New, efficient and clean strategies to explore CP violation through neutral B decays

Abstract

We point out that decays of the kind Bd→D±KS(L) and Bs→D±η(′),D±φ,…, where D+ and D− denote the CP-even and CP-odd eigenstates of the neutral D-meson system, respectively, provide very efficient, theoretically clean determinations of the angle γ of the unitarity triangle. In this new strategy, we use the B0q–B0q (q∈{d,s}) mixing phase φq as an input, and employ only “untagged” and mixing-induced CP-violating observables, which satisfy a very simple relation, allowing us to determine tanγ. Using a plausible dynamical assumption, γ can be fixed in an essentially unambiguous manner. The corresponding formalism can also be applied to Bd→D±π0,D±ρ0,… and Bs→D±KS(L) decays. Although these modes appear less attractive for the extraction of γ, they provide interesting determinations of sinφq. In comparison with the conventional Bd→J/ψKS(L) and Bs→J/ψφ methods, these extractions do not suffer from any penguin uncertainties, and are theoretically cleaner by one order of magnitude.