Nuclear Theory·nucl-th

Tuesday·August 11, 2020

22 papers—9 primary·13 cross-listed

01
[Submitted on 8 Aug 2020]
Unveiling the correlations of tidal deformability with the nuclear symmetry energy parameters
Tuhin Malik · B. K. Agrawal · Constança Providência · J. N. De
The chi-squared based covariance approach allows one to estimate the correlations among desired observables related to nuclear matter directly from a set of fit data without taking recourse to the distributions of the nuclear matter parameters (NMPs). Such an approach is applied to study the correlations of tidal deformability of neutron star with the slope and the curvature parameters of nuclear symmetry energy governed by an extensive set of fit data on the finite nuclei together with the maximum mass of the neutron star. The knowledge of the distributions of NMPs consistent with the fit data is implicitly inbuilt in the Hessian matrix which is central to this covariance approach. Comparing our results with those obtained with the explicit use of the distributions of NMPs, we show that the appropriate correlations among NMPs as induced by the fit data are instrumental in strengthening the correlations of the tidal deformability with the symmetry energy parameters, without it, the said correlations tend to disappear. The interplay between isoscalar and isovector NMPs is also emphasized.
Comments:
7 pages, 3 figure
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
arXiv:
2008.03469 [pdf]
PRC(2020)·28 citations
02
[Submitted on 8 Aug 2020]
Direct photon emission and influence of dynamical wave packets in an extended quantum molecular dynamics model
C.Z. Shi · Y. G. Ma · X. G. Cao · D. Q. Fang · W. B. He · C. Zhong
Direct photon produced from first proton-neutron ( $p$ - $n$ ) collision during the early stage of heavy ion reaction is a sensitive probe to reflect energy and momentum distribution of nucleons. In this work, we embedded the hard photon production channel in an extended quantum molecular dynamics (EQMD) model, and took the direct photon as a possible probe to improve namely the Fermi motion in the EQMD model. A possible scheme is offered to handle the dynamical wave packet width within incoherent bremsstrahlung process. Direct photons calculated by our modified EQMD were compared with data of $^{14}$ N + $^{12}$ C at beam energies $E / A$ = 20, 30 and 40 MeV, and it is found that the yield, inverse slope and angular distribution of direct photons could be reasonably reproduced. In addition, asymmetric reaction systems of $^{4}$ He + C and $^{4}$ He + Zn at $E / A$ = 53 MeV are also simulated in this work. It is found that the symmetric angular distribution in the nucleon-nucleon ( $N$ - $N$ ) center-of-mass (c.m.) frame and the velocity of $t h e γ$ -emission source can be reasonably obtained from our method although there is some quantitative differences.
Comments:
9 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2008.03514 [pdf]
PRC(2020)·11 citations
03
[Submitted on 9 Aug 2020]
Screening of nucleon electric dipole moments in atomic systems
Kota Yanase🇯🇵
The electric dipole moments (EDMs) of diamagnetic atoms are expected to be sensitive to charge-parity violation particularly in nuclei through the nuclear Schiff moment. I explicitly demonstrate that the well-known form of the Schiff moment operator originating from the nucleon EDM is obtained by considering the screening of the nucleon EDMs in a neutral atom. Consequently, an additional contribution to the Schiff moment arises from the screening of the nuclear EDM induced by the interaction of the nucleon EDMs with the protons. This correction to the Schiff moment of $^{199}$ Hg is evaluated in the independent particle model.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2008.03678 [pdf]
PRC(2021)·13 citations
04
[Submitted on 9 Aug 2020]
The comparative role of 7Li(n,{\gamma}) reaction in primordial nucleosynthesis
N.A. Burkova🇰🇿 · S.B. Dubovichenko🇰🇿 · A.V. Dzhazairov-Kakhramanov🇰🇿 · S.Zh. Nurakhmetova🇰🇿
Within the framework of the modified potential cluster model with forbidden states and their classification according to Young diagrams, the possibility of describing experimental data on the total cross sections of the neutron radiative capture on 7Li is considered. It is shown that the model used and the methods for constructing potentials make it possible to correctly describe the behavior of experimental cross sections at energies of 5 meV (5 10-3 eV) to 1 MeV(1 10+6 eV), where experimental data are available. Based on the obtained total cross sections up to 5 MeV, the reaction rate was calculated and its analytical approximation was carried out. It was shown that the 7Li(n,g)8Li reaction dominates at T9 < 0.1-0.2 as against with the burning of 7Li in reactions 7Li(3H,n)9Be and 7Li(4He,g)11B.
Comments:
17p., 6 fig., 2 tab., 60 ref
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2008.03695 [pdf]
J.Phys.G(2021)·2 citations
05
[Submitted on 9 Aug 2020]
Hadronic effects on charmonium elliptic flows in heavy-ion collisions
Baoyi Chen · Liu Jiang · Yunpeng Liu
Transport and Langevin equations are employed to study hadronic medium effects on charmonium elliptic flows in heavy-ion collisions. In Pb-Pb collisions, the anisotropic energy density of the quark-gluon plasma (QGP) in the transverse plane is transformed into hadron momentum anisotropy after the phase transition. Charmonia with high transverse momentum $p_{T}$ are produced via the primordial hard process and undergo different degrees of dissociation along different paths in the QGP. They then scatter with light hadrons in the hadron phase. Both contributions to the charmonium elliptic flows are studied at moderate and high transverse momenta. The elliptic flows of the prompt $J / ψ$ are found to be considerably enhanced at high transverse momentum when the charmonium diffusion coefficients in the hadronic medium are parametrized through the geometry scale approximation. This hadronic medium effect is negligible for quarkonia with larger mass such as bottomonia.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2008.03705 [pdf]
PRC(2021)·1 citation
06
[Submitted on 10 Aug 2020]
The non-resonance shake mechanism of the neutrinoless double electronic capture
F.F. Karpeshin🇷🇺 · M.B. Trzhaskovskaya🇷🇺 · L.F. Vitushkin🇷🇺
It is generally accepted that double neutrinoless electron capture is a resonance process. The calculations of the probability of shaking with the ionization of the electron shell occurring during the transformation of 152Gd and 164Er nuclei are performed below. These nuclides have the lowest resonance defect among all known nuclei, being considered as main candidates for discovering the neutrinoless mode of the transformation. The results show predominant contribution of the new mechanism for most of the candidate nuclei. The value of this amendment rapidly increases with an increasing resonance defect. Thus, in principle, double neutrinoless electron capture appears not to be a resonance process at all.
Comments:
12 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2008.03906 [pdf]
Phys.Atom.Nucl.(2020)·9 citations
07
[Submitted on 10 Aug 2020]
Dynamical spectral structure of density fluctuation near QCD critical point
Md Hasanujjaman🇮🇳 · Golam Sarwar🇮🇳 · Mahfuzur Rahaman🇮🇳 · Abhijit Bhattacharyya🇮🇳 · Jan-e Alam🇮🇳
The expression for the dynamical spectral structure of the density fluctuation near the QCD critical point has been derived using linear response theory within the purview of Israel-Stewart relativistic viscous hydrodynamics. The change in spectral structure of the system as it moves toward critical end point has been studied. The effects of the critical point have been introduced in the system through a realistic equation of state and the scaling behaviour of various transport coefficients and thermodynamic response functions. We have found that the Brillouin and the Rayleigh peaks are distinctly visible when the system is away from critical point but the peaks tend to merge near the critical point. The sensitivity of structure of the spectral function on wave vector ( $k$ ) of the sound wave has been demonstrated. It has been shown that the Brillouin peaks get merged with the Rayleigh peak because of the absorption of sound waves in the vicinity of the critical point.
Comments:
One LaTeX file with 6 eps files for figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2008.03931 [pdf]
EPJA(2021)·8 citations
08
[Submitted on 10 Aug 2020]
Charge-exchange dipole excitations in deformed nuclei
Kenichi Yoshida
Background: The electric giant-dipole resonance (GDR) is the most established collective vibrational mode of excitation. A charge-exchange analog, however, has been poorly studied in comparison with the spin (magnetic) dipole resonance (SDR). Purpose: I investigate the role of deformation on the charge-exchange dipole excitations and explore the generic features as an isovector mode of excitation. Methods: The nuclear energy-density functional method is employed for calculating the response functions based on the Skyrme--Kohn--Sham--Bogoliubov method and the proton-neuton quasiparticle-random-phase approximation. Results: The deformation splitting into $K = 0$ and $K = \pm 1$ components occurs in the charge-changing channels and is proportional to the magnitude of deformation as is well known for the GDR. For the SDR, however, a simple assertion based on geometry of a nucleus cannot be applied for explaining the vibrational frequencies of each $K$ -component. A qualitative argument on the strength distributions for each component is given based on the non-energy-weighted sum rules taking nuclear deformation into account. The concentration of the electric dipole strengths in low energy and below the giant resonance is found in neutron-rich unstable nuclei. Conclusions: The deformation splitting occurs generically for the charge-exchange dipole excitions as in the neutral channel. The analog pygmy dipole resonance can emerge in deformed neutron-rich nuclei as well as in spherical systems.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2008.03947 [pdf]
PRC(2020)·4 citations
09
[Submitted on 10 Aug 2020]
Quartic cumulant of baryon number in the presence of QCD critical point
D. Mroczek🇺🇸 · J. Noronha-Hostler🇺🇸 · A. R. Nava Acuna🇺🇸 · C. Ratti🇩🇪 · P. Parotto🇺🇸 · M.A. Stephanov🇺🇸
In the context of the ongoing search for the QCD critical point at the Relativistic Heavy-Ion Collider, we study the equation of state near the critical point in the temperature and baryon chemical potential plane. We use the parametric representation introduced in earlier literature, which maps the universal 3D Ising equation of state onto the QCD phase diagram using several non-universal parameters. We focus on the quartic cumulant of the baryon number, or baryon number susceptibility~ $χ_{4}^{B}$ , which can be accessed experimentally via net-proton fluctuation kurtosis measurements. It was originally predicted, through universality arguments based on the {\em leading} singular contribution, that $χ_{4}^{B}$ and net-proton kurtosis should show a specific non-monotonic behavior due to the critical point. In particular, when following the freeze-out curve on the phase diagram by decreasing beam energy, the kurtosis is expected to dip, and then peak, when the beam energy scan passes close to the critical point. We study the effects of the non-universal and thus far unknown parameters of the Ising-to-QCD mapping on the behavior of~ $χ_{4}^{B}$ . We find that, while the peak remains a solid feature, the presence of the critical point does not necessarily cause a dip in $χ_{4}^{B}$ on the freezeout line {\em below} the transition temperature. The critical point contribution to the dip appears only for a narrow set of mapping parameters, when subleading singular terms are sufficiently suppressed.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2008.04022 [pdf]
PRC(2021)·53 citations

Affiliations

first authorsco-authorsvia INSPIRE