Nuclear Theory·nucl-th

Friday·September 15, 2023

10 papers—2 primary·8 cross-listed

01
At the borderline of shape coexistence: Mo and Ru
E. Maya-Barbecho · S. Baid · J.M. Arias · J.E. García-Ramos
Background Even-even isotopes of Mo ( $Z = 42$ ) and Ru ( $Z = 44$ ) are nuclei close to the subshell closure at $Z = 40$ , where shape coexistence plays a significant role. As a result, their spectroscopic properties are expected to resemble those of Sr ( $Z = 38$ ) and Zr ( $Z = 40$ ). Exploring the evolution of these properties as they move away from the subshell closure is of great interest. Purpose The purpose of this study is to reproduce the spectroscopic properties of even-even $_{961 - 42}^{96 - 110}$ Mo and $_{961 - 44}^{98 - 114}$ Ru isotopes and to determine the influence of shape coexistence. Method We have employed the interacting boson model with configuration mixing as the framework to calculate all the observables for Mo and Ru isotopes. We have considered two types of configurations: 0-particle-0-hole and 2-particle-2-hole excitations. The model parameters have been determined using a least-squares fitting to match the excitation energies and the $B (E 2)$ transition rates. Results We have obtained the excitation energies, $B (E 2)$ values, two-neutron separation energies, nuclear radii, and isotope shifts for the entire chain of isotopes. Our theoretical results have shown good agreement with experimental data. Furthermore, we have conducted a detailed analysis of the wave functions and obtained the mean-field energy surfaces and the nuclear deformation parameter, $β$ , for all considered isotopes. Conclusions Our findings reveal that shape coexistence plays a significant role in Mo isotopes, with the crossing of intruder and regular configurations occurring at neutron number $60$ ( $A = 102$ ), which induces a quantum phase transition. In contrast, in Ru isotopes, the intruder states have minimal influence, remaining at higher energies. However, at neutron number $60$ , also a quantum phase transition occurs in Ru isotopes.
nucl-thnucl-exPRC(2023)·10 citations
02
Shell-model study for allowed and forbidden $β^{-}$ decay properties in the mass region "south" of $^{208}$ Pb
Shweta Sharma · Praveen C. Srivastava · Anil Kumar · Toshio Suzuki · Cenxi Yuan · Noritaka Shimizu
The large-scale shell-model calculations have been performed for the neutron-rich nuclei in the south region of $^{208}$ Pb in the nuclear chart. The $β$ -decay properties, such as the $lo g f t$ , average shape factor values, half-lives, and partial decay rates are calculated for these neutron-rich nuclei using recent effective interaction for the $^{208}$ Pb region. These calculations have been performed without truncation in a particular model space for nuclei $N \leq 126$ ; additionally, particle-hole excitations are included in the case of core-breaking nuclei ( $Z \leq 82, N > 126$ ). An extensive comparison with the experimental data has been made, and spin parities of several states have been proposed.
nucl-thnucl-exPRC(2024)·6 citations
03
Field Theory of the Fermi Function
Richard J. Hill🇺🇸 · Ryan Plestid🇺🇸
The Fermi function $F (Z, E)$ accounts for QED corrections to beta decays that are enhanced at either small electron velocity $β$ or large nuclear charge $Z$ . For precision applications, the Fermi function must be combined with other radiative corrections and with scale- and scheme-dependent hadronic matrix elements. We formulate the Fermi function as a field theory object and present a new factorization formula for QED radiative corrections to beta decays. We provide new results for the anomalous dimension of the corresponding effective operator complete through three loops, and resum perturbative logarithms and $π$ -enhancements with renormalization group methods. Our results are important for tests of fundamental physics with precision beta decay and related processes.
