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The Discrepancy Between tau and e+e- Spectral Functions Revisited and the Consequences for the Muon Magnetic Anomaly
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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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Forward citations
Cited by 2 Pith papers
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The anomalous magnetic moment of the muon in the Standard Model: an update
The updated SM prediction for the muon anomalous magnetic moment is 116592033(62)×10^{-11}, showing no tension with the experimental average of 38(63)×10^{-11}.
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Comparison of the hadronic vacuum polarization between hadronic $\tau$-decay data and lattice QCD
Lattice QCD and tau-decay dispersive calculations of isospin-one HVP generally agree, except for a significant difference in the 2π−π+π0 four-pion mode contribution to window quantities.
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