Bs(Bd) → γνν

We study the loop induced rare decays Bs(Bd) → γνν within the standard model. Both constituent quark model and pole model are used and the branching ratios turn out to be of the orders of 10−8 for Bs → γνν and 10−9 for Bd → γνν. These processes can be served to determine the decay constants of Bs and Bd.