Nuclear Theory·nucl-th

Friday·April 22, 2016

11 papers—9 primary·2 cross-listed

01
Determining astrophysical three-body radiative capture reaction rates from inclusive Coulomb break-up measurements
J. Casal · M. Rodríguez-Gallardo · J. M. Arias · J. Gómez-Camacho
A relationship between the Coulomb inclusive break-up probability and the radiative capture reaction rate for weakly-bound three-body systems is established. This direct link provides a robust procedure to estimate the reaction rate for nuclei of astrophysical interest by measuring inclusive break-up processes at different energies and angles. This might be an advantageous alternative to the determination of reaction rates from the measurement of $B (E 1)$ distributions through exclusive Coulomb break-up experiments. In addition, it provides a reference to assess the validity of different theoretical approaches that have been used to calculate reaction rates. The procedure is applied to $^{11}$ Li ( $^{9}$ Li+n+n) and $^{6}$ He ( $^{4}$ He+n+n) three-body systems for which some data exist.
nucl-thnucl-exPRC(2016)·6 citations
02
Importance of separated efficiencies between positively and negatively charged particles for cumulant calculations
Toshihiro Nonaka🇯🇵 · Tetsuro Sugiura🇯🇵 · ShinIchi Esumi🇯🇵 · Hiroshi Masui🇯🇵 · Xiaofeng Luo🇨🇳
We show the importance of separated efficiency corrections between positively and negatively charged particles for cumulant calculations by Monte Carlo toy models and analytical calculations. Our results indicate that S{\sigma} in published net-proton results from the STAR experiment will be suppressed about 5 to 10% in central collisions, and 10 to 20% in peripheral collisions at the beam energy of \sqrt s_{NN} = 62.4 and 200 GeV if the separated efficiencies are used to efficiency correction.
nucl-thphysics.data-anPRC(2016)·11 citations
03
Shells, orbit bifurcations and symmetry restorations in Fermi systems
A.G. Magner · M.V. Koliesnik · K. Arita
The periodic-orbit theory based on the improved stationary-phase method within the phase-space path integral approach is presented for the semiclassical description of the nuclear shell structure, concerning the main topics of the fruitful activity of V. G. Solovjov. We apply this theory to study bifurcations and symmetry breaking phenomena in a radial power-law potential which is close to the realistic Woods-Saxon one up to about the Fermi energy. Using the realistic parametrization of nuclear shapes we explain the origin of the double-humped fission barrier and the asymmetry in the fission isomer shapes by the bifurcations of periodic orbits. The semiclassical origin of the oblate-prolate shape asymmetry and tetrahedral shapes is also suggested within the improved periodic-orbit approach. The enhancement of shell structures at some surface diffuseness and deformation parameters of such shapes are explained by existence of the simple local bifurcations and new non-local bridge-orbit bifurcations in integrable and partially integrable Fermi systems. We obtained good agreement between the semiclassical and quantum shell-structure components of the level density and energy for several surface diffuseness and deformation parameters of the potentials, including their symmetry breaking and bifurcation values.
nucl-thPhys.Atom.Nucl.(2016)·6 citations
04
Second--order equation of state with the Skyrme interaction. Cutoff and dimensional regularization with the inclusion of rearrangement terms
C.J. Yang🇫🇷 · M. Grasso🇫🇷 · X. Roca-Maza🇮🇹 · G. Colò🇮🇹 · K. Moghrabi🇱🇧
We evaluate the second--order (beyond--mean--field) contribution to the equation of state of nuclear matter with the effective Skyrme force and use cutoff and dimensional regularizations to treat the ultraviolet divergence produced by the zero--range character of this interaction. An adjustment of the force parameters is then performed in both cases to remove any double counting generated by the explicit computation of beyond--mean--field corrections with the Skyrme force. In addition, we include at second order the rearrangement terms associated to the density--dependent part of the Skyrme force and discuss their effect. Sets of parameters are proposed to define new effective forces which are specially designed for second--order calculations in nuclear matter.
nucl-thPRC(2016)·22 citations
05
On {\gamma}-rigid regime of the Bohr-Mottelson Hamiltonian in the presence of a minimal length
M. Chabab🇲🇦 · A. El Batoul🇲🇦 · A. Lahbas🇲🇦 · M. Oulne🇲🇦
A prolate {\gamma}-rigid regime of the Bohr-Mottelson Hamiltonian within the minimal length formalism, involving an infinite square well like potential in {\beta} collective shape variable, is developed and used to describe the spectra of a variety of vibrational-like nuclei. The effect of the minimal length on the energy spectrum and the wave function is duly investigated. Numerical calculations are performed for some nuclei revealing a qualitative agreement with the available experimental data.
nucl-thPLB(2016)·25 citations
06
Octupole correlations in low-lying states of 150Nd and 150Sm and their impact on neutrinoless double-beta decay
J. M. Yao🇺🇸 · J. Engel🇺🇸
We present a generator-coordinate calculation, based on a relativistic energy-density functional, of the low-lying spectra in the isotopes $^{150}$ Nd and $^{150}$ Sm and of the nuclear matrix element that governs the neutrinoless double-beta decay of the first isotope to the second. We carefully examine the impact of octupole correlations on both nuclear structure and the double-beta decay matrix element. Octupole correlations turn out to reduce quadrupole collectivity in both nuclei. Shape fluctuations, however, dilute the effects of octupole deformation on the double-beta decay matrix element, so that the overall octupole-induced quenching is only about 7\%.
nucl-thnucl-exPRC(2016)·41 citations
07
Electromagnetic probes of a pure-glue initial state in nucleus-nucleus collisions at energies available at the CERN Large Hadron Collider
V. Vovchenko🇩🇪 · Iu. A. Karpenko🇺🇦 · M. I. Gorenstein🇺🇦 · L. M. Satarov🇩🇪 · I. N. Mishustin🇩🇪 · B. Kämpfer🇩🇪 · H. Stoecker🇩🇪
Partonic matter produced in the early stage of ultrarelativistic nucleus-nucleus collisions is assumed to be composed mainly of gluons, and quarks and antiquarks are produced at later times. To study the implications of such a scenario, the dynamical evolution of a chemically nonequilibrated system is described by the ideal (2+1)-dimensional hydrodynamics with a time dependent (anti)quark fugacity. The equation of state interpolates linearly between the lattice data for the pure gluonic matter and the lattice data for the chemically equilibrated quark-gluon plasma. The spectra and elliptic flows of thermal dileptons and photons are calculated for central Pb+Pb collisions at the CERN Large Hadron Collider energy of $s_{_{NN}} = 2.76$ TeV. We test the sensitivity of the results to the choice of equilibration times, including also the case where the complete chemical equilibrium of partons is reached already at the initial stage. It is shown that a suppression of quarks at early times leads to a significant reduction of the yield of the thermal dileptons, but only to a rather modest suppression of the $p_{T}$ -distribution of direct photons. It is demonstrated that an enhancement of photon and dilepton elliptic flows might serve as a promising signature of the pure-glue initial state.
nucl-thhep-phPRC(2016)·34 citations
08
Deformation effects in the alpha accompanied cold ternary fission of even-even $^{244 - 260}$ Cf isotopes
K P Santhosh · Sreejith Krishnan
Within the Unified ternary fission model (UTFM), the alpha accompanied ternary fission of even-even $^{244 - 260}$ Cf isotopes has been studied by taking the interacting barrier as the sum of Coulomb and proximity potential. For the alpha accompanied ternary fission of 244^Cf isotope, the highest yield is obtained for the fragment combination 108^Ru+4^He+132^Te, which contain near doubly magic nuclei 132^Te (N=80, Z=52). In the case of 246^Cf and 248^Cf isotopes, the highest yield is obtained for the fragment combinations with near doubly magic nuclei 134^Te (N=82, Z=52) as the heavier fragment. The highest yield obtained for 250^Cf, 252^Cf, 254^Cf, 256^Cf, 258^Cf and 260^Cf isotopes is for the fragment combination with doubly magic nuclei 132^Sn (N=82, Z=50) as the heavier fragment. We have included the effect of deformation and orientation of fragments and this has revealed that in addition to closed shell effect, ground state deformation also plays an important role in the calculation of relative yield of favorable fragment combinations. The computed isotopic yields for alpha accompanied ternary fission of 252^Cf isotope are found to be in agreement with the experimental data. The emission probability and kinetic energy of long range alpha particle is calculated for the various isotopes of Cf and are found to be in good agreement with the experimental data.
nucl-thnucl-exEPJA(2016)·10 citations
09
Energy, centrality and momentum dependence of dielectron production at collider energies in a coarse-grained transport approach
Stephan Endres🇩🇪 · Hendrik van Hees🇩🇪 · Marcus Bleicher🇩🇪
Dilepton production in heavy-ion collisions at collider energies - i.e., for the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) - is studied within an approach that uses coarse-grained transport simulations to calculate thermal dilepton emission applying in-medium spectral functions from hadronic many-body theory and partonic production rates based on lattice calculations. The microscopic output from the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model is hereby put on a grid of space-time cells which allows to extract the local temperature and chemical potential in each cell via an equation of state. The resulting dilepton spectra are in good agreement with the experimental results for the range of RHIC energies, $s_{N N} = 19.6 - 200$ GeV. The comparison of data and model outcome shows that the newest measurements by the PHENIX and STAR collaborations are consistent and that the low-mass spectra can be described by a cocktail of hadronic decay contributions together with thermal emission from broadened vector-meson spectral functions and from the Quark-Gluon Plasma phase. Predictions for dilepton results at LHC energies show no significant change of the spectra as compared to RHIC, but a higher fraction of thermal contribution and harder slopes of the transverse momentum distributions due to the higher temperatures and flow obtained.
nucl-thhep-phPRC(2016)·24 citations

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first authorsco-authorsvia INSPIRE