Searcharxiv⌕ Search

arXiv subjects

I. T. Obukhovsky

Publications and source records attributed to I. T. Obukhovsky.

13 recordsLinked to original sources
arXiv2022

Dibaryon resonances and short-range $NN$ interaction

The dibaryon concept for the nuclear force is presented, assuming that the main attraction between the nucleons at medium distances is determined by the $s$-channel exchange of an intermediate six-quark (dibaryon) state. To construct the respective $NN$ interaction model, a microscopic six-quark description of the $NN$ system is used, in which symmetry aspects play a special role. It is shown that the $NN$ interaction in all important partial waves can be described properly by a superposition of the long-range $t$-channel one-pion exchange and the $s$-channel exchange by an intermediate dibaryon. The developed model gives a good description of both elastic phase shifts and inelasticities of $NN$ scattering in all $S$, $P$, $D$ and $F$ partial waves at energies from zero to 600 - 800 MeV and even higher.The parameters of the intermediate six-quark states corresponding to the best fit of $NN$ scattering data are found to be consistent with the parameters of the known dibaryon resonances in those $NN$ partial configurations where their existence has been experimentally confirmed. Predictions for new dibaryon states are given as well.

nucl-th↗
arXiv2010

Quasielastic rho0 electroproduction on the proton at intermediate energy: Role of scalar and pseudoscalar meson exchange

We present a detailed analysis of rho(0) electroproduction at intermediate energy for quasi-elastic knockout kinematics. The approach is based on an effective Lagrangian which generates exchanges of scalar, pseudoscalar, axial-vector and tensor mesons. The specific role of mesons with different values for J(PC) is analyzed. We show that the pi(0) exchange amplitude and its interference terms with eta(eta') and f1 exchanges dominate in the transverse part of the cross section sigmaT. The main role plays the pi(0) to rho(0) M1 spin transition when coupling the virtual photons to the nucleon. In contrast, the longitudinal cross section sigmaL is generated by a series of scalar meson exchanges. To extract the dominant term more detailed information on the inner structure of scalar mesons is required. It turns out that recent data of the CLAS Collaboration on sigmaL and sigmaT can be described with reasonable accuracy if one proposes the quarkonium structure for the heavy scalar mesons (M > 1.3 GeV). On this basis the differential cross sections dsigmaL/dt and dsigmaT/dt are calculated and compared with the latest CLAS data.

hep-ph↗
arXiv2006

Isoscalar short-range current in the deuteron induced by an intermediate dibaryon

A new model for short-range isoscalar currents in the deuteron and in the NN system is developed; it is based on the generation of an intermediate dibaryon which is the basic ingredient for the medium- and short-range NN interaction which was proposed recently by the present authors.This new current model can very well describe the experimental data for the three basic deuteron observables of isoscalar magnetic type, viz. the magnetic moment, the circular polarization of the photon in the $np\to dγ$ process at thermal neutron energies and the structure function B up to Q$^2$=60 fm$^{-2}$.

nucl-th↗
arXiv2006

Quark model description of quasi-elastic pion knockout from the proton at JLAB

The interference term between s- and t-pole contributions to the p(e,e' pi+)n cross section is evaluated on the basis of the constituent quark model. It is shown that the contribution of baryon s-poles can be modeled by a nonlocal extension of the Kroll-Rudermann contact term. This contribution is in a destructive interference with the pion t-pole that is essential to improve the description of recent JLab data at the invariant mass W=1.95 GeV. Some predictions are made for a new JLab measurement at higher values W=2.1-2.3 GeV and Q2 centered at 1.6 and 2.45 GeV2/c2.

hep-ph↗
arXiv2004

Quasi-elastic knockout of pions and kaons from nucleons by high-energy electrons and quark microscopy of "soft" meson degrees of freedom in the nucleon

Electro-production of pions and kaons at the kinematics of quasi-elastic knockout (which is well known in the physics of atomic nucleus and corresponds to the $t$-pole diagram) is proposed for obtaining their momentum distribution (MD) in various channels of virtual decay $N \to B+π$, $B=N$, $Δ$, $N^*$, $N^{**}$, and $N \to Y+K$, $Y=Λ$, $Σ$. It is a powerful tool for investigation of a quark microscopic picture of the meson cloud in the nucleon. A model of scalar $q \bar{q}$ ($^3P_0$) fluctuation in the non-trivial QCD vacuum is used to calculate pion and kaon momentum distributions (MD) in these channels.

nucl-th↗
arXiv2002

A dressed bag model study of the final-state $NΔ$ interaction in photoproduction processes off the deuteron

The impact of the short-range $NΔ$ interaction on the pion photoproduction processes off the deuteron in the $Δ$-resonance region is studied in the framework of recently proposed dressed-bag model. A common dressing procedure for bare three- and six-quark states is used to describe both the pion decay widths of baryon resonances and the effective $NN$ (or $NΔ$) interaction at short ranges related to the inner dressed-bag states. It is shown that the effect of short-range $NΔ$ interaction for the forward-angle $π^\mathrm{o}$ photoproduction off the deuteron cannot be neglected. The prospects for further development of the model to describe the short-range $NN$ (or $NΔ$) correlations in the lightest nuclei are discussed.

nucl-th↗
arXiv2000

To the nature of intermediate- and short-range nucleon-nucleon interaction

Instead of the Yukawa mechanism for intermediate- and short-range interaction some new approach based on formation of the symmetric six-quark bag in the state $|(0s)^6[6]_X,L=0>$ dressed due to strong coupling to $π$, $σ$ and $ρ$ fields are suggested. This new mechanism offers both a strong intermediate-range attraction which replaces the effective $σ$-exchange (or excitation of two isobars in the intermediate state) in traditional force models and also short-range repulsion. Simple illustrative model is developed which demonstrates clearly how well the suggested new mechanism can reproduce $NN$ data.

nucl-th↗
arXiv2000

The new mechanism for intermediate- and short-range nucleon-nucleon interaction

Arguments against the traditional Yukawa-type approach to $NN$ intermediate- and short-range interaction due to scalar-isoscalar meson exchange are presented. Instead of the Yukawa mechanism for intermediate-range attraction some new approach based on formation of the symmetric six-quark bag in the state $|(0s)^6[6]_X,L=0>$ dressed due to strong coupling to $π$, $σ$ and $ρ$ fields are suggested. These new mechanism offers a strong intermediate-range attraction which replaces the effective $σ$-exchange (or excitation of two isobars in the intermediate state) in traditional force models. A similar mechanism with vector $ρ$-meson production in the intermediate six-quark state is expected to lead to a strong short-range spin-orbital nonlocal interaction in the $NN$ system, which may resolve the long-standing puzzle of the spin-orbit force in baryons and in two-baryon systems. Illustrative examples are developed which demonstrate clearly how well the suggested new model can reproduce $NN$ data. Strong interrelations have been shown to exist between the proposed microscopic model and the one-component Moscow $NN$ potential developed by the authors previously and also with some hybrid models and the one-term separable Tabakin potential. The new implications of the proposed model for nuclear physics are discussed.

nucl-th↗
arXiv1997

Pionic decay of a possible d'-dibaryon and the short-range NN interaction

We study the pionic decay of a possible dibaryon d' --> N N πin the microscopic quark shell model. The initial d' dibaryon wave function (J^P=0^-, T=0) consists of one 1\hbarωsix-quark shell-model s^5p[51]_X configuration. The most important final six-quark configurations s^6[6]_X, s^4p^2[42]_X and (s^4p^2-s^52s)[6]_X are properly projected onto the NN channel. The final state NN interaction is investigated by means of two phase-equivalent - but off-shell different - potential models. We demonstrate that the decay width Γ_d' depends strongly on the short-range behavior of the NN wave function. In addition, the width Γ_d' is very sensitive to the mass and size of the d' dibaryon. For dibaryon masses slightly above the experimentally suggested value M_d'=2.065 GeV, we obtain a pionic decay width of Γ_d' = 0.18 - 0.32 MeV close to the experimental value Γ_d' = 0.5 MeV.

nucl-th↗
arXiv1996

Six-quark configurations in the NN system correlated with experiment

The nucleon-nucleon interaction at short range is analyzed in terms of six-quark configurations on a base of numerical solutions of modified RGM equations. It is shown that in low partial waves L=0,1 the system has a two-channel character: the $NN$ channel and the inner six-quark state ("bag") with specific color-spin structure. Starting from this analysis it is shown that polarization observables could be a good tool for investigation of a quark structure of the deuteron.

nucl-th↗