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N. V. Shevchenko

Publications and source records attributed to N. V. Shevchenko.

32 records · Page 2Linked to original sources
arXiv2007

$\bar{K}NN$ quasi-bound state and the $\bar{K}N$ interaction: coupled-channel Faddeev calculations of the $\bar{K}NN - πΣN$ system

Coupled-channel three-body calculations of an $I=1/2$, $J^π=0^-$ $\bar{K}NN$ quasi-bound state in the $\bar{K}NN - πΣN$ system were performed and the dependence of the resulting three-body energy on the two-body $\bar{K}N - πΣ$ interaction was investigated. Earlier results of binding energy $B_{K^-pp} \sim 50 -70$ MeV and width $Γ_{K^-pp} \sim 100$ MeV are confirmed [N.V. Shevchenko {\it et al.}, Phys. Rev. Lett. {\bf 98}, 082301 (2007)]. It is shown that a suitably constructed energy-independent complex $\bar{K}N$ potential gives a considerably shallower and narrower three-body quasi-bound state than the full coupled-channel calculation. Comparison with other calculations is made.

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arXiv2007

Faddeev calculation of a $K^- p p$ quasi-bound state

We report on the first genuinely three-body ${\bar K}NN - πΣN$ coupled-channel Faddeev calculation in search for quasi-bound states in the $K^- p p$ system. The main absorptivity in the $K^- p$ subsystem is accounted for by fitting to $K^- p$ data near threshold. Our calculation yields one such quasi-bound state, with $I=1/2$, $J^π=0^-$, bound in the range $B \sim 55-70$ MeV, with a width of $Γ\sim 95-110$ MeV. These results differ substantially from previous estimates, and are at odds with the $K^- p p \to Λp$ signal observed by the FINUDA collaboration.

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arXiv2006

Binding of charmonium with two- and three-body nuclei

The energies of the (eta_c d) and (eta_c 3He) bound states are calculated on the basis of exact three- and four-body AGS equations. For the eta_c N interaction a Yukawa-type potential has been adopted. The calculations are done for a certain range of its strength parameter. The results obtained are quite different from calculations based on the folding model.

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arXiv2005

Capture of slow antiprotons by helium atoms

A consistent quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. For the four-body scattering wave function, corresponding to the initial state, as well as for the antiprotonic helium wave function, appearing in the final tate, adiabatic approximations was used. Calculations were carried out for a wide range of antiprotonic helium states and incident energies of the antiproton. Obtained energy dependances of some cross sections show a rich low energy structure.

physics.atom-ph↗
arXiv2004

Primary population of antiprotonic helium states

A full quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. Calculations were carried out for a wide range of antiprotonic helium states and incident (lab) energies of the antiproton.

physics.atom-ph↗
arXiv2002

Near-Threshold Photoproduction of eta-mesons on Three-Nucleon Nuclei

A microscopic few-body description of near-threshold coherent photoproduction of the eta meson on tritium and 3He targets is given. The photoproduction cross-section is calculated using the Finite Rank Approximation (FRA) of the nuclear Hamiltonian. The results indicate a strong final state interaction of the eta meson with the residual nucleus. Sensitivity of the results to the choice of the eta N T-matrix is investigated.

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arXiv2001

Coherent Photoproduction of eta-mesons on Three-Nucleon Systems

A microscopic few-body description of near-threshold coherent photoproduction of the eta-meson on tritium and He3 targets is given. The photoproduction cross-section is calculated using the Finite Rank Approximation (FRA) of the nuclear Hamiltonian. The results indicate a strong final state interaction of the eta-meson with the residual nucleus. Sensitivity of the results to the choice of the eta-N T-matrix is investigated. The importance of obeying the two-body unitarity condition in the eta-N system is demonstrated.

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arXiv2001

Microscopic description of $η$-photoproduction on light nuclei

A microscopic four-body description of near-threshold coherent photoproduction of the $η$ meson on the (3N)-nuclei is given. The photoproduction cross-section is calculated using the Finite Rank Approximation (FRA) of the nuclear Hamiltonian. The results indicate that the final state interaction of the $η$ meson with the residual nucleus plays an important role in the photoproduction process. Sensitivity of the results to the choice of the $ηN$ T-matrix is investigated. The importance of obeying the condition of $ηN$ unitarity is demonstrated.

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arXiv2001

Low energy scattering and photoproduction of $η$-mesons on deuterons

Photo-production of $η$-mesons and their collisions with light nuclei are studied within the Alt-Grassberger-Sandhas (AGS) formalism for different parameters of $ηN$ interaction. A three-body resonance or a quasi-bound state is found close to the $ηd$ threshold. Expected manifestation of this resonant behavior of $ηd$ elastic scattering in various processes involving $ηd$-system in their final states was found in calculations of the $γd \to ηd$ reaction in the framework of modified AGS equations. These calculations revealed peaks in the energy dependence of the total cross-section almost at the same energies as in the elastic $ηd$ scattering. Meanwhile, such peaks did not appear in the impulse approximation (i.e. when $ηd$ resonance was not taken into account). This sheds some light on the nature of the enhancement of $η$ photo-production on deuteron observed recently in the low energy experiments.

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arXiv2001

Photoproduction of $η$-mesons off light nuclei

Photoproduction of $η$-mesons off deuteron is studied within the Alt-Grassberger-Sandhas formalism for different parameters of $ηN$ interaction. The calculations revealed peaks in the energy dependence of the total cross-section.

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arXiv1999

Faddeev-type calculation of eta-d threshold scattering

The scattering length for the eta-meson collision with deuteron is calculated on the basis of rigorous few-body equations (AGS) for various eta-N input. The results obtained strongly support the existence of a resonance or quasi-bound state close to the eta-d threshold.

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arXiv1999

Low-energy eta-d resonance

Elastic eta-d scattering is considered within the Alt-Grassberger-Sandhas (AGS) formalism for various eta-N input data. A three-body resonant state is found close to the eta-d threshold. This resonance is sustained for different choices of the two-body eta-N scattering length a_{ηN}. The position of the resonance moves towards the eta-d threshold when Re a_{ηN} is increased, and turns into a quasi-bound state at Re a_{ηN}=0.733 fm.

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arXiv1998

Non-radiative synthesis of Be7 in solar plasma

The nuclear reaction e + He3 + He4 ---> e + Be7 is considered at thermonuclear energies. The motion of the electron is treated within the adiabatic approximation and the He3-He4 scattering state is calculated using an effective He3-He4 potential constructed via the Marchenko inverse scattering method. The reaction rate thus obtained for solar interior conditions is approximately 10^{-4} of the corresponding rate for the radiative capture He3 + He4 ----> Be7 + gamma. However, at the conditions corresponding to the early stages of the primordial nucleosynthesis, the non-radiative fusion is five times faster than the radiative one. The importance of the non-radiative processes for the energy balance in the sun, which for electrons is totally opaque, is discussed.

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