Analyticity and minimality of nonperturbative contributions in perturbative region for (α)over-bars

It is shown that the possibility of freezing a QCD running coupling constant at zero with the approach of "forced analyticity" is not in agreement with Schwinger-Dyson equation for the gluon propagator. We propose to add to the analytic expression the well-known infrared singular term 1/q(2) as well as a pole term corresponding to "excited gluon". By this example we formulate the principle of minimality of nonperturbative contributions in perturbative (ultraviolet) region, which allows us to fix ambiguities when introducing nonperturbative terms and maintain the finiteness of the gluon condensate. As a result, we obtain estimates of the gluon condensate, which agree quite well with the existing data. The value of the "excited gluon" mass is also of considerable interest.