PION FORM FACTOR IN QCD SUM RULES WITH NONLOCAL CONDENSATES AND IN THE LOCAL-DUALITY APPROACH

Abstract

We discuss the QCD sum-rule approach for the spacelike electromagnetic pion form factor in the O(αs) approximation. We show that the nonlocality of the condensates is a key point to include nonperturbative contributions to the pion form factor. We compare our results with the Local-Duality predictions and show that the continuum threshold s0(Q2) parameter is highly underestimated in the Local-Duality approach at Q2 ≳ 2 GeV 2. Using our fit for this parameter, [Formula: see text] and applying the fractional analytic perturbation theory, we estimate with an accuracy of the order of 1% the [Formula: see text] contribution to the pion's form factor.