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Nuclear Theory·nucl-th

Monday·September 28, 2015

14 papers—6 primary·8 cross-listed

All14Primary6Cross-lists8
  1. 01

    Additional strange resonances from Lattice QCD

    Michał Marczenko🇵🇱

    Recent Lattice QCD (LQCD) studies suggest that there are missing resonances in the strange sector of the Hadron Resonance Gas (HRG) model. By adopting the continuous Hagedorn mass spectrum, we present how different medium compositions influence the HRG predictions of conserved charge fluctuations. It is shown that missing strange resonances may be partially accounted for by applying the Hagedorn mass spectrum extracted from experimentally established hadrons. On the other hand, the strange-baryonic spectra, extracted from LQCD results for fluctuations, are found to be consistent with the unconfirmed states in the Particle Data Group (PDG) database, whilst the strange-mesonic spectrum points towards yet undiscovered states in the intermediate mass region.

    nucl-thhep-latJ.Phys.Conf.Ser.(2016)·0 citations
  2. 02

    Extension and parameterization of high-order density dependence in Skyrme forces

    Xueyu Xiong🇨🇳 · Junchen Pei🇨🇳 · Wenjun Chen🇨🇳

    The three-body force is indispensable in nuclear energy density functionals which leads to a density dependent two-body term in the Hartree-Fock approach. Usually a single factional power of density dependency has been adopted. We consider the possibility of an additional higher-order density dependence in extended Skyrme forces. As a result, new extended Skyrme parametertizations based on the SLy4 force are obtained and the improvements in descriptions of global nuclei have been demonstrated. The higher-order term can also substantially affect nuclear properties in the high density region in general ways.

    nucl-thPRC(2016)·20 citations
  3. 03

    Matching effective few-nucleon theories to QCD

    Johannes Kirscher🇮🇱

    The emergence of complex macroscopic phenomena from a small set of parameters and microscopic concepts demonstrates the power and beauty of physical theories. A theory which relates the wealth of data and peculiarities found in nuclei to the small number of parameters and symmetries of quantum chromodynamics is by that standard of exceptional beauty. Decade-long research on computational physics and on effective field theories facilitate the assessment of the presumption that quark masses and strong and electromagnetic coupling constants suffice to parameterize the nuclear chart. By presenting the current status of that enterprise, this article touches the methodology of predicting nuclei by simulating the constituting quarks and gluons and the development of effective field theories as appropriate representations of the fundamental theory. While the nuclear spectra and electromagnetic responses analyzed computationally so far with lattice QCD are in close resemblance to those which intrigued experimentalists a century ago, they also test the theoretical understanding which was unavailable to guide the nuclear pioneers but developed since then. This understanding is shown to be deficient in terms of correlations amongst nuclear observables and their sensitivity to fundamental parameters. By reviewing the transition from one effective field theory to another, from QCD to pionful chiral theories to pionless and eventually to cluster theories, we identify some of those deficiencies and conceptual problems awaiting a solution before QCD can be identified as the high-energy theory from which the nuclear landscape emerges.

    nucl-thhep-latIJMPE(2016)·6 citations
  4. 04

    Microscopic calculations of the characteristics of radiative nuclear reactions for double-magic nuclei

    Oleg Achakovskiy · Sergei Kamerdzhiev · Victor Tselyaev · Mikhail Shitov

    The neutron capture cross sections and average radiative widths of neutron resonances for two double-magic nuclei 132Sn and 208Pb have been calculated using the microscopic photon strength functions, which were obtained within the microscopic self-consistent version of the extended theory of finite Fermi systems in the time blocking approximation. For the first time, the microscopic PSFs have been obtained within the fully self-consistent approach with exact accounting for the single particle continuum (for 208Pb). The approach includes phonon coupling effects in addition to the standard RPA approach. The known Skyrme force has been used. The calculations of nuclear reaction characteristics have been performed with the EMPIRE 3.1 nuclear reaction code. Here, three nuclear level density (NLD) models have been used: the so-called phenomenological GSM, the EMPIRE specific (or Enhanced GSM) and the microscopical combinatorial HFB NLD models. For both considered characteristics we found a significant disagreement between the results obtained with the GSM and HFB NLD models. For 208Pb, a reasonable agreement has been found with systematics for the average radiative widths values with HFB NLD and with the experimental data for the HFB NLD average resonance spacing D0, while for these two quantities the differences between the values obtained with GSM and HFB NLD are of several orders of magnitude. The discrepancies between the results with the phenomenological EGLO PSF and microscopic RPA or TBA are much less for the same NLD model.

    nucl-thEPJ Web Conf.(2016)·2 citations
  5. 05

    A three-body model for the analysis of quasi-free scattering reactions in inverse kinematics

    Antonio M. Moro

    A new method to calculate cross sections for and reactions measured under inverse kinematics conditions is proposed. The method uses the prior form of the scattering transition amplitude, and replaces the exact three-body wave function appearing in this expression by an expansion in terms of - or - states, covering the physically relevant excitation energies and partial waves. A procedure of discretization, similar to that used in continuum-discretized coupled-channels calculations, is applied in order to make this expansion finite and numerically tractable. The proposed formalism is non-relativistic but several relativistic kinematical corrections are applied to extend its applicability to energies of current interest. The underlying optical potentials for the entrance and exit channels are generated microscopically, by folding an effective density-dependent G-matrix with the density of the composite nucleus. Numerical calculations for C(,), C(,) and O(,) at 400~MeV/nucleon are presented to illustrate the method. The role of final-state interactions and Pauli principle between the outgoing nucleons is also discussed.

    nucl-thPRC(2015)·38 citations
  6. 06

    Nuclear rotation in the continuum

    K. Fossez🇺🇸 · W. Nazarewicz🇺🇸 · Y. Jaganathen🇺🇸 · N. Michel🇫🇷 · M. Płoszajczak🇫🇷

    Atomic nuclei often exhibit collective rotational-like behavior in highly excited states, well above the particle emission threshold. What determines the existence of collective motion in the continuum region, is not fully understood. In this work, by studying the collective rotation of the positive-parity deformed configurations of the one-neutron halo nucleus Be, we assess different mechanisms that stabilize collective behavior beyond the limits of particle stability. To solve a particle-plus-core problem, we employ a non-adiabatic coupled-channel formalism and the Berggren single-particle ensemble, which explicitly contains bound states, narrow resonances, and the scattering continuum. We study the valence-neutron density in the intrinsic rotor frame to assess the validity of the adiabatic approach as the excitation energy increases. We demonstrate that collective rotation of the ground band of Be is stabilized by (i) the fact that the one-neutron decay channel is closed, and (ii) the angular momentum alignment, which increases the parentage of high- components at high spins; both effects act in concert to decrease decay widths of ground-state band members. This is not the case for higher-lying states of Be, where the neutron-decay channel is open and often dominates. We demonstrate that long-lived collective states can exist at high excitation energy in weakly bound neutron drip-line nuclei such as Be.

    nucl-thPRC(2016)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE