${\alpha }_s$ from the updated ALEPH data for hadronic $\tau$ decays

We extract the strong coupling ${\alpha }_s(m_{\tau }^2)$ from the recently updated ALEPH non-strange spectral functions obtained from hadronic $\tau$ decays. We apply a self-consistent analysis method, first tested in the analysis of OPAL data, to extract ${\alpha }_s(m_{\tau }^2)$ and non-perturbative contributions. The analysis yields ${\alpha }_s^{\mathrm{F}\mathrm{O}}(m_{\tau }^2)=0.296\pm 0.010$, using Fixed Order Perturbation Theory (FOPT), and ${\alpha }_s^{\mathrm{C}\mathrm{I}}(m_{\tau }^2)=0.310\pm 0.014$, using Contour Improved Perturbation Theory (CIPT). The weighted average of these results with those previously obtained from OPAL data give $\alpha_s^{\rm FO}(m_\tau^2)=0.303\pm 0.009$and$\alpha_s^{\rm CI}(m_\tau^2)=0.319\pm 0.012$, which gives, after evolution to the $Z$ boson mass scale, $\alpha^{\rm FO}_s(m_Z^2)=0.1165\pm0.0012 $and$\alpha_s^{\rm CI}(m_Z^2)=0.1185\pm0.0015 $, respectively. We observe that non-perturbative effects limit the accuracy with which ${\alpha }_s$ can be extracted from $\tau$ decay data.