Perturbative Logarithms and Power Corrections in QCD Hadronic Functions.
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I present a unifying scheme for hadronic functions that comprises logarithmic corrections due to gluon emission in perturbative QCD, as well as power-behaved corrections of nonperturbative origin. The latter are derived by demanding that perturbatively resummed partonic observables should be analytic in the whole Q 2-plane if they are to be related to physical observables measured in experiments. I also show phenomenological consequences of this approach. The focus is on the electromagnetic pion form factor to illustrate both effects, Sudakov logarithms and power corrections in leading order of Λ2 QCD/Q 2. The same approach applied to the inclusive Drell-Yan cross section enables us to perform an absolutely normalized calculation of the leading power correction in b 2Λ2 QCD (b being the impact parameter), which after exponentiation, gives rise to a nonperturbative Sudakov-type contribution that provides enhancement rather than suppression, hence partly counteracting the perturbative Sudakov suppression.
KeywordsForm Factor Transverse Momentum Power Correction Pion Form Factor Sudakov Form Factor
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