Nuclear Theory·nucl-th

Friday·June 5, 2020

10 papers—4 primary·6 cross-listed

01
[Submitted on 4 Jun 2020]
Contribution of the rho meson and quark sub-structure to the nuclear spin-orbit potential
Guy Chanfray🇫🇷 · Jérôme Margueron🇫🇷
The microscopic origin of the spin-orbit (SO) potential in terms of sub-baryonic degrees of freedom is explored and discussed for application to nuclei and hyper-nuclei. We thus develop a chiral relativistic approach where the coupling to the scalar- and vector-meson fields are controlled by the quark substructure. This approach suggests that the isoscalar and isovector density dependence of the SO potential can be used to test the microscopic ingredients which are implemented in the relativistic framework: the quark substructure of the nucleon in its ground-state and its coupling to the rich meson sector where the $ρ$ meson plays a crucial role. This is also in line with the Vector Dominance Model (VDM) phenomenology and the known magnetic properties of the nucleons. We explore predictions based on Hartree and Hartree-Fock mean field, as well as various scenarios for the $ρ$ -nucleon coupling, ranked as weak, medium and strong, which impacts the isoscalar and isovector density dependence of the SO potential. We show that a medium to strong $ρ$ coupling is essential to reproduce Skyrme phenomenology in $N = Z$ nuclei as well as its isovector dependence. Assuming an SU(6) valence quark model our approach is extended to hyperons and furnishes a microscopic understanding of the quenching of the $N Λ$ spin-orbit potential in hyper-nuclei. It is also applied to other hyperons, such as $Σ$ , $Ξ$ and $Ω$ .
Comments:
9 pages, 3 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.02698 [pdf]
PRC(2020)·10 citations
02
[Submitted on 4 Jun 2020]
Factorial cumulants from global baryon number conservation
Michał Barej🇵🇱 · Adam Bzdak🇵🇱
The proton, antiproton and mixed proton-antiproton factorial cumulants originating from the global conservation of baryon number are calculated analytically up to the sixth order. Our results can be directly tested in experiments.
Comments:
15 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2006.02836 [pdf]
PRC(2020)·10 citations
03
[Submitted on 4 Jun 2020]
Zero-pairing limit of Hartree-Fock-Bogoliubov reference states
T. Duguet🇫🇷 · B. Bally🇪🇸 · A. Tichai🇩🇪
The variational Hartree-Fock-Bogoliubov (HFB) mean-field theory is the starting point of various (ab initio) many-body methods dedicated to superfluid systems. While taking the zero-pairing limit of HFB equations constitutes a text-book problem when the system is of closed-(sub)shell character, it is typically, although wrongly, thought to be ill-defined whenever the naive filling of single-particle levels corresponds to an open-shell system. The present work demonstrates that the zero-pairing limit of an HFB state is mathematically well-defined, independently of the closed- or open-shell character of the system in the limit. Still, the nature of the limit state strongly depends on the underlying shell structure and on the associated naive filling reached in the zero-pairing limit for the particle number A of interest. All the analytical findings are confirmed and illustrated numerically. While HFB theory has been intensively scrutinized formally and numerically over the last decades, it still uncovers unknown and somewhat unexpected features. From this general perspective, the present analysis demonstrates that HFB theory does not reduce to Hartree-Fock theory even when the pairing field is driven to zero in the HFB Hamiltonian matrix.
Comments:
20 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con); physics.chem-ph (physics.chem-ph)
arXiv:
2006.02871 [pdf]
PRC(2020)·20 citations
04
[Submitted on 4 Jun 2020]
A Bayesian Analysis of Nuclear Deformation Properties with Skyrme Energy Functionals
N. Schunck · K. R. Quinlan · J. Bernstein
In spite of numerous scientific and practical applications, there is still no comprehensive theoretical description of the nuclear fission process based solely on protons, neutrons and their interactions. The most advanced simulations of fission are currently carried out within nuclear density functional theory (DFT). In spite of being fully quantum-mechanical and rooted in the theory of nuclear forces, DFT still depends on a dozen or so parameters characterizing the energy functional. Calibrating these parameters on experimental data results in uncertainties that must be quantified for applications. This task is very challenging because of the high computational cost of DFT calculations for fission. In this paper, we use Gaussian processes to build emulators of DFT models in order to quantify and propagate statistical uncertainties of theoretical predictions for a range of nuclear deformations relevant to describing the fission process.
Comments:
18 pages, 7 figures, 4 tables, 46 references
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.02906 [pdf]
J.Phys.G(2020)·5 citations
05
[Submitted on 1 Jun 2020] (cross-list from hep-ph)
Dynamical Evidence For a Fifth Force Explanation of the ATOMKI Nuclear Anomalies
Jonathan L. Feng🇺🇸 · Tim M. P. Tait🇺🇸 · Christopher B. Verhaaren🇺🇸
Recent anomalies in $^{8}$ Be and $^{4}$ He nuclear decays can be explained by postulating a fifth force mediated by a new boson $X$ . The distributions of both transitions are consistent with the same $X$ mass, 17 MeV, providing kinematic evidence for a single new particle explanation. In this work, we examine whether the new results also provide dynamical evidence for a new particle explanation, that is, whether the observed decay rates of both anomalies can be described by a single hypothesis for the $X$ boson's interactions. We consider the observed $^{8}$ Be and $^{4}$ He excited nuclei, as well as a $^{12}$ C excited nucleus; together these span the possible $J^{P}$ quantum numbers up to spin 1. For each transition, we determine whether scalar, pseudoscalar, vector, or axial vector $X$ particles can mediate the decay, and we construct the leading operators in a nuclear physics effective field theory that describes them. Assuming parity conservation, the scalar case is excluded and the pseudoscalar case is highly disfavored. Remarkably, however, the protophobic vector gauge boson, first proposed to explain only the $^{8}$ Be anomaly, also explains the $^{4}$ He anomaly within experimental uncertainties. We predict signal rates for other closely related nuclear measurements, which, if confirmed, will provide overwhelming evidence that a fifth force has been discovered.
Comments:
32 pages, 6 figures; Corrected small typos and added references
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.01151 [pdf]
PRD(2020)·69 citations
06
[Submitted on 3 Jun 2020] (cross-list from hep-ph)
Inhomogeneous phases in the quark-meson model with explicit chiral-symmetry breaking
Michael Buballa🇩🇪 · Stefano Carignano🇪🇸 · Lennart Kurth🇩🇪
We investigate the existence of inhomogeneous chiral phases in the quark-meson model with explicit chiral-symmetry breaking. We find that the inhomogeneous region shrinks with increasing pion masses but survives for the physical value of m_pi. The instability towards inhomogeneous matter occurs in the scalar channel, while pseudoscalar modes are disfavored.
Comments:
14 pages, 5 figures, contains ancillary files with plot data; v2: figures and typos corrected, corresponds to published version in the EPJ ST Special Issue: Strong Correlations in Dense Matter Physics
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.02133 [pdf]
Eur.Phys.J.ST(2020)·26 citations
07
[Submitted on 3 Jun 2020] (cross-list from astro-ph.CO)
Stellar Signatures of Inhomogeneous Big Bang Nucleosynthesis
Alexandre Arbey🇫🇷 · Jérémy Auffinger🇫🇷 · Joseph Silk🇫🇷
We evaluate abundance anomalies generated in patches of the universe where the baryon-to-photon ratio was locally enhanced by possibly many orders of magnitude in the range $η = 1 0^{- 10} - 1 0^{- 1}$ . Our study is motivated by the possible survival of rare dense regions in the early universe, the most extreme of which, above a critical threshold, collapsed to form primordial black holes. If this occurred, one may expect there to also be a significant population of early-forming stars that formed in similar but subthreshold patches. We derive a range of element abundance signatures by performing BBN simulations at high values of the baryon-to-photon ratio that may be detectable in any surviving first generation stars of around a solar mass. Our predictions apply to metal-poor galactic halo stars, to old globular star clusters and to dwarf galaxies, and we compare with observations in each of these cases.
Comments:
9 pages, 4 figures, raw and plotted data in ancillary files
Subjects:
Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2006.02446 [pdf]
PRD(2020)·15 citations
08
[Submitted on 4 Jun 2020] (cross-list from hep-ph)
Two-loop HTL-resummed thermodynamics for N=4 supersymmetric Yang-Mills theory
Qianqian Du🇨🇳 · Michael Strickland🇺🇸 · Ubaid Tantary🇺🇸 · Ben-Wei Zhang🇨🇳
We compute the two-loop hard-thermal-loop (HTL) resummed thermodynamic potential for N=4 supersymmetric Yang-Mills (SYM). Our final result is manifestly gauge-invariant and was renormalized using only simple vacuum energy, gluon mass, scalar mass, and quark mass counter terms. The HTL mass parameters m_D, M_D, and m_q are then determined self-consistently using a variational prescription which results in a set of coupled gap equations. Based on this, we obtain the two-loop HTL-resummed thermodynamic functions of N=4 SYM. We compare our final result with known results obtained in the weak- and strong-coupling limits. We also compare to previously obtained approximately self-consistent HTL resummations and Padé approximants. We find that the two-loop HTL resummed results for the scaled entropy density is a quantitatively reliable approximation to the scaled entropy density for 0 <= lambda <~ 2 and is in agreement with previous approximately self-consistent HTL resummation results for lambda <~ 6.
Comments:
38 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2006.02617 [pdf]
JHEP(2020)·11 citations
09
[Submitted on 4 Jun 2020] (cross-list from nucl-ex)
Examining the $N$ = 28 shell closure through high-precision mass measurements of $^{46 - 48}$ Ar
Maxime Mougeot🇫🇷 · Dinko Atanasov🇩🇪 · Carlo Barbieri🇬🇧 · Klaus Blaum🇩🇪 · Martin Breitenfeld🇨🇭 · Antoine de Roubin🇩🇪 · Thomas Duguet🇫🇷 · Sebastian George🇩🇪 · Frank Herfurth🇩🇪 · Alexander Herlert🇩🇪 · Jason D. Holt🇨🇦 · Jonas Karthein🇩🇪 and 12 other authors
The strength of the $N$ = 28 magic number in neutron-rich argon isotopes is examined through high-precision mass measurements of $^{46 - 48}$ Ar, performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN. The new mass values are up to 90 times more precise than previous measurements. While they suggest the persistence of the $N$ = 28 shell closure for argon, we show that this conclusion has to be nuanced in light of the wealth of spectroscopic data and theoretical investigations performed with the \emph{SDPF-U} phenomenological shell model interaction. Our results are also compared with \emph{ab initio} calculations using the Valence Space In-Medium Similarity Renormalization Group and the Self-Consistent Green's Function approaches. Both calculations provide a very good account of mass systematics at and around $Z$ = 18 and, generally, a consistent description of the physics in this region. This combined analysis indicates that $^{46}$ Ar is the transition between the closed-shell $^{48}$ Ca and collective $^{44}$ S.
Comments:
17 pages, 14 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.02712 [pdf]
PRC(2020)·15 citations
10
[Submitted on 4 Jun 2020] (cross-list from hep-ph)
Polarized electron-deuteron deep-inelastic scattering with spectator nucleon tagging
W. Cosyn🇺🇸 · C. Weiss🇺🇸
Background: DIS on the polarized deuteron with detection of a proton in the nuclear breakup region (spectator tagging) represents a unique method for extracting the neutron spin structure functions and studying nuclear modifications. The tagged proton momentum controls the nuclear configuration during the DIS process and enables a differential analysis of nuclear effects. Such measurements could be performed with the future electron-ion collider (EIC) and forward proton detectors if deuteron beam polarization could be achieved. Purpose: Develop theoretical framework for polarized deuteron DIS with spectator tagging. Formulate procedures for neutron spin structure extraction. Methods: A covariant spin density matrix formalism is used to describe general deuteron polarization in collider experiments (vector/tensor, pure/mixed). Light-front (LF) quantum mechanics is employed to factorize nuclear and nucleonic structure in the DIS process. A 4-dimensional representation of LF spin structure is used to construct the polarized deuteron LF wave function and efficiently evaluate the spin sums. Free neutron structure is extracted using the impulse approximation and analyticity in the tagged proton momentum (pole extrapolation). Results: General expressions of the polarized tagged DIS observables in collider experiments. Analytic and numerical study of the polarized deuteron LF spectral function and nucleon momentum distributions. Practical procedures for neutron spin structure extraction from the tagged deuteron spin asymmetries. Conclusions: Spectator tagging provides new tools for precise neutron spin structure measurements. D-wave depolarization and nuclear binding effects can be eliminated through the tagged proton momentum dependence. The methods can be extended to tensor-polarized observables, spin-orbit effects, and diffractive processes.
Comments:
52 pages, 19 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.03033 [pdf]
PRC(2020)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE