A. Yu. Illarionov

Small x behavior of parton distributions: a study of higher twist effects

We review the double asymptotic scaling phenomenon for the structure functions of the deepinelastic scattering process. We present an analytical parameterization of the contributions from the twist-two operators of the Wilson operator product expansion and power suppressed terms. Higher twist corrections to F2 at small x are studied for the case of a flat initial condition for the twist-two QCD evolution in the next-to-leading order approximation. Higher twist terms are estimated using two different approaches: one motivated by BFKL and the other motivated by the renormalon formalism. The results of the latter approach are in very good agreement with deep inelastic scattering data from HERA.

ANGLE DEPENDENCE OF POLARIZATION OBSERVABLES BY FRAGMENTATION OF DEUTERONS TO PIONS

The fragmentation of deuterons into pions with nonzero angle emitted in the kinematical region forbidden for free nucleon-nucleon collisions is analyzed. The inclusive relativistic invariant spectrum of pions and the tensor analyzing power AYY are investigated within the framework of an impulse approximation using different kinds of the deuteron wave function. The influence of P-wave contribution to the deuteron wave function is studied, too. Our results are compared with the experimental data and other calculations performed within both the non-relativistic and relativistic approaches. It was found that theoretical calculations based on IA do not provide a consistent understanding of the new data in a whole cumulative region that can be caused by a influence of non-nucleon degrees of freedom.

Deuteron distribution in nuclear matter

Abstract We analyze the properties of deuteron-like structures in infinite, correlated nuclear matter, described by a realistic hamiltonian containing the Urbana v 14 two-nucleon and the Urbana TNI many-body potentials. The distribution of neutron–proton pairs, carrying the deuteron quantum numbers, is obtained as a function of the total momentum by computing the overlap between the nuclear matter in its ground state and the deuteron wave functions in correlated basis functions theory. We study the differences between the S- and D-wave components of the deuteron and those of the deuteron-like pair in the nuclear medium. The total number of deuteron type pairs is computed and compared with the predictions of Levingers quasideuteron model. The resulting Levingers factor in nuclear matter at equilibrium density is 11.63. We use the local density approximation to estimate the Levingers factor for heavy nuclei, obtaining results which are consistent with the available experimental data from photoreactions.

Polarization phenomena by deuteron fragmentation into pions

Abstract:The fragmentation of deuterons into pions emitted forward in the kinematic region forbidden for free nucleon-nucleon collisions is analyzed. The inclusive relativistic invariant spectrum of pions and the tensor analyzing power T20 are investigated within the framework of an impulse approximation using various deuteron wave functions. The influence of -wave inclusion in the deuteron wave function is also studied. The invariant spectrum is shown to be more sensitive to the amplitude of the NN↦πX process than the tensor analyzing power T20. It is shown that the inclusion of the non-nucleonic degrees of freedom in a deuteron results in a satisfactory description of the data for the inclusive pion spectrum and improves the description of the data about T20. According to the data, T20 has very small positive values, less than 0.2, which contradicts the theoretical calculations ignoring these degrees of freedom.

Deuteron P wave in elastic backward proton-deuteron scattering

The elastic backward proton-deuteron scattering is analyzed within a fully covariant approach based on the invariant expansion of the reaction amplitude. The method of calculation of any observables for any reaction mechanism is developed. The cross section and spin observables, like tensor analyzing power and polarization transfer coefficient etc., are investigated in explicit form within framework of the impulse approximation using different kinds of the relativistic deuteron wave function (DWF) with P-wave components. Our results of numerical calculation for complete set of polarization observables are compared with the experimental data and other calculations performed within both the non-relativistic and relativistic approaches. An experimental verification of the reaction mechanism is suggested by constructing some combinations of different observables.

F{sub 2}{sup c} at low x

We study the heavy-quark contributions to the proton structure function F2(x,Q2) at next-to-leading order using compact formulas at small values of Bjorken’s x variable. The formulas provide a good agreement with the modern HERA data for F2c (x,Q2).We study the heavy-quark contributions to the proton structure function F{sub 2}(x,Q{sup 2}) at next-to-leading order using compact formulas at small values of Bjorkens x variable. The formulas provide a good agreement with the modern HERA data for F{sub 2}{sup c} (x,Q{sup 2}).

OPEN CHARM PRODUCTION IN BINARY REACTIONS WITHIN THE REGGE THEORY

We analyze the open charm production in the binary

Theoretical investigation of tensor analyzing powers in deuteron fragmentation into pions

\pi p \to \bar{D} \Lambda_c

Probing the deuteron structure at small N-N distances by cumulative pion production

and

Polarization phenomena in NN ↔ Dπ reactions

\pi(\rho) J/\psi