Measurement of CP observables in B 0DK ∗0 with DK + K

Abstract

The decay B 0DK *0 and the charge conjugate mode are studied using 1.0 fb−1 of pp collision data collected by the LHCb experiment at \( \sqrt{s}=7 \) TeV in 2011. The CP asymmetry between the B 0DK *0 and the \( {{\overline{B}}^0}\to D{{\overline{K}}^{*0 }} \) decay rates, with the neutral D meson in the CP-even final state K + K , is found to be

$ \mathcal{A}_d^{KK }=-0.45\pm 0.23\pm 0.02, $

where the first uncertainty is statistical and the second is systematic. In addition, favoured B 0DK *0 decays are reconstructed with the D meson in the non-CP eigenstate K +π. The ratio of the B-flavour averaged decay rates in D decays to CP and non-CP eigenstates is measured to be

$ \mathcal{R}_d^{KK }=1.36_{-0.32}^{+0.37}\pm 0.07, $

where the ratio of the branching fractions of D 0K π+ to D 0K + K decays is included as multiplicative factor. The CP asymmetries measured with two control channels, the favoured B 0DK *0 decay with DK +π and the \( \overline{B}_s^0\to D{K^{*0 }} \) decay with DK + K , arealsoreported.

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