Hadronic part of the tauʹs (g - 2) from QCD

The hadronic part of the tauʹs (g - 2), aH(τ), is relatively important due to the large mass of the lepton. A purely theoretical calculation of aH(τ), using QCD and the analytic properties of the vacuum polarization tensor is presented. We obtain aH(τ) ≅ 3 × 10−6 as compared to the pure QED contribution aQED(τ) = 1.17319 × 10−3.