Nuclear Theory·nucl-th

Tuesday·November 3, 2020

16 papers—8 primary·8 cross-listed

01
[Submitted on 31 Oct 2020]
A study of nuclear radii and neutron skin thickness of neutron-rich nuclei near the neutron drip line
Usuf Rahaman · M.Ikram · M. Imran · Anisul Ain Usmani
We studied the charge radius ( $r_{c}$ ), neutron radius ( $r_{n}$ ), and neutron skin-thickness ( $Δ r = r_{n} - r_{p}$ ) over a chain of isotopes from C to Zr with the stable region to the neutron drip line. Theoretical calculations are done with axially deformed self-consistent relativistic mean-field theory (RMF) with effective nonlinear NL3 and NL3* interactions. The theoretically estimated values are compared with available experimental data and a reasonable agreement are noted. We additionally assessed the two-neutron separation energy ( $S_{2 n}$ ) to mark the drip line nuclei of the considered isotopic series. In the reference of $S_{2 n}$ , neutron magicity is also discussed. The calculated neutron radii are compared with empirical estimation made by $r = r_{0} N^{1/3}$ to examine the abnormal trend of the radius for neutron drip line nuclei. In view to guide the long tails, the density distribution for some skin candidates is analyzed. Finally, neutron skin thickness is observed for the whole considered isotopic series.
Comments:
36 pages, 18 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2011.00271 [pdf]
IJMPE(2020)·4 citations
02
[Submitted on 31 Oct 2020]
Effect of quantizing magnetic field on the inner crusts of hot Neutron Stars
Rana Nandi · Somnath Mukhopadhyay · Sarmistha Banik
In the present work we study the effects of strongly quantizing magnetic fields and finite temperature on the properties of inner crusts of hot neutron stars. The inner crust of a neutron star contains neutron-rich nuclei arranged in a lattice and embedded in gases of free neutrons and electrons. We describe the system within the Wigner-Seitz (WS) cell approximation. The nuclear energy is calculated using Skyrme model with SkM* interaction. To isolate the properties of nuclei we follow the subtraction procedure presented by Bonche, Levit and Vautherin, within the Thomas-Fermi approximation. We obtain the equilibrium properties of inner crust for various density, temperatures and magnetic fields by minimizing the free energy of the WS cell satisfying the charge neutrality and $β -$ equilibrium conditions. We infer that at a fixed baryon density and temperature, strong quantizing magnetic field reduces the cell radii, neutron and proton numbers in the cell compared with the field free case. However, the nucleon number in the nucleus increases in presence of magnetic field. The free energy per nucleon also decreases in magnetized inner crust. On the other hand, we find that finite temperature tends to smear out the effects of magnetic field. Our results can be important in the context of $r -$ process nucleosynthesis in the binary neutron star mergers.
Comments:
6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2011.00296 [pdf]
PRC(2021)·2 citations
03
[Submitted on 1 Nov 2020]
Multiplicity-dependent saturation momentum in $p$ -Pb collisions at 5.02 TeV
Takeshi Osada🇯🇵
Semi-inclusive transverse momentum spectra observed in proton-proton and proton-lead nuclear collisions at LHC energies obey a geometric scaling with a scaling variable using multiplicity-dependent saturation momentum. The saturation momentum extracted from the experimental data is proportional to the 1/6 power of the hadron multiplicity in the final state. On the other hand, the system's transverse size is proportional to the 1/3 power of the multiplicity, and the saturation momentum and the transverse size of the system are strongly correlated with the hadron multiplicity in the final state. Since the saturation momentum is proportional to the average transverse momentum of hadrons, one predicts average transverse momentum is also proportional to the 1/6 power of the multiplicity, which is consistent with experimental results at the LHC energy. We found that a nuclear modification factor $R_{pPb}$ calculated by the multiplicity-dependent saturation momentum decreases at $p_{T} ≲$ 1GeV/ $c$ and that our model can partially explain the $R_{pPb}$ 's behavior thought to be caused by nuclear shadowing. On the other hand, Cronin enhancement experimentally observed at $2 ≲ p_{T} ≲$ 6 GeV/ $c$ is not reproduced. However, the experimental result, including the Cronin effect, can be reproduced well by introducing $p_{T}$ dependence as a 4 $\sim$ 5\% correction to the multiplicity-dependent saturation momentum.We also discuss a relation between the geometric scaling in the semi-inclusive distributions and the string percolation model.
Comments:
Second edition. 11 pages, 8 figures. Added discussion of percolation-string model. Figure 6 and references added
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2011.00456 [pdf]
PRC(2021)·5 citations
04
[Submitted on 2 Nov 2020]
Low-energy dipole excitation mode in $^{18}$ O with antisymmetrized molecular dynamics
Yuki Shikata · Yoshiko Kanada-En'yo
Low-energy dipole (LED) excitations in $^{18}$ O were investigated using a combination of the variation after $K$ -projection in the framework of antisymmetrized molecular dynamics with $β$ -constraint with the generator coordinate method. We obtained two LED states, namely, the $1_{1}^{-}$ state with a dominant shell-model structure and the $1_{2}^{-}$ state with a large $^{14} C + α$ cluster component. Both these states had significant toroidal dipole (TD) and compressive dipole (CD) strengths, indicating that the TD and CD modes are not separated but mixed in the LED excitations of $^{18}$ O. This is unlike the CD and TD modes for well-deformed nuclei such as $^{10}$ Be, where the CD and TD modes are generated as $K^{π} = 0^{-}$ and $K^{π} = 1^{-}$ excitations, respectively, in a largely deformed state.
Comments:
19 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2011.00821 [pdf]
PRC(2021)·3 citations
05
[Submitted on 2 Nov 2020]
Light quark energy loss in a soft-wall AdS/QCD model
Xiangrong Zhu🇨🇳 · Zi-qiang Zhang🇨🇳
We investigate the energy loss of light quarks in a holographic QCD model with conformal invariance broken by a background dilaton. We perform the analysis within falling string and shooting string, respectively. It turns out that the two methods give the same result: the presence of chemical potential and confining scale tends to enhance the energy loss, in accord with previous findings of drag force and jet quenching parameter.
Comments:
6 pages, 4figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2011.00920 [pdf]
EPJA(2021)·8 citations
06
[Submitted on 2 Nov 2020]
An effective field theory approach to fermionic rotational bands in nuclei
I. K. Alnamlah · E. A. Coello Pérez · D. R. Phillips
We extend an effective field theory developed to describe rotational bands in even-even nuclei to the odd-mass case. This organizes Bohr and Mottelson's treatment of a particle coupled to a rotor as a model-independent expansion in powers of the angular velocity of the overall system. We carry out this expansion up to fourth order in the angular velocity and present results for $^{99}$ Tc, $^{159}$ Dy, $^{167, 169}$ Er, $^{167, 169}$ Tm, $^{183}$ W, $^{235}$ U and $^{239}$ Pu. In each case, the accuracy and breakdown scale of the effective field theory can be understood based on the single-particle and vibrational energy scales in that nucleus.
Comments:
20 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2011.01083 [pdf]
PRC(2021)·11 citations
07
[Submitted on 2 Nov 2020]
$α$ -nucleus optical potentials from chiral effective field theory $N N$ interactions
V. Durant · P. Capel
We present a determination of optical potentials for $^{4}$ He-target collisions using the double-folding method. We use chiral effective field theory nucleon-nucleon interactions at next-to-next-to-leading order combined with state-of-the-art nucleonic densities. The imaginary part of the optical potential is obtained from the real double-folding interaction either through a proportionality constant or applying Kramers-Kronig dispersion relations. With these potentials, we compute the elastic scattering of $^{4}$ He off various targets, from $^{4}$ He to $^{120}$ Sn. We study the sensitivity of our predicted cross sections to the choice of nucleon-nucleon interactions and nuclear densities. Very good agreement is obtained with existing elastic-scattering data for $^{4}$ He energies between 100 and 400 MeV.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2011.01101 [pdf]
PRC(2022)·6 citations
08
[Submitted on 2 Nov 2020]
Decipher the $R_{Ψ_{m}}$ correlator in search for the chiral magnetic effect in relativistic heavy ion collisions
Yicheng Feng · Jie Zhao · Hao-jie Xu · Fuqiang Wang
Background: The chiral magnetic effect (CME) is extensively studied in heavy-ion collisions at RHIC and the LHC. An azimuthal correlator called $R_{Ψ_{m}}$ was proposed to measure the CME. By observing the same $R_{Ψ_{2}}$ and $R_{Ψ_{3}}$ (convex) distributions from A Multi-Phase Transport (AMPT) model, by contrasting data and model as well as large and small systems and by event shape engineering (ESE), a recent preprint (arXiv:2006.04251v1) from STAR suggests that the $R_{Ψ_{m}}$ observable is sensitive to the CME signal and relatively insensitive to backgrounds, and their Au+Au data are inconsistent with known background contributions. Purpose: We examine those claims by studying the robustness of the $R_{Ψ_{m}}$ observable using AMPT as well as toy model simulations. We compare $R_{Ψ_{m}}$ to the more widely used $Δ γ$ azimuthal correlator to identify their commonalities and differences. Methods: We use AMPT to simulate Au+Au, p+Au, and d+Au collisions at $s_{N N} = 200 GeV$ , and study the responses of $R_{Ψ_{m}}$ to anisotropic flow backgrounds in the model. We also use a toy model to simulate resonance flow background and input CME signal to investigate their effects in $R_{Ψ_{2}}$ . Additionally we use the toy model to perform an ESE analysis to compare to STAR data as well as predict the degree of sensitivity of $R_{Ψ_{2}}$ to isobar collisions with the event statistics taken at RHIC. ...
Comments:
18 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2011.01123 [pdf]
PRC(2021)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE