Nuclear Theory·nucl-th

Tuesday·July 11, 2023

14 papers—8 primary·6 cross-listed

01
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.
nucl-thhep-phhep-thPPNP(2024)·86 citations
02
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.
nucl-thastro-ph.HEnucl-exPRC(2024)·33 citations
03
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.
nucl-thhep-phPRC(2023)·20 citations
04
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.
nucl-thMNRAS(2025)·5 citations
05
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.
nucl-thphysics.atom-phPRC(2024)·8 citations
06
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.
nucl-thCPC(2023)·9 citations
07
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.
nucl-thnucl-exFew Body Syst.(2023)·1 citation
08
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.
nucl-th0 citations
09
Thermal behavior as indicator for hyperons in binary neutron star merger remnants
Sebastian Blacker🇩🇪 · Hristijan Kochankovski🇪🇸 · Andreas Bauswein🇩🇪 · Angels Ramos🇪🇸 · Laura Tolos🇪🇸
We provide the first comprehensive study of hyperons in neutron star mergers and quantify their specific impact. We discuss the thermal behavior of hyperonic equations of state~(EoSs) as a distinguishing feature from purely nucleonic models in the remnants of binary mergers using a large set of numerical simulations. Finite temperature enhances the production of hyperons, which leads to a reduced pressure as highly degenerate nucleons are depopulated. This results in a characteristic increase of the dominant postmerger gravitational-wave frequency by up to $\sim 150$ ~Hz compared to purely nucleonic EoS models. By our comparative approach we can directly link this effect to the occurrence of hyperons. Although this feature is generally weak, it is in principle measurable if the EoS and stellar parameters of cold neutron stars are sufficiently well determined. Considering that the mass-radius relations of purely nucleonic and hyperonic EoSs may be indistinguishable and the overall challenge to infer the presence of hyperons in neutron stars, these findings are important as a new route to answer the outstanding question about hyperonic degrees of freedom in high-density matter.
↳ astro-ph.HEnucl-thPRD(2024)·39 citations
10
Transverse momentum dependent feed-down fractions for bottomonium production
Jacob Boyd🇺🇸 · Sabin Thapa🇺🇸 · Michael Strickland🇺🇸
We extract transverse momentum dependent feed-down fractions for bottomonium production using a data-driven approach. We use data published by the ATLAS, CMS, and LHCb Collaborations for sqrt(s) = 7 TeV proton-proton collisions. Based on this collected data, we produce fits to the differential cross sections for the production of both S- and P-wave bottomonium states. Combining these fits with branching ratios for excited state decays from the Particle Data Group, we compute the feed-down fractions for both the Upsilon(1S) and Upsilon(2S) as a function of transverse momentum. Our results indicate a strong dependence on transverse momentum, which is consistent with prior extractions of the feed-down fractions. When evaluated at the average momentum of the states, we find that approximately 75% of Upsilon(1S) and Upsilon(2S) states are produced directly. Our results for the transverse momentum dependent feed-down fractions are provided in tabulated form so that they can be used by other research groups.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·6 citations
11
Quantum techniques for eigenvalue problems
Dean Lee🇺🇸
This article is a brief introduction to quantum algorithms for the eigenvalue problem in quantum many-body systems. Rather than a broad survey of topics, we focus on providing a conceptual understanding of several quantum algorithms that cover the essentials of adiabatic evolution, variational methods, phase detection algorithms, and several other approaches. For each method, we discuss the potential advantages and remaining challenges.
↳ quant-phcond-mat.quant-gasnucl-thEPJA(2023)·5 citations
12
Diffusion and fluctuations of open charmed hadrons in an interacting hadronic medium
Kangkan Goswami🇮🇳 · Kshitish Kumar Pradhan🇮🇳 · Dushmanta Sahu🇮🇳 · Raghunath Sahoo🇮🇳
Heavy quarks are excellent probes to understand the hot and dense medium formed in ultra-relativistic collisions. In a hadronic medium, studying the transport properties, e.g. the drag ( $γ$ ), momentum diffusion ( $B_{0}$ ), and spatial diffusion ( $D_{s}$ ) coefficients of open charmed hadrons can provide useful information about the medium. Moreover, the fluctuations of charmed hadrons can help us to locate the onset of their deconfinement. In this work, we incorporate attractive and repulsive interactions in the well-established van der Waals hadron resonance gas model (VDWHRG) and study the diffusion and fluctuations of charmed hadrons. This study helps us understand the importance of interactions in the system, which affect both the diffusion and fluctuations of charmed hadrons.
↳ hep-phhep-exnucl-exnucl-thPRD(2023)·14 citations
13
$ϕ (2170)$ decaying to $ϕ π π$ and $ϕ K K ˉ$
Yun-Hua Chen🇨🇳
Within the framework of dispersion theory, we study the the processes $e^{+} e^{-} \to ϕ (2170) \to ϕ π π (K K ˉ)$ . The strong pion-pion final-state interactions, especially the $K K ˉ$ coupled channel in the $S$ -wave, are taken into account in a model-independent way using the Omnès function solution. Through fitting the experimental data of the $π π$ and $ϕ π$ invariant mass distributions of the $e^{+} e^{-} \to ϕ (2170) \to ϕ π^{+} π^{-}$ process, the low-energy constants in the chiral Lagrangian are determined. The theoretical prediction for the cross sections ratio $σ (e^{+} e^{-} \to ϕ (2170) \to ϕ K^{+} K^{-}) / σ (e^{+} e^{-} \to ϕ (2170) \to ϕ π^{+} π^{-})$ is given, which could be useful for selecting the physical solution when the fit to the $e^{+} e^{-} \to ϕ K^{+} K^{-}$ cross section distribution is available in the future. Our results suggest that above the kinematical threshold of $ϕ K K ˉ$ , the mechanism $e^{+} e^{-} \to ϕ K^{+} K^{-}$ with the kaons rescattering to a pion pair plays an important role in the $e^{+} e^{-} \to ϕ π^{+} π^{-}$ transition.
↳ hep-phhep-exnucl-thUniverse(2023)·2 citations
14
Toward a generative modeling analysis of CLAS exclusive $2 π$ photoproduction
T. Alghamdi🇺🇸 · Y. Alanazi🇺🇸 · M. Battaglieri🇮🇹 · L. Bibrzycki🇵🇱 · A. V. Golda🇷🇺 · A. N. Hiller Blin🇩🇪 · E. L. Isupov🇷🇺 · Y. Li🇺🇸 · L. Marsicano🇮🇹 · W. Melnitchouk🇺🇸 · V. I. Mokeev🇺🇸 · G. Montana🇺🇸 and 4 other authors
AI-supported algorithms, particularly generative models, have been successfully used in a variety of different contexts. In this work, we demonstrate for the first time that generative adversarial networks (GANs) can be used in high-energy experimental physics to unfold detector effects from multi-particle final states, while preserving correlations between kinematic variables in multidimensional phase space. We perform a full closure test on two-pion photoproduction pseudodata generated with a realistic model in the kinematics of the Jefferson Lab CLAS g11 experiment. The overlap of different reaction mechanisms leading to the same final state associated with the CLAS detector's nontrivial effects represents an ideal test case for AI-supported analysis. Uncertainty quantification performed via bootstrap provides an estimate of the systematic uncertainty associated with the procedure. The test demonstrates that GANs can reproduce highly correlated multidifferential cross sections even in the presence of detector-induced distortions in the training datasets, and provides a solid basis for applying the framework to real experimental data.
↳ hep-phhep-exnucl-thPRD(2023)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE