105 research outputs found

    Pionic Degrees of Freedom in Atomic Nuclei and Quasielastic Knockout of Pions by High-Energy Electrons

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    The nonlinear model of pionic condensate in nuclei by G. Preparata can be efficiently verified by investigation of the quasielastic knockout process of pions out of nuclei by high energy electrons. First, a momentum distribution (MD) of the collective pions has a bright maximum at q=0.3 Gev.Second the excitation spectrum of a recoil nucleus is concentrated at low energies E lesser than 1MeV. The results for the pion knockout from mesonic clouds of individual nucleons are absolutely different. The latter results are presented both for pion and rho-meson clouds localized on nucleons.Comment: 13 pages, 3 figure

    Nucleon-nucleon wave function with short-range nodes and high-energy deuteron photodisintegration

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    We review a concept of the Moscow potential (MP) of the NNNN interaction. On the basis of this concept we derive by quantum inversion optical partial potentials from the modern partial-wave analysis (PWA) data and deuteron properties. Point-form (PF) relativistic quantum mechanics (RQM) is applied to the two-body deuteron photodisintegration. Calculations of the cross-section angular distributions cover photon energies between 1.1 and 2.5 GeV. Good agreement between our theory and recent experimental data confirms the concept of deep attractive Moscow potential with forbidden SS- and PP-states.Comment: 31 pages, 9 figures. typos, extended formalism, review of the Moscow potential model adde

    Kvazilastično izbijanje mezona iz nukleona. Razvoj i budućnost

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    The electroproduction of pions and kaons at the kinematics of quasi-elastic knockout is a powerful tool for investigation of mesonic cloud. A model of scalar qqÂŻ ( 3P0) fluctuation in the non-trivial QCD vacuum is used to calculate pion and kaon momentum distributions in the channels N→B+π, B = N, ∆, N∗ , N∗∗, and N→Y + K, Y=Λ, ÎŁ0.Elektrotvorba piona i kaona u uvjetima kvazielastičnog izbijanja je moćna metoda za istraĆŸivanje elektronskog oblaka. Primijenili smo model skalarnih fluktuacija qqÂŻ ( 3P0) u netrivijalnom QCD vakuumu radi računanja raspodjela impulsa piona i kaona u kanalima N→B+π, B = N, ∆, N∗ , N∗∗, i N→Y + K, Y=Λ, ÎŁ0

    Examination of the astrophysical S-factors of the radiative proton capture on 2H, 6Li, 7Li, 12C and 13C

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    Astrophysical S-factors of radiative capture reactions on light nuclei have been calculated in a two-cluster potential model, taking into account the separation of orbital states by the use of Young schemes. The local two-body potentials describing the interaction of the clusters were determined by fitting scattering data and properties of bound states. The many-body character of the problem is approximatively accounted for by Pauli forbidden states. An important feature of the approach is the consideration of the dependence of the interaction potential between the clusters on the orbital Young schemes, which determine the permutation symmetry of the nucleon system. Proton capture on 2H, 6Li, 7Li, 12C, and 13C was analyzed in this approach. Experimental data at low energies were described reasonably well when the phase shifts for cluster-cluster scattering, extracted from precise data, were used. This shows that decreasing the experimental error on differential elastic scattering cross sections of light nuclei at astrophysical energies is very important also to allow a more accurate phase shift analysis. A future increase in precision will allow more definite conclusions regarding the reaction mechanisms and astrophysical conditions of thermonuclear reactions.Comment: 40p., 9 fig., 83 ref. arXiv admin note: substantial text overlap with arXiv:1005.1794, arXiv:1112.1760, arXiv:1005.198

    The Nucleon-Nucleon Interaction in a Chiral Constituent Quark Model

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    We study the short-range nucleon-nucleon interaction in a chiral constituent quark model by diagonalizing a Hamiltonian comprising a linear confinement and a Goldstone boson exchange interaction between quarks. The six-quark harmonic oscillator basis contains up to two excitation quanta. We show that the highly dominant configuration is ∣s4p2[42]O[51]FS>\mid s^4p^2[42]_O [51]_{FS}> due to its specific flavour-spin symmetry. Using the Born-Oppenheimer approximation we find a strong effective repulsion at zero separation between nucleons in both 3S1^3S_1 and 1S0^1S_0 channels. The symmetry structure of the highly dominant configuration implies the existence of a node in the S-wave relative motion wave function at short distances. The amplitude of the oscillation of the wave function at short range will be however strongly suppressed. We discuss the mechanism leading to the effective short-range repulsion within the chiral constituent quark model as compared to that related with the one-gluon exchange interaction.Comment: 31 pages, LaTe

    Multi-channel phase-equivalent transformation and supersymmetry

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    Phase-equivalent transformation of local interaction is generalized to the multi-channel case. Generally, the transformation does not change the number of the bound states in the system and their energies. However, with a special choice of the parameters, the transformation removes one of the bound states and is equivalent to the multi-channel supersymmetry transformation recently suggested by Sparenberg and Baye. Using the transformation, it is also possible to add a bound state to the discrete spectrum of the system at a given energy E<0E<0 if the angular momentum at least in one of the coupled channels l≄2l\ge 2.Comment: 9 pages, revtex; to be published in Phys. At. Nucl. (Oct. 2000
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