1,292 research outputs found
QCD coupling up to third order in standard and analytic perturbation theories
We analyze two sets of specific functions, that/which form the basis of the
nonpower asymptotic expansions both in the timelike and spacelike regions for
single scale dependent QCD observables in the Shirkov--Solovtsov's Analytic
Perturbation Theory (APT) free of unphysical singularities. These functions are
explicitly derived up to the third order in the closed form in terms of the
Lambert-W function. As an input we used the exact two loop and the three loop
(corresponding to Pad\'e transformed beta-function) RG solutions for common
invariant coupling \alpha_s. The elegant recurrence formulas, helpful for
numerical analysis, are obtained for the both sets of the APT functions. Then
we construct the global versions of APT functions using the continuity
conditions (at the quark thresholds) on the \alpha_s in the \bar{MS} scheme and
give numerical results. For first three of these functions \mathfrak{A}_n(s)
and {\cal A}_n(Q^2); n=1,2,3 in the large interval of the momentum transfer and
energy (1 GeV <Q,{\sqrt s}< 170 GeV), numerical tables are presented. From
these we observe that, for the timelike arguments, the differences between
functions \mathfrak{A}_n(s) and the corresponding powers of the standard
iteratively approximated coupling \alpha_s^n(s) are not negligible even for
moderate energies in the five--flavor region.Comment: 21 pages, Latex, 12 tables. Abstract is changed. The recurrence
formulas (18)-(20) are added. Formula (35) corrected and Table 2 is revised.
Misprint in formula (37) is corrected. Formula (38) adde
Generalization of the BLM procedure and its scales in any order of pQCD
The Brodsky--Lepage--Mackenzie procedure is sequentially and unambiguously
extended to any fixed order of perturbative QCD beyond the so called
``large--\beta_0 approximation''. As a result of this procedure, the obtained
perturbation series looks like a continued-fraction representation. A
subsequent generalization of this procedure is developed, in order to optimize
the convergence of the final series, along the lines of the Fastest Convergence
Prescription. This generalized BLM procedure is applied to the Adler D function
and also to R_{e^+e^-} in QCD at NLO. A further extension of the sequential
BLM is presented which makes use of additional parameters to optimize the
convergence of the power-series at any fixed order of expansion.Comment: 24 pages, JHEP3, 4 figures are enclosed as eps-file, final version to
be published in JHE
Monitoring and Optimization of ATLAS Tier 2 Center GoeGrid
The demand on computational and storage resources is growing along with the amount of infor-
mation that needs to be processed and preserved. In order to ease the provisioning of the digital
services to the growing number of consumers, more and more distributed computing systems and
platforms are actively developed and employed. The building block of the distributed computing
infrastructure are single computing centers, similar to the Worldwide LHC Computing Grid, Tier
2 centre GoeGrid. The main motivation of this thesis was the optimization of GoeGrid perfor-
mance by efficient monitoring. The goal has been achieved by means of the GoeGrid monitoring
information analysis. The data analysis approach was based on the adaptive-network-based
fuzzy inference system (ANFIS) and machine learning algorithm such as Linear Support Vector
Machine (SVM).
The main object of the research was the digital service, since availability, reliability and ser-
viceability of the computing platform can be measured according to the constant and stable
provisioning of the services. Due to the widely used concept of the service oriented architecture
(SOA) for large computing facilities, in advance knowing of the service state as well as the quick
and accurate detection of its disability allows to perform the proactive management of the com-
puting facility. The proactive management is considered as a core component of the computing
facility management automation concept, such as Autonomic Computing. Thus in time as well
as in advance and accurate identification of the provided service status can be considered as a
contribution to the computing facility management automation, which is directly related to the
provisioning of the stable and reliable computing resources.
Based on the case studies, performed using the GoeGrid monitoring data, consideration of the
approaches as generalized methods for the accurate and fast identification and prediction of the
service status is reasonable. Simplicity and low consumption of the computing resources allow
to consider the methods in the scope of the Autonomic Computing component
Complete Renormalization Group Improvement-Avoiding Factorization and Renormalization Scale Dependence in QCD Predictions
For moments of leptoproduction structure functions we show that all
dependence on the renormalization and factorization scales disappears, provided
that all the ultraviolet logarithms involving the physical energy scale Q are
completely resummed. The approach is closely related to Grunberg's method of
Effective Charges. A direct and simple method for extracting the universal
dimensional transmutation parameter of QCD from experimental data is advocated.Comment: 16 pages, no figure
FAPT: a Mathematica package for calculations in QCD Fractional Analytic Perturbation Theory
We provide here all the procedures in \texttt{Mathematica} which are needed
for the computation of the analytic images of the strong coupling constant
powers in Minkowski ( and ) and Euclidean (
and ) domains at arbitrary energy scales
( and , correspondingly) for both schemes --- with fixed number of
active flavours and the global one with taking into account
all heavy-quark thresholds. These singularity-free couplings are inevitable
elements of Analytic Perturbation Theory (APT) in QCD and its generalization
--- Fractional APT, needed to apply the APT imperative for
renormalization-group improved hadronic observables.Comment: 23 pages, 6 figures. Citations added. Now it matches version approved
for publication in Comp. Phys. Commu
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