Nuclear Theory·nucl-th

Friday·April 24, 2020

7 papers—5 primary·2 cross-listed

01
[Submitted on 22 Apr 2020]
Fission of $^{240}$ Pu with symmetry-restored density functional theory
Petar Marević · Nicolas Schunck
Nuclear fission plays an important role in fundamental and applied science, from astrophysics to nuclear engineering, yet it remains a major challenge to nuclear theory. Theoretical methods used so far to compute fission observables rely on symmetry-breaking schemes where basic information on the number of particles, angular momentum, and parity of the fissioning nucleus is lost. In this work, we analyze the impact of restoring broken symmetries in the benchmark case of $^{240}$ Pu.
Comments:
7 pages, 3 figures, 1 table; Phys. Rev. Lett, in press
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2004.10804 [pdf]
PRL(2020)·25 citations
02
[Submitted on 22 Apr 2020]
Structure of Krypton Isotopes using the Generalised Bohr Hamiltonian Method
David Muir · Leszek Próchniak · Alessandro Pastore · Jacek Dobaczewski
We investigate the properties of the excited spectra of the even-even isotopes of krypton using a Generalised Bohr Hamiltonian with three different Skyrme functionals. In particular, we investigate the evolution of the low-lying $2_{1}^{+}$ and $4_{1}^{+}$ states and their associated electromagnetic transitions. The model reproduces quite nicely the energy trends apart from $^{88}$ Kr, where none of the interactions used here are able to grasp a sudden change in the energy spectrum. Additionally, we explore the neutron deficient region $^{72 - 76}$ Kr which is a proposed region for shape coexistence. We observe that the model can reproduce the structure of the experimental spectrum of $^{72}$ Kr exceedingly well.
Comments:
Presented at the 27th International Nuclear Physics Conference (INPC) 2019, Glasgow, Scotland, UK, 29th July - 2 August
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2004.10835 [pdf]
J.Phys.Conf.Ser.(2020)·2 citations
03
[Submitted on 23 Apr 2020]
Entropy Production in Dissipationless Hydrodynamics with an order parameter
Shu Lin · Gezheng Zhou
We study hydrodynamics coupled to order parameter based on linear sigma model. We obtain numerical solutions for both boost invariant and non-boost invariant solutions. Both solutions show the order parameter rises with oscillations, which persist at late time. The temperature drops with correlated oscillations, which can be approximated by a power law at mid-rapidity. We also find the entropy is conserved in the boost invariant case, but entropy production is seen in non-boost invariant solution. We interpret the entropy production as due to smoothening of inhomogeneity in the off-equilibrium state.
Comments:
13 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2004.10935 [pdf]
0 citations
04
[Submitted on 23 Apr 2020]
Thresholds of ultraperipheral processes
I.M. Dremin🇷🇺
Threshold behavior of the cross sections of ultraperipheral nuclear interactions is studied. Production of $e^{+} e^{-}$ and $μ^{+} μ^{-}$ pairs as well as $π^{0}$ and parapositronium is treated. The values of corresponding energy thresholds are presented and the total cross sections of these processes at the newly constructed NICA and FAIR facilities are estimated.
Comments:
8 pg
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2004.11074 [pdf]
Int.J.Mod.Phys.A(2020)·2 citations
05
[Submitted on 23 Apr 2020]
Designing Optimal Experiments: An Application to Proton Compton Scattering
J. A. Melendez · R. J. Furnstahl · H. W. Griesshammer · J. A. McGovern · D. R. Phillips · M. T. Pratola
Interpreting measurements requires a physical theory, but the theory's accuracy may vary across the experimental domain. To optimize experimental design, and so to ensure that the substantial resources necessary for modern experiments are focused on acquiring the most valuable data, both the theory uncertainty and the expected pattern of experimental errors must be considered. We develop a Bayesian approach to this problem, and apply it to the example of proton Compton scattering. Chiral Effective Field Theory ( $χ$ EFT) predicts the functional form of the scattering amplitude for this reaction, so that the electromagnetic polarizabilities of the nucleon can be inferred from data. With increasing photon energy, both experimental rates and sensitivities to polarizabilities increase, but the accuracy of $χ$ EFT decreases. Our physics-based model of $χ$ EFT truncation errors is combined with present knowledge of the polarizabilities and reasonable assumptions about experimental capabilities at HI $γ$ S and MAMI to assess the information gain from measuring specific observables at specific kinematics, \emph{i.e.}, to determine the relative amount by which new data are apt to shrink uncertainties. The strongest gains would likely come from new data on the spin observables $Σ_{2 x}$ and $Σ_{2 x^{'}}$ at $ω ≃ 140$ to $200$ MeV and $4 0^{\circ}$ to $12 0^{\circ}$ . These would tightly constrain $γ_{E 1 E 1} - γ_{E 1 M 2}$ . New data on the differential cross section between $100$ and $200$ \,MeV and over a wide angle range will substantially improve constraints on $α_{E 1} - β_{M 1}$ , $γ_{π}$ and $γ_{M 1 M 1} - γ_{M 1 E 2}$ . Good signals also exist around $160$ MeV for $Σ_{3}$ and $Σ_{2 z^{'}}$ . Such data will be pivotal in the continuing quest to pin down the scalar polarizabilities and refine understanding of the spin polarizabilities.
Comments:
47 pages LaTeX2e (pdflatex) including 33 figures as .jpg files using includegraphics. Improved presentation with corrections do not affect the conclusions by details of the figures. Higher-resolution figures are available at https://home.gwu.edu/~hgrie/Compton/one-N-comprehensive-observables-delta4.v2.0.high-resolution-figures.tgz. Final version with minor corrections published in EPJA57(2021)81
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Data Analysis, Statistics and Probability (physics.data-an)
arXiv:
2004.11307 [pdf]
EPJA(2021)·28 citations
06
[Submitted on 23 Apr 2020] (cross-list from nucl-ex)
Astrophysics in the Laboratory: The CBM Experiment at FAIR
P. Senger · for the CBM collaboration
The future Facility for Antiproton and Ion Research (FAIR) is an accelerator-based international center for fundamental and applied research, which presently is under construction in Darmstadt, Germany. An important part of the program is devoted to questions related to astrophysics, including the origin of elements in the universe and the properties of strongly interacting matter under extreme conditions, which are relevant for our understanding of the structure of neutron stars and the dynamics of supernova explosions and neutron star mergers. The Compressed Baryonic Matter (CBM) experiment at FAIR is designed to measure promising observables in high-energy heavy-ion collisions, which are expected to be sensitive to the high-density equation-of-state (EOS) of nuclear matter and to new phases of QCD matter at high densities. The CBM physics program, the relevant observables and the experimental setup will be discussed.
Comments:
16 pages, 9 figures, Selected Papers from The Modern Physics of Compact Stars and Relativistic Gravity 2019
Subjects:
Nuclear Experiment (nucl-ex); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2004.11214 [pdf]
Particles(2020)·14 citations
07
[Submitted on 23 Apr 2020] (cross-list from nucl-ex)
Probing the core of the strong nuclear interaction
A. Schmidt🇺🇸 · J. R. Pybus🇺🇸 · R. Weiss🇮🇱 · E. P. Segarra🇺🇸 · A. Hrnjic🇺🇸 · A. Denniston🇺🇸 · O. Hen🇺🇸 · E. Piasetzky🇮🇱 · L. B. Weinstein🇺🇸 · N. Barnea🇮🇱 · M. Strikman🇺🇸 · A. Larionov🇩🇪 and 153 other authors
The strong nuclear interaction between nucleons (protons and neutrons) is the effective force that holds the atomic nucleus together. This force stems from fundamental interactions between quarks and gluons (the constituents of nucleons) that are described by the equations of Quantum Chromodynamics (QCD). However, as these equations cannot be solved directly, physicists resort to describing nuclear interactions using effective models that are well constrained at typical inter-nucleon distances in nuclei but not at shorter distances. This limits our ability to describe high-density nuclear matter such as in the cores of neutron stars. Here we use high-energy electron scattering measurements that isolate nucleon pairs in short-distance, high-momentum configurations thereby accessing a kinematical regime that has not been previously explored by experiments, corresponding to relative momenta above 400 MeV/c. As the relative momentum between two nucleons increases and their separation thereby decreases, we observe a transition from a spin-dependent tensor-force to a predominantly spin-independent scalar-force. These results demonstrate the power of using such measurements to study the nuclear interaction at short-distances and also support the use of point-like nucleons with two- and three-body effective interactions to describe nuclear systems up to densities several times higher than the central density of atomic nuclei.
Comments:
Total 26 pages, 13 figures. Main text: 8 pages, 3 figures. Methods section: 6 pages. Extended Data: 8 figures, 1 table. Supplementary Materials: 8 pages, 2 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2004.11221 [pdf]
Nature(2020)·100 citations

Affiliations

first authorsco-authorsvia INSPIRE

Fission of 240Pu with symmetry-restored density functional theory

Structure of Krypton Isotopes using the Generalised Bohr Hamiltonian Method

Entropy Production in Dissipationless Hydrodynamics with an order parameter

Thresholds of ultraperipheral processes

Designing Optimal Experiments: An Application to Proton Compton Scattering

Astrophysics in the Laboratory: The CBM Experiment at FAIR

Probing the core of the strong nuclear interaction

Affiliations

Fission of $^{240}$ Pu with symmetry-restored density functional theory