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

Abstract

We report a study of B ± → D ∗ K ± decays with D ∗ decaying to D π 0 or D γ , using 383 × 10 6 B ¯¯¯ B pairs collected at the Υ ( 4 S ) resonance with the BABAR detector at the SLAC PEP-II B Factory. The D meson decays under study include a non- C P mode ( K ± π ∓ ) , C P -even modes ( K ± K ∓ , π ± π ∓ ) , and C P -odd modes ( K 0 S π 0 , K 0 S ϕ , K 0 S ω ) . We measure ratios ( R ∗ C P ± ) of branching fractions of decays to C P eigenmode states and to flavor-specific states as well as C P asymmetries ( A ∗ C P ± ). These measurements are sensitive to the unitarity triangle angle γ . We obtain A ∗ C P + = − 0.11 ± 0.09 ± 0.01 , R ∗ C P + = 1.31 ± 0.13 ± 0.04 , and A ∗ C P − = 0.06 ± 0.10 ± 0.02 , R ∗ C P − = 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 C P -violating charge asymmetry is found in either the flavor-specific mode D → K ± π ∓ or in B ± → D ∗ π ± decays.