Lepton flavour violation in D and B decays at Belle

We search for the flavour-changing neutral current decays D0→μ+μ− and D0→e+e−, and for the lepton-flavour violating decays D0→e±μ∓ using of data. We also search for lepton-number violating decays B+→D−e+e+, B+→D−μ+μ+ and B+→D−μ+e+ using of data. All the data is collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. We find no evidence for any of these decays. We obtain significantly improved upper limits on the branching fractions: B(D0→μ+μ−)<1.4×10−7, B(D0→e+e−)<7.9×10−8, B(D0→e+μ−)+B(D0→μ+e−)<2.6×10−7, B(B+→D−e+e+)<2.6×10−6, B(B+→D−e+μ+)<1.6×10−6 and B(B+→D−μ+μ+)<0.9×10−6 at 90% confidence level.