Measurement of $CP$ observables in the process $B^0\to D{K}^{\ast 0}$ with two- and four-body $D$ decays

Abstract

Measurements of $CP$ observables in $B^0\to D{K}^{\ast 0}$ decays are presented, where $D$ represents a superposition of $D^0$ and ${\bar{D}}^0$ states. The $D$ meson is reconstructed in the two-body final states $K^{+}\ddot{I}{€}^{-}$, $\ddot{I}{€}^{+}{K}^{-}$, $K^{+}{K}^{-}$ and $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$, and, for the first time, in the four-body final states $K^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$, $\ddot{I}{€}^{+}{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and $\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$. The analysis uses a sample of neutral $B$ mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 $\mathrm{f}{\mathrm{b}}^{-1}$ collected with the LHCb detector at centre-of-mass energies of $\sqrt{s}=$ 7, 8 and 13 TeV, respectively. First observations of the decays $B^0\to D(\ddot{I}{€}^{+}{K}^{-})K^{\ast 0}$ and $B^0\to D(\ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-})K^{\ast 0}$ are obtained. The measured observables are interpreted in terms of the $CP$-violating weak phase ${\hat{I}}^3$.

All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2019-021.html (LHCb public pages)