Complete next-to-leading order perturbative QCD prediction for the pion form factor
Abstract
We present the results of a complete leading-twist next-to-leading order QCD analysis of the spacelike pion electromagnetic form factor at large momentum transfer Q^2. We have studied their dependence on the form of the pion distribution amplitude and, out of the four distribution amplitudes considered, found that the final choice should be made between the asymptotic and the Chernyak - Zhitnitsky (CZ) distribution amplitudes. We have also examined the sensitivity of the predictions based on these two distributions to the choice of the renormalization and factorization scales.Choosing the renormalization scale to be of the order of the average virtuality of the particles in the corresponding parton subprocess, we have found that the next-to-leading order prediction for the pion form factor can reliably be calculated at momentum transfers of about 15 GeV^2 and 30 GeV^2 for the asymptotic and the CZ distribution amplitudes, respectively, with the correction to the leading-order results being of the order of ~20%. The difference between the results for the asymptotic and the CZ distribution amplitudes is sufficiently large for an unambiguous discrimination between these two distributions when the experimental data are obtained at higher Q^2 values.Keywords
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