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G. I. Lykasov

Publications and source records attributed to G. I. Lykasov.

At least 73 records · Page 4Linked to original sources
arXiv2002

Hadron Multiplicity in Lepton-Nucleon Interactions

Multi-hadron production in inelastic neutrino-nucleon interactions is investigated within the framework of the quark-gluon string model. The contributions of the planar (one-Reggeon exchange) and cylindrical (one-Pomeron exchange) graphs to different observables is computed using a Monte Carlo program for the generation of hadrons produced from the decay of colorless quark-antiquark strings. The suggested approach results in a satisfactory description of the experimental data on $ν(\barν) N\toμ^-(μ^+) h X$ reactions obtained recently at CERN by the NOMAD Collaboration. The data extends over a wide range of initial neutrino energies $E_ν$ $<$ 200 GeV/c and momentum transfers 1 $<$ Q $<$ 7 GeV/c, well into the region where perturbative QCD calculations are not applicable.

hep-ph↗
arXiv2001

Polarization Phenomena in Fragmentation of Deuterons to Pions and Non-Nucleon Degrees of Freedom in the Deuteron

The fragmentation of deuterons into pions emitted forward in the kinematic region forbidden for free nucleon-nucleon collisions is analyzed. It is shown that the inclusion of the non-nucleon degrees of freedom in a deuteron allows to describe the experimental data about inclusive pion spectrum rather satisfactory and improves the description of data concerning the deuteron analyzing power T_{20}. The experimental data show the positive sign and very small values, less than 0.2, of T_{20} what can't be reproduced by the calculations ignoring these degrees of freedom.

hep-ph↗
arXiv2001

$Q^2$-dependence of backward pion multiplicity in neutrino-nucleus interactions

The production of pions emitted backward in inelastic neutrino-nucleus interactions is analyzed within the impulse approximation in the framework of the dual parton model. We focus on the $Q^2$-dependence of the multiplicity of negative pions, normalized to the total cross section of the reaction $ν+ A \to μ+ X$. The inclusion of planar (one-Reggeon exchange) and cylindrical (one-Pomeron exchange) graphs leads to a multiplicity that decreases as $Q^2$ increases, in agreement with recent measurements carried out at CERN by the NOMAD collaboration. A realistic treatment of the high momentum tail of the nucleon distribution in a nucleus also allows for a satisfactory description of the semi-inclusive spectrum of backward pions.

nucl-th↗
arXiv2001

Polarization Phenomena by Deuteron Fragmentation into Pions

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 T_{20} are investigated within the framework of an impulse approximation using different kinds of the deuteron wave function. The influence of P-wave inclusion in the deuteron wave function is studied, too. The invariant spectrum is shown to be more sensitive to the amplitude of the $NN \to πX$ process than the tensor analyzing power T_{20}. It is shown that the inclusion of the non-nucleon degrees of freedom in a deuteron results a satisfactory description of experimental data about the inclusive pion spectrum and improves the description of data about T_{20}. According to the experimental data, T_{20} has the positive sign and very small values, less than 0.2, what contradicts to the theoretical calculations ignoring these degrees of freedom.

hep-ph↗
arXiv2001

Deuteron distribution in nuclear matter

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 Levinger's quasideuteron model. The resulting Levinger's factor in nuclear matter at equilibrium densityis 11.63. We use the local density approximation to estimate the Levinger's factor for heavy nuclei, obtaining results which are consistent with the available experimental data from photoreactions.

nucl-th↗
arXiv2001

Open charm enhancement by secondary interactions in relativistic nucleus-nucleus collisions?

We calculate open charm production in $Pb+Pb$ reactions at SPS energies within the HSD transport approach - which is based on string, quark, diquark ($q, \bar{q}, qq, \bar{q}\bar{q}$) and hadronic degrees of freedom - including the production of open charm pairs from secondary 'meson'-'baryon' (or quark-diquark and antiquark-diquark) collisions. It is argued that at collision energies close to the $c\bar{c}$ pair threshold the dominant production mechanism is related to the two body (or quasi two body) reactions $πN \to \bar{D} (\bar{D^*}) Λ_c, (Σ_c)$. Estimates within the framework of the Quark-Gluon String model suggest cross sections of a few $μb$ for $πN \to \bar{D} Λ_c$ in the region of 1 GeV above threshold. The dynamical transport calculations for $Pb + Pb$ at 160 A$\cdot$GeV indicate that the open charm enhancement reported by the NA50 Collaboration might be due to such secondary reaction mechanisms.

hep-ph↗
arXiv2001

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 ${\rm A}_{YY}$ are investigated within the framework of an impulse approximation using different kinds of the deuteron wave function. The influence of ${\rm P}$-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.

hep-ph↗
arXiv2000

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.

nucl-th↗
arXiv2000

Possibly to Test the Mechanism of Elastic Backward Proton-Deuteron Scattering ?

The elastic backward proton-deuteron scattering is analyzed within a covariant approach based on the invariant expansion of the reaction amplitude. The relativistic invariant equations for all the polarization observables are presented. Within the impulse approximation the relation of the tensor analyzing power $T_{20}$ and the polarization transfer $κ_0$ to $P$-wave components of the deuteron wave function is found. The comparison of the theoretical calculations with experimental data is presented. An experimental verification of the reaction mechanism is suggested by constructing some combinations of different observables.

nucl-th↗
arXiv2000

Nuclear structure functions and off-shell corrections

The $n$-th moments of the nuclear structure function $F_2^A(x,Q^2)$ are analyzed using the off-shell kinematics appropriate to describe deep inelastic electron-nucleus scattering within the impulse approximation. It is shown that off-shell effects are sensitive to the form of both the nuclear spectral function and the nucleon structure function $F_2^N(x,Q^2)$, and can be as large as $\sim 10%$ at Q$^2~\sim~2$~(GeV/c)$^2$.

hep-ph↗
arXiv1999

$ωN$ final state interactions and $ω$-meson production from heavy-ion collisions

We calculate the elastic and inelastic $ωN\to ωN, \to πN, \to ρN, \to ρπN, \to ππN, \to σN$ reactions within a boson exchange approximation where the $ωρπ$ coupling constant and form factor are fixed by the reaction $πN \to ωN$ in comparison to the experimental data. We find rather large $ωN$ cross sections at low relative momenta of the $ω$-meson which leads to a substantial broadening of the $ω$-meson width in nuclear matter. The implications of the $ωN$ final state interactions are studied for $ω$ production in $^{12}C{+}^{12}C, ^{40}Ca{+}^{40}Ca$ and $^{58}Ni{+}^{58}Ni$ reactions at about 2 A GeV within the HSD transport approach; the drastic changes of the transverse mass spectra relative to a general m_T-scaling (for $π^0$ and $η$ mesons) might be controlled experimentally by the TAPS Collaboration.

nucl-th↗
arXiv1999

Backward hadron production in neutrino-nucleus interactions

The production of backward pions in lepton-nucleus collisions is analyzed. We show that a large yield of high momentum backward pions can be explained by the Regge asymptotic of the distribution of nucleons carrying a large momentum fraction in the nuclear target. The calculated spectra of pions emitted in the neutrino + Ne --> muon + pion + X reaction are in satisfactory agreement with the available experimental data.

nucl-th↗
arXiv1998

Relativistic Calculation of Polarization Observables in NN -> DπProcesses

A detailed analysis of processes of the type NN -> dπis presented taking into account the exchange graphs of a nucleon and a pion. A large sensitivity of polarization observables to the off-mass shell effects of nucleons inside the deuteron is shown. The influence of the inclusion of the P-wave in the deuteron wave function (DWF) is studied. We have analyzed the sensitivity of all the observables to the form of πNN - current taking into account the off-shellnis of the nucleon and the choice of the DWF relativistic form. From the results one can see the very large sensitivity of all the observables, especially of the polarization characteristics to the choice of the DWF form.

nucl-th↗
arXiv1998

Relativistic and Polarization Phenomena in NN -> Dπprocesses

A detailed analysis of the processes of the type NN -> Dπis presented taking into account the exchange graphs of a nucleon and a pion. A large sensitivity of polarization observables to the off-mass shell effects of nucleons inside the deuteron is shown. The influence of the inclusion of the P-wave in the Deuteron Wave Function (DWF) is studied. We have analysed the sensitivity of all the observables to the form of πNN - current taking into account the off-shellnis of the nucleon and the choice of the DWF relativistic form. One can see the very large sensitivity of all the observables, especialy of the polarization characteristics to the choice of the DWF form. The inclusion of the P-wave contribution to the DWF within framework of Gross's approach results in a better description of the experimental data on the differential cross section and the polarization observables.

nucl-th↗
arXiv1997

Delta-Isobar Production in Antiproton Annihilation on the Deuteron

The annihilation of antiprotons on deuterons at rest are investigated for the case when pion-nucleon and pion-delta-isobar pairs are produced. The two-step mechanism is investigated by analysing these processes when either neutral particles and charged ones are produced. Some predictions for the branching ratios are presented.

hep-ph↗