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Nuclear Theory·nucl-th

Tuesday·June 7, 2016

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 01

    Geometrical symmetries of nuclear systems: D(3h) and T(d) symmetries in light nuclei

    Roelof Bijker

    The role of discrete (or point-group) symmetries in alpha-cluster nuclei is discussed in the framework of the algebraic cluster model which describes the relative motion of the alpha-particles. Particular attention is paid to the discrete symmetry of the geometric arrangement of the alpha-particles, and the consequences for the structure of the corresponding rotational bands. The method is applied to study cluster states in the nuclei 12C and 16O. The observed level sequences can be understood in a simple way as a consequence of the underlying discrete symmetry that characterizes the geometrical configuration of the alpha-particles, i.e. an equilateral triangle with D(3h) symmetry for 12C, and a tetrahedron with T(d) symmetry for 16O. The structure of rotational bands provides a fingerprint of the underlying geometrical configuration of alpha-particles.

    nucl-thnucl-exPhys.Scripta(2016)·13 citations
  2. 02

    Charmonium dissociation cross sections and charmonium dissociation rates in hadronic matter

    Feng-Rong Liu🇨🇳 · Shi-Tao Ji🇨🇳 · Xiao-Ming Xu🇨🇳

    K*-charmonium dissociation reactions in hadronic matter are studied in the Born approximation, in the quark-interchange mechanism, and with a temperature-dependent quark potential. We obtain the temperature dependence of unpolarized cross sections for K*-charmonium dissociation reactions which produce charmed mesons and charmed strange mesons. We use the cross sections for charmonium dissociation in collisions with pion, rho meson, kaon, vector kaon, and eta meson to calculate dissociation rates of charmonium with the five types of mesons. Because of the temperature dependence of the meson masses, dissociation cross sections, and meson distribution functions, the charmonium dissociation rates generally increase with the increase of temperature and decrease with the increase of charmonium momentum from 2.2 GeV/c. We find that the first derivative of the dissociation rate with respect to the charmonium momentum is zero when the charmonium is at rest. While the eta + psi' and eta + chi_c dissociation reactions can be neglected, the J/psi, psi', and chi_c dissociation are caused by the collisions with pion, rho meson, kaon, vector kaon, and eta meson.

    nucl-thhep-phJ.Korean Phys.Soc.(2016)·8 citations
  3. 03

    Constraining the surface properties of effective Skyrme interactions

    R. Jodon🇫🇷 · M. Bender🇫🇷 · K. Bennaceur🇫🇮 · J. Meyer🇫🇷

    The purpose of this study is threefold: first, to identify a scheme for the determination of the surface energy coefficient a_surf that offers the best compromise between robustness, precision, and numerical efficiency; second, to analyze the correlation between values for a_surf and the characteristic energies of the fission barrier of Pu240; and third, to lay out a procedure how the deformation properties of the Skyrme energy density functional (EDF) can be constrained during the parameter fit. There are several frequently used possibilities to define and calculate the surface energy coefficient a_surf of effective interactions. The most direct access is provided by the model system of semi-infinite nuclear matter, but a_surf can also be extracted from the systematics of binding energies of finite nuclei. Calculations can be carried out either self-consistently (HF), which incorporates quantal shell effects, or in one of the semi-classical Extended Thomas-Fermi (ETF) or Modified Thomas-Fermi (MTF) approximations. The surface energy coefficient of 76 parameterizations of the Skyrme EDF have been calculated. Values obtained with the HF, ETF and MTF methods are not identical, but differ by fairly constant systematic offsets. Despite having some drawbacks compared to the other methods studied here, the MTF approach provides sufficiently precise values for a_surf such that it can be used as a very robust constraint on surface properties during a parameter fit at negligible additional cost. Through the construction of a series of eight parameterizations SLy5s1-SLy5s8 of the standard Skyrme EDF with systematically varied a_surf value it is shown how to arrive at a fit with realistic deformation properties. [Note: The abstract has been abbreviated because of length restrictions imposed by the arXiv. See the paper for the full abstract.]

    nucl-thPRC(2016)·45 citations
  4. 04

    Two-nucleon scattering in a modified Weinberg approach with a symmetry-preserving regularization

    J. Behrendt🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · Ulf-G. Meißner🇩🇪 · A. Nogga🇩🇪

    We consider the nucleon-nucleon scattering problem by applying time-ordered perturbation theory to the Lorentz invariant formulation of baryon chiral perturbation theory. Using a symmetry preserving higher derivative form of the effective Lagrangian, we exploit the freedom of the choice of the renormalization condition and obtain an integral equation for the scattering amplitude with an improved ultraviolet behavior. The resulting formulation is used to quantify finite regulator artifacts in two-nucleon phase shifts as well as in the chiral extrapolations of the S-wave scattering lengths and the deuteron binding energy. This approach can be straightforwardly extended to analyze few-nucleon systems and processes involving external electroweak sources.

    nucl-thEPJA(2016)·16 citations
  5. 05

    Point kinetic model of the early phase of a spherically symmetric nuclear explosion

    Andreas Aste

    A concise point kinetic model of the explosion of a prompt supercritical sphere driven by a nuclear fission chain reaction is presented. The findings are in good agreement with the data available for Trinity, the first detonation of a nuclear weapon conducted by the United States Army as part of the Manhattan project. Results are presented for an implosion device containing pure plutonium-239, although the model can be easily applied to, e.g., uranium-235. The fizzle probability and corresponding yield of a fission bomb containing plutonium recovered from reactor fuel and therefore containing significant amounts of spontaneously fissioning plutonium-240 which can induce a predetonation of the device is illustrated by adding a corresponding source term in the presented model. Related questions whether a bomb could be made by developing countries or terrorist organizations can be tackled this way. Although the information needed to answer such questions is in the public domain, it is difficult to extract a consistent picture of the subject for members of organizations who are concerned about the proliferation of nuclear explosives.

    nucl-th0 citations
  6. 06

    Nuclear response functions with finite range Gogny force: tensor terms and instabilities

    A. De Pace🇮🇹 · M. Martini🇫🇷

    A fully-antisymmetrized random phase approximation calculation employing the continued fraction technique is performed to study nuclear matter response functions with the finite range Gogny force. The most commonly used parameter sets of this force, as well as some recent generalizations that include the tensor terms are considered and the corresponding response functions are shown. The calculations are performed at the first and second order in the continued fraction expansion and the explicit expressions for the second order tensor contributions are given. Comparison between first and second order continued fraction expansion results are provided. The differences between the responses obtained at the two orders turn to be more pronounced for the forces including tensor terms than for the standard Gogny ones. In the vector channels the responses calculated with Gogny forces including tensor terms are characterized by a large heterogeneity, reflecting the different choices for the tensor part of the interaction. For sake of comparison the response functions obtained considering a G-matrix based nuclear interaction are also shown. As first application of the present calculation, the possible existence of spurious finite-size instabilities of the Gogny forces with or without tensor terms has been investigated. The positive conclusion is that all the Gogny forces, but the GT2 one, are free of spurious finite-size instabilities. In perspective, the tool developed in the present paper can be inserted in the fitting procedure to construct new Gogny-type forces.

    nucl-thPRC(2016)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE