FORM-FACTOR OF THE PROCESS GAMMA-ASTERISK-GAMMA-ASTERISK-]PI-0 QCD SUM-RULES (I) - STRUCTURE OF THE INFRARED SINGULARITIES

The method of QCD sum rules is used to study the form factor F(gamma*gamma*-->pi0)(q1(2),q2(2)) in the region of small virtuality of one of the photons (\q1(2)\ much less than \q2(2)\ greater than or similar to 1 GeV2), where it is necessary to factorize the contributions of large and small distances. As a first step the form factor is investigated in the region of moderate vitualities (\q1(2)\ approximately \q2(2)\ greater-than-or-equal-to 1 GeV2), where the total [0\G(munu)(alpha)G(munu)alpha\0], [0\psipsiBAR\0]2 corrections in the sum rule are obtained. It is shown that the infrared (mass) singularities can be subtracted in the corresponding operator expansion for essentially nonsymmetric kinematics due to the operators of the lowest two twists. For a simple scalar example the most important steps of the further calculations are demonstrated.