The discrepancy between τ and e + e − spectral functions revisited and the consequences for the muon magnetic anomaly

2009/06/30 by M. Davier, A. Hoecker, G. Lopez Castro +8 · 166 citations
Physics and Astronomy · #Annihilation #Anomalous magnetic dipole moment #Anomaly (physics) #Branching fraction #Condensed matter physics #Hadron #High-Energy Particle Collisions Research #Isospin #Muon #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #Spectral function #hep-ph

paper · pdf · doi:10.1140/epjc/s10052-009-1219-4

published in The European Physical Journal C 66(1-2), 127-136 (Springer Science+Business Media) · 10 pages, 6 figures, submitted to Eur. Phys. J. C; (v2): Revised version with improved and uniform treatment of tau and e+e- data with HVPTools and a few minor bug fixes; (v3): Final version accepted for publication

arxiv created 2009/12/11 · openalex publication_date 2010/01/25 · arxiv updated 2014/11/20 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

We revisit the procedure for comparing the pi pi spectral function measured in tau decays to that obtained in e+e- annihilation. We re-examine the isospin-breaking corrections using new experimental and theoretical input, and find improved agreement between the tau- --> pi- pi0 nu_tau branching fraction measurement and its prediction using the isospin-breaking-corrected e+e- --> pi+pi- spectral function, though not resolving all discrepancies. We recompute the lowest order hadronic contributions to the muon g-2 using e+e- and tau data with the new corrections, and find a reduced difference between the two evaluations. The new tau-based estimate of the muon magnetic anomaly is found to be 1.9 standard deviations lower than the direct measurement.

Citations

• Review of Particle Physics
• Long distance radiative corrections to the decayτ−→π−π0ντ
• Improved predictions for g−2 of the muon and αQED(MZ2)
• Isospin breaking in the relation between theτ−→ντπ−π0ande+e−→π+π−versions of|Fπ(s)|2and implications for(g−2)μ
• Global aspects of current algebra
• Current algebra formulation of radiative corrections in gauge theories and the universality of the weak interactions
• CP violation and the CKM matrix: assessing the impact of the asymmetric B factories
• High-statistics measurement of the pion form factor in the ρ-meson energy range with the CMD-2 detector
• Decay Correlations of Heavy Leptons ine++e−→l++l−
• Big Bang Nucleosynthesis (in "The Review of Particle Properties" 2004)
• Improved determination of the hadronic contribution to the muon (

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