Strong coupling constant at NNLO from DIS data

We discuss the results of our recent analysis [1] of deep inelastic scattering data on F2 structure function in the non-singlet approximation with next-to-next-to-leading-order accuracy. The study of high statistics deep inelastic scattering data provided by BCDMS, SLAC, NMC and BFP collaborations was performed with a special emphasis placed on the higher twist contributions. For the coupling constant the following value alfa_s(MZ2) = 0.1167 +- 0.0022 (total exp. error) was found.Comment: 6 pages, 2 figures, PoS(QFTHEP2010)050, presented on the XIXth International Workshop on High Energy Physics and Quantum Field Theory, 8-15 September 2010, Golitsyno, Moscow, Russi

The NNLO QCD analysis of the CCFR data for xF_3: is there still the room for the twist-4 terms?

The results of the more detailed NNLO QCD analysis of the CCFR data for $xF_3$ SF are presented. The factorization scale uncertainties are analysed. The NNLO results for $alpha_s(M_Z)$ and twist-4 contributions are obtained. Despite the fact that the amplitude of the $x$-shape of the twist-4 factor is consequently decreasing at the NLO and NNLO, our new QCD analysis seems to reveal the remaining twist-4 structure at the NNLO level. The definite N$^3$LO uncertainties are fixed using the [0/2] Pad\'e resummation technique.Comment: LaTeX, 3 pages, 1 figure; to be published in the Proceedings of DIS99 Workshop, Zeuthen, April 19-23; some technical shortcomings are fixed in the file, 2 referencies correcte

Effect of the analytic and frozen coupling constants in QCD up to NNLO from DIS data

We give a short review of our recent analysis [1] of the deep inelastic scattering data (provided by BCDMS, SLAC, NMC) on F2 structure function in the non-singlet approximation with up to next-to-next-to-leading-order accuracy and analytic and frozen modifications of the strong coupling constant featuring no unphysical singularity (the Landau pole). Improvement of agreement between theory and experiment, with respect to the case of the standard perturbative definition of the strong coupling constant considered recently in [2], was observed.Comment: 28pp, 7 figs, contribution to the Proceedings of XLV PNPI Winter School held in Roschino (Russia) on 28 feb - 5 March, 201

About QCD coupling constant at NNLO from DIS data

We give a brief review of our recent QCD analysis carried out over the deep inelastic scattering data on F2 structure function and in the non-singlet approximation to the accuracy up to next-to-next-to-leading-order. Specifically, analysis was performed over high statistics deep inelastic scattering data provided by BCDMS, SLAC, NMC and BFP collaborations. For the coupling constant the following value alpha_s(M_Z^2) = 0.1167 \pm 0.0022 was found.Comment: 11 pp, 2 figs, contribution to the Proceedings of XLIV PNPI Winter School held in Roschino (Russia) on 9-14 March, 201

The NLO DGLAP extraction of alpha_s and higher twist terms from CCFR xF_3 and F_2 structure functions data: results and scale dependence

We perform a detailed NLO analysis of the combined CCFR xF_3 and F_2 structure functions data and extract the value of alpha_s, parameters of distributions and higher-twist (HT) terms using a direct solution of the DGLAP equation. The value of alpha_s(M_Z)=0.1222\pm 0.0048 (exp) \pm 0.0026 (theor) is obtained. Our results has a larger central value and errors than the original one of the CCFR collaboration due to model independent parameterization of the HT contributions. The dependence of HT contributions on the QCD renormalization scale is studied.Comment: Contributed to Nucleon99 Proceedings (Frascati, June 7-9, 1999, Italy), to appear in Nucl.Phys.

An approach to NLO QCD analysis of the semi-inclusive DIS data with modified Jacobi polynomial expansion method

It is proposed the modification of the Jacobi polynomial expansion method (MJEM) which is based on the application of the truncated moments instead of the full ones. This allows to reconstruct with a high precision the local quark helicity distributions even for the narrow accessible for measurement Bjorken $x$ region using as an input only four first moments extracted from the data in NLO QCD. It is also proposed the variational (extrapolation) procedure allowing to reconstruct the distributions outside the accessible Bjorken $x$ region using the distributions obtained with MJEM in the accessible region. The numerical calculations encourage one that the proposed variational (extrapolation) procedure could be applied to estimate the full first (especially important) quark moments

Analytic and "frozen" QCD coupling constants up to NNLO from DIS data

Deep inelastic scattering data on the F_2 structure function provided by the BCDMS, SLAC and NMC collaborations are analyzed in the non-singlet approximation with the analytic and "frozen" modifications of the strong coupling constant featuring no unphysical singularity (the Landau pole). Improvement of agreement between theory and experiment, with respect to the case of the standard perturbative definition of alpha_s considered recently, is observed and the behavior of the higher twist terms in the next-to-next-to-leading-order is found to be confirming earlier studies on the subject.Comment: 22 pp, 8 fig

Jacobi evolution of structure functions: convergence and stability

The Jacobi evolution method has been widely used in the QCD analysis of structure function data. However a recent paper claims that there are serious problems with its convergence and stability. Here we briefly review the evidence for the adequate convergence of the method; and show that there are errors in the above paper which undermine its conclusions.Comment: 6 pages revtex. Shortened version for publication. Some details are omitted, but are still accessible on hep-ph/9901253v

Next-to-Next-to-Leading Order QCD Analysis of DIS Structure Functions

It is performed for the first time a next-to-next-to-leading order analysis of deep inelastic structure functions $F_2$ and $F_L$ using the recently determined first moments of the non-singlet anomalous dimensions and the corresponding Wilson coefficients. {}From a comparison to BCDMS data we found a slight decrease in the energy scale of perturbative QCD with respect to the next-to-leading order analysis, which brings the scale closer to the value predicted from a scheme invariant approach.Comment: Latex 12 pages, 2 figures available on request, preprint UCI-TR/94-