Nuclear Theory·nucl-th

Tuesday·January 9, 2018

17 papers—12 primary·5 cross-listed

01
Constraining the speed of sound inside neutron stars with chiral effective field theory interactions and observations
Ingo Tews🇺🇸 · Joseph Carlson🇺🇸 · Stefano Gandolfi🇺🇸 · Sanjay Reddy🇺🇸
The dense matter equation of state (EOS) determines neutron star (NS) structure but can be calculated reliably only up to one to two times the nuclear saturation density, using accurate many-body methods that employ nuclear interactions from chiral effective field theory constrained by scattering data. In this work, we use physically motivated ansatzes for the speed of sound $c_{S}$ at high density to extend microscopic calculations of neutron-rich matter to the highest densities encountered in stable NS cores. We show how existing and expected astrophysical constraints on NS masses and radii from X-ray observations can constrain the speed of sound in the NS core. We confirm earlier expectations that $c_{S}$ is likely to violate the conformal limit of $c_{S}^{2} \leq c^{2} /3$ , possibly reaching values closer to the speed of light $c$ at a few times the nuclear saturation density, independent of the nuclear Hamiltonian. If QCD obeys the conformal limit, we conclude that the rapid increase of $c_{S}$ required to accommodate a $2$ M $_{⊙}$ NS suggests a form of strongly interacting matter where a description in terms of nucleons will be unwieldy, even between one and two times the nuclear saturation density. For typical NSs with masses in the range $1.2 - 1.4$ M $_{⊙}$ , we find radii between $10$ and $14$ km, and the smallest possible radius of a $1.4$ M $_{⊙}$ NS consistent with constraints from nuclear physics and observations is $8.4$ km. We also discuss how future observations could constrain the EOS and guide theoretical developments in nuclear physics.
nucl-thhep-phApJ(2018)·465 citations
02
Davydov-Chaban Hamiltonian within the formalism of deformation-dependent effective mass for Davidson potential
P. Buganu · M. Chabab · A. El Batoul · A. Lahbas · M. Oulne
In this work, we modify the Davydov-Chaban Hamiltonian describing the collective motion of a $γ$ -rigid atomic nucleus by allowing the mass to depend on nuclear deformation. Exact analytical expressions are derived for energy spectra as well as normalized wave functions for Davidson potential. The model, called Z(4)-DDMD (Deformation Dependent Mass with Davidson potential), is achieved by using the Asymptotic Iteration Method (AIM). The numerical calculations for energy spectra and B(E2) transition probabilities are compared to the experimental data of $^{192 - 196}$ Pt isotopes. The obtained results show an overall agreement with the experiment and an important improvement in respect to other models.
nucl-thNucl.Theor.(2017)·0 citations
03
Ground-state properties of light kaonic nuclei signaling symmetry energy at high densities
Rong-Yao Yang🇨🇳 · Si-Na Wei🇨🇳 · Wei-Zhou Jiang🇨🇳
A sensitive correlation between the ground-state properties of light kaonic nuclei and the symmetry energy at high densities is constructed under the framework of relativistic mean-field theory. Taking oxygen isotopes as an example, we see that a high-density core is produced in kaonic oxygen nuclei, due to the strongly attractive antikaon-nucleon interaction. It is found that the $1 S_{1/2}$ state energy in the high-density core of kaonic nuclei can directly probe the variation of the symmetry energy at supranormal nuclear density, and a sensitive correlation between the neutron skin thickness and the symmetry energy at supranormal density is established directly. Meanwhile, the sensitivity of the neutron skin thickness to the low-density slope of the symmetry energy is greatly increased in the corresponding kaonic nuclei. These sensitive relationships are established upon the fact that the isovector potential in the central region of kaonic nuclei becomes very sensitive to the variation of the symmetry energy. These findings might provide another perspective to constrain high-density symmetry energy, and await experimental verification in the future.
nucl-thCPC(2018)·2 citations
04
Pairing-energy coefficients of neutron-rich fragments in spallation reactions
Fei Niu · Chun-Wang Ma
The ratio of pairing-energy coefficient to temperature ( $a_{p} / T$ ) of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model. A series of spallation reactions, 0.5 $A$ and 1 $A$ GeV $^{208}$ Pb + $p$ , 1 $A$ GeV $^{238}$ U + $p$ , 0.5 $A$ GeV $^{136}$ Xe + $d$ , 0.2 $A$ , 0.5 $A$ and 1 $A$ GeV $^{136}$ Xe + $p$ , and $^{56}$ Fe + $p$ with incident energy ranging from 0.3 $A$ to 1.5 $A$ GeV, has been analysed. An obvious odd-even staggering is shown in the fragments with small neutron excess ( $I \equiv N - Z$ ), and in the relatively small- $A$ fragments which have large $I$ . The values of $a_{p} / T$ for the fragments, with $I$ from 0 to 36, have been found to be in a range from -4 to 4, and most values of $a_{p} / T$ fall in the range from -1 to 1. It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions. It is also concluded that the method proposed in this article is not good for fragments with $A / A_{s} >$ 85\% (where $A_{s}$ is the mass number of the spallation system).
nucl-thnucl-exCPC(2018)·2 citations
05
Massive neutron star with strangeness in a relativistic mean-field model with a high-density cut-off
Ying Zhang · Jinniu Hu🇨🇳 · Peng Liu🇨🇳
The properties of strangeness neutron star are studied within relativistic mean-field (RMF) model via including a logarithmic interaction as a function of scalar meson field. This logarithmic interaction, named as the $σ$ -cut potential, can largely reduce the attractive contributions of scalar meson field at high density without any influence on nuclear structure around normal saturation density. In this work, the TM1 parameter set is chosen as the RMF interaction, while the strengths of logarithmic interaction are constrained by the properties of finite nuclei so that we can obtain a reasonable effective nucleon-nucleon interaction. The hyperons, $Λ, Σ$ , and $Ξ$ are also considered in neutron stars within this framework, whose coupling constants with mesons are determined by the latest hyperon-nucleon and $Λ$ - $Λ$ potentials extracted from the experimental data of hypernuclei. The maximum mass of neutron star can be larger than two solar mass with these hyperons. Furthermore, the nucleon mass at high density will be saturated due to this additional $σ$ -cut potential, which is consistent with the conclusions from the microscopic calculations such as, Brueckner-Hartree-Fock theory and quark mean-field model.
nucl-thPRC(2018)·25 citations
06
Investigation of ground-state properties of even-even and odd Pb isotopes within Hartree-Fock-Bogoliubov theory
Younes El Bassem · Mustapha Oulne
The nuclear structure of even-even and odd lead isotopes (178-236 Pb) is investigated within the Hartree-Fock-Bogoliubov theory. Calculations are performed for a wide range of neutron numbers, starting from the proton-rich side up to the neutron-rich side, by using the SLy4 Skyrme interaction and a new proposed formula for the pairing strength which is more precise for this region of nuclei as we did in previous works in the regions of Neodymium (Nd, Z=60) [Int. J. Mod. Phys. E 24, 1550073 (2015)] and Molybdenum (Mo, Z=42) [Nuc. Phys. A 957 22-32 (2017)]. Such a new pairing strength formula allows reaching exotic nuclei region where the experimental data are not available. Calculated values of various physical quantities such as binding energy, two-neutron separation energy, and rms-radii for protons and neutrons are discussed and compared with experimental data and some estimates of other nuclear models like Finite Range Droplet Model (FRDM), Relativistic Mean Field (RMF), Density-Dependent Meson-Exchange Relativistic Energy Functional (DD-ME2) and results of Hartree-Fock-Bogoliubov calculations based on the D1S Gogny effective nucleon-nucleon interaction (Gogny D1S).
nucl-thNucl.Theor.(2017)·1 citation
07
Nuclear structure investigation of even-even and odd Pb isotopes by using the Hartree-Fock-Bogoliubov method
Younes El Bassem · Mustapha Oulne
The nuclear structure of even-even and odd lead isotopes (178-236 Pb) is investigated within the Hartree-Fock-Bogoliubov theory. Calculations are performed for a wide range of neutron numbers, starting from the proton-rich side up to the neutron-rich side, by using the SLy4 Skyrme interaction and a new proposed formula for the pairing strength which is more precise for this region of nuclei as we did in previous works in the regions of Neodymium (Nd, Z=60) [Int. J. Mod. Phys. E 24, 1550073 (2015)] and Molybdenum (Mo, Z=42) [Nuc. Phys. A 957 22-32 (2017)]. Such a new pairing strength formula allows reaching exotic nuclei region where the experimental data are not available. Calculated values of various physical quantities such as binding energy, two-neutron separation energy, quadrupole deformation, and rms-radii for protons and neutrons are discussed and compared with experimental data and some estimates of other nuclear models like Finite Range Droplet Model (FRDM), Relativistic Mean Field (RMF) model with NL3 functional (NL3), Density-Dependent Meson-Exchange Relativistic Energy Functional (DD-ME2) and results of Hartree-Fock-Bogoliubov calculations based on the D1S Gogny effective nucleon-nucleon interaction (Gogny D1S).
nucl-thIJMPE(2017)·3 citations
08
Shannon Information Entropy in Heavy-ion Collisions
Chun-Wang Ma🇨🇳 · Yu-Gang Ma🇨🇳
The general idea of information entropy provided by C.E. Shannon "hangs over everything we do" and can be applied to a great variety of problems once the connection between a distribution and the quantities of interest is found. The Shannon information entropy essentially quantify the information of a quantity with its specific distribution, for which the information entropy based methods have been deeply developed in many scientific areas including physics. The dynamical properties of heavy-ion collisions (HICs) process make it difficult and complex to study the nuclear matter and its evolution, for which Shannon information entropy theory can provide new methods and observables to understand the physical phenomena both theoretically and experimentally. To better understand the processes of HICs, the main characteristics of typical models, including the quantum molecular dynamics models, thermodynamics models, and statistical models, etc, are briefly introduced. The typical applications of Shannon information theory in HICs are collected, which cover the chaotic behavior in branching process of hadron collisions, the liquid-gas phase transition in HICs, and the isobaric difference scaling phenomenon for intermediate mass fragments produced in HICs of neutron-rich systems. Even though the present applications in heavy-ion collision physics are still relatively simple, it would shed light on key questions we are seeking for. It is suggested to further develop the information entropy methods in nuclear reactions models, as well as to develop new analysis methods to study the properties of nuclear matters in HICs, especially the evolution of dynamics system.
nucl-thcs.ITmath.ITPPNP(2018)·94 citations
09
On the Coulomb Interaction in a Nucleus for Odd J States
L.Zamick
With a certain approximation for the Coulomb matrix elements in a single j shell of protons and neutrons it is found that wave functions of states of odd angular momentum J in an even-even nucleus are not strongly affected by their presence,
nucl-th0 citations
10
Effect of simulating parity-odd observables in high energy heavy ion collisions on Balance Functions of charged particles and elliptic flow of pions
Sk Noor Alam🇮🇳 · Subhasis Chattopadhyay🇮🇳
At the early stage of heavy ion collisions, non-trivial topologies of the gauge fields can be created resulting in an imbalance of axial charge density and eventually separation of electric charges along the direction of the magnetic field produced in such collisions. This process is called the chiral magnetic effect (CME). In this work we implement such a charge separation at the partonic level in AMPT for Au+Au collisions at $s_{N N}$ = 200 GeV to study its consequence on experimental observables. We present the effects on the pion elliptic flow ( $v_{2}$ ) and the charged particle balance function (BF) for varying strengths of initial charge separation. We find that the shape of the balance function is sensitive to the increasing charge separation. $v_{2}$ of pion shows a strong decreasing trend at higher transverse momenta ( $p_{T}$ ) with increasing charge separation. Charge balance functions show a peak at $Δ ϕ \sim 180$ with charge separation implemented in the partonic level as expected for the parity violation. We have also calculated parity observable $γ$ in the form of BF's moments. $γ$ shows a decreasing trend with charge separation. It has a negative value for charge separation produced by flipping more than 30 $%$ of quarks in the parton level. We also notice that $< γ >$ for the same charge correlation and the opposite charge correlation shows negative and positive values, respectively.
nucl-thhep-phNPA(2018)·3 citations
11
Structure of $^{14}$ N nucleus within a five-cluster model
B. E. Grinyuk · D. V. Piatnytskyi
The spatial structure of $^{14}$ N nucleus is studied within a five-particle model (three $α$ -particles plus two nucleons). Using the variational approach with Gaussian bases, the ground-state energy and wave function are calculated for this five-particle system. Two spatial configurations in the ground-state wave function are revealed. The density distributions, pair correlation functions, and the momentum distributions of particles are analyzed and compared with those of the mirror nuclei $^{14}$ C and $^{14}$ O.
nucl-thUkr.J.Phys.(2017)·1 citation
12
Isobaric Multiplet Mass Equation within nuclear Density Functional Theory
P. Baczyk · W. Satula · J. Dobaczewski · M. Konieczka
We extend the nuclear Density Functional Theory (DFT) by including proton-neutron mixing and contact isospin-symmetry-breaking (ISB) terms up to next-to-leading order (NLO). Within this formalism, we perform systematic study of the nuclear mirror and triple displacement energies, or equivalently of the Isobaric Multiplet Mass Equation (IMME) coefficients. By comparing results with those obtained within the existing Green Function Monte Carlo (GFMC) calculations, we address the fundamental question of the physical origin of the ISB effects. This we achieve by analyzing separate contributions to IMME coefficients coming from the electromagnetic and nuclear ISB terms. We show that the ISB DFT and GFMC results agree reasonably well, and that they describe experimental data with a comparable quality. Since the separate electromagnetic and nuclear ISB contributions also agree, we conclude that the beyond-mean-field electromagnetic effects may not play a dominant role in describing the ISB effects in finite nuclei.
nucl-thJ.Phys.G(2019)·29 citations
13
On the clustering properties of produced particles in high-energy $pp$ collisions
Cheuk-Yin Wong🇺🇸 · Hanpu Jiang🇺🇸 · Nanxi Yao🇺🇸 · Liwen Wen🇺🇸 · Gang Wang🇺🇸 · Huan Zhong Huang🇺🇸
Minijets provide useful information on parton interactions in the low transverse-momentum (low- $p_{T}$ ) region. Because minijets produce clusters, we study the clustering properties of produced particles in high-energy $pp$ collisions as a first step to identify minijets. We develop an algorithm to find clusters by using the k-means clustering method, in conjunction with a k-number (cluster number) selection principle in the space of pseudorapidity and azimuthal angles. We test the clustering algorithm using events generated by PYTHIA 8.1, for $pp$ collision at $s = 200$ GeV. We find that clustering of low- $p_{T}$ hadrons occurs in high multiplicity events. However similar clustering properties are also present for particles produced randomly in a finite pseudorapidity and azimuthal angle space. To distinguish the dynamics from random generations of events, it is necessary to examine the correlation between particles and between clusters. We find that the correlations between clusters may provide a useful tool to distinguish the underlying dynamics of the reaction mechanism.
↳ hep-phhep-exnucl-exnucl-thPRD(2020)·4 citations
14
The formation of the heaviest elements
Anna Frebel (MIT) · Timothy C. Beers (Notre Dame)
The rapid neutron-capture process needed to build up many of the elements heavier than iron seems to take place primarily in neutron-star mergers, not supernova explosions.
↳ astro-ph.SRastro-ph.COastro-ph.GAnucl-ex+1Phys.Today·9 citations
15
Properties of $Σ_{Q}^{*}$ , $Ξ_{Q}^{*}$ and $Ω_{Q}^{*}$ heavy baryons in cold nuclear matter
K. Azizi🇮🇷 · N. Er🇹🇷
The in-medium properties of the heavy spin-3/2 $Σ_{Q}^{*}$ , $Ξ_{Q}^{*}$ and $Ω_{Q}^{*}$ baryons with $Q$ being $b$ or $c$ quark are investigated. The shifts in some spectroscopic parameters of these particles due to the saturated cold nuclear matter are calculated. The variations of those parameters with respect to the changes in the density of the cold nuclear medium are studied, as well. It is observed that the parameters of $Σ_{Q}^{*}$ baryons are considerably affected by the nuclear matter compared to the $Ξ_{Q}^{*}$ and $Ω_{Q}^{*}$ particles that roughly do not see the medium. The results obtained may be used in analyses of the data to be provided by the in-medium experiments like PANDA.
↳ hep-phhep-exhep-latnucl-thNPA(2018)·12 citations
16
$η$ and $η^{'}$ photoproduction with EtaMAID including Regge phenomenology
V.L. Kashevarov🇩🇪 · L. Tiator🇩🇪 · M. Ostrick🇩🇪
We present a new version of the EtaMAID model for $η$ and $η^{'}$ photoproduction on nucleons. The model includes 23 nucleon resonances parameterized with Breit-Wigner shapes. The background is described by vector and axial-vector meson exchanges in the $t$ channel using the Regge cut phenomenology. Parameters of the resonances were obtained from a fit to available experimental data for $η$ and $η^{'}$ photoproduction on protons and neutrons. The nature of the most interesting observations in the data is discussed.
↳ hep-phnucl-exnucl-thBled Workshops Phys.(2017)·1 citation
17
Interatomic interaction effects on second-order momentum correlations and Hong-Ou-Mandel interference of double-well-trapped ultracold fermionic atoms
Benedikt B. Brandt · Constantine Yannouleas · Uzi Landman
Identification and understanding of the evolution of interference patterns in two-particle momentum correlations as a function of the strength of interatomic interactions are important in explorations of the nature of quantum states of trapped particles. Together with the analysis of two-particle spatial correlations, they offer the prospect of uncovering fundamental symmetries and structure of correlated many-body states, as well as opening vistas into potential control and utilization of correlated quantum states as quantum information resources. With the use of the second-order density matrix constructed via exact diagonalization of the microscopic Hamiltonian, and an analytic Hubbard-type model, we explore here the systematic evolution of characteristic interference patterns in the two-body momentum and spatial correlation maps of two entangled ultracold fermionic atoms in a double well, for the entire attractive- and repulsive-interaction range. We uncover statistics-governed bunching and antibunching, as well as interaction-dependent interference patterns, in the ground and excited states, and interpret our results in light of the Hong-Ou-Mandel interference physics, widely exploited in photon indistinguishability testing and quantum information science.
↳ cond-mat.quant-gasnucl-thquant-phPRA(2018)·9 citations

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