Study of resonances in exclusive $B$ decays to ${\overline{D}}^{(*)}{D}^{(*)}K$

We present a study of resonances in exclusive decays of $B$ mesons to ${\overline{D}}^{(*)}{D}^{(*)}K$. We report the observation of the decays $B\to {\overline{D}}^{(*)}{D}_{s1}^{+}(2536)$ where the $D_{s1}^{+}(2536)$ is reconstructed in the $D^{*0}{K}^{+}$ and $D^{*+}{K}_S^0$ decay channels. We report also the observation of the decays $B\to \psi (3770)K$ where the $\psi (3770)$ decays to ${\overline{D}}^0{D}^0$ and $D^{-}{D}^{+}$. In addition, we present the observation of an enhancement for the ${\overline{D}}^{*0}{D}^0$ invariant mass in the decays $B\to {\overline{D}}^{*0}{D}^{0}K$, at a mass of $({3875.1}_{-0.5}^{+0.7}\pm 0.5)\mathrm{MeV}/c^2$ with a width of $({3.0}_{-1.4}^{+1.9}\pm 0.9)\mathrm{MeV}$ (the first errors are statistical and the second are systematic). Branching fractions and spin studies are shown for the three resonances. The results are based on $347{\mathrm{fb}}^{-1}$ of data collected with the BABAR detector at the PEP-II $B$ factory.

Figure 1

Top: Invariant mass distributions of $D^{*}K$ (a), $\overline{D}D$ (c) and ${\overline{D}}^{*0}{D}^0$ (e) in the data for events in the ($m_{ES}$, $\Delta E$) $B$ signal region. Points with statistical errors are data events, the solid line represents the fit to the data, the dashed line shows the contribution of the $D_{s1}^{+}(2536)$ (a), $\psi (3770)$ (c) and $X(3872)$ (e) signals, and the dotted line shows the background contribution. Bottom: background-subtracted and efficiency-corrected helicity angle distributions for the $D_{s1}^{+}(2536)$ (b) (containing only the $B\to \overline{D}{D}_{s1}^{+}(2536)$ modes), $\psi (3770)$ (d) and $X(3872)$ (f) signals in the data (points with statistical errors) and fitted distributions for different spin hypotheses: $J^P=0^{+}$ (dashed lines), $1^{-}$ (solid), $1^{+}$ with $S\mathrm{\text{−}}D$ wave admixture (dotted), $2^{-}$ (long-dashed) and $2^{+}$ (dotted-dashed).

Figure 2

Equidistant contours of ${\chi }^2-{\chi }_{\min }^2$ versus mass and width of the simulated $X(3872)$ signals. The contours are separated by ${\chi }^2$ values of 0.5. Solid contours represent values starting from 0.5, by step of 1, while dashed contours represent values starting from 1, by step of 1. The contour at ${\chi }^2-{\chi }_{\min }^2=1$ is indicated by a wider line. The cross shows the central values of the $X(3872)$ mass and width. The vertical and horizontal dotted lines indicate the errors on the mass and on the width, respectively.