Measurement of ratios of branching fractions and CP-violating asymmetries of B±→D*K± decays

We report a study of B±→D*K± decays with D* decaying to Dπ0 or Dγ, using 383×10^6 BB̅ pairs collected at the Υ(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±π∓), CP-even modes (K±K∓,π±π∓), and CP-odd modes (KS0π0,KS0ϕ,KS0ω). We measure ratios (RCP±*) of branching fractions of decays to CP eigenmode states and to flavor-specific states as well as CP asymmetries (ACP±*). These measurements are sensitive to the unitarity triangle angle γ. We obtain ACP+*=-0.11±0.09±0.01, RCP+*=1.31±0.13±0.04, and ACP-*=0.06±0.10±0.02, RCP-*=1.10±0.12±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±0.06±0.02 and x-*=0.00±0.06±0.02. No significant CP-violating charge asymmetry is found in either the flavor-specific mode D→K±π∓ or in B±→D*π± decays.