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

The first observations of $B^0\to {\overline{D}}^{*}(2007{)}^0{K}^{+}{\pi }^{-}$ and $B_s^0\to {\overline{D}}^{*}(2007{)}^0{K}^{-}{\pi }^{+}$ decays are presented, and their branching fractions relative to that of the $B^0\to {\overline{D}}^{*}(2007{)}^0{\pi }^{+}{\pi }^{-}$ 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 Cabibbo-Kobayashi-Maskawa unitarity triangle. It is also important to understand them as a source of potential background in determinations of $\gamma$ from $B^{+}\to D{K}^{+}$ and $B^0\to D{K}^{+}{\pi }^{-}$ decays. The analysis is based on a sample corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ of proton-proton collision data at 13 TeV center-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 ${\overline{D}}^0\to K^{+}{\pi }^{-}$ 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.

Figure 1

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

Figure 2

Difference between the ${\overline{D}}^{*0}$ and ${\overline{D}}^0$ candidate masses in $B^0\to {\overline{D}}^{*0}{\pi }^{+}{\pi }^{-}$ decays for (top) data and (bottom) simulated signal decays. The left and right plots show ${\overline{D}}^{*0}\to {\overline{D}}^0\gamma$ 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.

Figure 3

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

Figure 4

Invariant mass distributions of (top) $B^0\to {\overline{D}}^{*0}{K}^{+}{\pi }^{-}$, (middle) $B_s^0\to {\overline{D}}^{*0}{K}^{-}{\pi }^{+}$ and (bottom) $B^0\to {\overline{D}}^{*0}{\pi }^{+}{\pi }^{-}$ with (left) ${\overline{D}}^{*0}\to {\overline{D}}^0\gamma$ and (right) ${\overline{D}}^{*0}\to {\overline{D}}^0{\pi }^0$ candidates, with a 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 Fig. 3.

Figure 5

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

Figure 6

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