A Study of Heavy Flavor Physics in the Lepton Sector

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Facility of making high statistics simulation of production and decays of τ lepton pairs and rare decays of b quark, and skimming these samples from experimental data, are established in Nagoya University. Nagoya University takes responsibility of managing skimmed data of τ lepton events in the Belle collaboration. Those samples are opened to Belle collaborators through network "hepnet-J".Physics analyses were carried out in two stages. One were processes from which sizeable results were expected with rather low statistics (order of 10^<6-7>) such as CP/T violation in τ pair production, electric dipole moment (EDM) of τ, Cp violation in τ decays, a search for lepton flavor violation in τ decays. Others were processes we needed to accumulate high statistics, such as precision measurement of hadron mass spectrum in τ decay final states, and FCNC rare decay of b-quark associated with leptons.CP/T asymmetry in τ pair production indicates EDM of τ. We obtained new upper limit of τ EDM, one order of magnitude smaller than the existing ones, using τ decay modes to eμ, eπ, μπ, eρ, μρ, πρ, ππ, ρρ. Decay angular distribution of τ→ππ^0ν satisfied CP symmetry within a measurement limit. Lepton flavor violation was examined in the search for τ→μγ process. We have got smaller upper limit than the present best value, and analysis is in progress aiming to renew the limit by order of magnitude.As for the FCNC decay b → sll, we searched exclusive process of B → K(*)e^+e^- and B → K(*)μ^+μ^-, and first obtained sizeable decay branching fraction of B → Kl^+l^-, for which only upper limit had been obtained. Accumulating strange hadronic states we also obtained sizeable branching fraction of inclusive b → sll process.Those results were presented in journals and several international conferences like LP01, ICHEP00, ICHEP02, and heavy flavor workshop.