Nuclear Theory·nucl-th

Tuesday·January 23, 2018

10 papers—6 primary·4 cross-listed

01
[Submitted on 20 Jan 2018]
Fission Fragment Mass and Total Kinetic Energy Distributions of Spontaneously Fissioning Plutonium Isotopes
K. Pomorski🇵🇱 · B. Nerlo-Pomorska🇵🇱 · J. Bartel🇫🇷 · C. Schmitt🇫🇷
The fission-fragment mass and total kinetic energy (TKE) distributions are evaluated in a quantum mechanical framework using elongation, mass asymmetry, neck degree of freedom as the relevant collective parameters in the Fourier shape parametrization recently developed by us. The potential energy surfaces (PES) are calculated within the macroscopic-microscopic model based on the Lublin-Strasbourg Drop (LSD), the Yukawa-folded (YF) single-particle potential and a monopole pairing force. The PES are presented and analysed in detail for even-even Plutonium isotopes with $A = 236 - 246$ . They reveal deep asymmetric valleys. The fission-fragment mass and TKE distributions are obtained from the ground state of a collective Hamiltonian computed within the Born-Oppenheimer approximation, in the WKB approach by introducing a neck-dependent fission probability. The calculated mass and total kinetic energydistributions are found in good agreement with the data.
Comments:
10 pages, 7 figures, Eur. Phys. Journ. Web of Conf. (2018) Proc. of the THEORY-4 Scientific Workshop on the Nuclear Fission Dynamics and the Emission of Prompt Neutrons and Gamma Rays, 20-22 June, Varna, Bulgaria
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1801.06645 [pdf]
EPJ Web Conf.(2018)·10 citations
02
[Submitted on 20 Jan 2018]
On Gamov states of $Σ^{+}$ hyperons
Slawomir Wycech🇮🇹 · Kristian Piscicchia🇮🇹
Both the FINUDA and AMADEUS experiments evidenced a low $Σ^{+}$ momentum component when investigating $Σ^{+} π^{-}$ pairs produced in K $^{-}$ nuclear capture. This component is interpreted as a consequence of Gamov state formation, with the hyperon trapped in the Coulomb field of the residual nucleus. Description of such states and their participation in the capture reaction is presented. Some consequences are indicated.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1801.06675 [pdf]
Acta Phys.Polon.B(2017)·0 citations
03
[Submitted on 21 Jan 2018]
Combined Constraints on the Equation of State of Dense Neutron-Rich Matter from Terrestrial Experiments and Observations of Neutron Stars
Nai-Bo Zhang · Bao-An Li · Jun Xu
Within the parameter space of equation of state (EOS) of dense neutron-rich matter limited by existing constraints mainly from terrestrial nuclear experiments, we investigate how the neutron star maximum mass $M_{max} > 2.01 \pm 0.04$ M $_{⊙}$ , radius $10.62 < R_{1.4} < 12.83$ km and tidal deformability $Λ_{1.4} \leq 800$ of canonical neutron stars all together constrain the EOS of dense neutron-rich nucleonic matter. While the 3-D parameter space of $K_{sym}$ (curvature of nuclear symmetry energy), $J_{sym}$ and $J_{0}$ (skewness of the symmetry energy and EOS of symmetric nuclear matter, respectively) are narrowed down significantly by the observational constraints, more data are needed to pin down the individual values of $K_{sym}$ , $J_{sym}$ and $J_{0}$ with quantified uncertainties. The $J_{0}$ largely controls the maximum mass of neutron stars. While the EOS with $J_{0} = 0$ is sufficiently stiff to support neutron stars as massive as 2.37 M $_{⊙}$ , to support the hyperthetical ones as massive as 2.74 M $_{⊙}$ (composite mass of GW170817) requires $J_{0}$ to be larger than its currently known maximum value of about 400 MeV and beyond the causality limit. The upper limit on the tidal deformability of $Λ_{1.4} = 800$ from the recent observation of GW170817 is found to provide upper limits on some EOS parameters consistent with but far less restrictive than the existing constraints of other observables studied.
Comments:
More discussions on parameterizing the EOS of dense neutron-rich matter and why we do NOT use the widely used polytropes are added. The Astrophysical Journal in press
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1801.06855 [pdf]
ApJ(2018)·179 citations
04
[Submitted on 22 Jan 2018]
Neutrino-nucleon scattering in the neutrino-sphere
Paulo F. Bedaque🇺🇸 · Sanjay Reddy🇺🇸 · Srimoyee Sen🇺🇸 · Neill C. Warrington🇺🇸
We calculate the differential scattering rate for thermal neutrinos in a hot and dilute gas of interacting neutrons using linear response theory. The dynamical structure factors for density and spin fluctuations of the strongly interacting neutron matter, expected in the neutrino decoupling regions of supernovae and neutron star mergers, are calculated in the virial expansion for the first time. Correlations due to nucleon-nucleon interactions are taken into account using a pseudo-potential that reproduces measured nucleon-nucleon phase shifts, and we find that attractive s-wave interactions enhance the density response and suppress the spin response of neutron matter. The net effect of neutron correlations is to strongly suppress backscattering. Moreover, we find nearly exact scaling laws for the response functions, valid for the range $T = 5 - 10$ MeV and q < 30 MeV, allowing us to obtain analytic results for the dynamic structure factors at second-order in the fugacity of the neutron gas. We find that the modification of scattering rates depends on the energy and momentum exchanged, implying that dynamical structure factors are essential to describe neutrino decoupling in supernovae and neutron star mergers.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1801.07077 [pdf]
PRC(2018)·13 citations
05
[Submitted on 22 Jan 2018]
Hypernuclear stars from relativistic Hartree-Fock density functional theory
Jia Jie Li (1) · Wen Hui Long (2) · Armen Sedrakian (3) ((1) ITP Frankfurt · (2) Lanzhou University · (3) FIAS)
The hypernuclear matter is studied within the relativistic Hartree-Fock theory employing several parametrizations of the hypernuclear density functional with density-dependent couplings. The equations of state and compositions of hypernuclear matter are determined for each parametrization and compact stars are constructed by solving their structure equations in spherical symmetry. We quantify the softening effect of Fock terms on the equation of state, as well as discuss the impact of tensor interactions, which are absent in the Hartree theories. Starting from models of density functionals which are fixed in the nuclear sector to the nuclear phenomenology, we vary the couplings in the hyperonic sector around the central values which are fitted to the hyperon potentials in nuclear matter. We use the SU(6) spin-flavor and SU(3) flavor symmetric quark models to relate the hyperonic couplings to the nucleonic ones. We find, consistent with previous Hartree studies, that for the SU(6) model the maximal masses of compact stars are below the two-solar mass limit. In the SU(3) model we find sufficiently massive compact stars with cores composed predominantly of $Λ$ and $Ξ$ hyperons and a low fraction of leptons (mostly electrons). The parameter space of the SU(3) model is identified where simultaneously hypernuclear compact stars obey the astrophysical limits on pulsar masses and the empirical hypernuclear potentials in nuclear matter are reproduced.
Comments:
v2: 22 pages, 14 figures, minor changes and clarifications, matches published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1801.07084 [pdf]
EPJA(2018)·58 citations
06
[Submitted on 22 Jan 2018]
Relativistic effects in ab-initio electron-nucleus scattering
Noemi Rocco🇬🇧 · Winfried Leidemann🇮🇹 · Alessandro Lovato🇮🇹 · Giuseppina Orlandini🇮🇹
The electromagnetic responses obtained from Green's function Monte Carlo (GFMC) calculations are based on realistic treatments of nuclear interactions and currents. The main limitations of this method comes from its nonrelativistic nature and its computational cost, the latter hampering the direct evaluation of the inclusive cross sections as measured by experiments. We extend the applicability of GFMC in the quasielastic region to intermediate momentum transfers by performing the calculations in a reference frame that minimizes nucleon momenta. Additional relativistic effects in the kinematics are accounted for employing the two-fragment model. In addition, we developed a novel algorithm, based on the concept of first-kind scaling, to compute the inclusive electromagnetic cross section of $^{4}$ He through an accurate and reliable interpolation of the response functions. A very good agreement is obtained between theoretical and experimental cross sections for a variety of kinematical setups. This offers a promising prospect for the data analysis of neutrino-oscillation experiments that requires an accurate description of nuclear dynamics in which relativistic effects are fully accounted for.
Comments:
10 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex)
arXiv:
1801.07111 [pdf]
PRC(2018)·21 citations

Affiliations

first authorsco-authorsvia INSPIRE

Fission Fragment Mass and Total Kinetic Energy Distributions of Spontaneously Fissioning Plutonium Isotopes

On Gamov states of Σ+ hyperons

Combined Constraints on the Equation of State of Dense Neutron-Rich Matter from Terrestrial Experiments and Observations of Neutron Stars

Neutrino-nucleon scattering in the neutrino-sphere

Hypernuclear stars from relativistic Hartree-Fock density functional theory

Relativistic effects in ab-initio electron-nucleus scattering

Affiliations

On Gamov states of $Σ^{+}$ hyperons