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Nuclear Theory·nucl-th

Wednesday·October 7, 2015

13 papers—7 primary·6 cross-listed

All13Primary7Cross-lists6
  1. 01

    [Submitted on 5 Oct 2015]

    Liquid-gas phase transition in strange hadronic matter with relativistic models

    James R. Torres🇧🇷 · Francesca Gulminelli🇫🇷 · Débora P. Menezes🇧🇷

    Background: The advent of new dedicated experimental programs on hyperon physics is rapidly boosting the field, and the possibility of synthetizing multiple strange hypernuclei requires the addition of the strangeness degree of freedom to the models dedicated to nuclear structure and nuclear matter studies at low energy. Purpose: We want to settle the influence of strangeness on the nuclear liquid-gas phase transition. Because of the large uncertainties concerning the hyperon sector, we do not aim at a quantitative estimation of the phase diagram but rather at a qualitative description of the phenomenology, as model independent as possible. Method: We analyze the phase diagram of low density matter composed of neutrons, protons and hyperons using a Relativistic Mean Field (RMF) model. We largely explore the parameter space to pin down generic features of the phase transition, and compare the results to ab-initio quantum Monte Carlo calculations. Results: We show that the liquid-gas phase transition is only slightly quenched by the addition of hyperons. Strangeness is seen to be an order parameter of the phase transition, meaning that dilute strange matter is expected to be unstable with respect to the formation of hyper-clusters. Conclusions: More quantitative results within the RMF model need improved functionals at low density, possibly fitted to ab-initio calculations of nuclear and matter.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1510.01381 [pdf]
    PRC(2016)·16 citations
  2. 02

    [Submitted on 6 Oct 2015]

    Theoretical study of the elastic breakup of weakly bound nuclei at near barrier energies

    D. R. Otomar · P. R. S. Gomes · J. Lubian · L. F. Canto · M. S. Hussein

    We have performed CDCC calculations for collisions of Li projectiles on Co, Sm and Pb targets at near-barrier energies, to assess the importance of the Coulomb and the nuclear couplings in the breakup of Li, as well as the Coulomb-nuclear interference. We have also investigated scaling laws, expressing the dependence of the cross sections on the charge and the mass of the target. This work is complementary to the one previously reported by us on the breakup of Li. Here we explore the similarities and differences between the results for the two Lithium isotopes. The relevance of the Coulomb dipole strength at low energy for the two-cluster projectile is investigated in details.

    Comments:
    6 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1510.01408 [pdf]
    PRC(2015)·9 citations
  3. 03

    [Submitted on 6 Oct 2015]

    Thermalization of dense hadronic matter in Au + Au collisions at the energies available at FAIR

    Somnath De🇮🇳 · Sudipan De🇧🇷 · Subhasis Chattopadhyay🇮🇳

    The conditions of local thermodynamic equilibrium of baryons (non-strange, strange) and mesons (strange) are presented for central Au + Au collisions at FAIR energies using the microscopic transport model UrQMD. The net particle density, longitudinal-to-transverse pressure anisotropy and inverse slope parameters of the energy spectra of non-strange and strange hadrons are calculated inside a cell in the central region within rapidity window at different time steps after the collision. We observed that the strangeness content is dominated by baryons at all energies, however contribution from mesons become significant at higher energies. The time scale obtained from local pressure (momentum) isotropization and thermalization of energy spectra are nearly equal and found to decrease with increase in laboratory energy. The equilibrium thermodynamic properties of the system are obtained with statistical thermal model. The time evolution of the entropy densities at FAIR energies are found very similar with the ideal hydrodynamic behaviour at top RHIC energy.

    Comments:
    New figures, discussions added. To appear in Physical Review C
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1510.01456 [pdf]
    PRC(2016)·8 citations
  4. 04

    [Submitted on 6 Oct 2015]

    Proton-Neutron Pairs in Heavy Deformed Nuclei

    Dennis Bonatsos · I.E. Assimakis · Andriana Martinou

    The microscopic justification of the emergence of SU(3) symmetry in heavy nuclei remains an interesting problem. In the past, the pseudo-SU(3) approach has been used, with considerable success. Recent results seem to suggest that the key for understanding the emergence of SU(3) symmetry lies in the properties of the proton-neutron interaction, namely in the formation of (S=1, T=0) p-n pairs in heavy nuclei, especially when the numbers of valence protons and valence neutrons are nearly equal. Although this idea has been around for many years, since the introduction of the Federman-Pittel mechanism, it is only recently that information about the p-n interaction could be obtained from nuclear masses, which become available from modern facilities. Based on this information, a new coupling scheme for heavy deformed nuclei has been suggested and is under development.

    Comments:
    12 pages, 3 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1510.01473 [pdf]
    Bulg.J.Phys.(2015)·4 citations
  5. 05

    [Submitted on 6 Oct 2015]

    Hard Probes: After the dust has settled!

    Abhijit Majumder🇺🇸

    A lot has been learnt in the 15 years since the first data on jet modification at the Relativistic Heavy Ion Collider (RHIC). These proceedings will describe the portion of the theory that is unassailable, and attempt to chart a course for the next period of precision measurements and related calculations. In particular, we will focus on the emerging series of higher order calculations, which may reveal the scale, energy and temperature dependence of jet transport coefficients, as well as develop ingredients for a future NLO calculation of jet modification. Connections with the underlying degrees of freedom in the Quark Gluon Plasma (QGP) will be explored. We will discuss the challenges faced by Monte-Carlo event generators and their comparison with a broad spectrum of jet modification data. First principles calculations of transport coefficients, and the determination of new transport coefficients which encapsulate the transition of energy momentum from the jet scale to the medium scale will also be discussed.

    Comments:
    6 pages, 2 figures, Plenary talk at Hard Probes 2015 conference
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1510.01581 [pdf]
    Nucl.Part.Phys.Proc.(2016)·5 citations
  6. 06

    [Submitted on 1 Oct 2015]

    The effect of tensor interaction in splitting the energy levels of relativistic systems

    Mohammad Reza Shojaei · Mohsen Mousavi

    In this paper we solve analytically Dirac equation for Eckart plus Hulthen potentials with Coulomb-like and Yukawa-like tensor interaction in the presence of Spin and Pseudo-spin Symmetry for any k number. The Parametric Nikiforov-Uvarov method is used to obtain the energy Eigen-values and wave functions. We also discuss the energy Eigen-values and the Dirac spinors for the Eckart plus Hulthen potentials for the spin and pseudo-spin symmetry with PNU method. To show the accuracy of the present model, some numerical results are shown in both pseudo-spin and spin symmetry limits.

    Comments:
    19 Pages, 13 Figures,6 Table
    Subjects:
    Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    1510.01636 [pdf]
    Adv.High Energy Phys.(2016)·9 citations
  7. 07

    [Submitted on 6 Oct 2015]

    Microscopic description of fission in neutron-rich Radium isotopes with the Gogny energy density functional

    R.R. Rodriguez-Guzman · L.M. Robledo

    Mean field calculations, based on the D1S, D1N and D1M parametrizations of the Gogny energy density functional, have been carried out to obtain the potential energy surfaces relevant to fission in several Ra isotopes with the neutron number 144 N 176. Inner and outer barrier heights as well as first and second isomer excitation energies are given. The existence of a well developed third minimum along the fission paths of Ra nuclei, is analyzed in terms of the energetics of the "fragments" defining such elongated configuration. The masses and charges of the fission fragments are studied as functions of the neutron number in the parent Ra isotope. The comparison between fission and -decay half-lives, reveals that the former becomes faster for increasing neutron numbers. Though there exists a strong variance of the results with respect to the parameters used in the computation of the spontaneous fission rate, a change in tendency is observed at N=164 with a steady increase that makes heavier neutron-rich Ra isotopes stable against fission, diminishing the importance of fission recycling in the r-process.

    Comments:
    12 pages, 9 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1510.01652 [pdf]
    EPJA(2016)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE