Kinematical twist-3 effects in DVCS as a quark spin rotation

We point out that the kinematical twist-3 contributions to the DVCS amplitude, required to restore electromagnetic gauge invariance of the twist-2 amplitude up to O(t/q^2), can be understood as a spin rotation applied to the twist-2 quark density matrix in the target. This allows for a compact representation of the twist-3 effects, as well as for a simple physical interpretation.Comment: 4 pages, revtex, 3 eps figures included using eps

πη\pi\eta pair hard electroproduction and exotic hybrid mesons

We show that hard electroproduction is a promising way to study exotic hybrid mesons, in particular through the hybrid decay channel $H \to \pi\eta$. We discuss the $\pi\eta$ generalized distribution amplitude, calculate the production amplitude and propose a forward-backward asymmetry as a signal for the hybrid meson production.Comment: 4 pages, 1 figure, presented by I.V. Anikin at Xth International Conference "BARYONS'04", Palaiseau, Franc

Wandzura-Wilczek approximation from generalized rotational invariance

We present the alternative way of derivation of the Wandzura-Wilczek relations between the kinematical twist-3 and twist-2 functions, parameterizing hadronic matrix element in two-photon processes $\gamma^{\star}\pi\to \gamma\pi$ and $\gamma^{\star}\gamma\to\pi\pi$. The new equations, providing the independence of the physical cross-sections on the choice of the light-cone direction, are suggested and explored. The amplitude of $\gamma^{\star}\gamma\to\pi\pi$ up to genuine twist-3 accuracy is found.Comment: 14 pages, Late

On high Q2Q^{2} behavior of the pion form factor for transitions γ∗γ→π0\gamma^{\ast} \gamma \to \pi^{0} and γ∗γ∗→π0\gamma ^{\ast} \gamma^{\ast} \to \pi^{0} within the nonlocal quark-pion model

The behavior of the transition pion form factor for processes \gamma^*\gamma -> \pi^0 and \gamma^* \gamma^* -> \pi^0 at large values of space-like photon momenta is estimated within the nonlocal covariant quark-pion model. It is shown that, in general, the coefficient of the leading asymptotic term depends dynamically on the ratio of the constituent quark mass and the average virtuality of quarks in the vacuum and kinematically on the ratio of photon virtualities. The kinematic dependence of the transition form factor allows us to obtain the relation between the pion light-cone distribution amplitude and the quark-pion vertex function. The dynamic dependence indicates that the transition form factor \gamma^* \gamma -> \pi^0 at high momentum transfers is very sensitive to the nonlocality size of nonperturbative fluctuations in the QCD vacuum.Comment: LaTex file with 3 ps-figure

Off-diagonal quark distribution functions of the pion within an effective single instanton approximation

We develop a relativistic quark model for pion structure, which incorporates the non-trivial structure of the vacuum of Quantum Chromodynamics as modelled by instantons. Pions are boundstates of quarks and the strong quark-pion vertex is determined from an instanton induced effective lagrangian. The interaction of the constituents of the pion with the external electromagnetic field is introduced in gauge invariant form. The parameters of the model, i.e., effective instanton radius and constituent quark masses, are obtained from the vacuum expectation values of the lowest dimensional quark and gluon operators and the low-energy observables of the pion. We apply the formalism to the calculation of the pion form factor by means of the isovector nonforward parton distributions and find agreement with the experimental data.Comment: LaTeX; altered version; references and figures added. Published: paper has been accepted for publication in Nucl. Phys.

Information security risks assessment and management framework

Основная статьяProviding of information security becomes very essential for modern telecommunication networks. This task is often decided from the perspective of information security risks, but some problems arise in practice with risks assessment and management in quantitative form. They are uncertain, incomplete, fuzzy and qualitative character of source information about existing threats and vulnerabilities. In this paper we developed the framework for quantitative information security risks assessment and management under these challenges. We used the framework for risks assessment and management in electronic trading platform and found the optimal set of security safeguards

Pion light-cone wave function and pion distribution amplitude in the Nambu-Jona-Lasinio model

We compute the pion light-cone wave function and the pion quark distribution amplitude in the Nambu-Jona-Lasinio model. We use the Pauli-Villars regularization method and as a result the distribution amplitude satisfies proper normalization and crossing properties. In the chiral limit we obtain the simple results, namely phi_pi(x)=1 for the pion distribution amplitude, and = -M / f_pi^2 for the second moment of the pion light-cone wave function, where M is the constituent quark mass and f_pi is the pion decay constant. After the QCD Gegenbauer evolution of the pion distribution amplitude good end-point behavior is recovered, and a satisfactory agreement with the analysis of the experimental data from CLEO is achieved. This allows us to determine the momentum scale corresponding to our model calculation, which is close to the value Q_0 = 313 MeV obtained earlier from the analogous analysis of the pion parton distribution function. The value of is, after the QCD evolution, around (400 MeV)^2. In addition, the model predicts a linear integral relation between the pion distribution amplitude and the parton distribution function of the pion, which holds at the leading-order QCD evolution.Comment: mistake in Eq.(38) correcte

On exotic hybrid meson production in gamma* gamma collisions

We present a theoretical study of exotic hybrid meson (JPC=1-+) production in photon-photon collisions where one of the photons is deeply virtual, including twist 2 and twist 3 contributions. We calculate the cross section of this process which turns out to be large enough to imply sizeable counting rates in the present high luminosity electron-positron colliders. We emphasize theimportance of the pi eta decay channel for the detection of the hybrid meson candidate pi_1(1400) and calculate the cross section and the angular distribution for pi eta pair production in the unpolarized case. This angular distribution is a useful tool for disentangling the hybrid meson signal from the background. Finally, we calculate the single spin asymmetry associated with one initial longitudinally polarized lepton.Comment: 13 pages, 14 figure

Increasing the quality of pseudo-random number generator based on fuzzy logic

We consider previously suggested by authors pseudorandom number generator based on fuzzy logic (FRNG) and increase its quality by increasing the period of generated series. To increase the period of FRNG we use more LFSRs in its structure. At the beginning we will study the case of combining four LFSRs in constructing the FRNG then the case of using eight LFSRs. The new version of FRNG generates pseudorandom numbers which are more close to true random series that make it more suitable and attractive for many applications related to data security and cryptography

Secure gamma generation for stream cipher based on fuzzy logic

In this paper, we propose a new approach for secure bit stream gamma generation based on the concept of fuzzy logic and linear feedback shift registers (LFSRs), combined in pseudorandom number generator based on fuzzy logic (FPRNG). The original idea for ensuring security for gamma generation is based on the initial states (the seeds) of LFSRs used in the generator. In this paper, we suggested the updated version of FPRNG. We also improve gamma security by accompaniment seed some valuable secure information. We found that configurations of membership functions (MFs) in FPRNG can significantly affect the randomness of the output stream of the developed generator. We can increase the gamma security as well as stream cipher security by keeping these configurations in secret additionally to seeds