arXiv subjects

A. G. Shuvaev

Publications and source records attributed to A. G. Shuvaev.

47 records · Page 3Linked to original sources

arXiv2000

Classical pion fields in the presence of source

Classical pion field similar to Disoriented Chiral Condensate (DCC) is considered in the presence of the external source. This field is similar to DCC in the sense that its isotopic orientation is specified with a single vector at the whole space. We study the classical field solutions in the nonlinear sigma-model both in the chiral limit with massless pion and for the finite pion mass. In both cases the field resembles the Coulomb field of charged particle however the nonlinear pion interactions lead to the existence of several solutions. In the massless case and for the very small size of the source there is the lot of classical solutions with finite discrete energies. In the more realistic situation of large nucleus (heavy ion) there are no stable solutions of the above type, but there is the possibility for the formation of the quasistationary states. They can live for a long time slowly decaying through the emission of very soft pions. The structure and the energies of these solutions is investigated numerically.

hep-ph↗

arXiv1999

Charm Hadroproduction in $k_T$-Factorization Approach

We compare the theoretical status and the numerical predictions of two approaches for heavy quark production in the high energy hadron collisions, namely the conventional LO parton model with collinear approximation and $k_T$-factorization approach. The main assumptions used in the calculations are discussed. To extract the differences coming from the matrix elements we use very simple gluon structure function and fixed coupling. It is shown that the $k_T$-factorization approach calculated formally in LO and with Sudakov form factor accounts for many contributions related usually to NLO (and even NNLO) processes of the conventional parton model

hep-ph↗

arXiv1999

Asymptotic properties of DVCS

We compute the deeply virtual Compton scattering (DVCS) amplitude for forward and backward scattering in the asymptotic limit. We make use of the Regge calculus to resum important logarithmic contributions that are beyond those included by the DGLAP evolution. We find a power-like behavior for the forward DVCS amplitude.

hep-ph↗

arXiv1999

Skewed distributions fixed by diagonal partons at small x,ξand $γ^* p \to Vp$ at HERA

We show that the skewed parton distributions are completely determined at small x and ξby the conventional diagonal partons. We study the application to diffractive vector meson production at HERA.

hep-ph↗

arXiv1999

Asymptotic high energy behavior of the deeply virtual Compton scattering amplitude

We compute the deeply virtual Compton scattering (DVCS) amplitude for forward and backward scattering in the asymptotic limit. Since this calculation does not assume ordering of the transverse momenta, it includes important logarithmic contributions that are beyond those summed by the DGLAP evolution. These contributions lead to a power-like behavior for the forward DVCS amplitude.

hep-ph↗

arXiv1999

Off-diagonal distributions fixed by diagonal partons at small $x$ and $ξ$

We show that the off-diagonal (or skewed) parton distributions are completely determined at small $x$ and $ξ$ by the (conventional) diagonal partons. We present predictions which can be used to estimate the off-diagonal distributions at small $x$ and $ξ$ at any scale.

hep-ph↗

arXiv1998

t-dependences of vector meson diffractive production in ep collisions

We calculate $p_T$-dependences of diffractive vector meson photo- and electroproduction in electron-proton collisions with and without proton dissociation at small momenta transfers. The calculated slopes are in good agreement with the data.

hep-ph↗

arXiv1997

Heavy quark pair correlations in QCD

The azimutal correlations of heavy quarks produced in the high energy $pp$ ($p\bar{p}$) collisions are calculated in the framework of QCD without the usual assumptions of the parton model. The virtual nature of the interacting gluons as well as their transverse motion and different polarizations are taken into account. We give some predictions for the azimutal correlations of charm and beauty hadrons produced at Tevatron-collider and LHC.

hep-ph↗

arXiv1995

$F_2/xG(x,Q^2)$ Ratio at Small $x$ and the Role of the Contribution from Infrared Region

We consider the light quark electroproduction cross section and show that the contribution coming from the infrared ($q_T<300\, MeV$) region is not negligible. It changes the $F_2(x,Q^2)/xG(x,Q^2)$ ratio by 20-30\% (or even more) for small $x$ and $Q^2\sim 4\, GeV^2$.

hep-ph↗

arXiv1995

Heavy Quark Production in Parton Model and in QCD

The cross sections of heavy quark production in $pp$ collision and for their photo- and electroproduction are calculated in the framework of QCD. The virtual nature of the interacting gluons as well as their transverse motion and different polarizations are taken into account. The obtained cross sections exhibit more rapid growth with the initial energy than the parton model predictions and the $p_T$ distributions of produced heavy quarks are more smooth.

hep-ph↗

arXiv1993

Anomalous Dimensions of High Twist Operators in QCD at $N \rightarrow 1$ and large $Q^2

The anomalous dimensions of high-twist operators in deeply inelastic scattering ($γ_{2n}$) are calculated in the limit when the moment variable $N \rightarrow 1$ (or $x_B\rightarrow 0$) and at large $Q^2$ (the double logarithmic approximation) in perturbative QCD. We find that the value of $γ_{2n}(N-1)$ in this approximation behaves as ${N_c α_S \over π(N-1)} n^2(1 + {δ\over 3} (n^2-1))$ where $δ\approx 10^{-2}$. This implies that the contributions of the high-twist operators give rise to an earlier onset of shadowing than was estimated before. The derivation makes use of a Pomeron exchange approximation, with the Pomerons interacting attractively. We find that they behave as a system of fermions.

hep-ph↗