Test of the flavour independence of $\alpha_s$ using next-to-leading order calculations for heavy quarks

Abstract.

We present a test of the flavour independence of the strong coupling constant for charm and bottom quarks with respect to light (uds) quarks, based on a hadronic event sample obtained with the OPAL detector at LEP. Five observables related to global event shapes were used to measure $\alpha_s$ in three flavour tagged samples (uds, c and b). The event shape distributions were fitted by $\mathcal{O} (\alpha^2_s)$ calculations of jet production taking into account mass effects for the c and b quarks. We find: \begin{eqnarray*} \alpha^{\rm c}_s/\alpha^{\rm uds}_s&=& 0.997 \pm 0.038 (stat.) \pm 0.030 (syst.) \pm 0.012 (theory)\quad \mbox{ and} \nonumber \alpha^{\rm bh}_s/\alpha^{\rm uds}_s &=& 0.993 \pm 0.008 (stat.) \pm 0.006 (syst.) \pm 0.011 (theory). \end{eqnarray*}