Nuclear Theory·nucl-th

Tuesday·July 25, 2017

18 papers—11 primary·7 cross-listed

01
Modeling alignment enhancement for solid polarized targets
Dustin Keller🇺🇸
A model of dynamic orientation using optimized radiofrequency (RF) irradiation produced perpendicular to the holding field is developed for the spin-1 system required for tensor-polarized fixed-target experiments. The derivation applies to RF produced close to the Larmor frequency of the nucleus and requires the electron spin-resonance linewidth to be much smaller than the nuclear magnetic resonance frequency. The rate equations are solved numerically to study a semi-saturated steady-state resulting from the two sources of irradiation: microwave from the DNP process and the additional RF used to manipulate the tensor polarization. The steady-state condition and continuous-wave NMR lineshape are found that optimize the spin-1 alignment in the polycrystalline materials used as solid polarized targets in charged-beam nuclear and particle physics experiments.
nucl-thEPJA(2017)·8 citations
02
Emergence of low-energy monopole strength in the neutron-rich calcium isotopes
J. Piekarewicz
The isoscalar monopole response of neutron-rich nuclei is sensitive to both the incompressibility coefficient of symmetric nuclear matter and the density dependence of the symmetry energy. The main goal of this paper is to explore the emergence, evolution, and origin of low energy monopole strength along the even-even calcium isotopes: from 40Ca to 60Ca. The distribution of isoscalar monopole strength is computed in a relativistic random phase approximation (RPA) using three effective interactions that have been calibrated to the properties of finite nuclei and neutron stars. A non-spectral approach is adopted that allows for an exact treatment of the continuum without any reliance on discretization. For the stable calcium isotopes, no evidence of low-energy monopole strength is observed, even as the 1f7/2 neutron orbital is being filled and the neutron-skin thickness progressively grows. Further, in contrast to experimental findings, a mild softening of the monopole response with increasing mass number is predicted. Beyond 48Ca, a significant amount of low-energy monopole strength emerges as soon as the weak-binding neutron orbitals (2p and 1f5/2) become populated. The emergence and evolution of low-energy strength is identified with transitions from these weakly-bound states into the continuum. Moreover, given that models with a soft symmetry energy tend to reach the neutron-drip line earlier than their stiffer counterparts, we identify an inverse correlation between the neutron-skin thickness and the inverse energy weighted sum.
nucl-thnucl-exPRC(2017)·7 citations
03
Estimates and power counting in uniform matter with softened interactions
A. Dyhdalo🇺🇸 · S.K. Bogner🇺🇸 · R.J. Furnstahl🇺🇸
Modern softened nucleon-nucleon interactions are well-suited for perturbative many-body calculations, but a many-body power counting scheme is lacking. Estimates of diagrammatic contributions at finite density are important ingredients in such a scheme. Here we show how to make quantitative estimates of the particle-particle and hole-hole channel in uniform nuclear matter for soft interactions. We also use estimates to assess the role of normal-ordered three-body forces for a pure contact interaction.
nucl-thPRC(2017)·6 citations
04
Investigating different $Λ$ and $Λ ˉ$ polarizations in relativistic heavy-ion collisions
Zhang-Zhu Han🇨🇳 · Jun Xu🇨🇳
Based on the chiral kinetic equations of motion, spin polarizations of various quarks, due to the magnetic field induced by spectator protons as well as the quark-antiquark vector interaction, are studied within a partonic transport approach. Although the magnetic field in QGP enhances the splitting of the spin polarizations of partons compared to the results under the magnetic field in vacuum, the spin polarizations of $s$ and $s ˉ$ quarks are also sensitive to the quark-antiquark vector interaction, challenging that the different $Λ$ and $Λ ˉ$ spin polarization is a good measure of the magnetic field in relativistic heavy-ion collisions. It is also found that there is no way to obtain the large splitting of the spin polarization between $Λ$ and $Λ ˉ$ at $s_{N N} = 7.7$ GeV with partonic dynamics.
nucl-thhep-exnucl-exPLB(2018)·33 citations
05
$^{1} S_{0}$ pairing in neutron matter
H.-H. Fan · E. Krotscheck · J.W. Clark
We report calculations of the superfluid pairing gap in neutron matter for the $^{1} S_{0}$ components of the Reid soft-core $V_{6}$ and the Argonne $V_{4}^{'}$ two-nucleon interactions. Ground-state calculations have been carried out using the central part of the operator-basis representation of these interactions to determine optimal Jastrow-Feenberg correlations and corresponding effective pairing interactions within the correlated-basis formalism (CBF), the required matrix elements in the correlated basis being evaluated by Fermi hypernetted-chain techniques. Different implementations of the Fermi-Hypernetted Chain Euler-Lagrange method (FHNC-EL) agree at the percent level up to nuclear matter saturation density. For the assumed interactions, which are realistic within the low density range involved in $^{1} S_{0}$ neutron pairing, we did not find a dimerization instability arising from divergence of the in-medium scattering length, as was reported recently for simple square-well and Lennard-Jones potential models (Phys. Rev. A {\bf 92}, 023640 (2015)).
nucl-thcond-mat.quant-gasJ.Low Temp.Phys.(2017)·14 citations
06
Effects of hadronic mean-field potentials on Hanbury-Brown-Twiss correlations in relativistic heavy-ion collisions
Chun-Jian Zhang🇨🇳 · Jun Xu🇨🇳
With the parameters fitted by the particle multiplicity, the energy density at chemical freeze-out, and the charged particle elliptic flow, we have studied the effects of the hadronic mean-field potentials on the Hanbury-Brown and Twiss (HBT) correlation in relativistic heavy-ion collisions based on a multiphase transport model. The hadronic mean-field potentials are found to delay the emission time of the system and lead to large HBT radii extracted from the correlation function. Effects on the energy dependence of $R_{o}^{2} - R_{s}^{2}$ and $R_{o} / R_{s}$ as well as the eccentricity of the emission source are discussed. The HBT correlations can also be useful in understanding the mean-field potentials of protons, kaons, and antiprotons as well as baryon-antibaryon annihilations.
nucl-thhep-exnucl-exPRC(2017)·9 citations
07
Random-interaction study on linear systematics of $I^{π} = 11/ 2^{-}$ electromagnetic moments in Cd isotope chain
Z. Z. Qin · Y. Lei
In the random-interaction ensembles, electromagnetic moments of Cd $I^{π} = 11/ 2^{-}$ isomers predominately present linear systematics as changing the neutron number, which has been reported in realistic nuclear system. Quadrupole-like and $δ$ -like $p n$ interaction are responsible for such linear systematics of quadrupole and magnetic moments, respectively.
nucl-th0 citations
08
Correlations within the Non-Equilibrium Green's Function Method
M. H. Mahzoon (Michigan State U) · P. Danielewicz (Michigan State U) · A. Rios (U Surrey)
Non-equilibrium Green's Function (NGF) method is a powerful tool for studying the evolution of quantum many-body systems. Different types of correlations can be systematically incorporated within the formalism. The time evolution of the single-particle Green's functions is described in terms of the Kadanoff-Baym equations. The current work initially focuses on introducing the correlations within infinite nuclear matter in one dimension and then in a finite system in the NGF approach. Starting from the harmonic oscillator Hamiltonian, by switching on adiabatically the mean-field and correlations simultaneously, a correlated state with ground-state characteristics is arrived at within the NGF method. Furthermore the use of cooling to for improving the adiabatic switching is explored.
nucl-thnucl-exphysics.comp-phAIP Conf.Proc.(2017)·1 citation
09
Octupole deformation in the nuclear chart based on the 3D Skyrme Hartree-Fock plus BCS model
Shuichiro Ebata · Takashi Nakatsukasa
We have performed a systematic study of the ground state for even-even 1,002 nuclei in which 28 octupole-deformed nuclei are found. The interplay between the spatial deformation and the pairing correlation, plays important roles in nuclear structure. Our model is based on the Skyrme Hartree-Fock plus BCS model represented in the three-dimensional Cartesian coordinate space which can describe any kind of nuclear shape. The quadrupole and octupole deformed nuclei appear in the mass region with characteristic neutron and proton numbers which are consistent with previous studies. In our results, there appear only pear shape ( $β_{30}$ ) in the octupole deformed nuclei. We investigate the potential energy surfaces as functions of the octupole deformations ( $β_{3 m}, m = 0, 1, 2, 3$ ), which tells us that. $^{220}$ Rn has also local minima in the $β_{31}$ and $β_{32}$ potential energy surfaces.
nucl-thPhys.Scripta(2017)·56 citations
10
Shell model results for $T = 1$ and $T = 0$ bands in $^{66}$ As
Praveen C. Srivastava · R. Sahu · V.K.B. Kota
Results of a comprehensive shell model (SM) analyses, within the full $f_{5/2} p g_{9/2}$ model space, of the recently available experimental data [P. Ruotsalainen et al., Phy. Rec. C {88}, 024320 (2013)] with four $T = 0$ bands and one $T = 1$ band in the odd-odd $N = Z$ nucleus $^{66}$ As are presented. The calculations are performed using jj44b effective interaction developed recently by B.A. Brown and A.F. Lisetskiy for this model space. For the lowest two $T = 0$ bands and the $T = 1$ band, the results are in reasonable agreement with experimental data and deformed shell model is used to identify their intrinsic structure. For the $T = 1$ band, structural change at $8^{+}$ is predicted. For the third $9^{+}$ band with $T = 0$ , the shell model $B (E 2)$ values and quadrupole moments (in addition to energies) are consistent with the interpretation in terms of aligned isoscalar $n p$ pair in $g_{9/2}$ orbit coupled to the $^{64}$ Ge ground band. Similarly, the $9^{+}$ level of band 4 and a close lying $5^{+}$ level are found to be isomeric states in the analysis. Finally, energies of the band 5 members calculated using shell model with both positive and negative parity show that the observed levels are most likely negative parity levels. The SM results with jj44b are also compared with the results obtained using JUN45 interaction.
nucl-thJ.Phys.G(2017)·6 citations
11
Transverse Momentum Distribution and Elliptic Flow of Charged Hadrons in $U$ + $U$ collisions at $s_{N N} = 193$ GeV using HYDJET++
Arpit Singh🇮🇳 · P. K. Srivastava🇮🇳 · O. S. K. Chaturvedi🇮🇳 · S. Ahmad🇮🇳 · B. K. Singh🇮🇳
Recent experimental observations of the charged hadron properties in $U + U$ collisions at $193$ GeV contradict many of the theoretical models of particle production including two-component Monte Carlo Glauber model. The experimental results show a small correlation between the charged hadron properties and the initial geometrical configurations (e.g. body-body, tip-tip etc.) of $U + U$ collisions. In this article, we have modified the Monte Carlo HYDJET++ model to study the charged hadron production in $U + U$ collisions at $193$ GeV center-of-mass energy in tip-tip and body-body initial configurations. We have modified the hard as well as soft production processes to make this model suitable for $U + U$ collisions. We have calculated the pseudorapidity distribution, transverse momentum distribution and elliptic flow distribution of charged hadrons with different control parameters in various geometrical configurations possible for $U + U$ collision. We find that HYDJET++ model supports a small correlation between the various properties of charged hadrons and the initial geometrical configurations of $U + U$ collision. Further, the results obtained in modified HYDJET++ model regarding $d n_{c h} / d η$ and elliptic flow ( $v_{2}$ ) suitably matches with the experimental data of $U + U$ collisions in minimum bias configuration.
nucl-thhep-phEPJC(2018)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE