Duality violations in τ hadronic spectral moments

Evidence is presented for the necessity of including duality violations in a consistent description of spectral function moments employed in the precision determination of αs from τ decay. A physically motivated ansatz for duality violations in the spectral functions enables us to perform fits to spectral moments employing both pinched and unpinched weights. We describe our analysis strategy and provide some preliminary findings. Final numerical results await completion of an ongoing re-determination of the ALEPH covariance matrices incorpo-rating correlations due to the unfolding procedure which are absent from the currently posted versions. To what extent this issue affects existing analyses and our own work will require further study. © 2011 Elsevier B.V.