Nuclear Theory·nucl-th

Tuesday·July 11, 2023

14 papers—8 primary·6 cross-listed

01
[Submitted on 8 Jul 2023]
Hot QCD Phase Diagram From Holographic Einstein-Maxwell-Dilaton Models
Romulo Rougemont🇧🇷 · Joaquin Grefa🇺🇸 · Mauricio Hippert🇺🇸 · Jorge Noronha🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Israel Portillo🇺🇸 · Claudia Ratti🇺🇸
In this review, we provide an up-to-date account of quantitative holographic descriptions of the strongly coupled quark-gluon plasma (QGP) produced in heavy-ion collisions, based on the class of gauge-gravity Einstein-Maxwell-Dilaton (EMD) models. Holography is employed to tentatively map the QCD phase diagram at finite temperature onto a dual theory of charged, asymptotically AdS black holes in 5D. With a quantitative focus on the hot QCD phase diagram, the EMD models reviewed are adjusted to describe lattice results for the finite-temperature QCD equation of state, with 2+1 flavors and physical quark masses, at zero chemical potential and vanishing electromagnetic fields. The predictive power of EMD models is tested by quantitatively comparing their predictions for the hot QCD equation of state at nonzero baryon density and the corresponding state-of-the-art lattice QCD results. The shear and bulk viscosities predicted by these EMD models are also compared to the corresponding profiles favored by the latest phenomenological multistage models describing different heavy-ion data. We report preliminary results from a Bayesian analysis which provide systematic evidence that lattice results at finite temperature and zero baryon density strongly constrains the free parameters of EMD models. Remarkably, the set of parameters constrained by lattice results at zero chemical potential produces EMD models in quantitative agreement with lattice QCD results also at finite baryon density. We also review results for equilibrium and transport properties from magnetic EMD models, describing the QGP at finite temperatures and magnetic fields. Finally, we provide a critical assessment of the main limitations and drawbacks of the holographic models reviewed in the present work, and point out some perspectives we believe are of fundamental importance for future developments.
Comments:
76 pages, 14 figures, invited review accepted for publication in Progress in Particle and Nuclear Physics
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2307.03885 [pdf]
PPNP(2024)·86 citations
02
[Submitted on 8 Jul 2023]
Symmetry energy and neutron star properties constrained by chiral effective field theory calculations
Yeunhwan Lim🇰🇷 · Achim Schwenk🇩🇪
We investigate the nuclear symmetry energy and neutron star properties using a Bayesian analysis based on constraints from different chiral effective field theory calculations using new energy density functionals that allow for large variations at high densities. Constraints at high densities are included from observations of GW170817 and from NICER. In particular, we show that both NICER analyses lead to very similar posterior results for the symmetry energy and neutron star properties when folded into our equation-of-state framework. Using the posteriors, we provide results for the symmetry energy and the slope parameter, as well as for the proton fraction, the speed of sound, and the central density in neutron stars. Moreover, we explore correlations of neutron star radii with the pressure and the speed of sound in neutron stars. Our 95\% credibility ranges for the symmetry energy $S_{v}$ , the slope parameter $L$ , and the radius of a 1.4 $\msun$ neutron star, $R_{1.4}$ , are $S_{v} = (30.6 - 33.9)$ \,MeV, $L = (43.7 - 70.0)$ \,MeV, and $R_{1.4} = (11.6 - 13.2)$ \,km. Our analysis for the proton fraction shows that larger and/or heavier neutron stars are more likely to cool rapidly via the direct Urca process. Within our equation-of-state framework a maximum mass of neutron stars $M_{max} > 2.1 \msun$ indicates that the speed of sound needs to exceed the conformal limit.
Comments:
Published version, 12 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
2307.04063 [pdf]
PRC(2024)·33 citations
03
[Submitted on 9 Jul 2023]
Hyperon polarization and its relation with directed flow in high-energy nuclear collisions
Ze-Fang Jiang🇨🇳 · Xiang-Yu Wu🇨🇳 · Shanshan Cao🇨🇳 · Ben-Wei Zhang🇨🇳
We investigate the hyperon polarization and its relation with the directed flow of the quark-gluon plasma (QGP) in non-central Au+Au collisions at $s_{NN} = 27$ GeV. A modified 3-dimensional (3D) Glauber model is developed and coupled to a (3+1)-D viscous hydrodynamic evolution of the QGP. Within this framework, we obtain a satisfactory simultaneous description of the directed flow of identified particles and $Λ$ polarization, and show sensitivity of polarization to both the tilted geometry and the longitudinal flow profile of the QGP. A non-monotonic transverse momentum dependence of the $Λ$ polarization is found in our calculation, which is absent from hydrodynamic simulation using other initialization methods and can be tested by future experimental data with higher precision. The relation between the global polarization and directed flow of $Λ$ is explored as the longitudinal flow field or the medium deformation varies. Due to the common origin of these two observables, their combination may provide a more stringent constraint on the initial condition of the QGP.
Comments:
15 pages, 12 figures, published in Phy. Rev. C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2307.04257 [pdf]
PRC(2023)·20 citations
04
[Submitted on 9 Jul 2023]
Big-Bang Nucleosynthesis within the Scale Invariant Vacuum Paradigm
V. G. Gueorguiev · A. Maeder
The Scale Invariant Vacuum (SIV) paradigm is applied to the Big-Bang Nucleosynthesis using the known analytic expressions for the expansion factor $a$ and the plasma temperature $T$ as functions of the SIV time $τ$ since the Big-Bang when $a (τ = 0) = 0$ . The results are compared to the known standard BBNS model as calculated with the PRIMAT code. Potential SIV-guided deviations from the local statistical equilibrium are explored. Overall, we find that smaller than usual baryon and non-zero dark matter content, by a factor of three to five times reduction, result in compatible to the standard reproduction of the light elements abundances.
Comments:
12 pages, 3 figures, 4 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2307.04269 [pdf]
MNRAS(2025)·5 citations
05
[Submitted on 10 Jul 2023]
Schiff moments of deformed nuclei
Oleg P. Sushkov
Stimulated by recent suggestion of Cosmic Axion Spin Precession Experiment with Eu contained compound we develop a new method for accurate calculation of Schiff moments of even-odd deformed nuclei. The method is essentially based on experimental data on magnetic moments and E1,E3-amplitudes in the given even-odd nucleus and in adjacent even-even nuclei. Unfortunately such sets of data are not known yet for most of interesting nuclei. Fortunately the full set of data is available for $^{153}$ Eu. Hence, we perform the calculation for $^{153}$ Eu and find value of the Schiff moment. The value is about 30 times larger than a typical Schiff moment of a spherical heavy nucleus. The enhancement of the Schiff moment in $^{153}$ Eu is related to the low energy octupole mode. On the other hand the value of Schiff moment we find is 30 times smaller than that obtained in the assumption of static octupole deformation.
Subjects:
Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2307.04299 [pdf]
PRC(2024)·8 citations
06
[Submitted on 10 Jul 2023]
Density-dependent relativistic mean field approach and its application to single- $Λ$ hypernuclei in Oxygen isotopes
Shi Yuan Ding🇨🇳 · Wei Yang🇨🇳 · Bao Yuan Sun🇨🇳
The in-medium feature of nuclear force which includes both nucleon-nucleon ( $N N$ ) and hyperon-nucleon ( $Λ N$ ) interactions impacts the description of single- $Λ$ hypernuclei. With the alternated mass number or isospin of hypernuclei, such effects could be unveiled by analyzing systematical evolution of the bulk and single-particle properties. From a density-dependent meson-nucleon/hyperon coupling perspective, a new $Λ N$ effective interaction in the covariant density functional (CDF) theory, namely DD-LZ1- $Λ1$ , is obtained by fitting the experimental data of $Λ$ separation energies for several single- $Λ$ hypernuclei. It is then adopted to study the structure and transition properties of single- $Λ$ hypernuclei in Oxygen isotopes, comparing with several selected CDF Lagrangians. Discrepancy is observed explicitly in the isospin evolution of $Λ1 p$ spin-orbit splitting with various effective interactions, ascribed to their divergence of the meson-hyperon coupling strengths with increasing density. In particular, the density-dependent CDFs introduce an extra contribution to enhance the isospin dependence of the splitting, which is originated from the rearrangement terms of $Λ$ self-energies. In addition, the characteristics of hypernuclear radii are studied along the isotopic chain. Owing to the impurity effect of $Λ$ hyperon, a size shrinkage is observed in the matter radii of hypernuclei as compared to their cores of normal nuclei, while its magnitude is elucidated further to correlate with the incompressibility of nuclear matter. Besides, there exists a sizable model-dependent trend that $Λ$ hyperon radii evolve with the neutron number, which is decided partly by the in-medium $N N$ interactions as well as the core polarization effects.
Comments:
15 pages, 5 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2307.04432 [pdf]
CPC(2023)·9 citations
07
[Submitted on 10 Jul 2023]
On the experimental description of neutron resonances
Julien Gibelin🇫🇷
We present a collection of simple derivations for the neutron-induced resonance cross-sections. These formulae are commonly used to experimentally describe the fundamental properties of resonances for neutron-rich nuclei far from stability and to describe unbound nuclei. The main goal of this article is to illustrate their dependencies with basic observables in order to discuss the pertinence of experimental approaches in the derivation of their properties, especially for "N-body" resonances.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2307.04560 [pdf]
Few Body Syst.(2023)·1 citation
08
[Submitted on 10 Jul 2023]
A new approach to two-level model calculation of isospin mixing in nuclei
Sukhendusekhar Sarkar
A new method has been proposed for isolated two-level model to calculate isospin mixing probability in nuclei overcoming common limitations of usual shell model results with isoscalar nuclear Hamiltonian. The method is based on locating the unperturbed levels of the mixed doublet before mixing. Experimental and shell model level energies, electromagnetic/Gamow-Teller transition matrix elements associated with a doublet or two doublet pairs in a nucleus are used to calculate isospin mixing probability in seven self-conjugate nuclei. The four self-conjugate nuclei (P, S, Cl, Ar) considered here show large isospin mixing matrix elements and large unperturbed energy-gaps of the observed isospin-mixed doublet pairs. Large isospin mixing (31.40-48.76 %) is found in the observed doublet ( $1^{+}, 1^{+}$ ) at 9828.11 and 9967.19 keV, respectively, in $^{24} M g$ . This is probably the largest isospin mixing ever found in a nucleus. This is much larger than that $(20_{- 9.904}^{+ 9.142}$ %) has been found recently in $^{26}$ Si. The method is general enough to be applicable to other two-level/multi-level mixing problems and in particular, might be useful for consideration of isospin mixing in the context of Fermi beta decay also.
Comments:
6 pages, no figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2307.04656 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE