^+ \pi ^- $ decays.

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Invariant-mass distributions and fit projections for $ B ^0 $ candidates in (left) the signal and (right) control mode for all subsamples combined. The data are shown as black points with error bars and the fit components are as described in the legends. The small single-charm and charmless background is included in the signal component.

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Projections of background-subtracted data (black points) in (left) $m( D ^0 \overline{ D } {}^0 )$, (centre) $m( D ^0 K ^+ )$ and (right) $m( K ^+ \pi ^- )$ with the phase-space only distribution (orange dashed line) superimposed for reference. The data contain a few single-charm and charmless background candidates.

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The efficiency $\varepsilon_{\rm{con}},$ as a function of position in the Dalitz plot of $ B ^0 \rightarrow D ^{*-} D ^0 K ^+ $ decays obtained from simulated samples. The top row shows Run 1 samples for (left) TOS and (right) TIS. The bottom row shows the same trigger categories for 2016 samples.

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Invariant-mass distributions and fit projections for $ B ^0 \rightarrow D ^0 \overline{ D } {}^0 K ^+ \pi ^- $ candidates, shown separately for each run period, (top) Run 1 and (bottom) 2016, and trigger category, (left) TOS and (right) TIS. The data are shown as black points with error bars and the fit components are as described in the legends. Pull projections are shown beneath each distribution. The data contain a few single-charm and charmless background candidates.

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Invariant-mass distributions and fit projections for $ B ^0 \rightarrow D ^{*-} D ^0 K ^+ $ candidates, shown separately for each run period, (top) Run 1 and (bottom) 2016, and trigger category, (left) TOS and (right) TIS. The data are shown as black points with error bars and the fit components are as described in the legends. Pull projections are shown beneath each distribution.

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Invariant-mass distributions and fit projections for $ B ^0 \rightarrow D ^0 \overline{ D } {}^0 K ^+ \pi ^- $ candidates over an extended range, shown separately for each run period, (top) Run 1 and (bottom) 2016, and trigger category, (left) TOS and (right) TIS. The data are shown as black points with error bars and the fit components are as described in the legends, where the green shaded distribution describes partially reconstructed backgrounds. Pull projections are shown beneath each distribution. The data contain a few single-charm and charmless background candidates.

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Animated gif made out of all figures.

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Tables and captions

Systematic uncertainties expressed as a percentage of the branching fraction ratio $\mathcal{R}$. The statistical uncertainty is included for comparison. The single-charm and charmless backgrounds are considered together.

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Created on 14 January 2021.