Form factors and polarization in the elasticeD-scattering with inclusion of meson and quark degrees of freedom in a deuteron

A detailed analysis is made of the pair,ρπγ-currents, retardation effects and six-quark admixtures to the charge, quadrupole form factors and to the deuteron polarization. It is shown that the elasticeD-scattering cross section allowing for the meson exchange currents can be described by introducing a six-quark admixture with probability 3.5%. It is predicted that the behaviour of the deuteron polarization tensor at q>4 fm^?1 essentially depends on 6q-admixture.     

Nucleon-nucleon correlations with quark degrees of freedom

A dynamical equation of two nucleons in a nucleus is formulated in the nonrelativistic quark model including Pauli blocking due to the other nucleons. This equation is solved with a model wave function containing the possiblity of six-quark bags with different radii. It is shown that the Pauli blocking effect is emphasized by the non-nucleonic degrees of freedom represented by six-quark bags. The modification of the quark momentum distribution for correlated nucleons is calculated and probabilities of non-NN components in nuclei are estimated.     

Chiral dynamics with quark degrees of freedom

The possibility to detect DCC fluctuations is discussed. It is shown that interactions with quark background and dissipative effects due to interactions in the chiral field may result in damping of fluctuations. Since the magnitude of fluctuations depends strongly on the initial state and speed of chiral phase transition an accurate evaluation of all modifying processes is required to predict the observability of DCCs.     

Isobaric degrees of freedom in nuclei as determined from nonrelativistic quark model

Isobaric degrees of freedom δδ in nuclei are determined from the quark cluster model of a nucleus. These additional degrees of freedom are brought in by the coloured quark exchange between different nucleon clusters present in nuclei. They are found to be important in the region of momentum transfer near 3.5 fm⁻¹. The mass dependence of these isobaric degrees of freedom in nuclei turns out to beA ^5/6.     

Determination of vector meson properties by matching resonance saturation to a constituent quark model

The properties of mesonic resonances can be calculated in terms of the low-energy coefficients of chiral perturbation theory ( PT) by extending unitarized PT to higher energies. On the other hand, these low-energy coefficients can be calculated in two different models, namely i) by assuming resonance saturation and ii) within a constituent quark model. By matching the expressions of the two models combined with the results of unitarized PT and the Weinberg sum rules, the properties of vector and axial-vector mesons can be calculated in the combined large-N _c and chiral limit.Received: 30 September 2002, Published online: 22 October 2003PACS: 12.39.Fe Phenomenological quark models: Chiral Lagrangians - 14.40.Cs Properties of specific particles: Other mesons with S = C = 0, mass < 2.5 GeV     

Mechanism of near-threshold production of the eta meson

Measurements of the analyzing power for the pp-->pp eta reaction have been performed at excess energies of Q=10 and 36 MeV. The determined analyzing power is essentially consistent with zero, implying dominance of the s wave at both excess energies. The angular dependence of the analyzing power, combined with the isospin dependence of the total cross section for the eta meson production in nucleon-nucleon collisions, reveal that the excitation of the nucleon to the S11(1535) resonance is predominantly due to the exchange of the pi meson between the colliding nucleons.     

In-medium modification of meson properties in a chiral quark model

Two-photon decays of vector mesons and dilepton decays of scalar mesons which are forbidden in a vacuum and can occur in dense baryonic matter due to the explicit violation of Lorentz symmetry are described within a quark model of the Nambu-Jona-Lasinio type. The temperature and chemical potential dependence of these processes is investigated. Talk at the Helmoltz International Summer School “Dense Matter in Heavy Ion Collision and Astrophysics,” JINR, Dubna, August 21–September 1, 2006. The text was submitted by the authors in English.     

Asymptotic completeness for a quark model of meson scattering

We prove asymptotic completeness for the scattering of two non-relativistic spinless mesons, when each meson is composed of a quark and antiquark bound together by a confining potential, so that free quarks may not result from the collision.     

Charmed meson production in quark exchange model

Dynamical calculations of charmed meson production rates (via quark exchange) are presented, replacing previous kinematic predictions. Agreement with recent data on the ratio of production rates for different two-charmed-meson final states is reached, and other features of the calculated rates are also discussed.     

