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

Abstract

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 energeticK ⁰ _s 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 α_s 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 α_s values for quarks of diffrent weak isospin, charge and generation. No evidence for a dependence of α_s on any of these quark properties is observed. Finally, combining all samples and determining the α ^f_s /α ^incl_s ratio for each flavour, we do not find any dependence of the strong coupling constant on flavour.