Measurement of Ratios of Branching Fractions and CP-Violating Asymmetries of B -> D*K Decays

TL;DR

This study measures ratios of branching fractions and CP asymmetries in B -> D*K decays using a large dataset, providing insights into the unitarity triangle angle gamma and testing CP violation.

Contribution

The paper presents the first measurement of CP asymmetries and branching fraction ratios in B -> D*K decays with detailed analysis of various D meson decay modes.

Findings

Measured CP asymmetries A*_{CP+} and A*_{CP-} consistent with no CP violation.

Determined ratios R*_{CP+} and R*_{CP-} with uncertainties, constraining gamma.

Derived parameters x*_{+} and x*_{-} related to the unitarity triangle angle.

Abstract

We report a study of B -> D*K decays with D* decaying to D pi0 or D gamma, using 383 * 10**6 B Bbar pairs collected at the Upsilon(4S) resonance with the BaBar detector at the SLAC PEP-II B-Factory. The D meson decays under study include a non-CP mode (Kpi), CP-even modes (K+K-, pi^+pi^-) and CP-odd modes (KS pi0, KS phi, KS omega). We measure ratios (R*_{CP+-}) of branching fractions of decays to CP eigenmode states and to flavor-specific states as well as CP asymmetries (A*_{CP+-}). 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 -> K pi or in B -> D* pi decays.