Measurement of $CP$ observables in $B^{\pm} \to D^{(*)} K^{\pm}$ and $B^{\pm} \to D^{(*)}\pi^{\pm}$ decays

Abstract

Measurements of $CP$ observables in $B^{\pm} \to D^{(*)} K^{\pm}$ and $B^{\pm} \to D^{(*)}\pi^{\pm}$ decays are presented, where $D^{(*)}$ indicates a neutral $D$ or $D^*$ meson that is an admixture of $D^{(*)0}$ and $\overline{D}^{(*)0}$ states. Decays of the $D^*$ meson to the $D\pi^0$ and $D\gamma$ final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the $B$ candidate invariant mass distribution. Decays of the $D$ meson are fully reconstructed in the $K^{\pm}\pi^{\mp}, K^+K^-$ and $\pi^+\pi^-$ final states. The analysis uses a sample of charged $B$ mesons produced in $pp$ collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb$^{−1}$ taken at centre-of-mass energies of $\sqrt{s}$ = 7, 8 and 13TeV, respectively. The study of $ B^{\pm} \to D^*K^{\pm}$ and $B^{\pm} \to D^*\pi^{\pm}$ decays using a partial reconstruction method is the first of its kind, while the measurement of $B^{\pm} \to DK^{\pm}$ and $B^{\pm} \to D\pi^{\pm}$ decays is an update of previous LHCb measurements. The $B^{\pm} \to DK^{\pm}$ results are the most precise to date.