5. Theoretical Physics (CSN4)

The strong coupling from hadronic tau decays

by Prof. Maarten Golterman (San Francisco State University)

Aula Seminari (LNF)

Aula Seminari


Via Enrico Fermi, 40 00044 Frascati (Roma)
We review our recent determination of the strong coupling $\alpha_s$ from the OPAL data for non-strange hadronic tau decays. We find that $\alpha_s(m^2_\tau) =0.325\pm 0.018$ using fixed-order perturbation theory, and $\alpha_s(m^2_\tau)=0.347\pm 0.025$ using contour-improved perturbation theory. These errors are larger than those claimed in previous determinations of $\alpha_s$ from tau decays. The reasons for this are several: (1) The spectral-data moments used in the standard analysis are likely to have an unreliable perturbative expansion, and OPE corrections have not been treated systematically; (2) Violations of quark-hadron duality have been ignored; (3) The nominally more precise ALEPH data are flawed because the correlation matrix is incomplete. We thus consider our determination to supersede all previous values.