A. Sissakian

Straight-line paths approximation for studying high-energy elastic and inelastic hadron collisions in quantum field theory

Abstract The problem of the asymptotic behaviour of high-energy elastic and inelastic amplitudes is studied by means of the functional methods of quantum field theory. The straight-line paths approximation (SLPA), making it possible to effectively calculate the functional integrals which arise, is formulated.

NLO QCD procedure of the semi-inclusive deep inelastic scattering data analysis with respect to the light quark polarized sea

The semi-inclusive deep inelastic scattering (SIDIS) process is considered. A theoretical procedure is proposed allowing the direct extraction from the SIDIS data of the first moments of the polarized valence distributions and of the first moment difference of the light sea quark polarized distributions in the next to leading QCD order. The validity of the procedure is confirmed by the respective simulations.

Direct extraction of transversity and its accompanying T-odd distribution from the unpolarized and single-polarized Drell-Yan processes

The Drell-Yan processes with unpolarized colliding hadrons and with the single transversally polarized hadron are considered. The possibility of direct (without any model assumptions) extraction of both transversity and its accompanying T-odd parton distribution functions is discussed. For Drell-Yan processes measurements planned at GSI, the preliminary estimations demonstrate that it is quite real to extract both transversity and its accompanying T-odd PDF in the PAX conditions.

ß-function for the ϕ4-model in variational perturbation theory

Abstract We consider the renormalization procedure for the ϕ4-model in the variational perturbation theory. The nonperturbative s-function is derived in the framework of the proposed approach. The obtained result is in agreement with the four-loop approximation and has an asymptotic behaviour as g 3 2 for a large coupling constant.

Transversity and its accompanying T-odd distribution from Drell–Yan processes with pion-proton collisions

This paper studies the possibility of direct extraction of the transversity and its accompanying T-odd parton distribution function (PDF) from Drell–Yan (DY) processes with unpolarized pion beam and with both unpolarized and transversely polarized proton targets. At present, such an extraction can be performed with the COMPASS experiment at CERN. The preliminary estimations performed for the COMPASS kinematic region demonstrate that it is quite realistic to extract both transversity and its accompanying T-odd PDF under COMPASS conditions.

Gaussian effective potential in variational perturbation theory

Abstract The nonperturbative Gaussian effective potential is derived in the λϕ 4 -theory as the first nontrivial order of variational perturbation theory. In the framework of the proposed approach the algorithm of calculating corrections is determined from the very beginning. Various ways of constructing the variational procedure for the action functional and questions about the convergence of the variational perturbation theory series are discussed. The series convergence for the anharmonic variational perturbation theory functional is proved.

Convergent series in variational perturbation theory

Abstract The problem of convergenof series of the variational perturbation theory isanalyzed for the λλφ 4 ( d ) -model. It is shown that there exist such methods of choosing variational additions that lead to convergent series for any values of the coupling constants.

A study of an air medium influence on the rectilinearity of laser ray proliferation towards the using for large distances and high-precision metrology

The influence of a turbulent air medium on a laser beam space localization precision was studied experimentally. For a helium-neon one-mode laser LGN-302 and for a solid-state multimode laser DS-670, the laser ray coordinate measurement uncertainties were determined with 1 m step for the distances up to 9 m from the laser source. It was found that the σ values at 9 m distance are equal to σ(DS-670) = 21 μm and σ(LGN-302) = 12 μm. To reduce the turbulent air medium influence on the laser ray space localization precision, the laser beam was positioned inside a heat-isolating tube. Very significant decrease of σ values was achieved at 9 m from the source: σ*(DS-670) = 2 μm and σ*(LGN-302) = 2.5 μm. The work is made within a framework of a preparation to the creation of a high-precision large-distance laser metrology to be possibly used for long linear collider component alignment.

Relativistic quark models in the quasipotential approach

We describe the interaction of relativistic particles in the framework of the quasipotential approach. The description is based on the so-called covariant single-time formulation of quantum field theory in which the theory is considered on a spacelike three-dimensional hypersurface in the Minkowski space. Special attention is paid to methods for constructing various quasipotentials as well as to use of the quasipotential approach to describe the characteristics of relativistic particle interactions in quark models such as the amplitudes of hadron elastic scattering, the mass spectra and widths of meson decays, and the cross sections of deep inelastic scattering of leptons on hadrons.

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

The modification of the Jacobi polynomial expansion method (MJEM) is proposed on the basis of the application of the truncated moments instead of the full ones. This allows us to reconstruct the local quark helicity distributions with high precision even for the narrow Bjorken x region accessible for measurement, using as an input only the four first moments extracted from the data in the next to leading order QCD. The variational (extrapolation) procedure is also proposed allowing us 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.