Mass Dependent αₛ Evolution and the Light Gluino Existence

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There is an intriguing discrepancy between αₛ(MZ) values measured directly at the CERN Z₀-factory and low-energy (at few GeV) measurements transformed to Q=MZ₀ by a massless QCD αₛ(Q) evolution relation. There exists an attempt to reconcile this discrepancy by introducing a light gluino in the MSSM. We study in detail the influence of heavy thresholds on αₛ(Q) evolution. First, we consruct the "exact" explicit solution to the mass-dependent two-loop RG equation for the running αₛ(Q). This solution describes heavy thresholds smoothly. Second, we use this solution to recalculate anew αₛ(MZ) values corresponding to "low-energy" input data. Our analysis demonstrates that using mass-dependent RG procedure generally produces corrections of two types: Asymptotic correction due to effective shift of threshold position; Local threshold correction only for the case when input experiment lies in the close vicinity of heavy particle threshold: Qexpt ≃ Mₕ. Both effects result in the effective shift of the values of the order of 10⁻³. However, the second one could be enhanced when the gluino mass is close to a heavy quark mass. For such a case the sum effect could be important for the discussion of the light gluino existence as it further changes the mass.