Strong coupling constant from τ decay within a renormalization scheme invariant treatment

We extract a numerical value for the strong coupling constant ${\alpha }_s$ from the $\tau$-lepton decay rate into nonstrange particles. A new feature of our procedure is the explicit use of renormalization scheme invariance in analytical form in order to perform the actual analysis in a particular renormalization scheme. For the reference coupling constant in the $\overline{\mathrm{MS}}$ scheme we obtain ${\alpha }_s{(M}_{\tau })=0.3184\mathrm{}\pm {0.0060}_{\mathrm{expt}}$ which corresponds to ${\alpha }_s{(M}_Z)=0.1184\mathrm{}\pm {0.0007}_{\mathrm{expt}}\pm {0.0006}_{\mathrm{hq}\hspace{0.5em}\mathrm{mass}}.$ This new numerical value is smaller than the standard value from $\tau$ data quoted in the literature and is closer to ${\alpha }_s{(M}_Z)$ values obtained from high energy experiments.