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Nuclear Theory·nucl-th

Tuesday·July 7, 2020

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 01

    Isospin symmetry breaking in the mirror pair Sr-Br

    S.M.Lenzi · A.Poves · A.O.Macchiavelli

    The recent experimental observation of isospin symmetry breaking (ISB) in the ground states of the mirror pair Sr - Br is theoretically studied using large-scale shell model calculations. The large valence space and the successful PFSDG-U effective interaction used for the nuclear part of the problem capture possible structural changes and provide a robust basis to treat the ISB effects of both electromagnetic and non-electromagnetic origin. The calculated shifts and mirror-energy-differences are consistent with the inversion of the = 1/2 states between Sr - Br, and suggest that the role played by the Coulomb interaction is dominant. An isospin breaking contribution of nuclear origin is estimated to be keV.

    nucl-thnucl-exPRC(2020)·15 citations
  2. 02

    A field theoretical model for quarkyonic matter

    Gaoqing Cao🇨🇳 · Jinfeng Liao🇺🇸

    The possibility that nuclear matter at a density relevant to the interior of massive neutron stars may be a quarkynoic matter has attracted considerable recent interest. In this work, we construct a field theoretical model to describe the quarkyonic matter, that would allow quantitative and systematic calculations of its various properties. This is implemented by synthesizing the Walecka model together with the quark-meson model, where both quark and nucleon degrees of freedom are present based on the quarkyonic scenario. With this model we compute at mean-field level the thermodynamic properties of the symmetric nuclear matter and calibrate model parameters through well-known nuclear physics measurements. We find this model gives a very good description of the symmetric nuclear matter from moderate to high baryon density and demonstrates a continuous transition from nucleon-dominance to quark-dominance for the system.

    nucl-thJHEP(2020)·39 citations
  3. 03

    A New Radioactive Decay Mode, True Ternary Fission, the Decay of Heavy Nuclei Into Three Comparable Fragments

    W. von Oertzen (1 and 2) · A. K. Nasirov (3 and 4) ((1) Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany, (2) Fachbereich Physik Freie Universitaet Berlin, (3) Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna 141980 Russia, (4) Institute of Nuclear Physics, Ulugbek, Tashkent,100214, Uzbekistan)

    The ternary cluster decay of heavy nuclei has been observed in several experiments with binary coincidences between two fragments using detector telescopes (the FOBOS-detectors, JINR, Dubna) placed on the opposite sides from the source of fissioning nuclei. The binary coincidences at a relative angle of 180 deg. correspond to binary fission or to the decay into three cluster fragments by registration of two nuclei with different masses (e.g.Sn,Ca,Ni). This marks a new step in the physics of fission-phenomena of heavy nuclei. These experimental results for the collinear cluster tripartition (CCT), refer to the decay into three clusters of comparable masses. In the present work we discuss the various aspects of this ternary fission (FFF) mode. The question of collinearity is analysed on the basis of recent publications. Further insight into the possible decay modes is obtained by the discussion of the path towards larger deformation, towards hyper-deformation and by inspecting details of the potential energy surfaces (PES). In the path towards the extremely deformed states leading to ternary fission, the concept of deformed shells is most important. At the scission configuration the phase space determined by the PES's leads to the final mass distributions. The possibility of formation of fragments of almost equal size ( = 32, 34, 32, for =98) and the observation of several other fission modes in the same system can be predicted by the PES. The PES's show pronounced minima and valleys, namely for several mass/charge combinations of ternary fragments, which correspond to a variety of collinear ternary fission (multi-modal) decays. The case of the decay of Cf(sf,fff) turns out to be unique due to the presence of deformed shells in the total system and of closed shells in all three nuclei in the decay.

    nucl-thnucl-exEPJA(2020)·12 citations
  4. 04

    Shell Evolution in Neutron-rich Ge, Se, Kr and Sr Nuclei within RHB Approach

    M. El Adri · M. Oulne

    The exotic even-even isotopic chains from Z=32 to Z=38 are investigated by means of the relativistic Hartree-Bogoliubov (RHB) approach with the explicit Density Dependent Meson-Exchange (DD-ME2) and Density Dependent Point-Coupling (DD-PC1) models. The classic magic number N=50 is reproduced and the new number N=70 is predicted to be a robust shell closure by analysing several calculated quantities such as: two-neutron separation energies, two-neutron shell gap, neutron pairing energy, potential energy surface and neutron single particle energies with and without the tensor force. The obtained results are corroborated by shell model calculations and compared with the predictions of finite range droplet model (FRDM) and with the available experimental data. A reasonable and satisfactory agreement between the theoretical models and experiment is established.

    nucl-thIJMPE(2020)·2 citations
  5. 05

    Relativistic nuclear collisions: Establishing a non-critical baseline for fluctuation measurements

    Peter Braun-Munzinger🇩🇪 · Bengt Friman🇩🇪 · Krzysztof Redlich🇵🇱 · Anar Rustamov🇩🇪 · Johanna Stachel🇩🇪

    We study the influence of global baryon number conservation on the non-critical baseline of net baryon cumulants in heavy-ion collisions in a given acceptance, accounting for the asymmetry between the mean-numbers of baryons and antibaryons. We derive the probability distribution of net baryon number in a restricted phase space from the canonical partition function that incorporates exact conservation of baryon number in the full system. Furthermore, we provide tools to compute cumulants of any order from the generating function of uncorrelated baryons constrained by exact baryon number conservation. The results are applied to quantify the non-critical baseline for cumulants of net proton number fluctuations obtained in heavy-ion collisions by the STAR collaboration at different RHIC energies and by the ALICE collaboration at the LHC. Furthermore, volume fluctuations are added by a Monte Carlo procedure based on the centrality dependence of charged particle production as measured experimentally. Compared to the predictions based on the hadron resonance gas model or Skellam distribution a clear suppression of fluctuations is observed due to exact baryon-number conservation. The suppression increases with the order of the cumulant and towards lower collision energies. Predictions for net proton cumulants up to the eight order in heavy-ion collisions are given for experimentally accessible collision energies.

    nucl-thNPA(2021)·128 citations
  6. 06

    Variational Approach to Tunneling Dynamics. Application to Hot Superfluid Fermi Systems. Spontaneous and Induced Fission

    Shimon Levit

    We introduce a general variational framework to address the tunneling of hot Fermi systems. We use the representation of the trace of the imaginary time propagator as a functional integral type of a sum over complete sets of states at intermediate propagation slices. We assume that these states are -dependent and generated by an arbitrary trial Hamiltonian . We then use the convexity inequality to derive controlled variational bound for a trial action functional. This functional has a general structure consisting of two parts - statistically weighted quantum penetrability and dynamical tunneling entropy. We examine how this structure incorporates the basic physics of tunneling of hot Fermi systems. Using the variational inequality one can optimise the dynamical parameters controlling the action functional for any choice of the trial problem. As an application we take to describe imaginary time dynamics of non interacting Bogoliubov-de Gennes (BdG) quasiparticles. Optimising its dynamical parameters we extend the tunneling theory of hot Fermi systems to the Hartree-Fock-Bogoliubov(HFB) frame and derive the corresponding generalisation of imaginary time temperature dependent BdG mean field equations. As in the trial action the prominent feature of these equations is an inseparable interplay between quantum dynamical and entropic statistical effects. In the zero temperature limit these equations describe the "false ground state" tunneling decay of superfluid Fermi systems (spontaneous fission in nuclear physics). With increasing excitation energy (effective temperature) the decay process is gradually evolving from pure quantum tunneling to statistical "bottle neck" escape mechanism.

    nucl-thPLB(2021)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE