Nuclear Theory·nucl-th

Friday·October 27, 2023

7 papers—3 primary·4 cross-listed

01
Probing spin and pseudospin symmetries in deformed nuclei by the Green's function method
Ting-Ting Sun · Bing-Xin Li · Kun Liu
(Pseudo)spin symmetries play vital roles in nuclear physics and have been studied extensively in spherical nuclei. In this work, possible spin and pseudospin symmetries in deformed nuclei are examined by solving a coupled-channel Dirac equation with quadruple deformation. The Green's function method is taken which provides a novel way to exactly determine the single-particle levels and properly describe the spacial density distributions. Taking axially-deformed nucleus $^{154}$ Dy as an example, the spin doublets with a combination of Nilsson levels $Λ \pm 1/2 [N, n_{z}, Λ]$ and pseudospin doublets with a combination of $Λ \pm 1/2 [N, n_{z}, Λ]$ are determined. Different behaviors are displayed for the spin and pseudospin doublets. For the spin partners, those with smaller angular momentum $l$ and the third component $Λ$ owns better symmetry such as the $1 p$ doublet while good pseudospin symmetry appears in partners locating close to the continuum threshold. By examining the single-particle Nilsson levels $Ω [N, n_{z}, Λ]$ and the energy splittings between the partners, the conservation and breaking of SS and PSS are examined at different deformations. In the prolate side, the Nilsson levels for the spin and pseudospin doublets are almost parallel and the energy splittings are stable against varying deformations. By examining the density distributions, great similarities have been observed in the upper components for the spin doublets while great similarities in the lower component for the pseudospin doublets. Besides, these similarities maintain well at different deformations.
nucl-thPRC(2024)·6 citations
02
Baryon density dependence of viscosities of the quark-gluon plasma at hadronization
Zhidong Yang🇨🇳 · Yifeng Sun🇨🇳 · Lie-Wen Chen🇨🇳
The $ϕ$ meson and $Ω$ baryon provide unique probes of the properties of the quark-gluon plasma (QGP) at hadronization in relativistic heavy-ion collisions. Using the quark recombination model with the quark phase-space information parameterized in a viscous blastwave, we perform Bayesian inference of the shear and bulk viscosities of the QGP at hadronization with a temperature of $T \sim 160$ MeV by analyzing the $ϕ$ and $Ω$ data in Au+Au collisions at $s_{NN} =$ 19.6-200 GeV and Pb+Pb collisions at $s_{NN} =$ 2.76 TeV, corresponding to a baryon chemical potential variation from $μ_{B} \approx 0$ (at $s_{NN} = 2.76$ TeV) to $200$ MeV (at $s_{NN} = 19.6$ GeV). We find that the shear viscosity to enthalpy ratio $η T / (ϵ + P)$ of the QGP at hadronization decreases as $μ_{B}$ increases, with $η T / (ϵ + P) \approx 0.18$ at $μ_{B} = 0$ and $η T / (ϵ + P) \approx 0.08$ at $μ_{B} = 200$ MeV, while the corresponding specific bulk viscosity is essentially constant with $ζ T / (ϵ + P) = 0.02 \sim 0.04$ for $μ_{B} < 200$ MeV. Our results suggest that the QGP at hadronization ( $T \sim 160$ MeV) with finite baryon density is more close to perfect fluid than that with zero baryon density.
nucl-thastro-ph.HEhep-phnucl-exPRC(2024)·4 citations
03
Applications of emulation and Bayesian methods in heavy-ion physics
Jean-François Paquet🇺🇸
Heavy-ion collisions provide a window into the properties of many-body systems of deconfined quarks and gluons. Understanding the collective properties of quarks and gluons is possible by comparing models of heavy-ion collisions to measurements of the distribution of particles produced at the end of the collisions. These model-to-data comparisons are extremely challenging, however, because of the complexity of the models, the large amount of experimental data, and their uncertainties. Bayesian inference provides a rigorous statistical framework to constrain the properties of nuclear matter by systematically comparing models and measurements. This review covers model emulation and Bayesian methods as applied to model-to-data comparisons in heavy-ion collisions. Replacing the model outputs (observables) with Gaussian process emulators is key to the Bayesian approach currently used in the field, and both current uses of emulators and related recent developments are reviewed. The general principles of Bayesian inference are then discussed along with other Bayesian methods, followed by a systematic comparison of seven recent Bayesian analyses that studied quark-gluon plasma properties, such as the shear and bulk viscosities. The latter comparison is used to illustrate sources of differences in analyses, and what it can teach us for future studies.
nucl-thJ.Phys.G(2024)·34 citations
04
Maximal Mass Neutron Star as a Key to Superdense Matter Physics
D. D. Ofengeim · P. S. Shternin · T. Piran
We propose a universal approximation of the equation of state of superdense matter in neutron star (NS) interiors. It contains only two parameters, the pressure and the density at the center of the maximally massive neutron star. We demonstrate the validity of this approximation for a wide range of different types of equations of state, including both baryonic and hybrid models. Combined with recently discovered correlations of internal (density, pressure, and speed of sound at the center) and external (mass, radius) properties of a maximally massive neutron star, this approximation turns out to be an effective tool for determining the equation of state of superdense matter using astrophysical observations.
↳ astro-ph.HEastro-ph.SRnucl-thAstron.Lett.(2023)·9 citations
05
Further evidence for shape coexistence in $^{79}$ Zn $^{m}$ near doubly-magic $^{78}$ Ni
L. Nies (1 and 2)🇨🇭 · L. Canete (3 and 4)🇫🇮 · D. D. Dao (5)🇫🇷 · S. Giraud (6)🇫🇷 · A. Kankainen (3)🇫🇮 · D. Lunney (7)🇫🇷 · F. Nowacki (5)🇫🇷 · B. Bastin (6)🇫🇷 · M. Stryjczyk (3)🇫🇮 · P. Ascher (8)🇫🇷 · K. Blaum (9)🇩🇪 · R. B. Cakirli (10)🇹🇷 and 22 other authors
Isomers close to doubly-magic $_{28}^{78}$ Ni $_{50}$ provide essential information on the shell evolution and shape coexistence near the $Z = 28$ and $N = 50$ double shell closure. We report the excitation energy measurement of the $1/ 2^{+}$ isomer in $_{30}^{79}$ Zn $_{49}$ through independent high-precision mass measurements with the JYFLTRAP double Penning trap and with the ISOLTRAP Multi-Reflection Time-of-Flight Mass Spectrometer. We unambiguously place the $1/ 2^{+}$ isomer at 942(10) keV, slightly below the $5/ 2^{+}$ state at 983(3) keV. With the use of state-of-the-art shell-model diagonalizations, complemented with Discrete Non Orthogonal shell-model calculations which are used here the first time to interpret shape coexistence, we find low-lying deformed intruder states, similar to other $N = 49$ isotones. The $1/ 2^{+}$ isomer is interpreted as the band-head of a low-lying deformed structure akin to a predicted low-lying deformed band in $^{80}$ Zn, and points to shape coexistence in $^{79, 80}$ Zn similar to the one observed in $^{78}$ Ni. The results make a strong case for confirming the claim of shape coexistence in this key region of the nuclear chart.
↳ nucl-exnucl-thPRL(2023)·14 citations
06
The Four-Boson First-Excited State Near Two-Body Unitarity
Feng Wu🇺🇸 · T. Frederico🇧🇷 · R. Higa🇧🇷 · U. van Kolck🇫🇷
Near two-body unitarity, the three-boson system is characterized by an approximate discrete scale invariance manifest in a geometric tower of bound states (the Efimov effect). In the absence of a strong four-body force, the four-boson system has two states associated with each Efimov state, one very nearly unstable, the other several times deeper. We study correlations between the excited- and ground-state properties, such as binding energies and radii, up to next-to-leading order in an effective field theory for short-range forces. We obtain the parameters in these correlations from similar correlations arising from existing precise calculations based on short-range potentials. We also derive correlations among excited-state properties that emerge from the proximity of the state to the break-up threshold into a boson and a three-boson bound state, using an effective field theory for "halo" states.
↳ physics.atom-phnucl-thPRA(2024)·5 citations
07
Domain-wall Skyrmion phase in a rapidly rotating QCD matter
Minoru Eto🇯🇵 · Kentaro Nishimura🇯🇵 · Muneto Nitta🇯🇵
Based on the chiral perturbation theory at the leading order, we show the presence of a new phase in rapidly rotating QCD matter with two flavors, that is a domain-wall Skyrmion phase. Based on the chiral Lagrangian with a Wess-Zumino-Witten (WZW) term responsible for the chiral anomaly and chiral vortical effect, it was shown that the ground state is a chiral soliton lattice(CSL) consisting of a stack of $η$ -solitons in a high density region under rapid rotation. In a large parameter region, a single $η$ -soliton decays into a pair of non-Abelian solitons, each of which carries $SU (2)_{V} / U (1) ≃ C P^{1} ≃ S^{2}$ moduli as a consequence of the spontaneously broken vector symmetry $SU (2)_{V}$ . In such a non-Abelian CSL, we construct the effective world-volume theory of a single non-Abelian soliton to obtain a $d = 2 + 1$ dimensional $C P^{1}$ model with a topological term originated from the WZW term. We show that when the chemical potential is larger than a critical value, a topological lump supported by the second homotopy group $π_{2} (S^{2}) ≃ Z$ has negative energy and is spontaneously created, implying the domain-wall Skyrmion phase. This lump corresponds in the bulk to a Skyrmion supported by the third homotopy group $π_{3} [SU (2)] ≃ Z$ carrying a baryon number. This composite state is called a domain-wall Skyrmion, and is stable even in the absence of the Skyrme term. An analytic formula for the effective nucleon mass in this medium is obtained as $42 π f_{π} f_{η} / m_{π} \sim 1.21$ GeV with the decay constants $f_{π}$ and $f_{η}$ of the pions and $η$ meson, respectively, and the pion mass $m_{π}$ , which is surprisingly close to the nucleon mass in the QCD vacuum.
↳ hep-phhep-thnucl-thJHEP(2024)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE

Probing spin and pseudospin symmetries in deformed nuclei by the Green's function method

Baryon density dependence of viscosities of the quark-gluon plasma at hadronization

Applications of emulation and Bayesian methods in heavy-ion physics

Maximal Mass Neutron Star as a Key to Superdense Matter Physics

Further evidence for shape coexistence in 79Znm near doubly-magic 78Ni

The Four-Boson First-Excited State Near Two-Body Unitarity

Domain-wall Skyrmion phase in a rapidly rotating QCD matter

Affiliations

Further evidence for shape coexistence in $^{79}$ Zn $^{m}$ near doubly-magic $^{78}$ Ni