Hadronic Structure in the Decay $\tau^{-}\to \pi^{-}\pi^{0}\nu_{\tau}$

TL;DR

This paper analyzes the invariant mass spectrum of the hadronic system in tau decay to pi- pi0 nu_tau, fitting resonance models and comparing with e+ e- data to test theoretical principles and implications for muon magnetic moment estimates.

Contribution

It provides new measurements of resonance parameters and spectral functions in tau decay, testing the Conserved Vector Current theorem and informing muon g-2 calculations.

Findings

Resonance parameters for rho(770) and rho(1450) determined.

Spectral function consistent with e+ e- data within uncertainties.

Implications for hadronic contributions to muon g-2 discussed.

Abstract

We report on a study of the invariant mass spectrum of the hadronic system in the decay tau- -> pi- pi0 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(770) and rho(1450) mesons are determined. The pi- pi0 spectral function inferred from the invariant mass spectrum is compared with data on e+ e- -> 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.