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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/in2p3-00429651
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Submitted on : Thursday, January 28, 2010 - 5:22:28 PM
Last modification on : Tuesday, June 30, 2020 - 10:00:34 AM
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EPS-HEP_2009_373.pdf
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  • HAL Id : in2p3-00429651, version 1

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M. Davier, M. 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. 2009 Europhysics Conference on High Energy Physics (EPS HEP 2009), Jul 2009, Krakow, Poland. pp.373. ⟨in2p3-00429651⟩

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