Nonfactorizable contributions in anti-B0 -> Ds+ Ds- and anti-Bs0 -> D+ D- decays

The decay amplitudes for anti-B0 -> Ds+ Ds- and anti-Bs0 -> D+ D- have no factorizable contributions. We suggest that dominant contributions to the decay amplitudes arise from two chiral loop contributions and one soft gluon emission contribution. Then we determine branching ratios BR(anti-B0 -> Ds+ Ds-) ~ 7E-5 and BR(anti-Bs0 -> D+ D-) ~ 1E-3.