Nuclear Theory·nucl-th
10 papers—6 primary·4 cross-listed
The effect of the pion propagator on the -decay of neutron is investigated to account for the ratio of the axial-vector to the vector part by including the pole term. A suggestion is made that the sign and the size of the vertex correction is appropriate to improve the discrepancy between the result of the model hamiltonian and the experiment.
S. Amano · Y. Aritomo · M. Ohta
The capture cross section, the fusion cross section, and the quasi-fission yield producing symmetric fragments () in the Ca+U reaction are analyzed by the multidimensional Langevin equation taking account of the surface friction effect. From the experimental data, the strength of the tangential friction has been determined. It is presented that tangential friction increases in proportional to the power of the relative velocity of the projectile and the target.
In this study, my main goal is to examine the nuclear matter properties across a wide range of conditions, such as temperature, density, asymmetry, pressure, and magnetic field. Understanding the effect of these factors on nuclear matter is essential, given their relevance in various phenomena such as heavy-ion collisions, neutron stars, and supernovae. However, due to the absence of a fundamental nuclear theory, we must rely on models to describe the nuclear matter. Predicted properties like neutron star mass-radius relationships, tidal deformability, structure, critical points in the nuclear matter phase diagram etc. depend on the chosen model. This dependence arises because key parameters characterizing any nuclear model or equation of state (EoS) are not precisely known. Therefore, it is crucial to investigate how nuclear matter properties behave under various conditions and in relation to different EoS parameters. To accomplish this, I have examined three distinct forms of nuclear matter: infinite nuclear matter, finite nuclei, and neutron stars, using the effective relativistic mean field model (E-RMF).
Solutions of shock waves in anisotropic relativistic hydrodynamics in the absence of refraction of the flow passing through the shock wave are considered. The existence of a critical value of the anisotropy parameter is shown. This value is the upper limit below which an adequate description of shock waves is possible. Shock wave solutions also provide a mechanism for system isotropization.
Ling-Jun Guo · Jia-Ying Xiong · Yao Ma · Yong-Liang Ma
Due to its powerful capability and high efficiency in big data analysis, machine learning has been applied in various fields. We construct a neural network platform to constrain the behaviors of the equation of state of nuclear matter with respect to the properties of nuclear matter at saturation density and the properties of neutron stars. It is found that the neural network is able to give reasonable predictions of parameter space and provide new hints into the constraints of hadron interactions. As a specific example, we take the relativistic mean field approximation in a widely accepted Walecka-type model to illustrate the feasibility and efficiency of the platform. The results show that the neural network can indeed estimate the parameters of the model at a certain precision such that both the properties of nuclear matter around saturation density and global properties of neutron stars can be saturated. The optimization of the present modularly designed neural network and extension to other effective models are straightforward.
Manjia Chen · Dawei Guan · Chongji Jiang · Junchen Pei
The speed of sound is a novel probe of equation of state and phase transitions in dense cores of neutron stars. Recently nuclear experiments extracted a surprising thick neutron skin of Pb, causing tensions to reproduce the tidal deformability in gravitational-wave observations. This work finds that exotic structures in the speed of sound with a small softening slope followed by a steep-rising peak are required to reconcile the thick neutron skin of Pb with astronomical observations of neutron stars. Furthermore, the peak of speed of sound is narrowly constrained around two times the nuclear saturation density with the thick neutron skin. Consequently early and strong first-order phase transitions are comparatively more favorable.
Understanding the interactions between elementary particles and mapping out the internal structure of the hadrons are of fundamental importance in high energy nuclear and particle physics. This thesis concentrates on the strong interaction, described by Quantum Chromodynamics (QCD). We introduce a novel concept called "polarized jet fragmentation functions" and develop the associated theory framework known as QCD factorization which allows us to utilize jet substructure to probe spin dynamics of hadrons, especially nucleon's three-dimensional imaging. Furthermore, non-perturbative QCD studies, particularly of the QCD phase diagram, are important for understanding the properties of hadrons. The development of quantum computing and simulators can potentially improve the accuracy of finite-temperature simulations and allow researchers to explore extreme temperatures and densities in more detail. In this thesis, I present my work in two aspects of QCD studies: (1) investigating the nucleon structure using polarized jet fragmentation functions and (2) illustrating how to apply quantum computing techniques for studying phase diagram of a low energy QCD model. The first category investigates phenomena such as hadron production inside jets, spin asymmetries, etc., providing valuable insight into the behavior of quarks and gluons in hadrons. The second category provides potential applications of quantum computing in QCD and explores the non-perturbative nature of QCD.
A. V. Danilina🇷🇺 · N. V. Nikitin🇷🇺
We present first theoretical predictions for various observables related to the decay within the framework of the Standard Model. Our study encompasses the branching ratios, differential distributions, and forward-backward leptonic asymmetries. To obtain these predictions, we account for several contributions: resonance contribution from and significant contribution ; contributions from four charmonium resonances: , , , and ; additional contributions from the "tails" of and resonances; non-resonant contributions arising from virtual photon emission by a -quark of meson, bremsstrahlung, and weak annihilation. In our calculations we employ the model of vector meson dominance (VMD) to assess the resonance contributions accurately. We provide the predictions for the branching ratio of the decay both with and without the resonant contribution from .
We perform calculations of the energy shift of the nuclear clock transition frequency Th as a function of the number of electrons in Th ion. We demonstrate that the dependence of the nuclear frequency on electron configuration is significant. E.g., removing one electron from the atom leads to relative shift of the nuclear frequency , which is twelve orders of magnitude larger than expected relative uncertainty of the nuclear clock transition frequency (). This leads to difference of the nuclear clock frequencies in Th~IV, Th~III, Th~II and Th~I. The relative change of the nuclear frequency between neutral Th and its bare nucleus is 1\%. We also calculate the field shift constants for isotopic and isomeric shifts of atomic electron transitions in Th ions.
Hungchong Kim🇰🇷 · K.S.Kim🇰🇷
In this work, we compare the tetraquark mixing model and meson molecules in describing the two physical nonets in the channel, the light nonet [, , , ] and the heavy nonet [, , , ]. In particular, we focus on whether successful aspects of the tetraquark mixing model that apply to all members of each nonet can be reproduced from a model of meson molecules. By combining two mesons in the lowest-lying pseudoscalar nonet, we construct SU(3) molecular nonets that can be tested for the two physical nonets. This molecular approach can make two flavor nonets just as the tetraquark mixing model but this model has some difficulties in describing the universal features of the two nonets %Because of this, this molecular model cannot reproduce successful aspects of the tetraquark mixing model, such as mass splitting between the two nonets, and enhancement or suppression of the coupling strengths of the two nonets into two pseudoscalar mesons. We also compare the fall-apart modes of the tetraquark mixing model and the two-meson modes from the molecular model. A clear distinction can be seen by the two-pion modes in the isovector resonances. The two-pion modes appear in the molecular model, but not in the tetraquark mixing model. The absence of the two-pion modes is supported by the experimental decay modes of the isovector resonances.
first authorsco-authorsvia INSPIRE