Nuclear Theory·nucl-th

Thursday·April 16, 2015

12 papers—7 primary·5 cross-listed

01
Jet propagation within a Linearized Boltzmann Transport Model
Tan Luo (CCNU)🇨🇳 · Yayun He (CCNU)🇨🇳 · Xin-Nian Wang (CCNU & LBNL)🇨🇳 · Yan Zhu (Santiago de Compostela U.)🇪🇸
A Linear Boltzmann Transport (LBT) model has been developed for the study of jet propagation inside a quark-gluon plasma. Both leading and thermal recoiled partons are transported according to the Boltzmann equations to account for jet-induced medium excitations. In this talk, we present our study within the LBT model in which we implement the complete set of elastic parton scattering processes. We investigate elastic parton energy loss and their energy and length dependence. We further investigate elastic energy loss and transverse shape of reconstructed jets. Contributions from the recoiled thermal partons are found to have significant influences on the jet energy loss and transverse profile.
nucl-thhep-phNPA(2014)·3 citations
02
Semi-microscopic modeling of heavy-ion fusion reactions with multi-reference covariant density functional theory
K. Hagino · J.M. Yao
We describe low-lying collective excitations of atomic nuclei with the multi-reference covariant density functional theory, and combine them with coupled-channels calculations for heavy-ion fusion reactions at energies around the Coulomb barrier. To this end, we use the calculated transition strengths among several collective states as inputs to the coupled-channels calculations. This approach provides a natural way to describe anharmonic multi-phonon excitations as well as a deviation of rotational excitations from a simple rigid rotor. We apply this method to subbarrier fusion reactions of $^{58}$ Ni+ $^{58}$ Ni, $^{58}$ Ni+ $^{60}$ Ni and $^{40}$ Ca+ $^{58}$ Ni systems. We find that the effect of anharmonicity tends to smear the fusion barrier distributions, better reproducing the experimental data compared to the calculations in the harmonic oscillator limit.
nucl-thnucl-exPRC(2015)·14 citations
03
Principal component analysis within nuclear structure
A. Al-Sayed
The principal component analysis (PCA) of different parameters affecting collectivity of nuclei predicted to be candidate of the interacting boson model dynamical symmetries are performed. The results show that, the use of PCA within nuclear structure can give us a simple way to identify collectivity together with the parameters simultaneously affecting it.
nucl-thNPA(2015)·5 citations
04
Light exotic nuclei with extreme neutron excess and $2 \leq z \leq 8$
V.N. Tarasov · K.A. Gridnev · V.I. Kuprikov · D.K. Gridnev · D.V. Tarasov · K.S. Godbey · X. ViÑas · Walter Greiner
Using HF+BCS method we study light nuclei with nuclear charge in the range $2 \leq Z \leq 8$ and lying near the neutron drip line. The HF method uses effective Skyrme forces and allows for axial deformations. We find that the neutron drip line forms stability peninsulas at $^{18}$ He and $^{40}$ C. These isotopes are found to be stable against one neutron emission and possess the highest known neutron to proton ratio in stable nuclei.
nucl-thIJMPE(2015)·0 citations
05
Light clusters, pasta phases and phase transitions in core-collapse supernova matter
Helena Pais🇵🇹 · Silvia Chiacchiera🇵🇹 · Constanca Providência🇵🇹
The pasta phase in core-collapse supernova matter (finite temperatures and fixed proton fractions) is studied within relativistic mean field models. Three different calculations are used for comparison, the Thomas-Fermi (TF), the Coexisting Phases (CP) and the Compressible Liquid Drop (CLD) approximations. The effects of including light clusters in nuclear matter and the densities at which the transitions between pasta configurations and to uniform matter occur are also investigated. The free energy, pressure, entropy and chemical potentials in the range of particle number densities and temperatures expected to cover the pasta region are calculated. Finally, a comparison with a finite temperature Skyrme-Hartree-Fock calculation is drawn.
nucl-thPRC(2015)·64 citations
06
Quark-hadron duality constraints on \gamma Z box corrections to parity-violating elastic scattering
N. L. Hall🇨🇦 · P. G. Blunden🇨🇦 · W. Melnitchouk🇺🇸 · A. W. Thomas🇦🇺 · R. D. Young🇦🇺
We examine the interference \gamma Z box corrections to parity-violating elastic electron--proton scattering in the light of the recent observation of quark-hadron duality in parity-violating deep-inelastic scattering from the deuteron, and the approximate isospin independence of duality in the electromagnetic nucleon structure functions down to Q^2 \approx 1 GeV^2. Assuming that a similar behavior also holds for the \gamma Z proton structure functions, we find that duality constrains the \gamma Z box correction to the proton's weak charge to be \Re e\, \square_{\gamma Z}^V = (5.4 \pm 0.4) \times 10^{-3} at the kinematics of the Q_{\text{weak}} experiment. Within the same model we also provide estimates of the \gamma Z corrections for future parity-violating experiments, such as MOLLER at Jefferson Lab and MESA at Mainz.
nucl-thhep-phnucl-exPLB(2016)·29 citations
07
Robustness of the Baryon-Stopping Signal for the Onset of Deconfinement in Relativistic Heavy-Ion Collisions
Yu. B. Ivanov🇷🇺 · D. Blaschke🇷🇺
The impact of the experimental acceptance, i.e. transverse-momentum ( $p_{T}$ ) cut-off and limited rapidity region, on the earlier predicted irregularity in the excitation function of the baryon stopping is studied. This irregularity is a consequence of the onset of deconfinement occurring in the compression stage of a nuclear collision and manifests itself as a wiggle in the excitation function of the reduced curvature ( $C_{y}$ ) of the net-proton rapidity distribution at midrapidity. It is demonstrated that the wiggle is a very robust signal of a first-order phase transition that survives even under conditions of a very limited acceptance. At the same time the $C_{y}$ for pure hadronic and crossover transition scenarios become hardly distinguishable, if the acceptance cuts off too much of the low- $p_{T}$ proton spectrum and/or puts too narrow rapidity window around midrapidity. It is found that the shape of the net-proton rapidity distribution near midrapidity depends on the $p_{T}$ cut-off. This implies that the measurements should be taken at the same acceptance for all collision energies in order to reliably conclude on the presence or absence of the irregularity.
nucl-thhep-exhep-phPRC(2015)·31 citations
08
Isospin breaking decay $η (1405) \to f_{0} (980) π^{0} \to 3 π$
N.N. Achasov🇷🇺 · A.A. Kozhevnikov🇷🇺 · G.N. Shestakov🇷🇺
There are attempts in the literature to theoretically explain the large breaking of isotopic invariance in the decay $η (1405)$ \, $\to$ \, $f_{0} (980) π^{0}$ \, $\to$ \, $3 π$ by the mechanism containing the logarithmic (triangle) singularity, i.e., as being due to the transition $η (1405) \to (K^{*} K ˉ + K ˉ^{*} K) \to (K^{+} K^{-} + K^{0} K ˉ^{0}) π^{0} \to f_{0} (980) π^{0} \to 3 π$ . The corresponding calculations were fulfilled for a hypothetic case of the stable $K^{*}$ meson. Here, we show that the account of the finite width of the $K^{*}$ ( $Γ_{K^{*} \to K π} \approx 50$ MeV) smoothes the logarithmic singularities in the amplitude and results in the suppression of the calculated decay width $η (1405) \to f_{0} (980) π^{0} \to 3 π$ by the factor of $6 - 8$ as compared with the case of $Γ_{K^{*} \to K π}$ \,=\,0. We also analyze the difficulties related with the assumption of the dominance of the $η (1405) \to (K^{*} K ˉ + K ˉ^{*} K) \to K K ˉ π$ decay mechanism and discuss the possible dynamics of the decay $η (1405) \to η π π$ . The decisive improvement of the experimental data on the $K K ˉ$ , $K π$ , $η π$ , and $π π$ mass spectra in the decay of the resonance structure $η (1405/1475)$ to $K K ˉ π$ and $η π π$ , and on the shape of the resonance peaks themselves in the $K K ˉ π$ and $η π π$ decay channels is necessary for the further establishing the $η (1405) \to 3 π$ decay mechanism.
↳ hep-phhep-exnucl-thPRD(2015)·73 citations
09
Interacting Ensemble of the Instanton-dyons and Deconfinement Phase Transition in the SU(2) Gauge Theory
Rasmus Larsen🇺🇸 · Edward Shuryak🇺🇸
Instanton-dyons, also known as instanton-monopoles or instanton-quarks, are topological constituents of the instantons at nonzero temperature and holonomy. We perform numerical simulations of the ensemble of interacting dyons for the SU(2) pure gauge theory. Unlike previous studies, we focus on back reaction on the holonomy and the issue of confinement. We calculate the free energy as a function of the holonomy and the dyon densities, using standard Metropolis Monte Carlo and integration over parameter methods. We observe that as the temperature decreases and the dyon density grows, its minimum indeed moves from small holonomy to the value corresponding to confinement. We then report various parameters of the self-consistent ensembles as a function of temperature, and investigate the role of inter-particle correlations.
↳ hep-phhep-latnucl-thPRD(2015)·47 citations
10
Empirical description of beta-delayed fission partial half-lives
L. Ghys · AN. Andreyev · S. Antalic · M. Huyse · P. Van Duppen
Background: The process of beta-delayed fission (bDF) provides a versatile tool to study low-energy fission in nuclei far away from the beta-stability line, especially for nuclei which do not fission spontaneously. Purpose: The aim of this paper is to investigate systematic trends in bDF partial half-lives. Method: A semi-phenomenological framework was developed to systematically account for the behavior of bDF partial half-lives. Results: The bDF partial half-life appears to exponentially depend on the difference between the Q value for beta decay of the parent nucleus and the fission-barrier energy of the daughter (after beta decay) product. Such dependence was found to arise naturally from some simple theoretical considerations. Conclusions: This systematic trend was confirmed for experimental bDF partial half-lives spanning over 7 orders of magnitudes when using fission barriers calculated from either the Thomas-Fermi or the liquid-drop fission model. The same dependence was also observed, although less pronounced, when comparing to fission barriers from the finite-range liquid-drop model or the Thomas-Fermi plus Strutinsky Integral method.
↳ nucl-exnucl-thPRC(2015)·18 citations
11
The Vacuum Structure of Vector Mesons in QCD
Fabian Rennecke🇩🇪
We study the chiral dynamics of vector mesons in two-flavor QCD in vacuum by utilizing a functional renormalization group approach. This allows us to capture the dynamical transition from the quark-gluon phase at high energies to the hadronic phase at low energies without the necessity of model parameter tuning. We use this to analyze the scaling of vector meson masses towards the chiral symmetry breaking scale, the decoupling of the mesons at high energies and the validity of vector meson dominance.
↳ hep-phhep-thnucl-thPRD(2015)·114 citations
12
Thermal properties of hot and dense matter with finite range interactions
Constantinos Constantinou🇩🇪 · Brian Muccioli🇺🇸 · Madappa Prakash🇺🇸 · James M. Lattimer🇺🇸
We explore the thermal properties of hot and dense matter using a model that reproduces the empirical properties of isospin symmetric and asymmetric bulk nuclear matter, optical model fits to nucleon-nucleus scattering data, heavy-ion flow data in the energy range 0.5-2 GeV/A, and the largest well-measured neutron star mass of 2 $M_{⊙}$ . Results of this model which incorporates finite range interactions through Yukawa type forces are contrasted with those of a zero-range Skyrme model that yields nearly identical zero-temperature properties at all densities for symmetric and asymmetric nucleonic matter and the maximum neutron star mass, but fails to account for heavy-ion flow data due to the lack of an appropriate momentum dependence in its mean field. Similarities and differences in the thermal state variables and the specific heats between the two models are highlighted. Checks of our exact numerical calculations are performed from formulas derived in the strongly degenerate and non-degenerate limits. Our studies of the thermal and adiabatic indices, and the speed of sound in hot and dense matter for conditions of relevance to core-collapse supernovae, the thermal evolution of neutron stars from their birth and mergers of compact binary stars reveal that substantial variations begin to occur at sub-saturation densities before asymptotic values are reached at supra-nuclear densities.
↳ astro-ph.SRnucl-thPRC(2015)·82 citations

Affiliations

first authorsco-authorsvia INSPIRE