Axial quark number and the η meson

We show, in the framework of chiral Lagrangians, that a concept of axial quark number is conveniently used in formulating a departure from a naive quark model of pseudoscalar mesons. Problems of the η are investigated from this point of view.     

Chiral symmetry breaking and meson decays in a relativistic quark model

Applying two different Lorentz-covariant quark models, one of them being essentially nonrelativistic, chiral symmetry breaking parameters of strong interaction will be calculated. Also attention will be paid to meson decays. The model retaining relativistic spinor structure for quark-antiquark wave functions turns out to be more appropriate than the nonrelativistic one.     

Microscopics of mesonic degrees of freedom in nucleons and mesons in nuclei: Quasielastic meson knockout by high-energy electrons

The following questions are considered: (i) that of what quasielastic-knockout reactions are; (ii) that of what experience has been gained in measuring, in various channels, the momentum distributions and spectroscopic factors of nucleons and clusters in nuclei and of electrons in atoms, molecules, and solid-state bodies; (iii) that of how it is possible to introduce the concept of quasielastic knockout in the theory of meson-electroproduction processes p(e, e′m)B at beam energies of a few GeV and at moderate values of the square of the virtual-photon 4-momentum, Q ² = 2–4 (GeV/c)²; and (iv) that of how the momentum distributions of mesons in various channels of virtual proton decay, p → B + π, p → B + ρ, and p → Y + K, are predicted on the basis of the microscopic model of a fluctuation of the QCD vacuum in a nucleon. Proposals for relevant experiments are formulated. It is indicated that quasielastic-knockout processes like (e, e′π) provide the best way to study the problem of a scalar pion condensate in nuclei. In conclusion, it is emphasized that quasielastic processes ²H(e, e′p)B involving various spectator baryons B are of great value for determining the composition of multiquark configurations in nucleon-nucleon systems.     

Scalar σ meson at a finite temperature in a nonlocal quark model

The properties and temperature behavior of the π and σ bound states are studied in the framework of the nonlocal model with a separable interaction kernel, based on the quark Dyson-Schwinger and meson Bethe-Salpeter equations. M _π(T), f _π(T), M _σ(T), and Γ_{σ → ππ}(T) are considered above and below the deconfinement and chiral restoration transitions. Talk at the Round-Table Discussion “Searching for a Mixed Phase of Strongly Interacting Matter at the JINR Nuclotron,” Dubna, July 7–9, 2005. The text was submitted by the authors in English.     

Collectivity and single-particle degrees of freedom

Intruder rotational bands in ⁴⁵Sc and ⁴⁵Ti have been investigated up to the maximum aligned angular momentum by means of EUROBALL IV and the Recoil Filter Detector (RFD). The use of the RFD allowed for a reduction of the -line Doppler broadening and, moreover, for a determination of very short level lifetimes. In the studied nuclei, the estimated deformation shows a gradual disappearance of the collectivity at the highest available spins.Received: 19 November 2002, Revised: 14 March 2003, Published online: 2 March 2004PACS: 21.10.Tg Lifetimes - 21.60.Cs Shell model - 27.40. + z P. Bednarczyk: Present address: GSI, Darmstadt, GermanyM.B. Smith: Present address: TRIUMF, Vancouver, Canada     

Interaction of nonlinear energy sink with a two degrees of freedom linear system: Internal resonance

We investigate the dynamics of 2DOF linear subsystem with close frequencies with attached nonlinear energy sink (NES). In this system, simultaneous targeted energy transfer from both linear oscillators to the NES is possible. It was demonstrated that the process of the TET can be analytically described as transient beats of relaxation—like motion arising due to the internal resonance. Contrary to previously studied models, the approach based on Hamiltonian structure of the system (study of the periodic orbits in the absence of the damping) fails to provide insight into the TET process. The reason of that is large number of secondary resonances activated through interaction between two primary 1:1 resonances. In the damped system these resonances are eliminated and then averaging—based approach is applicable. It was shown by the Hilbert Vibration Decomposition (HVD) that in the damped case there is a single significant component of the response regarded to the 1:1:1 resonance. Analytical model was verified numerically and a fairly good correspondence was observed.