Mass dependent αs evolution and the light gluino existence

There is an intriguing discrepancy between anti 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 anti αs(Q) evolution relation. There exists an attempt to reconcile this discrepancy by introducing a light gluino g in the MSSM. We study in detail the influence of heavy thresholds on anti αs(Q) evolution. First, we construct the ''exact'' explicit solution to the mass-dependent two-loop RG equation for the running anti αs(Q). This solution describes heavy thresholds smoothly. Second, we use this solution to recalculate a new anti 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 anti αs(MZ) 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 g mass. (orig.)