Nuclear Theory·nucl-th

Tuesday·September 29, 2020

18 papers—9 primary·9 cross-listed

01
[Submitted on 25 Sept 2020]
A Novel Regularization Scheme for Nucleon-Nucleon Lattice Simulations with Effective Field Theory
M. Ahmadi🇮🇷 · M. R. Hadizadeh🇺🇸 · M. Radin🇮🇷 · S. Bayegan🇮🇷
We propose a new regularization scheme to study the bound state of two-nucleon systems in Lattice Effective Field Theory. Inspired by continuum EFT calculation, we study an exponential regulator acting on the leading-order (LO) and next-to-leading order (NLO) interactions, consisting of local contact terms. By fitting the low-energy coefficients (LECs) to deuteron binding energy and the asymptotic normalization coefficient (ANC) on a lattice simulation, we extract the effective range expansion (ERE) parameters in the $^{3} S_{1}$ channel to order $p^{2}$ . We explore the impact of different powers of the regulator on the extracted ERE parameters for the lattice spacing $a = 1.97$ fm. Moreover, we investigate how the implementation of the regularization scheme improves the predicted ERE parameters on the lattice spacing in the range of $1.4 \leq a \leq 2.6$ fm. Our numerical analysis indicates that for lattice spacing greater than $2$ fm, the predicted observables are very close to the experimental data.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.12402 [pdf]
PRC(2020)·3 citations
02
[Submitted on 26 Sept 2020]
Impact-Parameter Description of High-Energy Deuteron-Nucleus Collisions
V. Franco · R.J. Glauber
A theoretical analysis using an impact-parameter description of the collisions of deuterons with nuclei is carried out in the high-energy diffraction approximation. It is used to obtain the intensities and integrated cross sections for elastic scattering, for the emergence of the two incident nucleons from the collision whether they appear as an elastically scattered deuteron or as two unbound nucleons, and for the diffraction-induced dissociation of the deuteron into a free neutron and a free proton, as well as the total cross section. The cross section for collisions in which one or both of the nucleons is absorbed is derived in terms of the sum of the neutron-nucleus and proton-nucleus effective phase shifts. Expressions for the cross section for processes in which the proton (or neutron) is absorbed whether the neutron (or proton) is absorbed or not, and for the cross section for processes in which the neutron (or proton) is absorbed and the proton (or neutron) remains free are derived. A reduced form of a two-particle density matrix is introduced to directly derive expressions for the cross section for two-particle absorption in which both the proton and neutron are absorbed and for the cross section for stripping processes in which the proton (or neutron) is absorbed and the neutron (or proton) emerges as a free particle. The expression for the cross section for the breakup of the deuteron and the resulting emergence of one or two free nucleons is also derived. The mechanism by which the diffraction dissociation of the deuteron is induced is understood in an approximate semi-quantitative basis in classical terms (primarily the radial derivative of the radial impulse), allowing an estimate of where in the nuclear potential (beyond the "radius", near the "surface") the dissociation process tends to predominantly occur.
Comments:
18 pages plus 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.12586 [pdf]
0 citations
03
[Submitted on 26 Sept 2020]
Effect of Inner Crust EoS on Neutron star properties
Ishfaq Ahmad Rather · Anisul Ain Usmani · Suresh Kumar Patra
The neutron star maximum mass and the radius are investigated within the framework of the relativistic mean-field (RMF) model. The variation in the radius at the canonical mass, $R_{1.4}$ , using different inner crust equation of state (EoS) with different symmetry energy slope parameter is studied. It is found that although the NS maximum mass and the corresponding radius do not vary much with different inner crust EoSs, the radius and the tidal deformability at 1.4 $M_{⊙}$ vary with the different choice of crust EoS and variation of about 1-2 km is seen in the radius at the canonical mass. For non-unified EoSs, the crust with a low symmetry energy slope parameter produces a low NS radius at the canonical mass. The properties of maximally rotating neutron stars are also studied. The variation in the radius of rotating star at the canonical mass 1.4 $M_{⊙}$ is also seen with the slope parameter. Similar to the static neutron star, the radius at 1.4 $M_{⊙}$ of rotating neutron star is affected by slope parameter of the inner crust. Other important quantities like moment of inertia, frequency, rotational kinetic energy to gravitational energy ratio are also calculated. The variation in these quantities with the crust slope parameter is found to be more proportional to the mass and the radius of NS.
Comments:
27 pages, 14 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2009.12613 [pdf]
NPA(2021)·25 citations
04
[Submitted on 26 Sept 2020]
Study of Cluster Structures in Nuclei through the Ratio Method. A Tribute to Mahir Hussein
Pierre Capel · Ronald C. Johnson · Filomena M. Nunes
For one-neutron halo nuclei, the cross section for elastic scattering and breakup at intermediate energy exhibit similar angular dependences. The Recoil Excitation and Breakup (REB) model of reactions elegantly explains this feature. It also leads to the idea of a new reaction observable to study the structure of loosely-bound nuclear systems: the Ratio. This observable consists of the ratio of angular distributions for different reaction channels, viz. elastic scattering and breakup, which cancels most of the dependence on the reaction mechanism; in particular it is insensitive to the choice of optical potentials that simulate the projectile-target interaction. This new observable is very sensitive to the structure of the projectile. In this article, we review the Ratio Method and its extension to low beam energies and proton-halo nuclei.
Comments:
Submitted to the European Physical Journal A as a contribution to the Special Issue on "Cluster structure and dynamics of nuclei" dedicated to the memory of Mahir S. Hussein (1944-2019). 12 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2009.12624 [pdf]
EPJA(2020)·5 citations
05
[Submitted on 27 Sept 2020]
Unified description of the coupled-channels and statistical Hauser-Feshbach nuclear reaction theories for low energy neutron incident reactions
Toshihiko Kawano
We incorporate the coupled-channels optical model into the statistical Hauser-Feshbach nuclear reaction theory, where the scattering matrix is diagonalized by performing the Engelbrecht-Weidenmüller transformation. This technique has been implemented in the coupled-channels optical model code ECIS by J. Raynal, and we extend this method so that all the open channels in a nucleon-induced reaction on a deformed nucleus can be calculated consistently.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.12736 [pdf]
EPJA(2021)·13 citations
06
[Submitted on 25 Sept 2020]
QCD phase diagram at finite isospin and baryon chemical potentials with the self-consistent mean field approximation
Zu-Qing Wu🇨🇳 · Jia-Lun Ping🇨🇳 · Hong-Shi Zong🇨🇳
The self-consistent mean field approximation of two-flavor NJL model with introducing a free parameter $α$ to reflect the competition between "direct" channel and the "exchange" channel, is employed to study QCD phase structure at finite isospin chemical potential $μ_{I}$ , finite baryon chemical potential $μ_{B}$ and finite temperature $T$ , especially the location of the QCD critical point. It is found that, for fixed isospin chemical potentials the lower temperature of phase transition is obtained with $α$ increasing in the $T - μ_{I}$ plane, and the largest difference of the phase transition temperature with different $α$ 's appears at $μ_{I} \sim 1.5 m_{π}$ . At $μ_{I} = 0$ the temperature of the QCD critical end point (CEP) decreases with $α$ increasing, while the critical baryon chemical potential increases. At high isospin chemical potential ( $μ_{I} = 500$ MeV), the temperature of the QCD tricritical point (TCP) increases with $α$ increasing, and in the regions of low temperature the system will transit from pion superfluidity phase to the normal phase as $μ_{B}$ increases. At low temperatures, the critical temperature of QCD phase transition with different $α$ 's rapidly increases with $μ_{I}$ at the beginning, and then increases smoothly around $μ_{I} > 300$ MeV. In high baryon density region, the increase of the isospin chemical potential will raise the critical baryon chemical potential of phase transition.
Comments:
7 pages, 9 figures. arXiv admin note: substantial text overlap with arXiv:2003.02988
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2009.13070 [pdf]
CPC(2021)·7 citations
07
[Submitted on 28 Sept 2020]
The origin of the spin-orbit and pseudospin-orbit splittings' evolution in neutron drop
Yinghui Ge · Ying Zhang · Jinniu Hu
We found the same staggering pattern in the evolution of the spin-orbit (SO) and pseudospin-orbit (PSO) splittings in neutron drops obtained by the energy-density functional (EDF) theory using SAMi-T and SLy5 parameterizations, with and without the tensor terms respectively. This staggering evolution is similar to the results recently obtained by the relativistic Brueckner-Hartree-Fock (RBHF) theory with Bonn A potential, which was claimed to be a tensor effect. In this work, we present an intuitive but essential explanation on the origin of this staggering evolution in the Skyrme EDF theory. We found that for both the SO and PSO partners, the energy splittings mainly originate from the SO potential. The staggering evolution of both the SO and PSO splittings is mainly due to the drastic change of density while neutrons filling different single-particle orbits. The key to determine the specific staggering pattern is the strength of the neutron density gradient term and the SO density term in the SO potential, not necessarily the tensor force.
Comments:
11 pages, 3 figures, 1 tables, accepted by Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.13193 [pdf]
PRC(2020)·2 citations
08
[Submitted on 28 Sept 2020]
Hyperon halo structure of C and B isotopes
Ying Zhang · Hiroyuki Sagawa🇯🇵 · Emiko Hiyama🇯🇵
We study the hypernuclei of C and B isotopes by Hartree-Fock model with Skyrme-type nucleon-nucleon and nucleon-hyperon interactions. The calculated $Λ$ binding energies agree well with the available experiment data. We found halo structure in the hyperon $1 p$ -state with extended wave function beyond nuclear surface in the light C and B isotopes. We also found the enhanced electric dipole transition between $1 p$ - and $1 s$ -hyperon states, which could be the evidence for this hyperon halo structure.
Comments:
16 pages, 2 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.13196 [pdf]
PRC(2021)·29 citations
09
[Submitted on 28 Sept 2020]
Phase diagram of alpha matter with Skyrme-like scalar interaction
Leonid M. Satarov🇩🇪 · Roman V. Poberezhnyuk🇩🇪 · Igor N. Mishustin🇩🇪 · Horst Stoecker🇩🇪
The equation of state and phase diagram of strongly interacting matter composed of $α$ particles are studied in the mean-field approximation. The particle interactions are included via a Skyrme-like mean field, containing both attractive and repulsive terms. The model parameters are found by fitting known values of binding energy and baryon density in the ground state of $α$ matter, obtained from microscopic calculations by Clark and Wang. Thermodynamic quantities of $α$ matter are calculated in the broad domains of temperature and baryon density, which can be reached in heavy-ion collisions at intermediate energies. The model predicts both first-order liquid-gas phase transition and Bose-Einstein condensation of $α$ particles. We present the profiles of scaled variance, sound velocity and isochoric heat capacity along the isentropic trajectories of $α$ matter. Strong density fluctuations are predicted in the vicinity of the critical point at temperature $T_{c} \approx 14 MeV$ and density $n_{c} \approx 0.012 fm^{- 3}$ .
Comments:
29 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2009.13487 [pdf]
PRC(2021)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE