First observations and measurements of the branching fractions of thedecays are presented using 1:0 fb À1 of data collected by the LHCb experiment. These branching fractions are normalized to those of "respectively. An excess of events consistent with the decay " B 0 ! D 0 " D 0 is also seen, and its branching fraction is measured relative to that of B À ! D 0 D À s . Improved measurements of the branching fractionsThe ratios of branching fractions are