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Aleksander V. Sidorov

Publications and source records attributed to Aleksander V. Sidorov.

13 recordsLinked to original sources
arXiv2010

Determination of Polarized PDFs from a QCD Analysis of Inclusive and Semi-inclusive Deep Inelastic Scattering Data

A new combined next to leading order QCD analysis of the polarized inclusive and semi-inclusive deep inelastic lepton-hadron scattering (DIS) data is presented. In contrast to previous combined analyses, the $1/Q^2$ terms (kinematic - target mass corrections, and dynamic - higher twist corrections) in the expression for the nucleon spin structure function $g_1$ are taken into account. The new COMPASS data are included in the analysis. The impact of the semi-inclusive data on the polarized parton densities (PDFs) and on the higher twist corrections is discussed. The new results for the PDFs are compared to our (Leader, Sidorov, Stamenov) LSS'06 PDFs, obtained from the fit to the inclusive DIS data alone, and to those obtained from the de Florian, Sassot, Stratmann, and Vogelsang global analysis.

hep-ph↗
arXiv2009

Some Remarks on Methods of QCD Analysis of Polarized DIS Data

The results on polarized parton densities (PDFs) obtained using different methods of QCD analysis of the present polarized DIS data are discussed. Their dependence on the method used in the analysis, accounting or not for the kinematic and dynamic 1/Q^2 corrections to spin structure function g_1, is demonstrated. It is pointed out that the precise data in the preasymptotic region require a more careful matching of the QCD predictions to the data in this region in order to determine the polarized PDFs correctly.

hep-ph↗
arXiv2007

Polarized Parton Densities and Higher Twist in the Light of the Recent CLAS and COMPASS data

The impact of the recent very precise CLAS and COMPASS g_1/F_1 data on polarized parton densities and higher twist effects is discussed. We demonstrate that the low Q^2 CLAS data improve essentially our knowledge of higher twist corrections to the spin structure function g1, while the large Q^2 COMPASS data influence mainly the strange quark and gluon polarizations which slightly decrease. We find also that the present inclusive DIS data cannot rule out a negative polarized and changing in sign gluon densities.

hep-ph↗
arXiv2007

Impact of CLAS and COMPASS data on Polarized Parton Densities and Higher Twist

We have re-analyzed the world data on inclusive polarized DIS including the very precise CLAS proton and deuteron data, as well as the latest COMPASS data on the asymmetry $A_1^d$, and have studied the impact of these data on polarized parton densities and higher twist effects. We demonstrate that the low $Q^2$ CLAS data improve essentially our knowledge of higher twist corrections to the spin structure function $g_1$, while the large $Q^2$ COMPASS data influence mainly the strange quark density. In our new analysis we find that a negative polarized gluon density, or one that changes sign as a function of x, cannot be ruled out from the present DIS data.

hep-ph↗
arXiv2006

Target Mass Effects in Polarized Deep Inelastic Scattering

The target mass effects in polarized DIS have been studied. It was demonstrated that taking into account the first order target mass corrections to g1 a very good approximation of the exact formula is achieved. It was also shown that their magnitude in the preasymptotic DIS region is small except for x > 0.65, where their large effect is partially suppressed by the large values of $Q^2$ due to the cut $W^2 > 4 GeV^2$. The difference between the size of the target mass and higher twist corrections is illustrated.

hep-ph↗
arXiv2005

Longitudinal Polarized Parton Densities Updated

We have re-analyzed the world data on inclusive polarized DIS, in both NLO and LO QCD, including the new HERMES and COMPASS data. The updated NLO polarized densities are given in both the $\rm \bar{MS}$ and JET schemes. The impact of the new data on the results is discussed.

hep-ph↗
arXiv2005

The Effect of Positivity Constraints on Polarized Parton Densities

The impact of positivity constraints on the polarized parton densities has been studied. Special attention has been paid to the role of positivity constraints in determining the polarized strange quark and gluon densities, which are not well determined from the present data on inclusive polarized DIS.

hep-ph↗
arXiv2005

Role of Positivity Constraints in Determining Polarized Parton Densities

We have re-analyzed the world data on inclusive polarized DIS, in both NLO and LO QCD, including the very precise JLab Hall A neutron data, and have studied the role of positivity constraints, and demonstrated their importance, in determining the strange and gluon densities. We have shown that higher twist corrections are essential in the analysis of the present data on the structure function g1. A consistent QCD analysis is achieved, and results for the polarized parton densities are given in both the MSbare and JET schemes.

hep-ph↗
arXiv2001

Polarized Parton Densities in the Nucleon

We present a new NLO QCD analysis of the world data on inclusive polarized deep inelastic scattering. Comparing to our previous analysis: i) the values of g_A and a_8=3F-D are updated ii) the MRST'99 instead of the MRST'98 parametrization for the input unpolarized parton densities is used and iii) the recent SLAC E155 proton data on the spin asymmetry A1 are included in the analysis. A new set of polarized parton densities is extracted from the data and the sensitivity of the results to different positivity constraints is discussed.

hep-ph↗
arXiv1995

Constraints on "Fixed Point" QCD from the CCFR Data on Deep Inelastic Neutrino-Nucleon Scattering

The results of LO {\it Fixed point} QCD (FP-QCD) analysis of the CCFR data for the nucleon structure function $~xF_3(x,Q^2)~$ are presented. The predictions of FP-QCD, in which $~α_{s}(Q^2)~$ tends to a nonzero coupling constant $α_{0}$ as $~Q^2\to \infty~,$ are in good agreement with the data. If $~α_{0}~$ is a first order zero of the $~β~$ function, constraints for the possible values of the $~β~$ function parameter $~b~$ regulating how fast $~α_ s(Q^2)~$ tends to its asymptotic value $~α_{0}~$ are found from the data. The corresponding values of $~α_{0}~$ are also determined. Having in mind the recent QCD fits to the same data we conclude that in spite of the high precision and the large $~(x,Q^2)~$ kinematic range of the CCFR data they cannot discriminate between QCD and FP-QCD predictions for $~xF_3(x,Q^2)~$. PACS: 12.38.Qk; 19.90+b; 13.60 Hb

hep-ph↗
arXiv1994

The Gross--Llewellyn Smith Sum Rule: Theory vs Experiment

We describe the results of our recent work on the determination of the value of the parameter $Λ_{\overline{MS}}^{(4)}$ and of the $Q^2$-dependence of the Gross--Llewellyn Smith (GLS) sum rule from the experimental data of the CCFR collaboration on neutrino--nucleon deep-inelastic scattering, using the Jacobi polynomials QCD analysis. The obtained results are compared with the information, available in the literature, information on the previous experimental measurements of the GLS sum rule.

hep-ph↗
arXiv1994

The Jacobi Polinomials QCD Analysis of the CCFR Data for xF_3 and the Q^2-Dependence of the Gross-Llewllyn Smith Sum Rule

We present the results of our QCD analysis of the recent CCFR data for the structure function $xF_3 (x,Q^2)$ of the deep-inelastic neutrino--nucleon scattering. The analysis is based on the Jacobi polynomials expansion of the structure functions. The concrete results for the parameter $Λ_{\overline {MS}}^{(4)}$ and the shape of quark distributions are determined. At the reference scale $|Q_0^2|$=3 $GeV^2$ our results are in satisfactory agreement with the ones obtained by the CCFR group with the help of another method. The $Q_0^{2}$-dependence of the experimental data for the Gross--Llewellyn Smith sum rule is extracted in the wide region of high-momentum transfer. Within systematical experimental uncertainties the results obtained are consistent with the perturbative QCD predictions. We reveal the effect of the discrepancy between our results and the analysed perturbative QCD predictions at the level of the statistical error bars. The importance of taking account, in our procedure, of a still unknown next-next-to-leading approximation of the moments of the structure function $xF_3 (x,Q^2)$ is stressed.

hep-ph↗