Nuclear Theory·nucl-th

Wednesday·April 14, 2021

12 papers—6 primary·6 cross-listed

01
Properties of a quantum vortex in neutron matter
Daniel Pęcak🇵🇱 · Nicolas Chamel🇧🇪 · Piotr Magierski🇵🇱 · Gabriel Wlazłowski🇵🇱
We have studied systematically microscopic properties of a quantum vortex in neutron matter at finite temperatures and densities corresponding to different layers of the inner crust of a neutron star. To this end and in preparation of future simulations of the vortex dynamics, we have carried out fully self-consistent 3D Hartree-Fock-Bogoliubov calculations, using one of the latest nuclear energy-density functionals from the Brussels-Montreal family, which has been developed specifically for applications to neutron superfluidity in neutron-star crusts. By analyzing the flow around the vortex, we have determined the effective radius relevant for the vortex filament model. We have also calculated the specific heat in the presence of the quantum vortex and have shown that it is substantially larger than for a uniform system at low temperatures. The low temperature limit of the specific heat has been identified as being determined by Andreev states inside the vortex core. We have shown that the specific heat in this limit does not scale linearly with temperature. The typical energy scale associated with Andreev states is defined by the minigap, which we have extracted for various neutron-matter densities. Our results suggest that vortices may be spin-polarized in the crust of magnetars. Finally, we have obtained a lower bound for the specific heat of a collection of vortices with given surface density, taking into account both the contributions from the vortex core states and from the hydrodynamic flow.
nucl-thastro-ph.HEPRC(2021)·15 citations
02
Non-extensive Boltzmann Transport Equation: the Relaxation Time Approximation and Beyond
Trambak Bhattacharyya🇷🇺
We derive approximate iterative analytical solutions of the non-extensive Boltzmann transport equation in the relaxation time approximation. The approximate solutions almost overlap with the exact solution for a considerably wide range of the parameter values found in describing particle spectra originated in high-energy collisions. We also discuss the Landau kinetic approximation of the non-extensive Boltzmann transport equation and the emergence of the non-extensive Fokker-Planck equation, and use it to estimate the drag and diffusion coefficients of highly energetic light quarks passing through a gluonic plasma.
nucl-thhep-exhep-phPhysica A(2023)·8 citations
03
Heavy Magnetic Neutron Stars
I. A. Rather🇮🇳 · Usuf Rahaman🇮🇳 · V. Dexheimer🇺🇸 · A. A. Usmani🇮🇳 · S. K. Patra🇮🇳
We systematically study the properties of pure nucleonic and hyperonic magnetic stars using a density-dependent relativistic mean field (DD-RMF) equations of state. We explore several parameter sets and hyperon coupling schemes within the DD-RMF formalism. We focus on sets that are in better agreement with nuclear and other astrophysical data, while generating heavy neutron stars. Magnetic field effects are included in the matter equation of state and in general relativity solutions, which in addition fulfill Maxwell's equations. We find that pure nucleonic matter, even without magnetic field effects, generates neutron stars that satisfy the potential GW190814 mass constraint; however, this is not the case for hyperonic matter, which instead only satisfies the more conservative 2.1 M $_{⊙}$ constraint. In the presence of strong but still somehow realistic internal magnetic fields $\approx 1 0^{17}$ G, the stellar charged particle population re-leptonizes and de-hyperonizes. As a consequence, magnetic fields stiffen hyperonic equations of state and generate more massive neutron stars, which can satisfy the possible GW190814 mass constraint but present a large deformation with respect to spherical symmetry.
nucl-thastro-ph.HEApJ(2021)·35 citations
04
Spin-triplet proton-neutron pair in spin-dipole excitations
Kenichi Yoshida · Yusuke Tanimura
Background: Spin-triplet ( $S = 1$ ) proton-neutron (pn) pairing in nuclei has been under debate. It is well known that the dynamical pairing affects the nuclear matrix element of the Gamow-Teller (GT) transition and the double beta decay. Purpose: We investigate the effect of the pn-pair interaction in the $T = 0, S = 1$ channel on the low-lying spin-dipole (SD) transition. We then aim at clarifying the distinction of the role in between the SD and GT transitions. Method: We perform a three-body model calculation for the transition $^{80} Ni \to^{80} Cu$ , where $^{78} Ni$ is taken as a core. The strength of the pair interaction is varied to see the effect on the SD transition-strength distribution. To fortify the finding obtained by the three-body model, we employ the nuclear energy-density functional method for the SD transitions in several nuclei, where one can expect a strong effect. Results: The effect of the $S = 1$ pn-pair interaction depends on the spatial overlap of the pn pair and the angular momentum of the valence nucleons; the higher the angular momentum of the orbitals, the more significant the effect. Conclusions: The dynamical $S = 1$ pairing is effective even for SD states although the spatial overlap of the pn pair can be smaller than GT states. The SD transition involving high- $ℓ$ orbitals with the same principal quantum number is strongly affected by the dynamical $S = 1$ pairing.
nucl-thPRC(2021)·2 citations
05
Thermonuclear fusion and generalized Gamow penetrability factor in intense laser fields
Jintao Qi🇨🇳
A theoretical study on thermonuclear fusion including deuterium-tritium (D-T) fusion and D- $^{3}$ He fusion in intense laser fields has been shown in this article. With the laser fields expected to be available in the near future, some quantitative results for the laser-induced modifications to the cross-sections are given. It is reported that the cross-sections are more sensitive to the external laser fields at the lower energies. An explicit generalized form of the Gamow penetrability factor is given for the predictions of the laser-induced effects for some other similar nuclear processes.
nucl-thNPA(2022)·5 citations
06
The Neutron-Rich Edge of the Nuclear Landscape. Experiment and Theory
Frédéric Nowacki🇫🇷 · Alexandre Obertelli🇩🇪 · Alfredo Poves🇪🇸
In this review, we describe the experimental facilities and methods which make it possible to produce and measure the properties of the extreme neutron rich nuclei. We then develop the theoretical framework that will accompany us along the review; the shell-model approach with large scale configuration interaction (mixing) SM-CI, with special emphasis in the competition between the spherical mean field and the nuclear correlations (mainly pairing and quadrupole-quadrupole). The symmetry properties of the latter are treated in detail as they will show to be of great heuristic value. We explore in detail the Islands of Inversion (IoI) at N=20 and N=28. We make a side excursion into the heavier Calcium and Potassium isotopes, to discuss current issues on shell evolution and new magic numbers far from stability. We visit the N=40 Island of Inversion. We discuss the doubly magic nucleus 78Ni, its shape coexistence and the prospect of a new IoI at N=50 below Z=28. We examine the N=70 and N=82 neutron closures approaching the neutron drip line.
nucl-thPPNP(2021)·96 citations
07
QCD phase diagram in a magnetized medium from the chiral symmetry perspective: The linear sigma model with quarks and the Nambu--Jona-Lasinio model effective descriptions
Alejandro Ayala🇲🇽 · Luis A. Hernández🇲🇽 · Marcelo Loewe🇨🇱 · Cristian Villavicencio🇨🇱
We review the main features of the QCD phase diagram description, at finite temperature, baryon density and in the presence of a magnetic field, from the point of view of effective models, whose main ingredient is chiral symmetry. We concentrate our attention on two of these models: The linear sigma model with quarks and the Nambu--Jona-Lasinio model. We show that a main ingredient to understand the characteristics of the phase transitions is the inclusion of plasma screening effects that capture the physics of collective, long-wave modes, and thus describe a prime property of plasmas near transition lines, namely, long distance correlations. Inclusion of plasma screening makes possible to understand the inverse magnetic catalysis phenomenon even without the need to consider magnetic field-dependent coupling constants. Screening is also responsible for the emergence of a critical end point in the phase diagram even for small magnetic field strengths. Although versatile, the NJL model is also a more limited approach since, being a non-renormalizable model, a clear separation between pure vacuum and medium effects is not always possible. The model cannot describe inverse magnetic catalysis unless a magnetic field dependent coupling is included. The location of the critical end point strongly depends on the choice of the type of interaction and on the magnetic field dependence of the corresponding coupling. Overall, both models provide sensible tools to explore the properties of magnetized, strongly interacting matter. However, a cross talk among them as well as a consistent physical approach to determine the model parameters is much needed.
↳ hep-phhep-thnucl-thEPJA(2021)·44 citations
08
Investigating high energy proton proton collisions with a multi-phase transport model approach based on PYTHIA8 initial conditions
Liang Zheng🇨🇳 · Guang-Hui Zhang🇨🇳 · Yun-Fan Liu🇨🇳 · Zi-Wei Lin🇺🇸 · Qi-Ye Shou🇨🇳 · Zhong-Bao Yin🇨🇳
The striking resemblance of high multiplicity proton-proton (pp) collisions at the LHC to heavy ion collisions challenges our conventional wisdom on the formation of the Quark-Gluon Plasma (QGP). A consistent explanation of the collectivity phenomena in pp will help us to understand the mechanism that leads to the QGP-like signals in small systems. In this study, we introduce a transport model approach connecting the initial conditions provided by PYTHIA8 with subsequent AMPT rescatterings to study the collective behavior in high energy pp collisions. The multiplicity dependence of light hadron productions from this model is in reasonable agreement with the pp $s = 13$ TeV experimental data. It is found in the comparisons that both the partonic and hadronic final state interactions are important for the generation of the radial flow feature of the pp transverse momentum spectra. The study also shows that the long range two particle azimuthal correlation in high multiplicity pp events is sensitive to the proton sub-nucleon spatial fluctuations.
↳ hep-phnucl-thEPJC(2021)·18 citations
09
Ambiguities in the hadro-chemical freeze-out of Au+Au collisions at SIS18 energies and how to resolve them
Anton Motornenko🇩🇪 · Jan Steinheimer🇩🇪 · Volodymyr Vovchenko🇺🇸 · Reinhard Stock🇩🇪 · Horst Stoecker🇩🇪
The thermal fit to preliminary HADES data of Au+Au collisions at $s_{_{N N}} = 2.4$ GeV shows two degenerate solutions at $T \approx 50$ MeV and $T \approx 70$ MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both solutions yield the same number of hadrons after resonance decays, the feeddown contribution is very different for both cases. This highlights that two systems with different chemical composition can yield the same multiplicities after resonance decays. The nature of these two minima is further investigated by studying the time-dependent particle yields and extracted thermodynamic properties of the UrQMD model. It is confirmed, that the evolution of the high temperature solution resembles cooling and expansion of a hot and dense fireball. The low temperature solution displays an unphysical evolution: heating and compression of matter with a decrease of entropy. These results imply that the thermal model analysis of systems produced in low energy nuclear collisions is ambiguous but can be interpreted by taking also the time evolution and resonance contributions into account.
↳ hep-phnucl-exnucl-thPLB(2021)·27 citations
10
Implications of Feebly Interacting Dark Sector on Neutron Star Properties and Constraints from GW170817
Debashree Sen🇮🇳 · Atanu Guha🇮🇳
We investigate the effect of feeble interaction of dark matter (DM) with hadronic matter on the equation of state (EoS) and structural properties of neutron stars (NSs) in static conditions. For the purpose we adopt the effective chiral model for the hadronic sector and for the first time in the context of possible existence of DM inside NSs, we introduce DM-SM interaction through light new physics mediator. Moreover, the mass of DM fermion, the mediator and the coupling are adopted from the self-interaction constraint from Bullet cluster and from present day relic abundance. Within the considered framework, the work highlights the underlying stiffening of EoS in presence of DM fermion of mass of the order of a few GeV compared to the no-DM scenario. Consequently, the maximum gravitational mass of NS is obtained consistent with the bounds from the most massive pulsars which were not satisfied with the hadronic matter EoS alone. The estimates of radius and tidal deformability of 1.4 $M_{⊙}$ NS and the tidal deformabilities of the individual components of the binary neutron stars (BNS) associated with GW170817 are all in good agreement with the individual constraints obtained from GW170817 observation of BNS merger.
↳ hep-phastro-ph.COastro-ph.HEhep-th+1MNRAS(2021)·59 citations
11
Structure in the Event-by-Event Energy-Dependent Neutron-Gamma Multiplicity Correlations in $^{252} Cf$ (sf)
Stefano Marin🇺🇸 · Mustapha Stephan Okar🇺🇸 · Eoin P. Sansevero🇺🇸 · Isabel E. Hernandez🇺🇸 · Catherine A. Ballard🇺🇸 · Ramona Vogt🇺🇸 · Jørgen Randrup🇺🇸 · Patrick Talou🇺🇸 · Amy E. Lovell🇺🇸 · Ionel Stetcu🇺🇸 · Olivier Serot🇫🇷 · Olivier Litaize🇫🇷 and 4 other authors
The emission of neutrons and gamma rays by fission fragments reveal important information about the properties of fragments immediately following scission. The initial fragment properties, correlations between fragments, and emission competition give rise to correlations in neutron-gamma emission. Neutron-gamma correlations are important in nonproliferation applications because the characterization of fissionable samples relies on the identification of signatures in the measured radiation. Furthermore, recent theoretical and experimental advances have proposed to explain the mechanism of angular momentum generation in fission. In this paper, we present a novel analysis method of neutrons and gamma rays emitted by fission fragments that allows us to discern structure in the observed correlations. We have analyzed data collected on \ce{^{252}Cf}(sf) at the Chi-Nu array at the Los Alamos Neutron Science Center. Through our analysis of the energy-differential neutron-gamma multiplicity covariance, we have observed enhanced neutron-gamma correlations, corresponding to rotational band gamma-ray transitions, at gamma-ray energies of $0.7$ and $1.2$ MeV. To shed light on the origin of this structure, we compare the experimental data with the predictions of three model calculations. The origin of the observed correlation structure is understood in terms of a positive spin-energy correlation in the generation of angular momentum in fission.
↳ nucl-exnucl-thPRC(2021)·13 citations
12
Gluon Parton Distribution of the Pion from Lattice QCD
Zhouyou Fan🇺🇸 · Huey-Wen Lin🇺🇸
We present the first determination of the $x$ -dependent pion gluon distribution from lattice QCD using the pseudo-PDF approach. We use lattice ensembles with 2+1+1 flavors of highly improved staggered quarks (HISQ), generated by MILC Collaboration, at two lattice spacings $a \approx 0.12$ and 0.15~fm and three pion masses $M_{π} \approx 220$ , 310 and 690 MeV. We use clover fermions for the valence action and momentum smearing to achieve pion boost momentum up to 2.29 GeV. We find that the dependence of the pion gluon parton distribution on lattice spacing and pion mass is mild. We compare our results from the lightest pion mass ensemble with the determination by JAM and xFitter global fits.
↳ hep-lathep-phnucl-thPLB(2021)·76 citations

Affiliations

first authorsco-authorsvia INSPIRE