Nuclear Theory·nucl-th

Tuesday·August 13, 2019

12 papers—5 primary·7 cross-listed

01
[Submitted on 10 Aug 2019]
Radiative parton energy loss and baryon stopping in $AA$ collisions
B.G. Zakharov🇷🇺
We study the radiative energy loss contribution to proton stopping in $AA$ collisions. The analyses is performed within the light-cone path integral approach to induced gluon emission. We have found that the radiative correction can fill in partly the midrapidity dip in the net proton rapidity distribution in $AA$ collisions at $s \sim 10$ GeV. We argue that at $s \sim 10$ GeV the net proton fluctuations at midrapidity may be dominated by the initial fluctuations of the proton flow, which, to a good accuracy, should be binomial.
Comments:
7 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1908.03723 [pdf]
JETP Lett.(2019)·3 citations
02
[Submitted on 10 Aug 2019]
Above-barrier heavy-ion fusion cross-sections using the relativistic mean-field approach: case of spherical colliding nuclei
Maria V. Chushnyakova · Mrutunjaya Bhuyan · Igor I. Gontchar · Natalya A. Khmyrova
The double folding (DF) approach is one of the widely used methods for finding nucleus-nucleus interaction potential. In the present work, the influence of the nuclear matter density on the DF potential and on the Coulomb barrier parameters is studied systematically for collisions of spherical nuclei. The value of the parameter $B_{Z} = Z_{P} Z_{T} / (A_{P}^{1/3} + A_{T}^{1/3})$ (estimating the Coulomb barrier height) varies in these calculations from 10 MeV up to 150 MeV. The novel feature of this study is that the nuclear densities came from the Relativistic Mean Field approach (RMF). For the nucleon-nucleon effective interaction, the M3Y forces with the finite range exchange term and density dependence are employed. The above barrier fusion cross sections are calculated within the framework of the trajectory model with surface friction. Results are compared with the previous study in which the nuclear density came from the Hartree-Fock (HF) calculations and with the high precision experimental data. This comparison demonstrates that i) agreement between the theoretical and experimental cross sections obtained with RMF and HF densities is of the same quality and ii) the values of the only adjustable parameter (friction strength) obtained with RMF and HF densities strongly correlate.
Comments:
10 figures, 5 tables; SKX vs NL3 densities in TMSF CS
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1908.03807 [pdf]
NPA(2020)·6 citations
03
[Submitted on 11 Aug 2019]
Testing the energy diffusion approximation for the escape of a Brownian particle from a potential pocket
Igor I. Gontchar · Maria V. Chushnyakova
For the first time, the energy diffusion approximation is confronted at the percent level with the exact numerical modeling of thermal decay of a metastable state. The latter is performed using the quasistationary decay rates resulting from the Langevin equations for the coordinate and conjugated momentum. For the energy (or action) diffusion approach, a Langevin-type equation for the action is constructed, validated, and solved numerically. The comparison of two approaches is performed for four potentials (two of which are anharmonic) in a wide range of two dimensionless scaling parameters: the governing parameter $G$ reflecting how high is the barrier with respect to the temperature and the damping parameter $φ$ expressing the friction strength. It turns out that the action diffusion approach produces the rate which is in 50% agreement with the exact one only at $φ < 0.02$ contrary to $φ < 1$ as claimed in the literature.
Comments:
10 pages, 6 figures; LEI vs LEqp for 4 pots
Subjects:
Nuclear Theory (nucl-th); Statistical Mechanics (cond-mat.stat-mech)
arXiv:
1908.03940 [pdf]
Chin.J.Phys.(2020)·0 citations
04
[Submitted on 12 Aug 2019]
Puzzling Radii of Calcium Isotopes: $^{40} Ca \to^{44} Ca \to^{48} Ca \to^{52} Ca$ , and Duality in the Structure of $_{14}^{42} Si_{28}$ and $_{20}^{48} Ca_{28}$
Syed Afsar Abbas · Anisul Ain Usmani · Usuf Rahaman · Mohammad Ikram
In this paper we study the issue of the puzzle of the radii of calcium isotopes. Despite an excess of eight neutrons, strangely $^{48} Ca$ exhibits essentially the same charge radius as $^{40} Ca$ does. A fundamental microscopic description of this is still lacking. Also strange is a peak in charge radius of calcium at N = 24. The $^{52} Ca$ (N = 32) nucleus, well known to be doubly magical, amazingly has recently been found to have a very large charge radius. Also amazing is the property of $_{14}^{42} Si_{28}$ which simultaneously appears to be both magical/spherical and strongly deformed as well. We use a Quantum Chromodynamics based model, which treats triton as elementary entity to make up $_{14}^{42} Si_{28}$ . We show here how this QCD based model is able to provide a consistent physical understanding of simultaneity of magicity/sphericity and strong deformation of a single nucleus. This brings in an essential duality in the structure of $_{14}^{42} Si_{28}$ and subsequently also that of $_{20}^{48} Ca_{28}$ We also provide consistent understanding of the puzzling radii of calcium isotopes. We predict that the radius of $^{54} Ca$ should be even bigger than that of $^{52} Ca$ ; and also that the radius of $^{60} Ca$ should be the same as that of $^{40} Ca$ . In addition we also show wherefrom arises the neutron E2 effective charge of $\frac{1}{2}$ .
Comments:
16 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1908.04026 [pdf]
0 citations
05
[Submitted on 9 Aug 2019]
Influence of correlations between yields on the chemical freeze-out temperature
Dariusz Prorok🇵🇱
A statistical (thermal) model is applied to the description of hadron yields measured at central nucleus-nucleus collisions at the top RHIC energy $s_{N N} = 200$ GeV and the LHC energy $s_{N N} = 2.76$ TeV. In contrast to the previous analyzes a more general form of the least squares test statistic is used, which takes into account also possible correlations between different species of yields. In addition to hadrons also light nuclei are included in the fits. Because of the lack of data, a toy model is constructed where the correlation coefficients are just free parameters. Because of this the presented considerations are speculative and should be treated as an imperfect illustration of the problem. Within these limitations it is impossible to formulate any definite conclusion, it might be only mentioned that for the considered examples the dependence of the freeze-out temperature and baryon chemical potential on correlations turned out to be weak.
Comments:
11 pages, 4 figures, matches published version. arXiv admin note: text overlap with arXiv:1804.05691
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1908.04201 [pdf]
Chin.J.Phys.(2021)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Radiative parton energy loss and baryon stopping in AA collisions

Above-barrier heavy-ion fusion cross-sections using the relativistic mean-field approach: case of spherical colliding nuclei

Testing the energy diffusion approximation for the escape of a Brownian particle from a potential pocket

Puzzling Radii of Calcium Isotopes: 40Ca→44Ca→48Ca→52Ca, and Duality in the Structure of 1442​Si28​ and 2048​Ca28​

Influence of correlations between yields on the chemical freeze-out temperature

Affiliations

Radiative parton energy loss and baryon stopping in $AA$ collisions

Puzzling Radii of Calcium Isotopes: $^{40} Ca \to^{44} Ca \to^{48} Ca \to^{52} Ca$ , and Duality in the Structure of $_{14}^{42} Si_{28}$ and $_{20}^{48} Ca_{28}$