A High Statistics Study of the Decay τ− → π−π0ντ

We report a measurement of the branching fraction for τ−→π−π0ντ and the invariant mass spectrum of the resulting π−π0 system using 72.2 fb−1 of data recorded by the Belle detector at the KEKB e+e− collider. The branching fraction obtained is (25.15 ± 0.04 ± 0.31)%, where the first error is statistical and the second is systematic. The unfolded π−π0 mass spectrum is used to determine resonance parameters for the ρ(770), ρ′(1450), and ρ″(1700) mesons. We also use this spectrum to estimate the hadronic contribution to the anomalous magnetic moment of the muon.