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Article

Model-independent measurement of the CKM angle $\gamma$ using $B^0 \to D K^{\ast 0}$ decays with $D \to K_{S}^{0} \pi^{+} \pi^{-}$ and $K_{S}^{0} K^{+} K^{-}$

Journal of High Energy Physics. 2016. Vol. 1606. No. 136.
Derkach D., Ustyuzhanin A., Likhomanenko T., Rogozhnikov A.
A binned Dalitz plot analysis of the decays \BtoDKst, with \DtoKsPiPi and \DtoKsKK, is performed to measure the observables $x_\pm$ and $y_\pm$, which are related to the CKM angle $\gamma$ and the hadronic parameters of the decays. The $D$ decay strong phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of the $D$ decay model. With a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 \invfb, collected by the LHCb experiment, the values of the \CP violation parameters are found to be $x_+ = 0.05 \pm 0.35 \pm 0.02$, $x_-=-0.31\pm 0.20 \pm 0.04$, $y_+=-0.81\pm 0.28\pm 0.06$ and $y_-=0.31\pm 0.21 \pm 0.05$, where the first uncertainties are statistical and the second systematic. These observables correspond to values $\gamma$ = $(71 \pm 20)^\circ$, $r_{B^0} = 0.56\pm 0.17$ and $\delta_{B^0} = (204\,^{+21}_{-20})^\circ$.  The parameters $r_{B^0}$ and $\delta_{B^0}$ are the magnitude ratio and strong phase difference between the suppressed and favoured $B^0$ decay amplitudes, and have been measured in a region of $\pm 50\mevcc$ around the $\Kstar(892)^{0}$ mass and with the magnitude of the cosine of the $\Kstar(892)^{0}$ helicity angle larger than 0.4.