Complete next-to-leading order perturbative QCD prediction for the pion electromagnetic form factor - art. no. 074004

We present the results of a complete leading-twist next-to-leading order (N LO) QCD analysis of the spacelike pion electromagnetic form factor at large momentum transfer Q. We have studied their dependence on the form of the p ion distribution amplitude, For a given distribution amplitude, we have exa mined the sensitivity of the predictions to the choice of the renormalizati on and factorization scales. Compared to the renormalization scale, the fac torization scale turns out to be of secondary importance. The renormalizati on scale dependence of the leading-order (LO) results has been significantl y reduced by including the NLO corrections. Adopting the criteria according to which a NLO prediction is considered reliable if both the ratio of the NLO to LO contributions and the strong coupling constant are reasonably sma ll, we find that reliable perturbative predictions for the pion electromagn etic form factor with all distribution amplitudes considered can already be made at a momentum transfer Q of the order 5-10 GeV, with corrections to t he LO results being up to similar to 30%. The theoretical uncertainty relat ed to the renormalization scale ambiguity has been estimated to be less tha n 10%. To check our predictions and to discriminate between the distributio n amplitudes, it is necessary to obtain experimental data extending to high er values of Q. [S0556-2821(99)03315-9].