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AbstractAbstract

[en] By calculating the contribution of the ππ three-body force to the three-nucleon binding energy in terms of the πN amplitude using perturbation theory, we are able to determine the importance of the energy dependence and the contribution of the different partial waves of the πN amplitude to the three nucleon force. A separable representation of the non-pole πN amplitude allows us to write the three-nucleon force in terms of the amplitude for NN → NN*, propagation of the NNN* system, and the amplitude for NN* → NN, with N* being the πN quasi-particle amplitude in a given state. The division of the πN amplitude into a pole and non-pole part gives a procedure for the determination of the πNN form factor within the model. The total contribution of the three-body force to the binding energy of the triton for the separable approximation to the Paris nucleon-nucleon potential (PEST) is found to be very small mainly as a result of the energy dependence of the πN amplitude, the cancellation between the S- and P-wave πN amplitudes, and the soft πNN form factor. (author)

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Few-Body Systems; ISSN 0177-7963; ; v. 18; p. 101-132

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[en] pp and πd scattering and pp → πd reaction processes at incident proton laboratory energies T

_{L}≤ 1 GeV are studied in the framework of πNN dynamics. For this purpose three-body calculations are performed with the πN interaction in the P_{11}, P_{33}, S_{11}and S_{31}states and NN forces in the^{3}S_{1}-^{3}D_{1},^{1}S_{0}, and^{3}P_{2}states. In addition, the backward-going pion contribution at the πNΔ vertex, the πN-ρN coupling, the heavy-meson exchanges in the NN → NN driving term, and the effect of the off-shell structure in the πN-ρN P_{33}interaction are taken into account. (author)Primary Subject

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Few-Body Systems; ISSN 0177-7963; ; v. 18; p. 133-146

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BARYON-BARYON INTERACTIONS, BOSONS, ELEMENTARY PARTICLES, ENERGY LEVELS, HADRON REACTIONS, HADRON-HADRON INTERACTIONS, HADRONS, INTERACTIONS, KINETICS, MANY-BODY PROBLEM, MESON REACTIONS, MESON-BARYON INTERACTIONS, MESON-NUCLEON INTERACTIONS, NUCLEAR REACTIONS, NUCLEON-NUCLEON INTERACTIONS, PARTICLE INTERACTIONS, PROTON-NUCLEON INTERACTIONS

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[en] Integro-differential equations avoiding the ghost contributions occurring in the Faddeev amplitudes are derived for a system of three identical particles in S-states. The equation for the mixed-symmetry state is given for the case of nucleons. Equations for non-identical particles in S-states are also provided. (author)

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Few-Body Systems; ISSN 0177-7963; ; v. 20; p. 129-154

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[en] A transformation of a three-body potential into a sum of two-body potentials is derived. It is applied to the quark-string-junction potential, which becomes the sum of three linear potentials, and to the three-body part of the Urbana nuclear potential. (author)

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Few-Body Systems; ISSN 0177-7963; ; v. 23; p. 75-86

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[en] Although there exists a vast literature devoted to the theory of deep-inelastic scattering, the restrictions imposed on the (electromagnetic or weak) current operator by its commutation relations with the representation operators of the Poincare group and locality have not been considered. We argue that there is a problem with the current operator, leading to the standard parton-model results, satisfying these restrictions. At the same time, there exist models where the correct commutation relations and locality are satisfied but the initial- and final-state interactions of the struck quark with the remnants of the target cannot be neglected even in the Bjorken limit. (author)

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Few-Body Systems; ISSN 0177-7963; ; v. 24; p. 109-121

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[en] Two algorithms are presented for calculating the transformation coefficients between hyperspherical harmonic functions constructed with different sets of Jacobi vectors. They have been tested in the case A = 4, where the transformation coefficients of states with grand angular quantum number K up to 40 have been studied. The applicability of the two algorithms to larger systems is discussed. The numbers of independent hyperspherical-spin-isospin states with given K values, entering the expansion of the alpha-particle ground-state wave function, are also evaluated. The use of complete non-redundant bases is important for future accurate applications of the hyperspherical harmonic technique. (author)

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Few-Body Systems; ISSN 0177-7963; ; v. 25; p. 177-197

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AbstractAbstract

[en] The reaction

^{2}H(e, e^{'}p) has been studied at an invariant mass W of 1050 MeV, i. e. well below the Δ(1232) resonance. Cross sections have been obtained at values of Q^{2}the four-momentum transfer squared, of 0.10, 0.20, and 0.28 (GeV/c)^{2}covering a missing-momentum range from 150 to 700 MeV/c. The data are compared to the results of covariant calculations of Tjon, and the results of calculations based on a Schroedinger formalism due to Laget and the Mainz group, respectively. The data are well described by the calculations of the Mainz group, whereas they, are underestimated by Tjon's calculations at high missing momenta. The calculations of Laget, on the other hand, overestimate the data at low missing momenta, but give a good account of the data at high missing momenta. More detailed considerations reveal that the Δ(1232) contributions are dominant at high missing momenta. However, the lacking Δ(1232) contribution in Tjon's calculations is not enough to explain the large discrepancy between his calculation and the present^{2}H(e, e^{'}p) data at high missing momentum. Probably, the deuteron wave function employed in the covariant calculations has a D-state contribution that is too small. (author)Primary Subject

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Few-Body Systems; ISSN 0177-7963; ; v. 25; p. 115-132

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[en] We propose a phase convention for the Clebsch-Gordan coefficients of S

_{n}and present tables of isoscalar factors for S_{3}, S_{4}, S_{5}, and S_{6}. The isoscalar factors have been calculated from a recursion relation due to Hamermesh and by using symmetry properties of the Clebsch-Gordan coefficients. Applications to the study of multiquark systems are discussed. (author)Primary Subject

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Few-Body Systems; ISSN 0177-7963; ; v. 26; p. 113-133

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[en] The Schroedinger equation of a two-dimensional three-electron quantum dot has been solved accurately. Features of the structures of low-lying states have been extracted from the wave functions. The states are classified according to their geometric characters and their internal modes of motion. The effect of symmetry is emphasized. Rotation bands have been found. (author)

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Few-Body Systems; ISSN 0177-7963; ; v. 22; p. 91-106

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[en] A review of hyperspherical-harmonics (HH) methods from the standpoint of their applications is given. In the first lecture, the symmetrized and unsymmetrized HH bases and symmetrization methods are presented. The physical obstacles to the straightforward application of the HH expansion are discussed, and expansion acceleration methods are described. In the second lecture, the main HH methods are described, including the correlation function hyperspherical harmonic method (CFHHM), the potential harmonic (PH) methods, and the correlated HH methods (PHH, CHH). The third lecture discusses the advantages and limitations of different HH methods in applications, and compares the results for specific few-body problems obtained by HH methods as well as non-HH methods. (author)

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Few-Body Systems; ISSN 0177-7963; ; v. 25; p. 199-238

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