6 research outputs found
The NNLO non-singlet QCD analysis of parton distributions based on Bernstein polynomials
A non-singlet QCD analysis of the structure function up to NNLO is
performed based on the Bernstein polynomials approach. We use recently
calculated NNLO anomalous dimension coefficients for the moments of the
structure function in scattering. In the fitting procedure, Bernstein
polynomial method is used to construct experimental moments from the
data of the CCFR collaboration in the region of which is inaccessible
experimentally. We also consider Bernstein averages to obtain some unknown
parameters which exist in the valence quark densities in a wide range of
and . The results of valence quark distributions up to NNLO are in good
agreement with the available theoretical models. In the analysis we determined
the QCD-scale MeV (LO), 259 MeV (NLO)
and 230 MeV (NNLO), corresponding to LO,
NLO and NNLO. We compare our
results for the QCD scale and the with those obtained from
deep inelastic scattering processes.Comment: 20 pages, 7 figures, published in JHE
The Jacobi Polynomials QCD analysis for the polarized structure function
We present the results of our QCD analysis for polarized quark distribution
and structure function . We use very recently experimental data
to parameterize our model. New parameterizations are derived for the quark and
gluon distributions for the kinematic range , GeV^2. The analysis is based on the Jacobi polynomials
expansion of the polarized structure functions. Our calculations for polarized
parton distribution functions based on the Jacobi polynomials method are in
good agreement with the other theoretical models. The values of
and are determined.Comment: 23 pages, 8 figures and 4 table
Non-perturbative momentum dependence of the coupling constant and hadronic models
Models of hadron structure are associated with a hadronic scale which allows
by perturbative evolution to calculate observables in the deep inelastic
region. The resolution of Dyson-Schwinger equations leads to the freezing of
the QCD running coupling (effective charge) in the infrared, which is best
understood as a dynamical generation of a gluon mass function, giving rise to a
momentum dependence which is free from infrared divergences. We use this new
development to understand why perturbative treatments are working reasonably
well despite the smallness of the hadronic scale.Comment: Changes in Acknowledgments and PACS number
The role of different schemes in the QCD analysis and determination of the strong coupling
In this article, we present a Next-to-Leading Order (NLO) QCD analysis to study the role and influence of different schemes on simultaneous determination of the Parton Distribution Functions (PDFs) and strong coupling, αs(MZ2). We perform our analysis based on three different data sets, HERA I and II combined data, H1-ZEUS charm combined data, and H1 and ZEUS beauty production cross sections data, in two different Thorne–Roberts (TR or RT) and Thorne–Roberts Optimal (RT OPT) schemes. We show in going from RT scheme to RT OPT scheme, in addition of reduction the uncertainty of some PDFs, specially for the gluon distribution, we get ∼0.4% and ∼0.7% improvement in the fit quality and ∼0.9% and ∼1.6% improvement for the strong coupling, αs(MZ2), without and with heavy flavor contributions, respectively