Nuclear Theory·nucl-th

Tuesday·November 10, 2020

16 papers—11 primary·5 cross-listed

01
Topology change and emergent scale symmetry in compact star matter via gravitational wave detection
Wen-Cong Yang🇨🇳 · Yong-Liang Ma🇨🇳 · Yue-Liang Wu🇨🇳
Topological structure has been extensively studied and confirmed in highly correlated condensed matter physics. We explore the gravitational waves emitted from binary neutron star mergers using the pseudoconformal model for dense nuclear matter for compact stars. This model considers the topology change and the possible emergent scale symmetry and satisfies all the constraints from astrophysics. We find that the location of the topology change affects gravitational waves dramatically owing to its effect on the equation of state. In addition, the effect of this location on the waveforms of the gravitational waves is within the ability of the on-going and up-coming facilities for detecting gravitational waves, thus suggesting a possible way to measure the topology structure in nuclear physics.
nucl-thastro-ph.HEhep-phSCPMA(2021)·8 citations
02
Hyperspherical few-body model calculation for cascade $Ξ$ exotic hypernuclei with reference to nuclear drip lines
Md. A. Khan🇮🇳 · M. Alam🇮🇳 · M. Hasan🇮🇳 · S. H. Mondal🇮🇳
In this paper, we presented the ground state energies calculated for some single and double cascade hyperon( $Ξ^{-}$ ) hypernuclei. For hypernuclei of the type $_{Ξ}^{A_{c} + 1}$ X we applied $Ξ +_{c}^{A}$ X two-body model and for hypernuclei of the type $_{ΞΞ}^{A_{c} + 2}$ X we adopted $Ξ + Ξ +_{c}^{A}$ X three-body model. A two-term Gaussian (Isle type) potential with adjustable parameters is chosen as the $Ξ$ -nucleus interaction, while a two-term Yukawa-type potential has been chosen for the $ΞΞ$ pair. In the three-body model calculation, we adopted the hyperspherical harmonics expansion (HHE) formalism. The resulting two- and three-body Schrödinger equations subject to appropriate boundary condition's have been solved numerically to get the ground-state energies and wavefunctions. Computed values are in excellent agreement with the observed ones as found in the literature. Analysis of the calculated observables indicates that the hyperons stay close to the core-nucleus. Hypernuclei formed as a result of absorption of one or more $Ξ$ -hyperon(s) by a normal nucleus (bound or unbound) are found to have more stability than those formed as a result of absorption of one or more $Λ$ hyperon(s) by the same nucleus. This fact flashes towards the possibility of the existence of a valley of strange hypernuclei near the drip lines.
nucl-thBulg.J.Phys.(2020)·1 citation
03
A hydrodynamic study of hyperon spin polarization in relativistic heavy ion collisions
Baochi Fu🇨🇳 · Kai Xu🇨🇳 · Xu-Guang Huang🇨🇳 · Huichao Song🇨🇳
We perform a systematic study of the spin polarization of hyperons in heavy-ion collisions using the MUSIC hydrodynamic model with A Multi-Phase Transport (AMPT) pre-equilibrium dynamics. Our model calculations nicely describe the measured collision-energy, centrality, rapidity, and $p_{T}$ dependence of $Λ$ polarization. We also study and predict the global spin polarization of $Ξ^{-}$ and $Ω^{-}$ as a function of collision energy, which provides a baseline for the studies of the magnetic moment, spin, and mass dependence of the spin polarization. For the local spin polarization, we calculate the radial and azimuthal components of the transverse $Λ$ polarization and find specific modulating behavior which could reflect the circular vortical structure. However, our model fails to describe the azimuthal-angle dependence of the longitudinal and transverse $Λ$ polarization, which indicates that the hydrodynamic framework with the spin Cooper-Frye formula under the assumption of thermal equilibrium of spin degree of freedom needs to be improved.
nucl-thhep-phnucl-exPRC(2021)·115 citations
04
Nuclear Potential of Final State Nucleons and Nucleons Plus Pions in Lepton Nucleus Scattering
Arie Bodek🇺🇸 · Tejin Cai🇺🇸
Within the impulse approximation, the modeling of the energy of final state leptons in electron and neutrino quasielastic and pion production processes on nuclear targets in the region of the $Δ$ resonance depends on several parameters. These parameters include the removal energy of the initial state nucleon from the nucleus $ϵ^{P, N}$ , the potentials of electrons, nucleons and pions in the Coulomb field of the nucleus $∣ V_{e f f} ∣$ , and the kinetic energy dependent nuclear potential for final state nucleons ( $U_{o pt}^{QE}$ ) and "nucleon plus pion" final states in the region of the $Δ$ resonance which we refer to as $U_{o pt}^{Δ}$ . We extract these parameters from electron scattering data. Previous studies have shown that real part of the optical potential for a nucleon bound in $_{6}^{12} C$ at zero kinetic energy $U_{o pt}^{P, N} (T = 0) \approx$ 44 MeV is larger than that for the $Δ$ (1232) resonance $U_{o pt}^{Δ} (T = 0) \approx$ 30 MeV. We find the reverse at higher kinetic energies. For example at T=100 MeV we find a nucleon potential $U_{o pt}^{P, N} (T = 100 M e V)$ =20 $\pm$ 5 MeV and $U_{o pt}^{Δ} (T = 100 M e V)$ = 30 $\pm$ 5 MeV. The two results are consistent for two reasons. First, theoretically the kinetic energy dependence of the $Δ$ potential is flatter than that of the nucleon. Secondly, in our analysis the extracted $U_{o pt}^{Δ}$ values are the nuclear potential for {\it"nucleon plus pion"} final states in the region of the $Δ$ resonances and therefore includes contributions from both resonance and non resonance pion production processes. For Monte Carlo generators that only include the effects of Fermi motion and nuclear potentials, the relevant parameter is the effective nuclear potential for the "nucleon plus pion" final state.
nucl-thhep-exhep-phnucl-exPoS(2021)·0 citations
05
Influence of modified light-flavor hadron spectra on particle yields in the statistical hadronization model
A. Andronic🇩🇪 · P. Braun-Munzinger🇩🇪 · D. Gündüz🇩🇪 · Y. Kirchhoff🇩🇪 · M. K. Köhler🇩🇪 · J. Stachel🇩🇪 · M. Winn🇫🇷
Hadron production in relativistic nuclear collisions is well described in the framework of the Statistical Hadronization Model (SHM). We investigate the influence on SHM predictions of hadron mass spectra for light-flavor baryons and mesons modified by the addition of about 500 new states as predicted by lattice QCD and a relativistic quark model. The deterioration of the resulting thermodynamic fit quality obtained for PbPb collision data at sqrt(s_nn) = 2.76 TeV suggests that the additional states are not suited to be naively used since also interactions among the states as well as non-resonant contributions need to be considered in the SHM approach. Incorporating these effects via the pion nucleon interaction determined from measured phase shifts leads again to excellent reproduction of the experimental data. This is a strong indication that at least the additional nucleon excited states cannot be understood and used as independent resonances.
nucl-thhep-lathep-phnucl-exNPA(2021)·20 citations
06
Providing physics guides in Bayesian neural networks from input layer: case of giant dipole resonance predictions
Xiaohang Wang · Jun Su · Long Zhu
The Bayesian neural network (BNN) has been applied to evaluate and predict the nuclear data. However, how to provide physics guides in BNN is a key but an open question. In this work, the case study on giant dipole resonance (GDR) energy is presented to illustrate the effectiveness and maneuverability of the method to provide physics guides in BNN from input layer. The Spearman's correlation coefficients are applied to assess the statistical dependence between nuclear properties in the ground state and the GDR energies. Then the optimal ground-state properties are employed as the input layer in the BNN for evaluating and predicting the GDR energies. Those selected ground-state properties actively contributes to reduce the predicted errors and avoid the risk of the non-physics divergence. This work gives a demonstration to find effects of the GDR energy by using the BNN without the physics motivated model, which may be helpful for discovering physics effects from the complex nuclear data.
nucl-thPRC(2021)·25 citations
07
R-Matrix theory with level-dependent boundary condition parameters
Tae-Sun Park
I present a new formalism of the R-matrix theory where the formal parameters for the resonance energies and widths are identical to the observed values. By allowing the boundary condition parameters to vary from level to level, the freedom required to adjust the formal parameters for the pole positions to the observed values is obtained. The basis of the resulting theory becomes nonorthogonal, and I describe the procedure to construct a consistent R-matrix theory with such a nonorthogonal basis. And by adjusting the normalization of the states that form the basis, the formal parameters for the reduced decay widths also become the same as those observed, leaving no formal parameters that are different from the observed ones. A demonstration of the developed theory to the elastic 12C+p scattering data is presented.
