Observation of B̄0 → D0η′ and B̄0 → D*0η′

We report the observation of B̄0 → D 0η′ and the first observation of B̄0 → D0η′, using 140 fb-1 of data collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. We find the branching fractions to be B(B̄0 → D0η′) = [1.14 ± 0.20(stat) + 0.10 -0.13(syst)] × 10-4 and B(B̄0 → D0η′) = [1.21 ± 0.34(stat) ± 0.22(syst)] × 10-4 with significances including systematic uncertainties of 8.9 and 5.3 standard deviations, respectively. © 2005 The American Physical Society.