Nuclear Theory·nucl-th

Friday·July 23, 2021

10 papers—6 primary·4 cross-listed

01
[Submitted on 21 Jul 2021]
On the linear causality and stability of third-order relativistic dissipative fluid dynamics
C. V. Brito🇧🇷 · G. S. Denicol🇧🇷
We analyze the linear causality and stability of third-order fluid dynamics considering perturbations around a global equilibrium state. We investigate the formulation derived from kinetic theory, using the Chapman-Enskog expansion, in PRC 88, 021903, which was shown to be in excellent agreement with solutions of the microscopic theory. From this analysis, we demonstrate that this theory is linearly acausal and unstable and that such instabilities cannot be corrected by tuning the transport coefficients. We then propose a modification of this theory, valid only in the linear regime, that can be constructed to be linearly causal and stable and obtain the conditions the transport coefficients must satisfy in order for this to be the case.
Comments:
20 pages, 8 figures; footnotes added, references changed
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
2107.10319 [pdf]
PRD(2022)·28 citations
02
[Submitted on 21 Jul 2021]
Impact of clustering on the $^{8}$ Li $β$ decay and recoil form factors
G. H. Sargsyan · K. D. Launey · M. T. Burkey · A. T. Gallant · N. D. Scielzo · G. Savard · A. Mercenne · T. Dytrych · D. Langr · L. Varriano · B. Longfellow · T. Y. Hirsh · J. P. Draayer
We place unprecedented constraints on recoil corrections in the $β$ decay of $^{8}$ Li, by identifying a strong correlation between them and the $^{8}$ Li ground state quadrupole moment in large-scale ab initio calculations. The results are essential for improving the sensitivity of high-precision experiments that probe the weak interaction theory and test physics beyond the Standard Model (BSM). In addition, our calculations predict a $2^{+}$ state of the $α + α$ system that is energetically accessible to $β$ decay but has not been observed in the experimental $^{8}$ Be energy spectrum, and has an important effect on the recoil corrections and $β$ decay for the $A = 8$ systems. This state and an associated $0^{+}$ state are notoriously difficult to model due to their cluster structure and collective correlations, but become feasible for calculations in the ab initio symmetry-adapted no-core shell-model framework.
Comments:
Accepted version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2107.10389 [pdf]
PRL(2022)·44 citations
03
[Submitted on 22 Jul 2021]
Relativistic Brueckner-Hartree-Fock Theory in Infinite Nuclear Matter
Peter Ring · Sibo Wang · Qiang Zhao · Jie Meng
On the way of a microscopic derivation of covariant density functionals, the first complete solution of the relativistic Brueckner-Hartree-Fock (RBHF) equations is presented for symmetric nuclear matter. In most of the earlier investigations, the $G$ -matrix is calculated only in the space of positive energy solutions. On the other side, for the solution of the relativistic Hartree-Fock (RHF) equations, also the elements of this matrix connecting positive and negative energy solutions are required. So far, in the literature, these matrix elements are derived in various approximations. We discuss solutions of the Thompson equation for the full Dirac space and compare the resulting equation of state with those of earlier attempts in this direction.
Comments:
8 pages, 2 figures, to appear in HINP 6th International Workshop; Perspectives on Nuclear Physics: from Fundamentals to Applications (online, May 14-16, 2021). arXiv admin note: text overlap with arXiv:2103.12960
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2107.10580 [pdf]
EPJ Web Conf.(2021)·2 citations
04
[Submitted on 22 Jul 2021]
Least-squares fitting applied to nuclear mass formulas. Resolution by the Gauss-Seidel method
Benyoucef Mohammed-Azizi · Hadj Mouloudj
A numerical method optimizing the coefficients of the semi empirical mass formula or those of similar mass formulas is presented. The optimization is based on the least-squares adjustments method and leads to the resolution of a linear system which is solved by iterations according to the Gauss-Seidel scheme. The steps of the algorithm are given in detail. In practice the method is very simple to implement and is able to treat large data in a very fast way. In fact, although this method has been illustrated here by specific examples, it can be applied without difficulty to any experimental or statistical data of the same type, i.e. those leading to linear system characterized by symmetric and positive-definite matrices.
Comments:
9 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2107.10581 [pdf]
Int.J.Mod.Phys.C(2022)·0 citations
05
[Submitted on 22 Jul 2021]
A formalism to assess the accuracy of nuclear-structure weak interaction effects in precision $β$ -decay studies
Ayala Glick-Magid🇮🇱 · Doron Gazit🇮🇱
Multiple high precision $β$ -decay measurements are being carried out these days on various nuclei, in search of beyond the Standard Model signatures. These measurements necessitate accurate standard model theoretical predictions to be compared with. Motivated by the experimental surge, we present a formalism for such a calculation of $β$ -decay observables, with controlled accuracy, based on a perturbative analysis of the theoretical observables related to the phenomena, including high order nuclear recoil and shape corrections. The accuracy of the corrections is analyzed by identifying a hierarchy of small parameters, related to the low momentum transfer characterizing $β$ -decays. Furthermore, we show that the sub-percent uncertainties, targeted by on-going and planned experiments, entail an accuracy of the order of 10\% for the solution of the nuclear many body problem, which is well within the reach of modern nuclear theory for light to medium mass nuclei.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2107.10588 [pdf]
J.Phys.G(2022)·19 citations
06
[Submitted on 22 Jul 2021]
Electroweak Currents from Chiral Effective Field Theory
Alessandro Baroni🇺🇸 · Garrett B. King🇺🇸 · Saori Pastore🇺🇸
Since the pioneering work of Weinberg, Chiral Effective Field Theory ( $χ$ EFT) has been widely and successfully utilized in nuclear physics to study many-nucleon interactions and associated electroweak currents. Nuclear $χ$ EFT has now developed into an intense field of research and is applied to study light to medium mass nuclei. In this contribution, we focus on the development of electroweak currents from $χ$ EFT and present applications to selected nuclear electroweak observables.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2107.10721 [pdf]
Few Body Syst.(2021)·14 citations
07
[Submitted on 21 Jul 2021] (cross-list from hep-lat)
Gluon gravitational structure of hadrons of different spin
Dimitra A. Pefkou🇺🇸 · Daniel C. Hackett🇺🇸 · Phiala E. Shanahan🇺🇸
The gravitational form factors (GFFs) of hadrons encode the matrix elements of the energy momentum tensor of QCD. These quantities describe how energy, spin, and various mechanical properties of hadrons are carried by their quark and gluon constituents. We present the gluon GFFs of the pion, nucleon, $ρ$ meson, and $Δ$ baryon as functions of the squared momentum transfer $t$ in the region $0 \leq - t < 2 GeV^{2}$ , as determined in a lattice QCD study with pion mass $m_{π} = 450 (5) MeV$ . By fitting the extracted GFFs using multipole and z-parameter expansion functional forms, we extract various gluon contributions to the energy, pressure, and shear force distributions of the hadrons in the 3D and 2D Breit frames as well as in the infinite momentum frame. We also obtain estimates for the corresponding gluon mechanical and mass radii, as well as the forward-limit gluon contributions to the momentum fraction and angular momentum of the hadrons.
Comments:
41 pages, 19 figures, as published in PRD. v2,v3: updated citations
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2107.10368 [pdf]
PRD(2022)·117 citations
08
[Submitted on 22 Jul 2021] (cross-list from hep-ph)
Electromagnetic form factors of $Λ$ hyperon in the vector meson dominance model and a possible explanation of the near-threshold enhancement of the $e^{+} e^{-} \to Λ Λ ˉ$ reaction
Zhong-Yi Li🇨🇳 · An-Xin Dai🇨🇳 · Ju-Jun Xie🇨🇳
The near-threshold $e^{+} e^{-} \to Λ Λ ˉ$ reaction is studied with the assumption that the production mechanism is due to a near- $Λ Λ ˉ$ -threshold bound state. The cross section of $e^{+} e^{-} \to Λ Λ ˉ$ reaction is parametrized in terms of the electromagnetic form factors of $Λ$ hyperon, which are obtained with the vector meson dominance model. It is shown that the contribution to the $e^{+} e^{-} \to Λ Λ ˉ$ reaction from a new narrow state with quantum numbers $J^{P C} = 1^{--}$ is dominant for energies very close to threshold. The mass of this new state is around 2231 MeV, which is very close to the mass threshold of $Λ Λ ˉ$ , while its width is just a few MeV. This gives a possible solution to the problem that all previous calculations seriously underestimate the near-threshold total cross section of the $e^{+} e^{-} \to Λ Λ ˉ$ reaction. We also note that the near-threshold enhancement can be also reproduced by including these well established vector resonances $ω (1420)$ , $ω (1650)$ , $ϕ (1680)$ , or $ϕ (2170)$ with a Flatt $e ˊ$ form for their total decay width, and a strong coupling to the $Λ Λ ˉ$ channel.
Comments:
Published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2107.10499 [pdf]
Chin.Phys.Lett.(2022)·27 citations
09
[Submitted on 22 Jul 2021] (cross-list from hep-ph)
The $K ˉ N$ interaction in higher partial waves
Albert Feijoo🇨🇿 · Daniel Gazda🇨🇿 · Volodymyr Magas🇪🇸 · Angels Ramos🇪🇸
We present a chiral $K ˉ N$ interaction model that has been developed and optimized in order to account for the experimental data of inelastic $K ˉ N$ reaction channels that open at higher energies. In particular, we study the effect of the higher partial waves which originate directly from the chiral Lagrangian, as they could supersede the role of high-spin resonances employed in earlier phenomenological models to describe meson-baryon cross sections in the 2~GeV region. We present a detailed derivation of the partial wave amplitudes that emerge from the chiral SU(3) meson-baryon Lagrangian up to the d-waves and next-to-leading order in the chiral expansion. We implement a nonperturbative unitarization in coupled channels and optimize the model parameters to a large pool of experimental data in the relevant energy range where these new contributions are expected to be important. The obtained results are encouraging. They indicate the ability of the chiral higher partial waves to extend the description of the scattering data to higher energies and to account for structures in the reaction cross sections that cannot be accommodated by theoretical models limited to the s-waves.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2107.10560 [pdf]
Symmetry(2021)·13 citations
10
[Submitted on 22 Jul 2021] (cross-list from hep-ph)
Self-consistent $O (4)$ model spectral functions from analytically continued FRG flows
Christopher Jung🇩🇪 · Jan-Hendrik Otto🇩🇪 · Ralf-Arno Tripolt🇦🇹 · Lorenz von Smekal🇩🇪
In this paper we explore practicable ways for self-consistent calculations of spectral functions from analytically continued functional renormalization group (aFRG) flow equations. As a particularly straightforward one we propose to include parametrizations of self-energies based on explicit analytic one-loop expressions. To exemplify this scheme we calculate the spectral functions of pion and sigma meson of the $O (4)$ model at vanishing temperature in the broken phase. Comparing the results with those from previous aFRG calculations, we explicitly demonstrate how self-consistency at all momenta fixes the tight relation between particle masses and decay thresholds. In addition, the two-point functions from our new semi-analytic FRG scheme have the desired domain of holomorphy built in and can readily be studied in the entire cut-complex frequency plane, on physical as well as other Riemann sheets. This is very illustrative and allows, for example, to trace the flow of the resonance pole of the sigma meson across an unphysical sheet. In order to assess the limitations due to the underlying one-loop structure, we also introduce a fully self-consistent numerical scheme based on spectral representations with scale-dependent spectral functions. The most notable improvement of this numerically involved calculation is that it describes the three-particle resonance decay of an off-shell pion, $π^{*} \to σ π \to 3 π$ . Apart from this further conceptual improvement, overall agreement with the results from the considerably simpler semi-analytic one-loop scheme is very encouraging, however. The latter can therefore provide a sound and practicable basis for self-consistent calculations of spectral functions in more realistic effective theories for warm and dense matter.
Comments:
21 pages, 16 figures v2: minor changes, agrees with published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2107.10748 [pdf]
PRD(2021)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE