Nuclear Theory·nucl-th

Tuesday·August 30, 2022

16 papers—9 primary·7 cross-listed

01
The Fundamental Nature of Low-Energy Pion-Nucleon Interactions
Gerald A. Miller🇺🇸
A historical review of pion-nucleon interactions at low energy is presented, with aims toward an introductory, pedagogic approach focusing on issues germane to current research. These topics include the use of chiral effective field theory, the sigma term, qualitative understanding of low-energy phase shifts, the physics of the $Δ$ resonance, and isospin violation. A theme is that low-energy pion-nucleon scattering is directly related to QCD via effective field theory. Another theme is that modern needs regarding the pion-nucleon sigma term and the study of isospin violation requires a better low-energy data set.
nucl-thnucl-ex2 citations
02
Unified neutron star EOSs and neutron star structures in RMF models
Cheng-Jun Xia · Toshiki Maruyama · Ang Li · Bao Yuan Sun · Wen-Hui Long · Ying-Xun Zhang
In the framework of Thomas-Fermi approximation, we study systematically the EOSs and microscopic structures of neutron star matter in a vast density range with $n_{b} \approx 1 0^{- 10}$ -2 $fm^{- 3}$ , where various covariant density functionals are adopted, i.e., those with nonlinear self couplings (NL3, PK1, TM1, GM1, MTVTC) and density-dependent couplings (DD-LZ1, DDME-X, PKDD, DD-ME2, DD2, TW99). It is found that the EOSs generally coincide with each other at $n_{b} ≲ 1 0^{- 4}$ fm $^{- 3}$ and 0.1 fm $^{- 3} ≲ n_{b} ≲ 0.3$ fm $^{- 3}$ , while in other density regions they are sensitive to the effective interactions between nucleons. By adopting functionals with larger slope of symmetry energy $L$ , the curvature parameter $K_{sym}$ and neutron drip density generally increase, while the droplet size, proton number of nucleus, core-crust transition density, and onset density of non-spherical nuclei decrease. All functionals predict neutron stars with maximum masses exceeding the two-solar-mass limit, while those of DD2, DD-LZ1, DD-ME2, and DDME-X predict optimum neutron star radii according to the observational constraints. Nevertheless, the corresponding skewness coefficients $J$ are much lager than expected, while only the functionals MTVTC and TW99 meet the start-of-art constraints on $J$ . More accurate measurements on the radius of PSR J0740+6620 and the maximum mass of neutron stars are thus essential to identify the functional that satisfies all constraints from nuclear physics and astrophysical observations. Approximate linear correlations between neutron stars' radii at $M = 1.4 M_{⊙}$ and $2 M_{⊙}$ , the slope $L$ and curvature parameter $K_{sym}$ of symmetry energy are observed as well, which is mainly attributed to the curvature-slope correlations in the functionals adopted here.
nucl-thastro-ph.HECommun.Theor.Phys.(2022)·44 citations
03
Addressing energy density functionals in the language of path-integrals I: Comparative study of diagrammatic techniques applied to the (0+0)-D $O (N)$ -symmetric $φ^{4}$ -theory
Kilian Fraboulet · Jean-Paul Ebran
The energy density functional (EDF) method is currently the only microscopic theoretical approach able to tackle the entire nuclear chart. Nevertheless, it suffers from limitations resulting from its empirical character and deteriorating its reliability. This paper is part of a larger program that aims at formulating the EDF approach as an effective field theory (EFT) in order to overcome these limitations. A relevant framework to achieve this is the path-integral (PI) formulation of quantum field theory (QFT). The latter indeed provides a wide variety of treatments of the many-body problem well suited to deal with non-perturbative interactions and to exploit a Lagrangian resulting from an EFT as a starting point. While developing the formalism in a general setting, we present a comparative study of such techniques applied to a toy model, i.e. the (0+0)-D $O (N)$ -symmetric $φ^{4}$ -theory. More specifically, our focus will be on the following diagrammatic techniques: loop expansion (LE), optimized perturbation theory (OPT) and self-consistent perturbation theory (SCPT). With these methods, we notably address the spontaneous breakdown of the $O (N)$ symmetry with care especially since spontaneous symmetry breakings (SSBs) play a paramount role in current implementations of the EDF approach.
nucl-thcond-mat.str-elEPJA(2023)·7 citations
04
Realizing the potential of deep neural network for analyzing neutron star observables and dense matter equation of state
Ameya Thete🇮🇳 · Kinjal Banerjee🇮🇳 · Tuhin Malik🇵🇹
The difficulty in describing the equation of state (EoS) for nuclear matter at densities above the saturation density ( $ρ_{0}$ ) has led to the emergence of a multitude of models based on different assumptions and techniques. These EoSs, when used to describe a neutron star (NS), lead to differing values of observables. An outstanding goal in astrophysics is to constrain the dense matter EoS by exploiting astrophysical and gravitational wave measurements. Nuclear matter parameters appear as Taylor coefficients in the expansion of the EoS around the saturation density of symmetric and asymmetric nuclear matter and provide a physically-motivated representation of the EoS. In this paper, we introduce a deep learning-based methodology to predict key neutron stars observables such as the NS mass, NS radius, and tidal deformability from a set of nuclear matter parameters. Using generated mock data, we confirm that the neural network model is able to accurately capture the underlying physics of finite nuclei and replicate inter-correlations between the symmetry energy slope, its curvature, and the tidal deformability arising from a set of physical constraints. We also test our network with mock data generated by a different class of physics model, which was not part of the training, to explore the limitations of model dependency in the results. We also study the validity of our trained model using Bayesian inference and show that the performance of our model is on par with physics-based models with the added benefit of much lower computational cost.
nucl-thastro-ph.HEphysics.comp-phPRD(2023)·20 citations
05
Neutron-proton differential transverse flow in $^{132}$ Sn + $^{124}$ Sn collisions at 270 MeV/nucleon
Xin Huang · Gao-Feng Wei · Qi-Jun Zhi · You-Chang Yang · Zheng-Wen Long
Within a transport model, we study the neutron-proton differential transverse flow and its excitation function in central $^{132}$ Sn + $^{124}$ Sn collisions at 270 MeV/nucleon. To more accurately evaluate effects of the high-density behavior of symmetry energy \esym on this observable, we also consider the uncertainties of \esym around the saturation density $ρ_{0}$ . It is shown that the neutron-proton differential transverse flow and its excitation function are mainly sensitive to the slope $L$ of \esym at $ρ_{0}$ . However, the effects of low-density behavior of \esym on this observable should also be considered. Therefore, it is suggested that measurements of the neutron-proton differential transverse flow and its excitation function may provide useful complements to the constraints on $L$ extracted from the spectral pion ratio in S $π$ RIT experiments.
nucl-thnucl-exPRC(2022)·4 citations
06
Nuclear fragmentation reactions as a probe of neutron skins in nuclei
E.A. Teixeira · T. Aumann · C.A. Bertulani · B.V. Carlson
We investigate the contributions of various reaction channels to the interaction, reaction, charge-changing and neutron-changing cross sections. The goal is to investigate the relation between microscopic interactions and the symmetry energy component of the equation of state (EoS) of interest for the structure of neutron stars. We have made a comparison of the neutron skins extracted from diverse experimental techniques with those obtained with Hartree-Fock-Bogoliubov calculations with 23 Skyrme and with 8 density-dependent interactions used in the relativistic mean field method. We have shown that no particular conclusion can be drawn on the best EoS in view of the wide range of uncertainty in the experimental data. We have further investigated the prospects of using neutron-changing reactions to assess the isospin dependence of the neutron-skin in neutron-rich nuclei.
nucl-thnucl-exEPJA(2022)·13 citations
07
Effects of the formation time of parton shower on jet quenching in heavy-ion collisions
Mengxue Zhang🇨🇳 · Yang He🇨🇳 · Shanshan Cao🇨🇳 · Li Yi🇨🇳
Jet quenching has successfully served as a hard probe to study the properties of Quark-Gluon Plasma (QGP). As a multi-particle system, jets take time to develop from a highly virtual parton to a group of partons close to mass shells. In this study, we present a systematical study on the effects of this formation time on jet quenching in relativistic nuclear collisions. Jets from initial hard scatterings were simulated with Pythia, and their interactions with QGP were described using a Linear Boltzmann Transport (LBT) model that incorporates both elastic and inelastic scatterings between jet partons and the thermal medium. Three different estimations of the jet formation time were implemented and compared, including instantaneous formation, formation from single splitting, and formation from sequential splittings, before which no jet-medium interaction was assumed. We found that deferring the jet-medium interaction with a longer formation time not only affects the overall magnitude of the nuclear modification factor of jets, but also its dependence on the jet transverse momentum.
nucl-thhep-phCPC(2023)·18 citations
08
Dynamics of Hot QCD Matter -- Current Status and Developments
Santosh K. Das🇮🇳 · Prabhakar Palni🇮🇳 · Jhuma Sannigrahi🇮🇳 · Jan-e Alam🇮🇳 · Cho Win Aung🇮🇳 · Yoshini Bailung🇮🇳 · Debjani Banerjee🇮🇳 · Gergely Gábor Barnaföldi🇭🇺 · Subash Chandra Behera🇮🇳 · Partha Pratim Bhaduri🇮🇳 · Samapan Bhadury🇮🇳 · Rajesh Biswas🇮🇳 and 55 other authors
The discovery and characterization of hot and dense QCD matter, known as Quark Gluon Plasma (QGP), remains the most international collaborative effort and synergy between theorists and experimentalists in modern nuclear physics to date. The experimentalists around the world not only collect an unprecedented amount of data in heavy-ion collisions, at Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory (BNL) in New York, USA, and the Large Hadron Collider (LHC), at CERN in Geneva, Switzerland but also analyze these data to unravel the mystery of this new phase of matter that filled a few microseconds old universe, just after the Big Bang. In the meantime, advancements in theoretical works and computing capability extend our wisdom about the hot-dense QCD matter and its dynamics through mathematical equations. The exchange of ideas between experimentalists and theoreticians is crucial for the progress of our knowledge. The motivation of this first conference named "HOT QCD Matter 2022" is to bring the community together to have a discourse on this topic. In this article, there are 36 sections discussing various topics in the field of relativistic heavy-ion collisions and related phenomena that cover a snapshot of the current experimental observations and theoretical progress. This article begins with the theoretical overview of relativistic spin-hydrodynamics in the presence of the external magnetic field, followed by the Lattice QCD results on heavy quarks in QGP, and finally, it ends with an overview of experiment results.
nucl-thhep-exhep-phhep-th+1IJMPE(2022)·39 citations
09
Status of the hyperon-nucleon interaction in chiral effective field theory
J. Haidenbauer🇩🇪 · U.-G. Meißner🇩🇪
The Jülich-Bonn group aims at an extensive study of the baryon-baryon ( $B B$ ) interaction involving strange baryons ( $Λ$ , $Σ$ , $Ξ$ ) within SU(3) chiral effective field theory. An overview of achievements and new developments over the past few years is provided. The topics covered are: 1) Derivation of the leading charge-symmetry breaking (CSB) interaction for the $Λ N$ system and its application in a study of CSB effects in $A$ = $4$ $Λ$ -hypernuclei. 2) Updated results for the $Ξ N$ interaction at NLO and predictions for $Ξ^{-} p$ correlation functions. 3) Extension of the $Λ N$ - $Σ N$ interaction to next-to-next-to-leading order.
nucl-thEPJ Web Conf.(2022)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE