arXiv subjects

Dorota Kotlorz

Publications and source records attributed to Dorota Kotlorz.

7 recordsLinked to original sources

arXiv2014

Evolution of the Truncated Mellin Moments of the parton distributions in QCD analysis

We review evolution equations for the truncated Mellin moments of the parton distributions and some their applications in QCD analysis. The main finding of the presented approach is that the $n$th truncated moment of the parton distribution obeys also the DGLAP equation but with a rescaled splitting function $P'(z)=z^n P(z)$. This allows one to avoid the problem of dealing with the experimentally unexplored Bjorken-$x$ region. The evolution equations for truncated moments are universal - they are valid in each order of perturbation expansion and can be useful additional tool in analysis of unpolarized as well as polarized nucleon structure functions.

hep-ph↗

arXiv2009

Evolution equations of the truncated moments of the parton densities. A possible application

A possible application of the evolution equation for the truncated Mellin moments to determination of the parton distributions in the nucleon is presented. We find that the reconstruction of the initial parton densities at scale $Q_0^2$ from their truncated moments at a given scale $Q^2$ is exact and unique for small number of free parameters ($\leq 3$), even for the limited $x$-region of experimental data. For larger number of adjustable parameters the obtained fits are not unique and one needs an additional knowledge of the small-$x$ behaviour of the parton densities to make the reconstruction procedure reliable. We apply successfully our method to HERMES and COMPASS spin-dependent valence quark data.

hep-ph↗

arXiv2008

Study of the nucleon spin-dependent structure function $g_1$. A comparison with recent HERMES and COMPASS data

Predictions for the spin dependent structure function $g_1$ of the nucleon are presented. We use an unified approach incorporating the LO DGLAP evolution and the resummation of double logarithmic terms $ln^2(x)$. We show, that the singular input parametrisation as $x\to 0$ can be a substitute of the $ln^2(x)$ resummation. An impact of the `more running' coupling is discussed. We determine the contribution to the Bjorken sum rule solving the evolution equation for the truncated moment of $g_1^{NS}$. A comparison with the re-analysed HERMES and COMPASS data is given.

hep-ph↗

arXiv2004

Low-x contribution to the Bjorken sum rule within double logarithmic $ln^2x$ approximation

The small-$x$ contributions to the Bjorken sum rule within double logarithmic $ln^2x$ approximation for different input parametrisations $g_1^{NS}(x,Q_0^2)$ are presented. Analytical solutions of the evolution equations for full and truncated moments of the unintegrated structure function $f^{NS}(x,Q^2)$ are used. Theoretical predictions for $\int_{0}^{0.003} g_1^{NS}(x,Q^2=10) dx$ are compared with the SMC small-$x$ data. Rough estimation of the slope $λ$, controlling the small-$x$ behaviour of $g_1^{NS}\sim x^{-λ}$ from the SMC data is performed. Double logarithmic terms $\sim (α_s ln^2x)^n$ become leading when $x\to 0$ and imply the singular behaviour of $g_1^{NS}\sim x^{-0.4}$. This seems to be confirmed by recent experimental SMC and HERMES data. Advantages of the unified $ln^2x$+LO DGLAP approach and the crucial role of the running coupling $α_s=α_s(Q^2/z)$ at low-$x$ are also discussed.

hep-ph↗

arXiv2003

Double Logarithmic Terms $ln^2x$ in the Heavy Quark Production $σ(P\bar P \to h\bar h) - σ(PP \to h\bar h)$ Cross Sections

Predictions for the difference of proton-antiproton and proton-proton cross sections in the heavy quark production within LO DGLAP analysis together with the $ln^2x$ terms resummation are presented. An important role of the double logarithmic $ln^2x$ corrections in a case of the large rapidity gap between a quark and an antiquark is discussed.

hep-ph↗

arXiv2001

Resummation of Double Logarithmic Terms LN^2(1/x) in the Polarized Nonsinglet Structure Function g_1 at Small x via GLAP-Like Approach

An alternative equation, resumming of the $\ln^2 1/x$ terms for the polarized nonsinglet structure function $g_1^{NS}$ at small $x$ is presented. Construction of the GLAP-like formula for the auxiliary function, corresponding to the $g_1^{NS}$ at rescaled $Q^2$ variable is shown. Predictions of this approach for the $g_1^{NS}$ function at small $x$ in a case of a flat as well as a dynamical input are given. The role of the fixed coupling constant and the running one is also discussed.

hep-ph↗

arXiv2000

Nucleon Spin Structure Functions

The review of the nucleon spin structure functions problems is presented. The perturbative QCD predictions for the small x behaviour of the nucleon spin structure functions are discussed. The role of the resummation of the ln^2 1/x terms is emphasized. Predictions for the nonsinglet structure function g_1 in case of a flat as well as a dynamical input are given. The so called "spin crisis" on the context of both theoretical and experimental future hopes are also briefly discussed.

hep-ph↗