Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
2000-05-09
Phys.Rev. D62 (2000) 113001
Physics
High Energy Physics
High Energy Physics - Phenomenology
12 pages, LaTeX; a few typos corrected, references added
Scientific paper
10.1103/PhysRevD.62.113001
We analyze the basic hard exclusive processes: \pi\gamma*\gamma - transition, pion and nucleon electromagnetic form factors, and discuss the analytic continuation of QCD formulas from the spacelike q^2<0 to the timelike region q^2 >0 of the relevant momentum transfers. We describe the construction of the timelike version of the coupling constant \alpha_s. We show that due to the analytic continuation of the collinear logarithms each eigenfunction of the evolution equation acqiures a phase factor and investigate the resulting interference effects which are shown to be very small. We found no sources for the K-factor-type enhancements in the perturbative QCD contribution to the hadronic form factors. To study the soft part of the pion electromagnetic form factor, we use a QCD sum rule inspired model and show that there are non-canceling Sudakov double logarithms which result in a K-factor-type enhancement in the timelike region.
Bakulev Alexander P.
Radyushkin Anatoly V.
Stefanis N. G.
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