Hadronic structure in the decay ${\tau }^{-}\to {\pi }^{-}{\pi }^0{\nu }_{\tau }$

We report on a study of the invariant mass spectrum of the hadronic system in the decay ${\tau }^{-}\to {\pi }^{-}{\pi }^0{\nu }_{\tau }.$ This study was performed with data obtained with the CLEO II detector operating at the CESR $e^{+}{e}^{-}$ collider. We present fits to phenomenological models in which resonance parameters associated with the $\rho \mathrm{}\left(770\right)\mathrm{}$ and $\rho \mathrm{}\left(1450\right)\mathrm{}$ mesons are determined. The ${\pi }^{-}{\pi }^0$ spectral function inferred from the invariant mass spectrum is compared with data on $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ as a test of the conserved vector current theorem. We also discuss the implications of our data with regard to estimates of the hadronic contribution to the muon anomalous magnetic moment.