Insights into the pion production mechanism and the symmetry energy at high density

Liu, Yangyang; Wang, Yongjia; Cui, Ying; Xia, Caichu; Li, Zhuxia; Chen, Yongjing; Li, Qingfeng; Zhang, Yingxun

doi:10.1103/physrevc.103.014616

Cited by 29 publications

(16 citation statements)

References 75 publications

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“…We now include recent SE constraints at higher densities. Pion emission in heavy ion reactions has recently yielded a SE value listed in Table I [37] at ρ ≈ 1.5 ρ 0 [41]. The open inverted triangle in Fig.…”

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confidence: 99%

Decoding the Density Dependence of the Nuclear Symmetry Energy

Lynch,

Tsang

2021

Preprint

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The large imbalance in the neutron and proton densities in very neutron rich systems increases the nuclear symmetry energy so that it governs many aspects of neutron stars and their mergers. Extracting the density dependence of the symmetry energy therefore constitutes an important scientific objective. Many analyses have been limited to extracting values for the symmetry energy, S0, and its "derivative", L, at saturation density ρ0 ≈ 2.6 × 10 14 g/cm 3 ≈ 0.16 nucleons/fm 3 , resulting in constraints that appear contradictory. We show that most experimental observables actually probe the symmetry energy at densities far from ρ0, making the extracted values of S0 or L imprecise. By focusing on the densities these observables actually probe, we obtain a detailed picture of the density dependence of the symmetry energy from 0.25ρ0 to 1.5ρ0. From this experimentally derived density functional, we extract L01 = 53.1 ± 6.1M eV at ρ ≈ 0.10 fm −3 , a neutron skin thickness for 208 P b of Rnp = 0.23 ± 0.04 fm, a symmetry pressure at saturation density of P0 = 3.2 ± 1.2M eV /f m 3 and suggests a radius for a 1.4 solar mass neutron star of 13.1 ± 0.6 km.

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confidence: 99%

Decoding the Density Dependence of the Nuclear Symmetry Energy

Lynch,

Tsang

2021

Preprint

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“…In Ref. [467], mean-field potentials with different parameter sets (e.g., different stiffness of the nuclear equation of state and different nucleon effective mass) were introduced, and potentials for Delta resonances were described in detail. More details about mean-field potentials for nucleons can be found in review papers [471,472].…”

Section: Mean-field Potentialmentioning

confidence: 99%

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Wolter,

Colonna,

Cozma

et al. 2022

Preprint

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Transport models are the main method to obtain physics information on the nuclear equation of state and in-medium properties of particles from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. To this end, calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, which test separately selected ingredients of a transport code, and more realistic calculations of heavy-ion collisions. Over the years, five studies have been performed within this project. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. After a compact description of the underlying transport approaches, we review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known under the names of Boltzmann-Uehling-Uhlenbeck (BUU) and Quantum Molecular Dynamics (QMD) type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. Our evaluation studies often indicate improved strategies in performing transport simulations and thus can provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review.

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“…Since the high-density behavior of E sym (ρ) has long been debated in nuclear physics, see, e.g., Refs. [42][43][44][45][46] and it has significant implications for neutron stars [47][48][49][50][51][52], a few more comments are necessary here. As noticed earlier, the curvature K sym ≈ −118 MeV is found from the relation (19) by adopting the empirical values of K 0 ≈ 240 MeV, J 0 ≈ −300 MeV and L ≈ 60 MeV.…”

Section: High-density Trend and Limit Of Nuclear Symmetry Energymentioning

confidence: 99%

Auxiliary Function Approach for Determining Symmetry Energy at Supra-saturation Densities

Cai,

2021

Preprint

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Nuclear symmetry energy E sym (ρ) at density ρ is normally expanded or simply parameterized as a function of χ = (ρ − ρ 0 )/3ρ 0 in the form of E sym (ρ) ≈ S + Lχ + 2 −1 K sym χ 2 + 6 −1 J sym χ 3 + • • • using its magnitude S , slope L, curvature K sym and skewness J sym at the saturation density ρ 0 of nuclear matter. Much progress has been made in recent years in constraining especially the S and L parameters using various terrestrial experiments and astrophysical observations. However, such kind of expansions/parameterizations do not converge at suprasaturation densities where χ is not small enough, hindering an accurate determination of high-density E sym (ρ) even if its characteristic parameters at ρ 0 are all well determined by experiments/observations. By expanding the E sym (ρ) in terms of a properly chosen auxiliary function Π sym (χ, Θ sym ) with a parameter Θ sym fixed accurately by an experimental E sym (ρ r ) value at a reference density ρ r , we show that the shortcomings of the χ-expansion can be completely removed or significantly reduced in determining the high-density behavior of E sym (ρ). In particular, using two significantly different auxiliary functions, we show that the new approach effectively incorporates higher χ-order contributions and converges to the same E sym (ρ) much faster than the conventional χ-expansion at densities 3ρ 0 . Moreover, the still poorly constrained skewness J sym plays a small role in determining the E sym (ρ) at these densities in the auxiliary function approach. The new approach thus provides a nearly modelindependent constraint on the E sym (ρ) at densities 3ρ 0 . Several quantitative demonstrations using Monte Carlo simulations are given.

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Insights into the pion production mechanism and the symmetry energy at high density

Cited by 29 publications

References 75 publications

Decoding the Density Dependence of the Nuclear Symmetry Energy

Decoding the Density Dependence of the Nuclear Symmetry Energy

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Auxiliary Function Approach for Determining Symmetry Energy at Supra-saturation Densities

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