Search for charge-parity violation in semileptonically tagged $D^0\to K^{+}\ddot{I}{€}^{-}$ decays

Abstract

An analysis of the flavour oscillations of the charmed neutral meson is presented. The ratio of $D^0\to K^{+}\ddot{I}{€}^{-}$ and $D^0\to K^{-}\ddot{I}{€}^{+}$ decay rates is measured as a function of the decay time of the $D^0$ meson and compared with the charge-conjugated system to search for charge-parity violation. The meson flavour at production is double-tagged by the charges of the muon and pion in the preceding $\overline{B}\to D^{\ast }(2010{)}^{+}\hat{I}{¼}^{-}X$ and $D^{\ast }(2010{)}^{+}\to D^0\ddot{I}{€}^{+}$ decays, respectively. These decays are selected from proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of $13\text{TeV}$ and corresponding to an integrated luminosity of $5.4{\text{fb}}^{-1}$. The flavour oscillation parameters, relating to the differences in mass and width of the mass eigenstates, are found to be $y^{\prime }=(5.8\pm 1.6)\times 10^{-3}$ and $(x^{\prime }{)}^2=(0.0\pm 1.2)\times 10^{-4}$. No evidence for charge-parity violation is seen either in the flavour oscillations or in the decay, where the direct charge-parity asymmetry is measured to be $A_D=(2.3\pm 1.7)\%$.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/3260/ (LHCb public pages)