# Measurement of CP observables in $B^0 \to D K^*0$ with $D \to K^+ K^-$

R. Aaij, J.F.J. van den Brand, F. Dettori, T.J. Ketel, R. Koopman, R.W. Lambert, D. Martinez-Santos, M.H.M. Merk, H.G. Raven, M. Schiller, V. Syropoulos, S. Tolk, Collaboration LHCb

## Abstract

The decay B0 → DK*0 and the charge conjugate mode are studied using 1.0 fb−1 of pp collision data collected by the LHCb experiment at √s = 7 TeV in 2011. The CP asymmetry between the B0 → DK*0 and the B0 → DK*0 decay rates, with the neutral D meson in the CP-even final state K+K‚ is found to be A<inf>d</inf>KK = −0.45 ± 0.23 ± 0.02, where the first uncertainty is statistical and the second is systematic. In addition, favoured B0 → DK*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 R<inf>d</inf>KK = 1.36 +0.37<inf>−0.32</inf> ± 0.07, where the ratio of the branching fractions of D0 → Kπ+ to D0 → K+K decays is included as multiplicative factor. The CP asymmetries measured with two control channels, the favoured B0 → DK*0 decay with D → K+π and the B0<inf>s</inf> → DK*0 decay with D → K+K, are also reported.
Original language English Journal of High Energy Physics 2013 3 https://doi.org/10.1007/JHEP03(2013)067 Published - 2013

Aaij:2012fd

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