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AbstractAbstract

[en] We study the pairing energy in the ground state of a system of N particles occupying a symmetric two-level model space with a level degeneracy Ω. Assuming a pairing Hamiltonian, we calculate the energies of the projected BCS states, using the exact, the Kamlah, and the Lipkin-Nogami particle number projection methods. We find that conclusions regarding the quality of the BCS approximation as well as various approximate projection methods, drawn from studying the N=Ω case alone, are not valid in the more general N≠Ω case when the pairing interaction is weak

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[en] Using a recent shape-independent approximation for the

^{3}S_{1}-^{3}D_{1}mixing parameter, theoretical prevision for the low-energy mixing parameters is made. The present prevision is consistent with the deuteron binding energy, its asymptotic D-state to S-state ratio, η_{d}, the triplet-scattering length, and the meson exchange tail of the tensor nucleon-nucleon potential. The theoretical prevision up to an incident laboratory energy of 25 MeV is consistent with the recent multi-energy determination of mixing parameters, but is much higher than many single-energy determinations of the same. The low single-energy values of the mixing parameter could be reproduced by meson-theoretical potentials only with a substantially reduced η_{d}Primary Subject

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[en] Following recent discussions of critical phase transitional behavior of nuclei, additional data are collected and used to test if there is further evidence supporting such phenomena. Data from nuclear masses, radii, and E2 transition rates are used to construct differential observables. Inspection of these for the rare earth region shows that they exhibit the characteristic phase transitional behavior found in condensed matter and thermodynamic systems, namely, nearly constant values before the critical point, and a sharp change in the critical region, followed by a different set of values after the critical point

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[en] We have calculated the binding energies, rms radii, and multipole moments of Ho isotopes (N=81--98) using a relativistic mean field theory. The quadrupole moments and the change in mean square charge radius are compared with the experimental and other theoretical results. We observed a shape transition from oblate to prolate deformations in going from lighter to heavier isotopes

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[en] Capture-fission cross sections for

^{40,48}Ca+^{197}Au and^{40,48}Ca+^{208}Pb have been measured at beam energies ranging from 195 to 416 MeV. The fissionlike fragments were detected in a pair of position-sensitive multiwire proportional counters and were identified from measurements of position and time using two-body kinematics. The data taken at energies above the barrier (up to 2.4 times the Coulomb barrier) were analyzed in terms of the extra push model showing a strong dependence on the Ca isotope. This dependence was also observed at energies below the barrier, where the results have been interpreted using a schematic coupled-channel codePrimary Subject

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Barrette, J.; Bellwied, R.; Bennett, S.; Braun-Munzinger, P.; Cleland, W.E.; Clemen, M.; Cole, J.D.; Cormier, T.M.; David, G.; Dee, J.; Dietzsch, O.; Drigert, M.W.; Hall, J.R.; Hemmick, T.K.; Herrmann, N.; Hong, B.; Kwon, Y.; Lacasse, R.; Lukaszew, A.; Li, Q.; Ludlam, T.W.; Mark, S.K.; McCorkle, S.; Matheus, R.; Murgatroyd, J.T.; O'Brien, E.; Panitkin, S.; Piazza, T.; Pruneau, C.; Rao, M.N.; Rosati, M.; daSilva, N.C.; Sedykh, S.; Sonnadara, U.; Stachel, J.; Starinsky, N.; Takagui, E.M.; Voloshin, S.; Wang, G.; Wessels, J.P.; Woody, C.L.; Xu, N.; Zhang, Y.; Zou, C.

(E887 Collaboration)

(E887 Collaboration)

AbstractAbstract

[en] We present the results of an analysis of charged particle pseudorapidity distributions in the central region in collisions of a Au projectile with Al, Cu, Au, and U targets at an incident momentum of 10.8 GeV/c per nucleon. The pseudorapidity distributions are presented as a function of transverse energy produced in the target or central pseudorapidity regions. The correlation between charged multiplicity and transverse energy measured in the central region, as well as the target and projectile regions, is also presented. We give results for transverse energy per charged particle as a function of pseudorapidity and centrality

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[en] In this paper, the three-body bound state collapse (BSC) is investigated in connection with the short-range orthogonality node by making use of the unitary pole approximation of a deep local 2N potential model. A rank-1 effective

^{3}S_{1}potential derived with respect to the excited bound state (the physical deuteron) supports two 3N bound states. The lower state shows a feature of the BSC when the node behavior is significant. When we impose a strict orthogonality condition with respect to the unphysical deep 2N state, such a collapsed state does not appear and we obtain only one 3N bound state. In the case where we do not impose the orthogonality condition, the collapsed state gets deeper as the mode behavior becomes more significant. When the node behavior is reduced, the BSC becomes less significant and disappears at a certain degree of node behavior, and the other bound state becomes the lowest state. The binding energy of this state is close to the binding energy of the 3N ground state obtained with the orthogonality condition, for both large and small degrees of node behaviorPrimary Subject

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[en] A simple formula for conditional fission barriers of rotating nuclei is proposed based on an extension of Swiatecki's dimensionless expressions for conditional barrier energies. The calculated barrier heights are compared with the measured values. The utility of the present formula in the analysis of experimental results in a typical heavy ion fusion reaction is discussed

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[en] The extremely neutron-deficient Ba isotopes close to the proton drip line are studied in a relativistic mean field approach. The charge radii and the deformations are found to be in good agreement with the known experimental values. An interesting crossing between the proton and neutron root mean square radii is predicted around

^{116}BaPrimary Subject

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[en] We present initial results in the calculation of nuclear ground state properties in a relativistic Hartree approximation. Our model consists of Skyrme-type interactions in four-, six-, and eight-fermion point couplings in a manifestly nonrenormalizable Lagrangian, which also contains derivative terms to simulate the finite ranges of the mesonic interactions. A self-consistent procedure has been developed to solve the model equations for several nuclei simultaneously by use of a generalized nonlinear least-squares adjustment algorithm. With this procedure we determine the nine coupling constants of our model so as to reproduce measured ground state binding energies, rms charge radii, and spin-orbit splittings of selected closed major shell and closed subshell nuclei in nondeformed regions. The coupling constants obtained in this way predict these same observables for a much larger set of closed shell spherical nuclei to good accuracy and also predict these quantities for similar nuclei far outside the valley of beta stability. Finally, they yield properties of saturated nuclear matter in agreement with recent relativistic mean meson field approaches

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