nucl-thPRC(2021)·6 citations
08
Impact of complex many-body correlations on electron capture in thermally excited nuclei around $^{78}$ Ni
Elena Litvinova🇺🇸 · Caroline Robin🇩🇪
We link complex many-body correlations, which play a decisive role in the structural properties of atomic nuclei, to the electron capture occurring during star evolution. The recently developed finite-temperature response theory, taking into account the coupling between single-nucleon and collective degrees of freedom, is applied to spin-isospin transitions, which dominate the electron capture rates. Calculations are performed for $^{78}$ Ni and for the surrounding even-even nuclei associated with a high-sensitivity region of the nuclear chart in the context of core-collapse supernova simulations. The obtained electron capture rates are compared to those of a simpler thermal quasiparticle random phase approximation (TQRPA), which is standardly used in such computations. The comparison indicates that correlations beyond TQRPA lead to significantly higher electron capture rates under the typical thermodynamical conditions.
nucl-thastro-ph.SRPRC(2021)·25 citations
09
Beyond the wake: non-hydrodynamic response of an expanding Quark-gluon plasma
Weiyao Ke🇺🇸 · Yi Yin🇨🇳
We study the response function which describes the evolution of energy density induced by an initial disturbance for a Bjorken-expanding quark-gluon plasma (QGP). We compare the results from solving linearized Boltzmann equation under the relaxation time approximation with those from viscous hydrodynamics. While in long time limit the response becomes hydrodynamics, the non-hydrodynamic response is important at intermediate times when excitations of wavelength larger than the inverse of the relaxation time $1/ τ_{R}$ are not fully damped. Therefore observables sensitive to the jet-induced medium excitations might be employed to explore the properties of QGP at the "mesoscopic scale".
nucl-thPoS(2021)·0 citations
10
Spin observables of proton-deuteron elastic scattering at SPD NICA energies within the Glauber model and pN amplitudes
Yu.N.Uzikov (1,2 3)🇷🇺 · J.Haidenbauer (4)🇩🇪 · A. Bazarova (5)🇰🇿 · A.A.Temerbayev (5,6) ((1) Joint Institute for Nuclear Researches, Dubna, Russia, (2) Dubna State University, Dubna, Russia, (3) Department of Physics, M.V. Lomonosov State University, Moscow, Russia, (4) Institute for Advanced Simulation and Institut für Kernphysik, Forschungszentrum Jülich GmbH, Jülich, Germany, (5) L.N. Gumilyov Eurasian National University, Nur-Sultan, Kazakhstan, (6) Institute of Nuclear Physics, Astana branch, Nur-Sultan, Kazakhstan)🇰🇿
A systematic analysis of nucleon-nucleon scattering amplitudes is available up to a laboratory energy of $3$ ~GeV in case of the $pp$ system and up to $1.2$ GeV for $p n$ . At higher energies there is only incomplete experimental information on $pp$ elastic scattering, whereas data for the $p n$ system are very scarce. We apply the spin-dependent Glauber theory to calculate spin observables of $p d$ elastic scattering at $3$ - $50$ GeV/c using $pp$ amplitudes available in the literature and parametrized within the Regge formalism. The calculated vector $A_{y}^{p}$ , $A_{y}^{d}$ and tensor $A_{xx}$ , $A_{y y}$ analyzing powers and the spin-correlation coefficients $C_{y, y}$ , $C_{x, x}$ , $C_{y y, y}$ , $C_{xx, y}$ can be measured at SPD NICA and, thus, will provide a test of the used $pN$ amplitudes.
nucl-thhep-phPhys.Part.Nucl.(2022)·9 citations
11
A first estimate of $η / s$ in Au+Au reactions at E $_{lab} = 1.23$ $A$ GeV
Tom Reichert🇩🇪 · Gabriele Inghirami🇩🇪 · Marcus Bleicher🇬🇧
The HADES experiment at GSI has recently provided data on the flow coefficients $v_{1}, ..., v_{4}$ for protons in Au+Au reactions at $E_{lab} = 1.23$ ~ $A$ GeV (or $s_{NN} = 2.4$ GeV). This data allows to estimate the shear viscosity over entropy ratio, $η / s$ at low energies via a coarse graining analysis of the UrQMD transport simulations of the flow harmonics in comparison to the experimental data. By this we can provide for the first time an estimate of $η / s \approx 0.65 \pm 0.15$ (or $(8 \pm 2) (4 π)^{- 1}$ ) at such low energies.
nucl-thnucl-exPLB(2021)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE