Muon and tau anomalies updated

We present a new independent evaluation of the hadronic vacuum polarization contributions alhad(l.o.) ≡ 1/2 (g - 2)lhad(l.o.) to the anomalous magnetic moment (anomaly) of the muon and tau leptons using τ-decays and e+e- data. The alone theoretical input used for describing the high-energy region not accessible experimentally is perturbative QCD plus (negligible) additional effects due to the QCD vacuum condensates. We obtain: aμhad(l.o.) = 7020.6(75.6) × 10-11 and a τhad (l.o.) = 353.6(3.8) × 10-8, which we compare with previous determinations. Confronting the theoretical Standard Model (SM) predictions of aμ with the recent BNL measurement leads to aμnew ≡aμexp - aμSM = 333 (173) × 10-11. Combined with existing determinations, this leads to a conservative range: 112 ≡ aμnew × 1011 ≡ 573 at 90% CL, from which we derive lower bounds on the scales of some new physics. We also update our old and first predictionsof SM contributions to aτ. Including QED to sixth order, higher order hadronic and electroweak contributions, we obtain aτSM = 117 711 (12) × 10-8, waiting for a future precise measurement of aτ. © 2001 Elsevier Science B.V. All rights reserved.