↳ hep-phhep-thnucl-exnucl-thPRL(2024)·32 citations
04
Signatures for tetraquark mixing from partial decay widths of the two light-meson nonets
Hungchong Kim🇰🇷 · K.S.Kim🇰🇷
In this talk, we present successful aspects of the tetraquark mixing model for the two light-meson nonets in the $J^{P C} = 0^{++}$ channel, the light nonet [ $a_{0} (980)$ , $K_{0}^{*} (700)$ , $f_{0} (500)$ , $f_{0} (980)$ ] and the heavy nonet [ $a_{0} (1450)$ , $K_{0}^{*} (1430)$ , $f_{0} (1370)$ , $f_{0} (1500)$ ]. In particular, we focus on how their experimental partial decay widths extracted from Particle Data Group (PDG) can support this mixing model. Currently, the experimental data exhibit an unnatural tendency that partial widths of the light nonet are consistently larger than those of the heavy nonet. This unnatural tendency can be explained if the coupling into two pseudoscalar mesons is enhanced in the light nonet and suppressed in the heavy nonet as predicted by the tetraquark mixing model. Therefore, this could be strong evidence to support for the tetraquark mixing model.
↳ hep-phhep-exnucl-thEPJ Web Conf.(2024)·5 citations
05
Solving Einstein equations using deep learning
Zhi-Han Li · Chen-Qi Li · Long-Gang Pang
Einstein field equations are notoriously challenging to solve due to their complex mathematical form, with few analytical solutions available in the absence of highly symmetric systems or ideal matter distribution. However, accurate solutions are crucial, particularly in systems with strong gravitational field such as black holes or neutron stars. In this work, we use neural networks and auto differentiation to solve the Einstein field equations numerically inspired by the idea of physics-informed neural networks (PINNs). By utilizing these techniques, we successfully obtain the Schwarzschild metric and the charged Schwarzschild metric given the energy-momentum tensor of matter. This innovative method could open up a different way for solving space-time coupled Einstein field equations and become an integral part of numerical relativity.
↳ gr-qcnucl-thphysics.comp-ph8 citations
06
Magnetic flutter effect on validated edge turbulence simulations
Kaiyu Zhang · Wladimir Zholobenko · Andreas Stegmeir · Konrad Eder · Frank Jenko
Small magnetic fluctuations ( $B_{1} / B_{0} \sim 1 0^{- 4}$ ) are intrinsically present in a magnetic confinement plasma due to turbulent currents. While the perpendicular transport of particles and heat is typically dominated by fluctuations of the electric field, the parallel stream of plasma is affected by fluttering magnetic field lines. In particular through electrons, this indirectly impacts the turbulence dynamics. Even in low beta conditions, we find that $E \times B$ turbulent transport can be reduced by more than a factor 2 when magnetic flutter is included in our validated edge turbulence simulations of L-mode ASDEX Upgrade. The primary reason for this is the stabilization of drift-Alfvén-waves, which reduces the phase shifts of density and temperature fluctuations with respect to potential fluctuations. This stabilization can be qualitatively explained by linear analytical theory, and appreciably reinforced by the flutter nonlinearity. As a secondary effect, the steeper temperature gradients and thus higher $η_{i}$ increase the impact of the ion-temperature-gradient mode on overall turbulent transport. With increasing beta, the stabilizing effect on $E \times B$ turbulence increases, balancing the destabilization by induction, until direct electromagnetic perpendicular transport is triggered. We conclude that including flutter is crucial for predictive edge turbulence simulations.
↳ physics.plasm-phnucl-thphysics.comp-phNucl.Fusion(2024)·0 citations
07
Recent Progress in Low Energy Neutrino Scattering Physics and Its Implications for the Standard and Beyond the Standard Model Physics
V. Pandey🇺🇸
Neutrinos continue to provide a testing ground for the structure of the standard model of particle physics as well as hints towards the physics beyond the standard model. Neutrinos of energies spanning over several orders of magnitude, originating in many terrestrial and astrophysical processes, have been detected via various decay and interaction mechanisms. At MeV scales, there has been one elusive process, until a few years ago, known as coherent elastic neutrino-nucleus scattering (CEvNS) that was theoretically predicted over five decades ago but was never observed experimentally. The recent experimental observation of the CEvNS process by the COHERENT collaboration at a stopped pion neutrino source has inspired physicists across many subfields. This has vital implications for nuclear physics, high-energy physics, astrophysics, and beyond. CEvNS, being a low-energy process, provides a natural window to study light, weakly-coupled, new physics in the neutrino sector. In this review, we intend to provide the current status of low energy neutrino scattering physics and its implications for the standard and beyond the standard model physics. We discuss the general formalism of calculating the tree-level CEvNS cross section and present estimated theoretical uncertainties on the CEvNS cross section stemming from different sources. We also discuss the inelastic scattering of tens of MeV neutrinos that have implications for supernova detection in future neutrino experiments. We discuss how the CEvNS experiments can be used as a testing ground for the Standard Model (SM) weak physics as well as in searching for the Beyond the Standard Model (BSM) physics signals. Any deviation from the SM predicted event rate either with a change in the total event rate or with a change in the shape of the recoil spectrum, could indicate new contributions to the interaction cross-section.
↳ hep-phhep-exnucl-exnucl-thPPNP(2024)·23 citations
08
Method for measuring the charge radii of charged hyperons from the time-like region
Yong-Hui Lin🇩🇪 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪
We propose a novel method for measuring the charge radii of charged stable hadrons, with which the first measurement of the charge radii of the $Σ^{+}$ and the $Ξ^{-}$ is foreseen. The method explores the facts that the Dalitz decay $ψ (2 S) \to Y Y ˉ e^{+} e^{-}$ contains the hyperon form factors and the lowest measurable four-momentum transfer squared can be as low as $\sim 4 m_{e}^{2} = 1.05 \times 1 0^{- 6} Ge V^{2}$ in the time-like region. We identify a kinematic region where the hyperon form factors are essential and propose a method for subtracting the background from the data. It is estimated that the hyperon charge radii can be measured to a precision of about {0.2~fm} with the BES\Rom{3} experiment and one order of magnitude better at the future Super $τ$ -Charm Facility. Moreover, the same method can be used to measure the charge radius of the proton, which provides an independent cross-check on the extraction of proton radius from elastic $e p$ scattering or leptonic hydrogen spectroscopy.
↳ hep-phhep-exnucl-exnucl-thPLB(2024)·3 citations
09
Covariant form factors for spin-1 particles
J. P. B. C. de Melo (Laboratório de Física Teórica e Computacional - LFTC, Universidade Cruzeiro do Sul and Universidade Cidade de São Paulo (UNICID), São Paulo, Brazil)🇧🇷
Spin-1 particles, is a fundamental bound state for the two quarks, and play a crucial role in elucidating the electromagnetic properties within the realm of hadronic physics. Their intrinsic relativistic nature mandates a quantum field theory (QFT) framework for a comprehensive analysis. In this investigation, we employ both the instant form of QFT and light-front quantum field theory (LFQFT) as our theoretical tools. While conventional LFQFT approaches predominantly focus on the plus component of the electromagnetic current to extract the properties of spin-1 vector particles, our study extends this analysis by systematically incorporating the minus component as well. Our findings demonstrate that achieving a rigorous equivalence between these distinct current components necessitates the inclusion of nonvalence terms within the electromagnetic current operator. This crucial inclusion serves to restore manifest covariance and ensures a robust consistency with the results independently derived from the more conventional instant form of quantum field theory.
↳ hep-phhep-thnucl-thPRD(2026)·1 citation
10
Pseudoscalar current and covariance with the light-front approach
Jurandi Leãoo (Laboratório de Física Teórica e Computacional-LFTC, Universidade Cruzeiro do Sul / Universidade Cidade de São Paulo, and Instituto Federal de São Paulo, Avenida Bahia, Caraguatatuba, 11665-071 São Paulo, Brazil)🇧🇷 · J. P. B. C. de Melo (Laboratório de Física Teórica e Computacional-LFTC, Universidade Cruzeiro do Sul / Universidade Cidade de São Paulo, 015060-000, São Paulo, SP, Brazil)🇧🇷
Quantum Field Theory (QFT) is used to describe the physics of particles in terms of their fundamental constituents. The Light-Front Field Theory~(LFFT), introduced by Paul Dirac in 1949, is an alternative approach to solve some of the problems that arise in quantum field theory. The LFFT is similar to the Equal Time Quantum Field Theory~(EQT), however, some particularities are not, such as the loss of covariance in the light-front. Pion electromagnetic form factor is studied in this work at lower and higher momentum transfer regions to explore the constituent quark models and the differences among these and other models. The electromagnetic current is calculated with both the ``plus'' and ``minus'' components in the light-front approach. The results are compared with other models, as well as with experimental data.
↳ hep-phnucl-thRev.Mex.Fis.(2023)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE