Nuclear Theory·nucl-th

Tuesday·November 22, 2022

21 papers—8 primary·13 cross-listed

01
[Submitted on 19 Nov 2022]
Pre-hydrodynamic evolution in large and small systems
Tiago Nunes da Silva🇧🇷 · David D. Chinellato🇧🇷 · André V. Giannini🇧🇷 · Maurício N. Ferreira🇪🇸 · Gabriel S. Denicol🇧🇷 · Maurício Hippert🇺🇸 · Matthew Luzum🇧🇷 · Jorge Noronha🇺🇸 · Jun Takahashi🇧🇷
We extend our previous investigation of the effects of pre-hydrodynamic evolution on final-state observables in heavy-ion collisions to smaller systems. We use a state-of-the-art hybrid model for the numerical simulations with optimal parameters obtained from a previous Bayesian study. By studying p-Pb collisions, we find that the effects due to the assumption of a conformal evolution in the pre-hydrodynamical stage are even more important in small systems. We also show that this effect depends on the time duration of the pre-equilibrium stage, which is further enhanced in small systems. Finally, we show that the recent proposal of a free-streaming with subluminal velocity for the pre-equilibrium stage, thus effectively breaking conformal invariance, can alleviate the contamination of final state observables. Our study further reinforces the need for moving beyond conformal approaches in pre-equilibrium dynamics modeling, especially when extracting transport coefficients from hybrid models in the high-precision era of heavy-ion collisions.
Comments:
15 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2211.10561 [pdf]
PRC(2023)·21 citations
02
[Submitted on 19 Nov 2022]
Effect of the $σ$ -cut potential on the properties of neutron stars with or without a hyperonic core
N. K. Patra · B. K. Sharma · A. Reghunath · A. K. H. Das · T. K. Jha
Motivated by the recent observation of high-mass pulsars ( $M ≃ 2 M_{⊙}$ ), we employ the $σ$ -cut potential on the equation of state (EOS) of high-density matter and the properties of neutron stars within the relativistic mean-field (RMF) model using TM1 $^{*}$ parameter set. The $σ$ -cut potential is known to reduce the contributions of the $σ$ field, resulting in a stiffer EOS at high densities and hence leading to larger neutron star masses without affecting the properties of nuclear matter at normal saturation density. We also analyzed the effect of the same on pure neutron matter and also on the neutron star matter with and without hyperonic core and compared it with the available theoretical, experimental, and observational data. The corresponding tidal deformability ( $Λ_{1.4}$ ) is also calculated. With the choice of meson-hyperon coupling fixed to hypernuclear potentials, we obtain $\approx 10 %$ increase in mass by employing the $σ$ -cut potential for $f_{s} = 0.6$ . Our results are in good agreement with various experimental constraints and observational data, particularly with the GW170817 data.
Comments:
7 Pages, 6 Figures and 1 Table (Accepted in Phys. Rev. C)
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2211.10616 [pdf]
PRC(2022)·14 citations
03
[Submitted on 20 Nov 2022]
Soft dipole resonance in neutron-rich $^{8}$ He
Takayuki Myo · Myagmarjav Odsuren · Kiyoshi Kato
In neutron-rich $^{8}$ He, we study the soft dipole resonance, which is regarded as a dipole oscillation of four valence neutrons against the $^{4}$ He core, and its effect on the low-energy electric dipole strength with a $^{4}$ He+ $n$ + $n$ + $n$ + $n$ five-body cluster model. This work is an extended study of an earlier letter [T. Myo and K. Katō, Phys. Rev. C106, L021302 (2022)]. The five-body unbound $1^{-}$ states of $^{8}$ He are obtained with the complex energy eigenvalues by using the complex scaling method and the dipole strength is calculated in terms of the complex-scaled Green's function. Two kinds of the dominant excitation modes are confirmed in the dipole strength below 20 MeV of the excitation energy. The strengths below 10 MeV are exhausted by the $^{7}$ He+ $n$ channel, which sequentially decays to $^{6}$ He+ $n$ + $n$ . Above 10 MeV, the strengths arise from the soft dipole mode of four neutrons ( $4 n$ ) oscillating against the $^{4}$ He core. We further explore the possibility of the soft dipole resonance for this state by carefully searching for the resonance pole and finally predict the corresponding resonance with the excitation energy of 14 MeV and the decay width of 21 MeV. The soft dipole resonance exhausts about half of the dipole strength in the relative motion between the $^{4}$ He core and $4 n$ .
Comments:
19 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2211.10930 [pdf]
PTEP(2022)·8 citations
04
[Submitted on 21 Nov 2022]
An expedition to the islands of stability in the first-order causal hydrodynamics
Rajesh Biswas · Sukanya Mitra · Victor Roy
The recently proposed connection between the Lorentz invariance of stability and the speed of signal propagation has been tested for a first-order relativistic dissipative hydrodynamic theory. The fact that the stability situation in different reference frames agrees with each other only as long as the signal propagation respects causality, has been explicitly established for the theory, which is microscopically derived from the covariant kinetic equation in general hydrodynamic frames with arbitrary momentum-dependent interactions.
Comments:
Accepted for the publication in Physics Letters B
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2211.11358 [pdf]
PLB(2023)·14 citations
05
[Submitted on 21 Nov 2022]
Kaon-meson condensation and $Δ$ resonance in hyperonic stellar matter within a relativistic mean-field model
Fu Ma🇨🇳 · Chen Wu🇨🇳 · Wenjun Guo🇨🇳
We study the equation of state of dense baryon matter within the relativistic mean-field model, and we include $Δ$ (1232) isobars into IUFSU model with hyperons and consider the possibility of kaon meson condensation. We find that it is necessary to consider the $Δ$ resonance state inside the massive neutron star. The critical density of Kaon mesons and hyperons is shifted to a higher density region, in this respect an early appearance of $Δ$ resonances is crucial to guarantee the stability of the branch of hyperonized star with the difference of the coupling parameter $x_{σ Δ}$ constrained based on the QCD rules in nuclear matter. The $Δ$ resonance produces a softer equation of state in the low density region, which makes the tidal deformability and radius consistent with the observation of GW170817. As the addition of new degrees of freedom will lead to a softening of the equation of state, the $σ$ -cut scheme, which states the decrease of neutron star mass can be lowered if one assumes a limited decrease of the $σ$ -meson strength at $ρ_{B}$ ( $ρ_{B} > ρ_{0}$ ), finally we get a maximum mass neutron star with $Δ$ resonance heavier than 2 $M_{⊙}$ .
Comments:
10 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2211.11498 [pdf]
PRC(2023)·14 citations
06
[Submitted on 21 Nov 2022]
Toy model to understand oscillatory behavior in timelike nucleon form factors
Ri-Qing Qian🇨🇳 · Zhan-Wei Liu🇨🇳 · Xu Cao🇨🇳 · Xiang Liu🇨🇳
To understand the oscillatory behavior exhibited in the timelike electromagnetic form factors of nucleons, we propose a toy model based on the Jost function of the $N N ˉ$ pair into the timelike form factors with the help of the distorted-wave Born approximation. By constructing a simple square-well potential reflecting the final-state interaction of $N N ˉ$ , we naturally represent the damped oscillatory phenomenon in the timelike electromagnetic form factors of nucleons. Especially, our study reveals that the ``period" of the oscillation is approximately determined by the Yukawa interaction range $1/ m_{π}$ . Other possible potentials are also discussed. The threshold enhancements of the cross sections for $e^{+} e^{-} \to n n ˉ$ , $Λ Λ ˉ$ , and $Λ_{c} Λ ˉ_{c}$ can also be understand within this scenario.
Comments:
7 pages, 3 figures. We provide supplemental materials to show that the new data from the BESIII collaboration (arXiv:2303.07629) are consistent with our earlier description
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2211.11555 [pdf]
PRD(2023)·17 citations
07
[Submitted on 21 Nov 2022]
Probing the Non-exponential Decay Regime in Open Quantum Systems
S. M. Wang · W. Nazarewicz · A. Volya · Y. G. Ma
The most important law of radioactivity is that of the exponential decay. In the realm of quantum mechanics, however, this decay law is neither rigorous nor fundamental. The deviations from the exponential decay have been observed experimentally at the early stage of a decay process, but there is little evidence for non-exponential behavior at long times. Yet such long-term non-exponentiality is expected theoretically to probe the non-resonant background components of the initial wave function which preserve the structural interference and the memory of how the state was created. In this paper, we propose new observables that can be used for experimental investigations of the post-exponential decay regime, including the decay of threshold resonances, particle correlations in three-body decays, and interference between near-lying resonances. While the specific examples presented in this work pertain to atomic nuclei, the properties of non-exponential decay are generic, i.e., they apply to other many-body open quantum systems, such as hadrons, atoms, molecules, and nanostructures.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
arXiv:
2211.11619 [pdf]
PRResearch(2023)·24 citations
08
[Submitted on 21 Nov 2022]
QCD Equation of State of Dense Nuclear Matter from a Bayesian Analysis of Heavy-Ion Collision Data
Manjunath Omana Kuttan🇩🇪 · Jan Steinheimer🇩🇪 · Kai Zhou🇩🇪 · Horst Stoecker🇩🇪
Bayesian methods are used to constrain the density dependence of the QCD Equation of State (EoS) for dense nuclear matter using the data of mean transverse kinetic energy and elliptic flow of protons from heavy ion collisions (HIC), in the beam energy range $s_{NN} = 2 - 10 G e V$ . The analysis yields tight constraints on the density dependent EoS up to 4 times the nuclear saturation density. The extracted EoS yields good agreement with other observables measured in HIC experiments and constraints from astrophysical observations both of which were not used in the inference. The sensitivity of inference to the choice of observables is also discussed.
Comments:
Replaced with the published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2211.11670 [pdf]
PRL(2023)·65 citations

Affiliations

first authorsco-authorsvia INSPIRE