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Nuclear Theory·nucl-th

Wednesday·June 24, 2015

9 papers—5 primary·4 cross-listed

All9Primary5Cross-lists4
  1. 01

    Event shape sorting

    Renata Kopecna🇨🇿 · Boris Tomasik🇨🇿

    We propose a novel method for sorting events of multiparticle production according to the azimuthal anisotropy of their momentum distribution. Although the method is quite general, we advocate its use in analysis of ultra-relativistic heavy-ion collisions where large number of hadrons is produced. The advantage of our method is that it can automatically sort out samples of events with histograms that indicate similar distributions of hadrons. It takes into account the whole measured histograms with all orders of anisotropy instead of a specific observable (e.g. , , ). It can be used for more exclusive experimental studies of flow anisotropies which are then more easily compared to theoretical calculations. It may also be useful in the construction of mixed-events background for correlation studies as it allows to select events with similar momentum distribution.

    nucl-thhep-phnucl-exphysics.data-anEPJA(2016)·10 citations
  2. 02

    Dynamical effects of spin-dependent interactions in low- and intermediate-energy heavy-ion reactions

    Jun Xu🇨🇳 · Bao-An Li🇺🇸 · Wen-Qing Shen🇨🇳 · Yin Xia🇨🇳

    It is well known that non-central nuclear forces, such as the spin-orbital coupling and the tensor force, play important roles in understanding many interesting features of nuclear structures. However, their dynamical effects in nuclear reactions are poorly known since only the spin-averaged observables are normally studied both experimentally and theoretically. Realizing that spin-sensitive observables in nuclear reactions may carry useful information about the in-medium properties of non-central nuclear interactions, besides earlier studies using the time-dependent Hartree-Fock approach to understand effects of spin-orbital coupling on the threshold energy and spin polarization in fusion reactions, some efforts have been made recently to explore dynamical effects of non-central nuclear forces in intermediate-energy heavy-ion collisions using transport models. The focuses of these studies have been on investigating signatures of the density and isospin dependence of the form factor in the spin-dependent single-nucleon potential. Interestingly, some useful probes were identified in the model studies while so far there is still no data to compare with. In this brief review, we summarize the main physics motivations as well as the recent progress in understanding the spin dynamics and identifying spin-sensitive observables in heavy-ion reactions at intermediate energies. We hope the interesting, important, and new physics potentials identified in the spin dynamics of heavy-ion collisions will stimulate more experimental work in this direction.

    nucl-thnucl-exFront.Phys.(Beijing)(2015)·7 citations
  3. 03

    Shape evolution and collective dynamics of quasifission in TDHF

    A.S. Umar · V.E. Oberacker · C. Simenel

    Background: At energies near the Coulomb barrier, capture reactions in heavy-ion collisions result either in fusion or in quasifission. The former produces a compound nucleus in statistical equilibrium, while the second leads to a reseparation of the fragments after partial mass equilibration without formation of a compound nucleus. Extracting the compound nucleus formation probability is crucial to predict superheavy-element formation cross-sections. It requires a good knowledge of the fragment angular distribution which itself depends on quantities such as moments of inertia and excitation energies which have so far been somewhat arbitrary for the quasifission contribution. Methods: We investigate the evolution of the nuclear density in time-dependent Hartree-Fock (TDHF) calculations leading to quasifission. Our main goal is to extract ingredients of the formula used in the analysis of experimental angular distributions. These include the moment-of-inertia and temperature. We study the dependence of these quantities on various initial conditions of the reaction process. Results: The evolution of the moment of inertia is clearly non-trivial and depends strongly on the characteristics of the collision. The temperature rises quickly when the kinetic energy is transformed into internal excitation. Then, it rises slowly during mass transfer. Conclusions: Fully microscopic theories are useful to predict the complex evolution of quantities required in macroscopic models of quasifission.

    nucl-thPRC(2015)·80 citations
  4. 04

    Antinucleon-nucleus interaction near threshold from the Paris potential

    E. Friedman🇮🇱 · A. Gal🇮🇱 · B. Loiseau🇫🇷 · S. Wycech🇵🇱

    A general algorithm for handling the energy dependence of hadron-nucleon amplitudes in the nuclear medium, consistently with their density dependence, has been recently applied to antikaons, eta mesons and pions interacting with nuclei. Here we apply this approach to antiprotons below threshold, analyzing experimental results for antiprotonic atoms across the periodic table. It is also applied to antiproton and antineutron interaction with nuclei up to 400 MeV/c, comparing with elastic scattering and annihilation cross sections. The underlying scattering amplitudes are derived from the Paris potential, including modifications in the medium. Emphasis is placed on the role of the -wave amplitudes with respect to the repulsive -wave amplitudes.

    nucl-thhep-phNPA(2015)·14 citations
  5. 05

    The concept of nuclear cluster forbiddenness

    Huitzilin H. Yepez-Martinez · Peter Otto Hess

    In nuclear cluster systems, a rigorous structural forbiddenness of virtual nuclear division into unexcited fragments is obtained. We re-analyze the concept of forbiddenness, introduced in Ref. 1 for the understanding of structural effects in nuclear cluster physics. We show that the concept is more involved than the one presented previously, where some errors were committed. Due to its importance, it is reanalyzed here. In the present contribution a simple way for the determination of forbiddenness is given, which may easily be extended to any number of clusters, though in this contribution we discuss only two-cluster systems, for illustrative reasons. A simple rule is obtained for the minimization of the forbiddenness, namely to start from a cluster system with a large SU(3) irrep (lambda,mu), but minimizing (lambda-mu), i.e. the system has to be oblate. The rule can be easily implemented in structural studies, done up to now with an oversimplified definition of forbiddenness. The new method is applied to various systems of light clusters and to some decay channels of 236U and 252Cf.

    nucl-thJ.Phys.G(2015)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE