Nuclear Theory·nucl-th

Tuesday·January 10, 2023

16 papers—9 primary·7 cross-listed

01
Hadron-quark phase transition in neutron star by combining the relativistic Brueckner-Hartree-Fock theory and Dyson-Schwinger equation approach
Pianpian Qin🇨🇳 · Zhan Bai🇨🇳 · Sibo Wang🇨🇳 · Chencan Wang🇨🇳 · Si-xue Qin🇨🇳
Starting from the relativistic Brueckner-Hartree-Fock theory for nuclear matter and the Dyson-Schwinger equation approach for quark matter, the possible hadron-quark phase transition in the interior of a neutron star is explored. The first-order phase transition and crossover are studied by performing the Maxwell construction and three-window construction respectively. The mass-radius relation and the tidal deformability of the hybrid star are calculated and compared to the joint mass-radius observation of a neutron star and the constraints from gravitational wave detection. For the Maxwell construction, no stable quark core is found in the interior of a neutron star. For the three-window construction, the parameters of the smooth interpolation function are chosen in such a way to keep the thermodynamic stability and lead to a moderate crossover density region. To support a two-solar-mass neutron star under the three-window construction, the effective width of medium screening effects in quark matter should be around $0.35$ GeV.
nucl-thPRD(2023)·12 citations
02
Can a pure neutron state of matter exist?
F. R. Xu
A short discussion on possible multineutron resonances.
nucl-thnucl-exSci.Bull.(2022)·2 citations
03
Temperature and density effects on the two-nucleon momentum correlation function from excited single nuclei
Ting-Ting Wang · Yu-Gang Ma · De-Qing Fang · Huan-Ling Liu
Two-nucleon momentum correlation functions are investigated for different single thermal sources at given initial temperature $(T)$ and density $(ρ)$ . To this end, the space-time evolutions of various single excited nuclei at $T$ $= 1 - 20$ $M e V$ and $ρ$ = 0.2 - 1.2 $ρ_{0}$ are simulated by using the thermal isospin-dependent quantum molecular dynamics $(T h I QM D)$ model. Momentum correlation functions of identical proton-pairs ( $C_{pp} (q)$ ) or neutron-pairs ( $C_{nn} (q)$ ) at small relative momenta are calculated by $L e d ni c k y ˊ$ and $L y u b os hi t z$ analytical method. The results illustrate that $C_{pp} (q)$ and $C_{nn} (q)$ are sensitive to the source size ( $A$ ) at lower $T$ or higher $ρ$ , but almost not at higher $T$ or lower $ρ$ . And the sensitivities become stronger for smaller source. Moreover, the $T$ , $ρ$ and $A$ dependencies of the Gaussian source radii are also extracted by fitting the two-proton momentum correlation functions, and the results are consistent with the above conclusions.
nucl-thPRC(2022)·8 citations
04
Directed flow and global polarization in Au+Au collisions across energies covered by the beam energy scan at RHIC
Ze-Fang Jiang🇨🇳 · Xiang-Yu Wu🇨🇳 · Shanshan Cao🇨🇳 · Ben-Wei Zhang🇨🇳
We study the directed flow of identified particles in Au+Au collisions at $s_{NN} = 7.7$ to 62.4 GeV. The Glauber model is extended to include both a tilted deformation of the QGP fireball with respect to the longitudinal direction and a non-zero longitudinal flow velocity gradient in the initial state. By combining this improved initial condition with a (3+1)-dimensional viscous hydrodynamic model calculation, we obtain a satisfactory description of the transverse momentum spectra and the rapidity dependent directed flow coefficient of different hadron species. Our calculation indicates the sensitivity of the hadron directed flow, especially its splitting between protons and antiprotons, to both the initial geometry and the initial longitudinal flow velocity. Therefore, the combination of directed flow of different hadrons can provide a tight constraint on the initial condition of nuclear matter created in heavy-ion collisions. The initial condition extracted from the directed flow is further tested with the global polarization of $Λ$ and $Λ ˉ$ within the same theoretical framework, where we obtain a reasonable description of these hyperon polarization observed at different collision energies at RHIC.
nucl-thhep-phnucl-exPRC(2023)·19 citations
05
Impacts of momentum dependent interaction, symmetry energy and near-threshold $N N \to N Δ$ cross sections on isospin sensitive flow and pion observables
Yangyang Liu🇨🇳 · Yingxun Zhang🇨🇳 · Junping Yang🇨🇳 · Yongjia Wang🇨🇳 · Qingfeng Li🇨🇳 · Zhuxia Li🇨🇳
Based on the ultra-relativistic quantum molecular dynamics (UrQMD) model, the impacts of momentum dependent interaction, symmetry energy and near-threshold $N N \to N Δ$ cross sections on isospin sensitive collective flow and pion observables are investigated. Our results confirm that the elliptic flow of neutrons and charged particles, i.e. $v_{2}^{n}$ and $v_{2}^{c h}$ , are sensitive to the strength of momentum dependence interaction and the elliptic flow ratio, i.e., $v_{2}^{n} / v_{2}^{c h}$ , is sensitive to the stiffness of symmetry energy. For describing the pion multiplicity near the threshold energy, accurate $N N \to N Δ$ cross sections are crucial. With the updated momentum dependent interaction and $N N \to N Δ$ cross sections in UrQMD model, seven observables, such as directed flow and elliptic flow of neutrons and charged particles, the elliptic flow ratio of neutrons to charged particles, charged pion multiplicity and its ratio $π^{-} / π^{+}$ , can be well described by the parameter sets with the slope of symmetry energy from 5 MeV to 70 MeV. To describe the constraints of symmetry energy at the densities probed by the collective flow and pion observables, the named characteristic density is investigated and used. Our analysis found that the flow characteristic density is around 1.2 $ρ_{0}$ and pion characteristic density is around 1.5 $ρ_{0}$ , and we got the constrains of symmetry energy at characteristic densities are $S (1.2 ρ_{0}) = 34 \pm 4$ MeV and $S (1.5 ρ_{0}) = 36 \pm 8$ MeV. These results are consistent with previous analysis by using pion and flow observable with different transport models, and demonstrate a reasonable description of symmetry energy constraint should be presented at the characteristic density of isospin sensitive observables.
nucl-thnucl-ex2 citations
06
Probing the structural evolution along the fission path in the superheavy nucleus $^{256}$ Sg
Ting-Ting Li · Hua-Lei Wang · Zhen-Zhen Zhang · Min-Liang Liu
The evolution of structure property along the fission path in the superheavy nucleus $^{256}$ Sg is predicted through the multi-dimensional potential-energy(or Routhian)-surface calculations,in which the phenomenological deformed Woods-Saxon potential is adopted. Calculated nuclear deformations and fission barriers for $_{106}^{256}$ Sg $_{150}$ and its neighbors, e.g., $^{258, 260}$ Sg, $^{254}$ Rf and $^{252}$ No are presented and compared with other theoretical results. A series of energy maps and curves are provided and used to evaluate the corresponding shape-instability properties, especially in the directions of triaxial $γ$ and different hexadecapole deformations (e.g., $α_{40}$ , $α_{42}$ and $α_{44}$ ). It is found that the triaxial deformation may help the nucleus bypass the first fission-barrier of the axial case. After the first minimum in the nuclear energy surface, the fission pathway of the nucleus can be affected by $γ$ and hexadecapole deformation degrees of freedom. In addition, microscopic single-particle structure, pairing and Coriolis effects are briefly investigated and discussed.
nucl-thIndian J.Phys.(2023)·2 citations
07
Analysis of realistic and empirical multipole interactions for shell-model calculations
Kamila Sieja🇫🇷
We perform analysis of realistic nucleon-nucleon interactions, as well as of empirically-corrected interactions, fitted to reproduce in detail the spectroscopic data in p and sd shells. We focus on the multipole part of the interactions, contrary to previous studies of that type which focused on monopole parts. We analyze how the different parts of the NN force (tensor, spin-orbit and central) contribute to the leading multipoles of the interaction and how do they renormalize in medium. We show that the leading coherent terms of the realistic and effective interactions are dominated by the central component as expected from their schematic operator structure. Convergence and cutoff dependence of multipole Hamiltonians is also discussed.
nucl-th0 citations
08
Particle-number fluctuations near the critical point of nuclear matter
A.G. Magner · S.N. Fedotkin · U.V. Grygoriev
The equation of state with quantum statistics corrections is used for particle number fluctuations $ω$ of isotopically symmetric nuclear matter with interparticle van der Waals and Skyrme local density interactions. The fluctuations, $ω \propto 1/ K$ , are analytically derived through the isothermal incompressibility $K$ at first order over a small quantum-statistics parameter. Our approximate analytical results appear to be in good agreement with the results of accurate numerical calculations. These results are also close to those obtained by using more accurate Tolman and Rowlinson expansions of the incompressibility $K$ near the critical point. A more general formula for fluctuations $ω$ , improved at the critical point, was obtained for a finite particle-number average $⟨ N ⟩$ by neglecting, for simplicity, small quantum statistics effects. It is shown that for a large dimensionless parameter, $α \propto K^{2} ⟨ N ⟩ / K^{''}$ , where $K^{''}$ is the second derivative of the incompressibility $K$ as function of the average particle density $n$ , far from the critical point ( $α ≫ 1$ ), one finds the traditional asymptote, $ω \propto 1/ K$ , for the fluctuations $ω$ . For a small parameter, $α ≪ 1$ , near the critical point, where $K = 0$ and $α = 0$ , one obtains another asymptote of $ω$ . These fluctuations, having a maximum near the critical point as function of the average density $n$ , for finite values of $⟨ N ⟩$ are finite and relatively small, in contrast to the results of the traditional calculations.
nucl-thPRC(2023)·0 citations
09
Impact of nuclear shape fluctuations in high-energy heavy ion collisions
Aman Dimri🇺🇸 · Somadutta Bhatta🇺🇸 · Jiangyong Jia🇺🇸
The shape of atomic nuclei is often interpreted to possess a quadrupole deformation that fluctuates around some average profile. We investigate the impact of nuclear shape fluctuations on the initial state geometry in heavy ion collisions, particularly its eccentricity $ε_{2}$ and inverse size $d_{⊥}$ , which can be related to the elliptic and radial flow in the final state. The fluctuation in overall quadrupole deformation enhances the variances and modifies the skewness and kurtosis of the $ε_{2}$ and $d_{⊥}$ in a controllable manner. The fluctuation in triaxiality reduces the difference between prolate and oblate shape for any observable, whose values, in the large fluctuation limit, approach those obtained in collisions of rigid triaxial nuclei. The method to disentangle the mean and variance of the quadrupole deformation is discussed.
nucl-thhep-phnucl-exEPJA(2023)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE