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Nuclear Theory·nucl-th

Tuesday·August 25, 2020

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 01

    Coupled-cluster calculations of neutrinoless double-beta decay in Ca

    S. J. Novario🇺🇸 · P. Gysbers🇨🇦 · J. Engel🇺🇸 · G. Hagen🇺🇸 · G. R. Jansen🇺🇸 · T. D. Morris🇺🇸 · P. Navrátil🇨🇦 · T. Papenbrock🇺🇸 · S. Quaglioni🇺🇸

    We use coupled-cluster theory and nuclear interactions from chiral effective field theory to compute the nuclear matrix element for the neutrinoless double-beta decay of Ca. Benchmarks with the no-core shell model in several light nuclei inform us about the accuracy of our approach. For Ca we find a relatively small matrix element. We also compute the nuclear matrix element for the two-neutrino double-beta decay of Ca with a quenching factor deduced from two-body currents in recent ab-initio calculation of the Ikeda sum-rule in Ca [Gysbers et al., Nature Physics 15, 428-431 (2019)].

    nucl-thPRL(2021)·115 citations
  2. 02

    Microscopic model for the collective enhancement of nuclear level densities

    Jie Zhao · Tamara Nikšić · Dario Vretenar

    A microscopic method for calculating nuclear level densities (NLD) is developed, based on the framework of energy density functionals. Intrinsic level densities are computed from single-quasiparticle spectra obtained in a finite-temperature self-consistent mean-field (SCMF) calculation that takes into account nuclear deformation, and is specified by the choice of the energy density functional (EDF) and pairing interaction. The total level density is calculated by convoluting the intrinsic density with the corresponding collective level density, determined by the eigenstates of a five-dimensional quadrupole or quadrupole plus octupole collective Hamiltonian. The parameters of the Hamiltonian (inertia parameters, collective potential) are consistently determined by deformation-constrained SCMF calculations using the same EDF and pairing interaction. The model is applied in the calculation of NLD of Mo, Pd, Cd, Dy, Er, and Yb, in comparison with available data. It is shown that the collective enhancement of the intrinsic level density, consistently computed from the eigenstates of the corresponding collective Hamiltonian, leads to total NLDs that are in excellent agreement with data over the whole energy range of measured values.

    nucl-thnucl-exPRC(2020)·19 citations
  3. 03

    Local energy-momentum conservation and initial conditions for quark-gluon plasma evolution in nucleus-nucleus collisions at SPS and RHIC BES energies

    Antoni Szczurek🇵🇱

    We investigate consequences of local energy-momentum conservation for initial eccentricity coefficients in heavy ion collisions at not too high energies relevant for CERN SPS and RHIC BES. Different models of energy density available for pion production are considered. We study dependence of eccentricity coefficients on space-time rapidity for different impact parameters. The naive formula how to define eccentricities breaks with our initial conditions and must be corrected. We predict considerable eccentricities for and specific dependence on space-time rapidity as well as on impact parameter for lower energies. The effect becomes smaller at larger energies when restricting to narrow rapidity interval arround zero. Our predictions are in principle input for further hydrodynamical evolution but it is not clear whether they can be easily used. Our initial condition suggest a strong preequilibrium phase which is difficult for modelling.

    nucl-thhep-ph0 citations
  4. 04

    The total reaction cross section of heavy-ion reactions induced by stable and unstable exotic beams: The low-energy regime

    L. F. Canto · V. Guimaraes · J. Lubian · M. S. Hussein

    In this review paper we present a detailed account of the extraction and the calculation of the total reaction cross section of strongly bound and weakly bound, stable and unstable, exotic, nuclei. We discuss the optical model and the more general coupled channels model of direct reactions. The effect of long-range absorption due to the coupling to excited states in the target and to the breakup continuum in the projectile is also discussed. The generalized optical theorem for charged particle scattering and the resulting sum-of differences method is then discussed. The so-called "quarter-point recipe" is discussed next, and the quarter-point angle is introduced as a simple and rapid mean to obtain the total reaction cross section. The last topic discussed is the reduction of the total reaction cross section that would allow a large body of data to sit on a single universal function. Such a universal function exists in the case of the fusion data, and the aim of this last topic of the review is to extend the fusion case to the total reaction, by adding the direct reaction contribution. Also discussed is the inclusive breakup cross section and how it can be used to extract the total reaction cross section of the interacting fragment with the target. This method is also known as the Surrogate method and represents a case of hybrid reactions. The sum of the integrated inclusive breakup cross section with the complete fusion cross section supplies the total fusion cross section. The main experimental methods to determine the total reaction cross section are also discussed, with emphasis in recent techniques developed to deal with reactions induced by unstable beams.

    nucl-thnucl-exEPJA(2020)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE