We describe in this paper the QCD prediction to calculate the strong coupling constant by using event shape variables as well as momentum spectra. By fitting the dispersive model and employing our parameters, on event shape distribution, we obtain the perturbative value of alpha_s(MZ0 ) = 0.1305 +- 0.0474 and also the nonperturbative value of alpha_0 = 0.5246+- 0.0516(GeV ) for ep interactions . Next by using momentum spectra for the same interactions, we obtain s = 0:1572 0:029. Our values in both methods are consistent with those values obtained from electron positron annihilations measured previously. When we find coupling constant for different flavors, we observe that, they do not affect our results considerably. This is in accord with the QCD theory. All these features will be explained in the main text.

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