Nuclear Theory·nucl-th

Tuesday·November 7, 2023

15 papers—9 primary·6 cross-listed

01
[Submitted on 3 Nov 2023]
Causality violations in simulations of large and small heavy-ion collisions
Renata Krupczak🇧🇷 · Tiago Nunes da Silva🇧🇷 · Thiago S. Domingues🇧🇷 · Matthew Luzum🇧🇷 · Gabriel S. Denicol🇧🇷 · Fernando G. Gardim🇧🇷 · Andre V. Giannini🇧🇷 · Mauricio N. Ferreira🇪🇸 · Mauricio Hippert🇺🇸 · Jorge Noronha🇺🇸 · David D. Chinellato🇧🇷 · Jun Takahashi🇧🇷
Heavy-ion collisions, such as Pb-Pb or p-Pb, produce extreme conditions in temperature and density that make the hadronic matter transition to a new state, called quark-gluon plasma (QGP). Simulations of heavy-ion collisions provide a way to improve our understanding of the QGP's properties. These simulations are composed of a hybrid description that results in final observables in agreement with accelerators like LHC and RHIC. However, recent works pointed out that these hydrodynamic simulations can display acausal behavior during the evolution in certain regions, indicating a deviation from a faithful representation of the underlying QCD dynamics. To pursue a better understanding of this problem and its consequences, this work simulated two different collision systems, Pb-Pb and p-Pb at $s_{N N} = 5.02$ TeV. In this context, our results show that causality violation, even though always present, typically occurs on a small part of the system, quantified by the total energy fraction residing in the acausal region. In addition, the acausal behavior can be reduced with changes in the pre-hydrodynamic factors and the definition of the bulk-viscous relaxation time. Since these aspects are fairly arbitrary in current simulation models, without solid guidance from the underlying theory, it is reasonable to use the disturbing presence of acausal behavior in current simulations to guide improvements towards more realistic modeling. While this work does not solve the acausality problem, it sheds more light on this issue and also proposes a way to solve this problem in simulations of heavy-ion collisions.
Comments:
15 pages, 17 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2311.02210 [pdf]
PRC(2024)·24 citations
02
[Submitted on 4 Nov 2023]
Coalescence sum rule and the electric charge- and strangeness-dependences of directed flow in heavy ion collisions
Kishora Nayak🇮🇳 · Shusu Shi🇨🇳 · Zi-Wei Lin🇺🇸
The rapidity-odd directed flows ( $v_{1}$ ) of identified hadrons are expected to follow the coalescence sum rule when the created matter is initially in parton degrees of freedom and then hadronizes through quark coalescence. A recent study has considered the $v_{1}$ of produced hadrons that do not contain $u$ or $d$ constituent quarks. It has constructed multiple hadron sets with a small mass difference but given difference in electric charge $Δ q$ and strangeness $Δ S$ between the two sides, where a nonzero and increasing $Δ v_{1}$ with $Δ q$ has been proposed to be a consequence of electromagnetic fields. In this study, we examine the consequence of coalescence sum rule on the $Δ v_{1}$ of the hadron sets in the absence of electromagnetic fields. We find that in general $Δ v_{1} \neq = 0$ for a hadron set with nonzero $Δ q$ and/or $Δ S$ due to potential $v_{1}$ differences between $u ˉ$ and $d ˉ$ and between $s$ and $s ˉ$ quarks. We further propose methods to extract the coefficients for the $Δ q$ - and $Δ S$ -dependences of the direct flow difference, where a nonzero constant term would indicate the breaking of the coalescence sum rule. The extraction methods are then demonstrated with transport model results.
Comments:
7 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2311.02307 [pdf]
PLB(2024)·7 citations
03
[Submitted on 4 Nov 2023]
Machine learning approach to analyze heavy quark diffusion coefficient in relativistic heavy-ion collisions
Rui Guo🇺🇸 · Yonghui Li🇨🇳 · Baoyi Chen🇨🇳
The diffusion coefficient of heavy quarks in the deconfined medium is examined in this research using a deep convolutional neural network (CNN) trained with data from relativistic heavy ion collisions involving heavy flavor hadrons. The CNN is trained using observables such as the nuclear modification factor $R_{AA}$ and the elliptic flow $v_{2}$ of non-prompt $J / ψ$ from B-hadron decay in different centralities, where B meson evolutions are calculated using the Langevin equation and the Instantaneous Coalescence Model. The CNN outputs the parameters characterizing the temperature and momentum dependence of the heavy quark diffusion coefficient. By inputting the experimental data of non-prompt $J / ψ$ $(R_{AA}, v_{2})$ from various collision centralities into multiple channels of the well-trained network, we derive the values of the diffusion coefficient parameters. Additionally, We evaluate the uncertainty in determining the diffusion coefficient by taking into account the uncertainties present in the experimental data $(R_{AA}, v_{2})$ , which serve as inputs to the deep neural network.
Comments:
7 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2311.02335 [pdf]
Entropy(2023)·8 citations
04
[Submitted on 5 Nov 2023]
The neutron skin of 48Ca and 208Pb: a critical analysis
Francesca Sammarruca
We discuss the neutron skins of 48Ca and 208Pb. We review and critically examine modern predictions and empirical constraints, with special attention to the different interpretations of the findings from the PREX-II experiment and the recently reported value of the neutron skin in 48Ca extracted from the CREX experiment. We argue that, in the spirit of the ab initio philosophy, the path to understanding the behavior of dense neutron-rich matter must not circumvent fundamental nuclear forces. Based only on that argument, a thick neutron skin in 208Pb is highly unlikely.
Comments:
10 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2311.02539 [pdf]
Symmetry(2024)·14 citations
05
[Submitted on 6 Nov 2023]
Magnetic moments of decuplet baryons in asymmetric strange hadronic matter at finite temperature
Arvind Kumar🇮🇳 · Suneel Dutt🇮🇳 · Harleen Dahiya🇮🇳
In the present work we study the masses and magnetic moments of decuplet baryons in isospin asymmetric strange hadronic medium at finite temperature using chiral SU(3) quark mean field model. In the strange isospin asymmetric medium, the properties of baryons in chiral SU(3) mean field model are modified through the exchange of scalar fields $σ$ , $ζ$ and $δ$ and the vector fields $ω$ , $ρ$ and $ϕ$ . The scalar-isovector field $δ$ and the vector-isovector field $ρ$ signifies the finite isospin asymmetry of the medium. We calculate the in-medium constituent quark masses and masses of decuplet baryons in asymmetric strange matter within the chiral SU(3) quark mean field model and use these as input in the constituent chiral quark model to calculate the in-medium magnetic moments of decuplet baryons for different values of isospin asymmetry and strangeness fraction of hot and dense medium. For calculating the magnetic moments of baryons, contributions of valence quarks, quark sea and orbital angular momentum of quark sea are considered in the calculations.
Comments:
33 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2311.02936 [pdf]
EPJA(2024)·18 citations
06
[Submitted on 6 Nov 2023]
Nucleonic models at finite temperature with in-medium effective fields
Odilon Lourenço🇫🇷 · Mariana Dutra🇫🇷 · Jérôme Margueron🇫🇷
We perform a calculation of dense and hot nuclear matter where the mean interaction between nucleons is described by in-medium effective fields and where we employ analytical approximations of the Fermi integrals. We generalize a previous work where we have addressed the case of the Fermi gas model with in-medium effective mass. In the present work, we fully treat the in-medium interaction by considering both its contribution to the in-medium effective fields, which can be subsumed by the mass in some cases, and to the potential term. Our formalism is general and could be applied to relativistic and nonrelativistic approaches. It is illustrated for different popular models -- Skyrme, nonlinear, and density-dependent relativistic mean-field models --, but also for the metamodel, and it provides a clear understanding of the in-medium correction to the pressure, which is present in the case of the Skyrme and metamodel but is not for the relativistic ones. For the Fermi integrals, we compare the analytical approximation to the, so-called, ``exact'' numerical calculations in order to quantitatively estimate the accuracy of the approximation.
Comments:
11 pages, 4 figures. Version accepted for publication in PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2311.03025 [pdf]
PRC(2024)·3 citations
07
[Submitted on 6 Nov 2023]
Triaxial nuclei and analytical solutions of the conformable fractional Bohr Hamiltonian with some exponential-type potentials
M. M. Hammad · M. M. Yahia · Dennis Bonatsos
New approximate analytical solutions have been obtained for the conformable fractional collective Bohr Hamiltonian suitable for triaxial nuclei, with the harmonic oscillator in {\gamma}-part of the collective potential and different exponential-type potentials (namely Morse, Tietz-Hua, and multi-parameter exponential-type potential) in \b{eta}-part. The conformable fractional Nikiforov-Uvarov approach is used to derive closed analytical formulas for energy spectra and wave functions. The relation between the conformable fractional spectra of the three potentials and the Z(5) spectrum has been studied. The evolution of the energy spectra as a function of the potential parameters has been investigated for the three potentials. The normalized B(E2) transition rates and spectra have been calculated and compared with the experimental data and theoretical predictions of Kratzer potential. The predictions can describe well the experimental results for 114,116Pd, 126,128Xe, and 192,194Pt isotopes.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2311.03066 [pdf]
NPA(2023)·5 citations
08
[Submitted on 6 Nov 2023]
Measurement of the energy of the 8.3-eV isomer of 229mTh with photoelectric effect
F. F. Karpeshin
It is proposed to use the photoelectric effect in the inner shells of the 229Th atoms to refine the energy of the 8.3-eV isomer. The calculation was performed using the Feinberg-Migdal shaking theory, which leads to the probability of isomer formation up to several units of 10^-4 in the case of the K shell. As a result, two lines are predicted in the photoelectron spectrum, their separation energy providing the energy of the isomer. Other ways of using the method to study the properties of the isomer are also discussed: through shaking during the formation of radioactive beams in storage rings, etc. Moreover, recording the effect in an experiment will provide the isomer's partial lifetime.
Comments:
11 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2311.03180 [pdf]
JETP Letters, vol. 118, issue 8 (2023)·1 citation
09
[Submitted on 6 Nov 2023]
Bayesian calibration of viscous anisotropic hydrodynamic (VAH) simulations of heavy-ion collisions
Ulrich Heinz (Ohio State Univ.)🇺🇸 · Dananjaya Liyanage (Ohio State Univ.)🇺🇸 · Cullen Gantenberg (Ohio State Univ., Univ. of Washington)🇺🇸
A Bayesian calibration, using experimental data from 2.76 $A$ TeV Pb-Pb collisions at the LHC, of a novel hybrid model is presented in which the usual pre-hydrodynamic and viscous relativistic fluid dynamic (vRFD) stages are replaced by a viscous anisotropic hydrodynamic (VAH) core that smoothly interpolates between the initial expansion-dominated, approximately boost-invariant longitudinally free-streaming and the subsequent collision-dominated (3+1)-dimensional standard vRFD stages. This model yields meaningful constraints for the temperature-dependent specific shear and bulk viscosities, $(η / s) (T)$ and $(ζ / s) (T)$ , for temperatures up to about $700$ MeV (i.e. over twice the range that could be explored with earlier models). With its best-fit model parameters the calibrated VAH model makes highly successful predictions for additional $p_{T}$ -dependent observables for which high-quality experimental data are available that were not used for the model calibration.
Comments:
4 pages, 3 figures, to appear in the proceedings of Quark Matter 2023 (Houston, TX, 3-9 Sep. 2023) published by EPJC. Reference added in this version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2311.03306 [pdf]
EPJ Web Conf.(2024)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE