Pion parameters and four quark condensates from τ-decay data

A modified finite energy sum rules procedure is presented and applied for the phenomenological analysis of the difference of vector and axial-vector two point current correlators. In the chiral limit π→eνγ decay axial formfactor FA, electro-magnetic difference of pion masses and the four quark condensates of dimensions six and eight are determined with improved accuracy, using the data on τ→ν+nπ decays obtained by ARGUS collaboration. Our values for FA and Δmem are close to the measured ones, while C6 exceeds 2.5-3 times the value given by the vacuum saturation hypothesis. (orig.)