Nuclear Theory·nucl-th

Tuesday·July 21, 2020

22 papers—12 primary·10 cross-listed

01
Entanglement Rearrangement in Self-Consistent Nuclear Structure Calculations
Caroline Robin🇺🇸 · Martin J. Savage🇺🇸 · Nathalie Pillet🇫🇷
Entanglement properties of $^{4}$ He and $^{6}$ He are investigated using nuclear many-body calculations, specifically the single-nucleon entanglement entropy, and the two-nucleon mutual information and negativity. Nuclear wavefunctions are obtained by performing active-space no-core configuration-interaction calculations using a two-body nucleon-nucleon interaction derived from chiral effective field theory. Entanglement measures within single-particle bases, the harmonic oscillator (HO), Hartree-Fock (HF), natural (NAT) and variational natural (VNAT) bases, are found to exhibit different degrees of complexity. Entanglement in both nuclei is found to be more localized within NAT and VNAT bases than within a HO basis for the optimal HO parameters, and, as anticipated, a core-valence (tensor product) structure emerges from the full six-body calculation of $^{6}$ He. The two-nucleon mutual information shows that the VNAT basis, which typically exhibits good convergence properties, effectively decouples the active and inactive spaces. We conclude that measures of one- and two-nucleon entanglement are useful in analyzing the structure of nuclear wave functions, in particular the efficacy of basis states, and may provide useful metrics toward developing more efficient schemes for ab initio computations of the structure and reactions of nuclei, and quantum many-body systems more generally.
nucl-thquant-phPRC(2021)·119 citations
02
Probing in-medium nucleon-nucleon inelastic scattering cross section by using energetic n/p ratio
Zong-Zhen Zhang🇨🇳 · Ya-Fei Guo🇨🇳 · Gao-Chan Yong🇨🇳
Based on the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, the in-medium nucleon-nucleon inelastic scattering ( which is dominated by pion production at low and intermediate energies) is explored. It is found that the in-medium modification of nucleon-nucleon inelastic scatterings appears to reduce the neutron to proton ratio n/p at higher kinetic energies. Although the in-medium modification of nucleon-nucleon inelastic scatterings, as expected, affects the value of $π^{-} / π^{+}$ ratio, considering a series of undetermined properties of delta resonance and $π$ in medium, the energetic neutron to proton ratio n/p is more suitable to be used to probe the in-medium correction of nucleon-nucleon inelastic scatterings.
nucl-thnucl-exPRC(2021)·4 citations
03
An efficient solution for Dirac equation in 3D lattice space with the conjugate gradient method
B. Li · Z. X. Ren · P. W. Zhao
An efficient method, preconditioned conjugate gradient method with a filtering function (PCG-F), is proposed for solving iteratively the Dirac equation in 3D lattice space for nuclear systems. The filtering function is adopted to avoid the variational collapsed problem and a momentum-dependent preconditioner is introduced to promote the efficiency of the iteration. The PCG-F method is demonstrated in solving the Dirac equation with given spherical and deformed Woods-Saxon potentials. The solutions given by the inverse Hamiltonian method in 3D lattice space and the shooting method in radial coordinate space are reproduced with a high accuracy. In comparison with the existing inverse Hamiltonian method, the present PCG-F method is much faster in the convergence of the iteration, in particular for deformed potentials. It may also provide a promising way to solve the relativistic Hartree-Bogoliubov equation iteratively in the future.
nucl-thnucl-exPRC(2020)·23 citations
04
Thermal photons as a sensitive probe of $α$ -cluster in C+Au collisions at the BNL Relativistic Heavy Ion Collider
Pingal Dasgupta🇨🇳 · Guo-Liang Ma🇨🇳 · Rupa Chatterjee🇮🇳 · Li Yan🇨🇳 · Song Zhang🇨🇳 · Yu-Gang Ma🇨🇳
Different orientations of $α$ -clustered carbon nuclei colliding with heavy ions can result in a large variation in the value of anisotropic flow. Thus, photon flow observables from clustered $^{12} C$ and $^{197} Au$ collisions could be a potential probe to study the `direct photon puzzle'. We calculate the transverse momentum spectra and anisotropic flow coefficients ( $v_{n}$ ) of thermal photons from collisions of triangular $α$ -clustered carbon and gold at $s_{NN} = 200$ GeV at RHIC using a hydrodynamic model framework and compare the results with those obtained from unclustered carbon and gold collisions. The slope of the thermal photon spectra is found to vary moderately for different orientations of collisions. However, we find that the elliptic ( $v_{2}$ ) and triangular flow ( $v_{3}$ ) coefficients of direct photons for specific configurations are significantly larger and predominantly formed by the QGP radiation. A strong anti-correlation between initial spatial ellipticity and triangularity is observed in an event-by-event framework of $α$ -clustered $C + Au$ collisions. These special features provide us an opportunity to detect the exotic nature of cluster structure inside carbon nucleus using the photon probe in the future experiments.
nucl-thhep-phnucl-exEPJA(2021)·20 citations
05
Probing high-density symmetry energy using heavy-ion collisions at intermediate energies
Gao-Chan Yong🇨🇳 · Ya-Fei Guo🇨🇳
The nuclear symmetry energy, which describes the energy difference of per proton and neutron in nuclear matter, has been extensively studied within the last two decades. Around saturation density, both the value and the slope of the nuclear symmetry energy have been roughly constrained, its high-density behavior is now still in argument. Probing high-density symmetry energy at terrestrial laboratories is being carried out at facilities that offer radioactive beams worldwide. While relevant experiments are being conducted, we theoretically developed more advanced isospin-dependent transport model including new physics such as nucleon-nucleon short-range correlations and in-medium isospin-dependence of baryon-baryon scattering cross section. New sensitive probes of high-density symmetry energy are provided, such as squeezed-out neutron to proton ratio, photon and light cluster as well as the production of mesons with strangeness or hidden strangeness. The blind spots of probing the high-density symmetry energy by sensitive observable are demonstrated. Model dependence of frequently used sensitive probes of the symmetry energy has been studied thoroughly based on different transport models. A qualitative observable of neutron to proton ratio at high emitting energy is proposed to probe the high-density symmetry energy qualitatively. The probed density regions of the symmetry energy are carefully studied. Effects of nucleon-nucleon short-range correlations on the some sensitive observables of the symmetry energy in heavy-ion collisions are explored carefully. Probing the curvature of the symmetry energy by involving the slope information of the symmetry energy at saturation point in the transport model is proposed.
nucl-thnucl-exNucl.Phys.Rev.(2020)·11 citations
06
Towards the continuum coupling in nuclear lattice effective field theory I: A three-particle model
J.-J. Wu🇨🇳 · Ulf-G. Meißner🇩🇪
Weakly bound states often occur in nuclear physics. To precisely understand their properties, the coupling to the continuum should be worked out explicitely. In a first step, we use a simple nuclear model in the continuum and on a lattice to investigate the influence of a third particle on a loosely bound state of a particle and a heavy core.
nucl-thhep-lathep-phCPC(2020)·1 citation
07
Lifetime of the hypertriton
F. Hildenbrand🇩🇪 · H.-W. Hammer🇩🇪
We calculate the lifetime of the hypertriton as function of the $Λ$ separation energy $B_{Λ}$ in an effective field theory with $Λ$ and deuteron degrees of freedom. We also consider the impact of new measurements of the weak decay parameter of the $Λ$ . While the sensitivity of the total width to $B_{Λ}$ is small, the partial widths for decays into individual final states and the experimentally measured ratio $R = Γ_{^{3} He} / (Γ_{^{3} He} + Γ_{p d})$ show a strong dependence. For the standard value $B_{Λ} = (0.13 \pm 0.05)$ MeV, we find $R = 0.37 \pm 0.05$ , which is in good agreement with past experimental studies and theoretical calculations. For the recent STAR value $B_{Λ} = (0.41 \pm 0.12 \pm 0.11)$ MeV, we obtain $R = 0.57 \pm 0.11$ .
nucl-thhep-phPRC(2020)·35 citations
08
Coulomb Corrections for Bose-Einstein Correlations from One- And Three-Dimensional Lévy-Type Source Functions
Bálint Kurgyis🇭🇺 · Dániel Kincses🇭🇺 · Márton Nagy🇭🇺 · Máté Csanád🇭🇺
In the study of femtoscopic correlations in high-energy physics, besides Bose--Einstein correlations, one has to take final-state interactions into account. Amongst them, Coulomb interactions play a prominent role in the case of charged particles. Recent measurements have shown that in heavy-ion collisions, Bose--Einstein correlations can be best described by Lévy-type sources instead of the more common Gaussian assumption. Furthermore, three-dimensional measurements have indicated that, depending on the choice of frame, a deviation from spherical symmetry observed under the assumption of Gaussian source functions persists in the case of Lévy-type sources. To clarify such three-dimensional Lévy-type correlation measurements, it is thus important to study the effect of Coulomb interactions in the case of non-spherical Lévy sources. We calculated the Coulomb correction factor numerically in the case of such a source function for assorted kinematic domains and parameter values using the Metropolis--Hastings algorithm and compared our results with previous methods to treat Coulomb interactions in the presence of Lévy sources.
nucl-thhep-phUniverse(2023)·22 citations
09
Near-threshold $K^{*} (892)^{+}$ meson production in the interaction of $π^{-}$ mesons with nuclei
E. Ya. Paryev🇷🇺
We study the inclusive strange vector meson $K^{*} (892)^{+}$ production in $π^{-} A$ reactions at near-threshold laboratory incident pion momenta of 1.4--2.0 GeV/c within a nuclear spectral function approach. The approach accounts for incoherent primary $π^{-}$ meson--proton $π^{-} p \to K^{*} (892)^{+} Σ^{-}$ production processes as well as the influence of the scalar $K^{*} (892)^{+}$ --nucleus potential (or the $K^{*} (892)^{+}$ in-medium mass shift) on these processes. We calculate the absolute differential and total cross sections for the production of $K^{*} (892)^{+}$ mesons off carbon and tungsten nuclei at laboratory angles of 0 $^{\circ}$ --45 $^{\circ}$ and at these momenta within five scenarios for the above shift. We show that the $K^{*} (892)^{+}$ momentum distributions and their excitation functions (absolute and relative) possess a high sensitivity to changes in the in-medium $K^{*} (892)^{+}$ mass shift in the low-momentum region of 0.1--0.6 GeV/c. Therefore, the measurement of such observables in a dedicated experiment at the GSI pion beam facility in the near-threshold momentum domain will allow to get valuable information on the $K^{*} (892)^{+}$ in-medium properties.
nucl-thhep-phnucl-exCPC(2020)·6 citations
10
Structure of Quark Star: A Comparative Analysis of Bayesian Inference and Neural Network Based Modeling
Silvia Traversi🇮🇹 · Prasanta Char🇮🇹
In this work, we compare two powerful parameter estimation methods namely Bayesian inference and Neural Network based learning to study the quark matter equation of state with constant speed of sound parametrization and the structure of the quark stars within the two-family scenario. We use the mass and radius estimations from several X-ray sources and also the mass and tidal deformability measurements from gravitational wave events to constrain the parameters of our model. The results found from the two methods are consistent. The predicted speed of sound is compatible with the conformal limit.
nucl-thastro-ph.HEApJ(2020)·27 citations
11
Comment on "Comparison of optical potential for nucleons and $Δ$ resonances" by Arie Bodek and Tejin Cai
U. Mosel🇩🇪
In \cite{Bodek:2020wbk} Bodek and Cai have tried to extract the potentials for nucleons and $Δ$ resonances from electron-nucleus inclusive scattering data. They find that the $Δ$ potential is considerably more attractive than that of the nucleons. This result is at variance with the results of a multitude of analyses of (e,A) and ( $γ A$ ) interactions, performed about 35 years ago.
nucl-thhep-exnucl-ex4 citations
12
Nature of the $Λ nn$ $(J^{π} = 1/ 2^{+}, I = 1)$ and $_{Λ}^{3} H^{*} (J^{π} = 3/ 2^{+}, I = 0)$ states
M. Schäfer🇨🇿 · B. Bazak🇮🇱 · N. Barnea🇮🇱 · J. Mareš🇨🇿
The nature of the $Λ nn$ and $_{Λ}^{3} H^{*} (J^{π} = 3/ 2^{+}, I = 0)$ states is investigated within a pionless effective field theory at leading order, constrained by the low energy $Λ N$ scattering data and hypernuclear 3- and 4-body data. Bound state solutions are obtained using the stochastic variational method, the continuum region is studied by employing two independent methods - the inverse analytic continuation in the coupling constant method and the complex scaling method. Our calculations yield both the $Λ nn$ and $_{Λ}^{3} H^{*}$ states unbound. We conclude that the excited state $_{Λ}^{3} H^{*}$ is a virtual state and the $Λ nn$ pole located close to the three-body threshold in a complex energy plane could convert to a true resonance with Re $(E) > 0$ for some considered $Λ N$ interactions. Finally, the stability of resonance solutions is discussed and limits of the accuracy of performed calculations are assessed.
nucl-thnucl-exPRC(2021)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE