Misura del rapporto $r_{charm} = \alpha_{s}^{charm} / \alpha_{s}^{udsb}$ nei decadimenti adronici della $Z^0$

I have measured the ratio of the strong coupling constant for charm-gluon coupling alphascharm and for udsb-gluon coupling alphasudsb in hadronic decays of the Z0 boson. This measurement allows to test the flavour independence of the strong interactions. The analysis has been performed on a sample of 4.1 million hadronic Z0 decays collected by ALEPH between 1991 and 1995. The ratio of shape variables (c-par, thrust, y3Jade, -ln(y3Durham)) distributions between a charmed (D*) enriched sample and the whole hadronic sample has been computed. Comparing the ratio of experimental distributions with the ratio of second order p-QCD theoretical distributions, I have obtained as combined result: alphascharm/alphasudsb=0.936+-0.075 compatible with the flavour independence of the strong interactions. The effects between the p-QCD parton level prediction and the experimental data (hadronization, particle decays, experimental resolution, event selection ...), have been simulated using transfer matrices and weight vectors obtained by MonteCarlo simulations or by theoretical calculations.