A test of the flavour independence of the strong interaction for five flavours

We report on a measurement of the ratio of the strong coupling constants$$\alpha _s (M_{Z^0 } )$$ for various data samples with different quark flavour compositions obtained frome+e− annihilation at LEP. We select events with muons, electrons, andD*± mesons from charm and bottom decays, events with highly energeticKs0 mesons originating predominantly from strange quarks, and events with highly energetic stable charged particles from a combination of up, down and strange quarks. From the jet production rates in these events we obtain from these samples the relative value of αs for the individual quark flavours as$$\begin{gathered} \frac{{\alpha _s^b }}{{\alpha _s^{udsc} }} = 1.017 \pm 0.036,\frac{{\alpha _s^c }}{{\alpha _s^{udsb} }} = 0.918 \pm 0.115, \hfill \\ \frac{{\alpha _s^s }}{{\alpha _s^{udcb} }} = 1.158 \pm 0.164,\frac{{\alpha _s^{uds} }}{{\alpha _s^{cb} }} = 1.038 \pm 0.221, \hfill \\ \end{gathered}$$ with quadratically combined statistical and systematic errors. We also compare the αs values for quarks of diffrent weak isospin, charge and generation. No evidence for a dependence of αs on any of these quark properties is observed. Finally, combining all samples and determining the αsf/αsincl ratio for each flavour, we do not find any dependence of the strong coupling constant on flavour.