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Observation of the $B^0\rightarrow\overline{D}^{*0}K^{+}\pi^{-}$ and $B_s^0\rightarrow\overline{D}^{*0}K^{-}\pi^{+}$ decays

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Abstract

The first observations of $B^0\rightarrow\overline{D}^{*}(2007)^{0}K^{+}\pi^{-}$ and $B_s^0\rightarrow\overline{D}^{*}(2007)^{0}K^{-}\pi^{+}$ decays are presented, and their branching fractions relative to that of the $B^0\rightarrow\overline{D}^{*}(2007)^{0}\pi^{+}\pi^{-}$ decay are reported. These modes can potentially be used to investigate the spectroscopy of charm and charm-strange resonances and to determine the angle $\gamma$ of the CKM unitarity triangle. It is also important to understand them as a source of potential background in determinations of $\gamma$ from $B^{+}\rightarrow DK^{+}$ and $B^{0}\rightarrow DK^{+}\pi^{-}$ decays. The analysis is based on a sample corresponding to an integrated luminosity of $5.4 \rm{fb}^{-1}$ of proton--proton collision data at $13 \rm{TeV}$ centre-of-mass energy recorded with the LHCb detector. The $\overline{D}^{*}(2007)^{0}$ mesons are fully reconstructed in the $\overline{D}^{0}\pi^{0}$ and $\overline{D}^{0}\gamma$ channels, with the $\overline{D}^{0} \rightarrow K^{+}\pi^{-}$ decay. A novel weighting method is used to subtract background while simultaneously applying an event-by-event efficiency correction to account for resonant structures in the decays.

Figures and captions

Leading diagrams for ($a$), ($c$) $ B ^0 \rightarrow \overline{ D }{} {}^{*0} K ^+ \pi ^- $ and ($b$), ($d$) $ B ^0_ s \rightarrow \overline{ D }{} {}^{*0} K ^- \pi ^+ $ decay channels. In the colour-suppressed diagrams, ($a$) and ($b$), the decay proceeds through an intermediate $\optbar{ K}{} {}^{*0}$ resonance with additional $ u \overline u $ production, while in the colour-allowed diagrams the decay proceeds through an excited charm ($c$) or charm-strange ($d$) resonance.

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Difference between the $\overline{ D }{} {}^{*0}$ and $\overline{ D }{} {}^0$ candidate masses in $ B ^0 \rightarrow \overline{ D }{} {}^{*0} \pi ^+ \pi ^- $ decays for (top) data and (bottom) simulated signal decays. The left and right plots show $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \gamma$ and $\overline{ D }{} {}^0 \pi ^0 $ candidates, respectively. The simulation distributions are shown separately for correctly reconstructed and misreconstructed signal components. All selection requirements have been imposed, except those on the plotted variable, which are indicated with dashed vertical lines.

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Invariant mass distributions of (top) $B^0\rightarrow \overline{ D }{} {}^{*0} K ^+ \pi ^- $, (middle) $ B ^0_ s \rightarrow \overline{ D }{} {}^{*0} K ^- \pi ^+ $, and (bottom) $B^0\rightarrow \overline{ D }{} {}^{*0} \pi ^+ \pi ^- $ with (left) $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \gamma$ and (right) $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \pi ^0 $ candidates, with linear $y$-axis. The total fit result is shown overlaid as a solid blue line, with individual components illustrated as indicated in the legends.

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Invariant mass distributions of (top) $B^0\rightarrow \overline{ D }{} {}^{*0} K ^+ \pi ^- $, (middle) $ B ^0_ s \rightarrow \overline{ D }{} {}^{*0} K ^- \pi ^+ $, and (bottom) $B^0\rightarrow \overline{ D }{} {}^{*0} \pi ^+ \pi ^- $ with (left) $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \gamma$ and (right) $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \pi ^0 $ candidates, with logarithmic $y$-axis scale. The total fit result is shown overlaid as a solid blue line, with individual components illustrated as indicated in the legends of \cref{fig:globalfit_lin}.

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Total efficiency as a function of SDP coordinates for (top) $ B ^0 \rightarrow \overline{ D }{} {}^{*0} K ^+ \pi ^- $, (middle) $ B ^0_ s \rightarrow \overline{ D }{} {}^{*0} K ^- \pi ^+ $, and (bottom) $ B ^0 \rightarrow \overline{ D }{} {}^{*0} \pi ^+ \pi ^- $, with (left) $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \gamma$ and (right) $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \pi ^0 $ decays.

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(Left) SDP and (right) conventional Dalitz plots of background-subtracted and efficiency-corrected data, for (top) $ B ^0 \rightarrow \overline{ D }{} {}^{*0} K ^+ \pi ^- $, (middle) $ B ^0_ s \rightarrow \overline{ D }{} {}^{*0} K ^- \pi ^+ $ and (bottom) $ B ^0 \rightarrow \overline{ D }{} {}^{*0} \pi ^+ \pi ^- $ decays.

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Animated gif made out of all figures.

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Tables and captions

Yields obtained from the simultaneous fit for the correctly reconstructed signal component. Uncertainties are statistical only.

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Correlations between the signal yields, as obtained from the simultaneous fit, accounting for statistical uncertainties only. The individual components are labelled with a shorthand, following the same ordering (left to right, and top to bottom) as in \cref{tab:FitResults}. The symbols $\overline{ D }{} {}^{*0}_{\gamma}$ and $\overline{ D }{} {}^{*0}_{\pi ^0 }$ refer to $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \gamma$ and $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \pi ^0 $ decays, respectively.

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Ordering convention used to define the SDP representation of the phase space for each of the signal decays.

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Systematic uncertainties (%) on the branching fraction ratios, relative to the central values, with the soft neutral particle emitted in the $\overline{ D }{} {}^{*0}$ decay indicated as a subscript for brevity of notation. The sources of uncertainty are presented in the same order as described in the text, with statistical uncertainties included to facilitate comparison. Systematic uncertainties are indicated as being considered to be either completely uncorrelated ($\dagger$) or completely correlated ($*$) between the ratios obtained with the $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \gamma$ and $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \pi ^0 $ decays. The total correlated and uncorrelated systematic uncertainties are obtained by summing the relevant sources in quadrature. The uncertainty due to the fragmentation fractions is quoted separately.

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Branching fraction ratios determined separately for $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \gamma$ and $\overline{ D }{} {}^{*0} \rightarrow \overline{ D }{} {}^0 \pi ^0 $ decays. The uncertainties are statistical, systematic and (where given) due to $f_s/f_d$.

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Created on 02 May 2024.