Measurement of the branching fractions of $\bar{B}\to D^{(\ast )}{K}^{-}{K}_{(S)}^{(\ast )0}$ and $\bar{B}\to D^{(\ast )}{D}_s^{-}$ decays at Belle II

Abstract

We present measurements of the branching fractions of eight $\overline{B}{}^0\to D^{(\ast )+}{K}^{-}{K}_{(S)}^{(\ast )0}$, $B^{-}\to D^{(\ast )0}{K}^{-}{K}_{(S)}^{(\ast )0}$ decay channels. The results are based on data from SuperKEKB electron-positron collisions at the $\hat{I}\yen (4S)$ resonance collected with the Belle II detector, corresponding to an integrated luminosity of $362{\text{fb}}^{-1}$. The event yields are extracted from fits to the distributions of the difference between expected and observed $B$ meson energy, and are efficiency-corrected as a function of $m(K^{-}{K}_{(S)}^{(\ast )0})$ and $m(D^{(\ast )}{K}_{(S)}^{(\ast )0})$ in order to avoid dependence on the decay model. These results include the first observation of $\overline{B}{}^0\to D^{+}{K}^{-}{K}_S^0$, $B^{-}\to D^{\ast 0}{K}^{-}{K}_S^0$, and $\overline{B}{}^0\to D^{\ast +}{K}^{-}{K}_S^0$ decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of the $K^{-}{K}_{(S)}^{(\ast )0}$ systems are compatible with quasi-two-body decays via a resonant transition with spin-parity $J^P=1^{-}$ for the $K^{-}{K}_S^0$ systems and $J^P=1^{+}$ for the $K^{-}{K}^{\ast 0}$ systems. We also present measurements of the branching fractions of four $\overline{B}{}^0\to D^{(\ast )+}{D}_s^{-}$, $B^{-}\to D^{(\ast )0}{D}_s^{-}$ decay channels with a precision compatible to the current world averages.

34 pages, 14 figures. arXiv admin note: text overlap with arXiv:2305.01321