Study of pure annihilation decays Bd,s→D0D0

Within the heavy quark limit and the hierarchy approximation λ_QCD<< m_D<B, we analyze the B→D⁰D⁰ and B_s→D⁰D⁰ decays, which occur purely via annihilation type diagrams. As a rough estimate, we calculate their branching ratios and CP asymmetries in the perturbative QCD (PQCD) approach. The branching ratio of B→D⁰D⁰ is about 3.8×10^－5 that is just below the latest experimental upper limit. The branching ratio of B_s→D⁰D⁰ is about 6.8×10^－4, which could be measured in LHC-b. From the calculation, it is found that this branching ratio is not sensitive to the weak phase angle γ. In these two decay modes, there exist CP asymmetries because of the interference between weak and strong interaction. However, these asymmetries are too small to be measured easily.