Measurement of $CP$ observables in $B^{\pm }\to D^{(\ast )}{K}^{\pm }$ and $B^{\pm }\to D^{(\ast )}\ddot{I}{€}^{\pm }$ decays using two-body $D$ final states

Abstract

Measurements of $CP$ observables in $B^{\pm }\to D^{(\ast )}{K}^{\pm }$ and $B^{\pm }\to D^{(\ast )}\ddot{I}{€}^{\pm }$ decays are presented, where $D^{(\ast )}$ indicates a neutral $D$ or $D^{\ast }$ meson that is an admixture of meson and anti-meson states. Decays of the $D^{\ast }$ meson to the $D\ddot{I}{€}^0$ and $D{\hat{I}}^3$ final states are partially reconstructed without inclusion of the neutral pion or photon. Decays of the $D$ meson are reconstructed in the $K^{\pm }\ddot{I}{€}^{\mp }$, $K^{+}{K}^{-}$, and $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ final states. The analysis uses a sample of charged $B$ mesons produced in proton-proton collisions and collected with the LHCb experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7 fb${}^{-1}$ taken at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The measurements of partially reconstructed $B^{\pm }\to D^{\ast }{K}^{\pm }$ and $B^{\pm }\to D^{\ast }\ddot{I}{€}^{\pm }$ with $D\to K^{\mp }\ddot{I}{€}^{\pm }$ decays are the first of their kind, and a first observation of the $B^{\pm }\to (D\ddot{I}{€}^0{)}_{D^{\ast }}\ddot{I}{€}^{\pm }$ decay is made with a significance of 6.1 standard deviations. All $CP$ observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle ${\hat{I}}^3$.

All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2020-036.html (LHCb public pages)