Measurement of ratios of branching fractions andCP-violating asymmetries ofB±→D*K±decays

We report a study of $B^{\pm }\to D^{*}{K}^{\pm }$ decays with $D^{*}$ decaying to $D{\pi }^0$ or $D\gamma$, using $383\times {10}^6$ $B\overline{B}$ pairs collected at the $\mathit{{\rm Y}}(4S)$ resonance with the BABAR detector at the SLAC PEP-II $B$ Factory. The $D$ meson decays under study include a non-$CP$ mode $(K^{\pm }{\pi }^{\mp })$, $CP$-even modes $(K^{\pm }{K}^{\mp },{\pi }^{\pm }{\pi }^{\mp })$, and $CP$-odd modes $(K_S^0{\pi }^0,K_S^0\varphi ,K_S^0\omega )$. We measure ratios ($R_{CP\pm }^{*}$) of branching fractions of decays to $CP$ eigenmode states and to flavor-specific states as well as $CP$ asymmetries ($A_{CP\pm }^{*}$). These measurements are sensitive to the unitarity triangle angle $\gamma$. We obtain $A_{CP+}^{*}=-0.11\pm 0.09\pm 0.01$, $R_{CP+}^{*}=1.31\pm 0.13\pm 0.04$, and $A_{CP-}^{*}=0.06\pm 0.10\pm 0.02$, $R_{CP-}^{*}=1.10\pm 0.12\pm 0.04$, where the first error is statistical and the second error is systematic. Translating our results into an alternative parametrization, widely used for related measurements, we obtain $x_{+}^{*}=0.11\pm 0.06\pm 0.02$ and $x_{-}^{*}=0.00\pm 0.06\pm 0.02$. No significant $CP$-violating charge asymmetry is found in either the flavor-specific mode $D\to K^{\pm }{\pi }^{\mp }$ or in $B^{\pm }\to D^{*}{\pi }^{\pm }$ decays.