Spectral functions from hadronic tau decays and QCD

Abstract

Hadronic decays of the $\tau$ lepton provide a clean environment to study hadron dynamics in an energy regime dominated by resonances. The interesting information is captured in the spectral functions. Recent results from ALEPH on exclusive channels are presented, with emphasis on the $π\piz$ final state which plays a crucial role for the determination of the hadronic contribution to the muon anomalous magnetic moment. A comparison between $2\pi$ spectral functions obtained in $\tau$ decays (after corrections for isospin-breaking) and $e^{+}{e}^{-}$ annihilation reveals some discrepancy in the line shape of the $\rho$ resonance which can be attributed to different pole mass values for the charged and neutral $\rho$'s, which are determined through a robust fitting procedure. However, after applying this correction, the normalization of the two spectral functions differ by 3.3%. Inclusive spectral functions are the basis for QCD analyses, which deliver an accurate determination of the strong coupling constant, quantitative information on nonperturbative contributions and a measurement of the mass of the strange quark.

11 pages, 8 figures, proceedings of the SIGHAD03 workshop (Pisa, October 2003) on e+ e- annihilation cross sections at low energy

References in corpus (1)

• Measurement of Branching Fractions in Tau Decays

Cited by in corpus (9)

• The Standard Model Prediction of the Muon Anomalous Magnetic Moment
• Vector and axial-vector correlators in a nonlocal chiral quark model
• Electron, muon and tau magnetic moments: a theoretical update
• Models of Isospin Breaking in the Pion Form Factor: Consequences for the Determination of Pi_{ρω}(m_rho^2) and (g-2)_mu/2
• Status of the Standard Model Prediction of the Muon g-2
• Isospin Breaking in the Relation Between the tau-->nu_tau pi pi and e^+e^- -->pi^+ pi^- Versions of |F_π(s)|^2$ and Implications for (g-2)_mu
• Prospects for e+e- physics at Frascati between the phi and the psi
• A Global Treatment Of VMD Physics Up To The phi: II. tau Decay and Hadronic Contributions To g-2
• Angular distribution asymmetry in tau^- --> pi^- pi^0 nu_tau decay in the two-Higgs-doublet model with large tan beta