Observation of (B)over-bar(0)->(D)over-bar(0)eta ' and (B)over-bar(0)->(D)over-bar(*0)eta '

We report the observation of (B) over bar (0)-> D(0)eta' and the first observation of (B) over bar (0)-> D(*0)eta', using 140 fb(-1) of data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e(+)e(-) collider. We find the branching fractions to be B((B) over bar (0)-> D(0)eta')=[1.14 +/- 0.20(stat)+0.10-0.13(syst)] x 10(-4) and B((B) over bar (0)-> D(*0)eta')=[1.21 +/- 0.34(stat)+/- 0.22(syst)] x 10(-4) with significances including systematic uncertainties of 8.9 and 5.3 standard deviations, respectively.