15 research outputs found
The Bjorken Sum Rule in the Analytic Approach to Perturbative QCD
Results of applying analytic perturbation theory (APT) to the Bjorken sum
rule are presented. We study the third-order QCD correction within the analytic
approach and investigate its renormalization scheme dependence. We demonstrate
that, in the framework of the method, theoretical predictions of the Bjorken
sum rule are, practically, scheme independent for the entire interval of
momentum transfer.Comment: 12 pages, 3 eps figures, uses elsart.cl
The Adler Function for Light Quarks in Analytic Perturbation Theory
The method of analytic perturbation theory, which avoids the problem of
ghost-pole type singularities and gives a self-consistent description of both
spacelike and timelike regions, is applied to describe the "light" Adler
function corresponding to the non-strange vector channel of the inclusive decay
of the lepton. The role of threshold effects is investigated. The
behavior of the quark-antiquark system near threshold is described by using a
new relativistic resummation factor. It is shown that the method proposed leads
to good agreement with the ``experimental'' Adler function down to the lowest
energy scale.Comment: 13 pages, one ps figure, REVTe
Remark on the perturbative component of inclusive -decay
In the context of the inclusive -decay, we analyze various forms of
perturbative expansions which have appeared as modifications of the original
perturbative series. We argue that analytic perturbation theory, which combines
renormalization-group invariance and -analyticity, has significant merits
favoring its use to describe the perturbative component of -decay.Comment: 5 pages, ReVTEX, 2 eps figures. Revised paper includes clarifying
remarks and corrected references. To be published in Phys. Rev.
Ten years of the Analytic Perturbation Theory in QCD
The renormalization group method enables one to improve the properties of the
QCD perturbative power series in the ultraviolet region. However, it ultimately
leads to the unphysical singularities of observables in the infrared domain.
The Analytic Perturbation Theory constitutes the next step of the improvement
of perturbative expansions. Specifically, it involves additional analyticity
requirement which is based on the causality principle and implemented in the
K\"allen--Lehmann and Jost--Lehmann representations. Eventually, this approach
eliminates spurious singularities of the perturbative power series and enhances
the stability of the latter with respect to both higher loop corrections and
the choice of the renormalization scheme. The paper contains an overview of the
basic stages of the development of the Analytic Perturbation Theory in QCD,
including its recent applications to the description of hadronic processes.Comment: 26 pages, 9 figures, to be published in Theor. Math. Phys. (2007
The Gross--Llewellyn Smith Sum Rule in the Analytic Approach to Perturbative QCD
We apply analytic perturbation theory to the Gross--Llewellyn Smith sum rule.
We study the evolution and the renormalization scheme dependence of the
analytic three-loop QCD correction to this sum rule, and demonstrate that the
results are practically renormalization scheme independent and lead to rather
different evolution than the standard perturbative correction possesses.Comment: 17 pages, 9 eps figures, REVTe
Infrared Properties of QCD from Dyson-Schwinger equations
I review recent results on the infrared properties of QCD from
Dyson-Schwinger equations. The topics include infrared exponents of
one-particle irreducible Green's functions, the fixed point behaviour of the
running coupling at zero momentum, the pattern of dynamical quark mass
generation and properties of light mesons.Comment: 47 pages, 19 figures, Topical Review to be published in J.Phys.G, v2:
typos corrected and some references adde