Novel Sets of Coupling Expansion Parameters for low-energy pQCD
Abstract
In quantum theory, physical amplitudes are usually presented in the form of Feynman perturbation series in powers of coupling constant . However, it is known that these amplitudes are not regular functions at α=0 . For QCD, we propose new sets of expansion parameters wk() that reflect singularity at =0 and should be used instead of powers k. Their explicit form is motivated by the so called Analytic Perturbation Theory. These parameters reveal saturation in a strong coupling case at the level eff(1)= w1( 1) 0.5 . They can be used for quanitative analysis of divers low-energy amplitudes. We argue that this new picture with non-power sets of perturbation expansion parameters, as well as the saturation feature, is of a rather general nature.
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