CCAST, World Lab, Beijing 100080, Peoples R China
; CAS, Inst High Energy Phys, Beijing 100049, Peoples R China
The rare decay B-0 -> phi phi can occur only via the penguin annihilation topology in the standard model. We calculate this channel in the perturbative QCD approach. The predicted branching ratio is very small: around 10(-8). We also give the polarization fractions, which show that the transverse polarization contribution is comparable to the longitudinal one, due to a big transverse contribution from factorizable diagrams. The small branching ratio in SM makes it sensitive to any new physics contributions.