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The Discrepancy Between tau and e+e- Spectral Functions Revisited and the Consequences for the Muon Magnetic Anomaly

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.
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http://hal.in2p3.fr/in2p3-00455617
Contributor : Sabine Starita <>
Submitted on : Wednesday, February 10, 2010 - 5:38:17 PM
Last modification on : Wednesday, September 16, 2020 - 4:21:49 PM

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M. Davier, A. Hoecker, G. Lopez Castro, B. Malaescu, X. H. Mo, et al.. The Discrepancy Between tau and e+e- Spectral Functions Revisited and the Consequences for the Muon Magnetic Anomaly. European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2010, 66, pp.127-136. ⟨10.1140/epjc/s10052-009-1219-4⟩. ⟨in2p3-00455617⟩

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