Measurement of indirect CP asymmetries in D⁰ → K⁻K⁺ and D⁰ → π⁻π⁺ decays using semileptonic B decays

Abstract

Time-dependent CP asymmetries in the decay rates of the singly Cabibbo-suppressed decays D⁰ → K⁻K⁺ and D⁰ → π⁻π⁺ are measured in pp collision data corresponding to an integrated luminosity of 3.0 fb⁻¹ collected by the LHCb experiment. The D⁰ mesons are produced in semileptonic b-hadron decays, where the charge of the accompanying muon is used to determine the initial state as D⁰ or ${\overline{D}}^0$. The asymmetries in effective lifetimes between D⁰ and ${\overline{D}}^0$ decays, which are sensitive to indirect CP violation, are determined to be

$$ \begin{array}{c}\hfill {A}_{\varGamma}\left({K}^{-}{K}^{+}\right)=\left(-0.134\pm 0.0{77}_{-0.034}^{-0.026}\right)\%,\hfill \\ {}\hfill {A}_{\varGamma}\left({\pi}^{-}{\pi}^{+}\right) = \left(-0.092\pm 0.{145}_{-0.033}^{-0.025}\right)\%,\hfill \end{array} $$

where the first uncertainties are statistical and the second systematic. This result is in agreement with previous measurements and with the hypothesis of no indirect CP violation in D⁰ decays.