Two different isospin splittings of nucleon effective mass in nuclear medium as the form of mn*>mp* and mn*<mp* have been implemented in an isospin and momentum dependent transport model.Their impacts on the iso...Two different isospin splittings of nucleon effective mass in nuclear medium as the form of mn*>mp* and mn*<mp* have been implemented in an isospin and momentum dependent transport model.Their impacts on the isospin emission in heavy-ion collisions is investigated thoroughly.It is found that the yield ratios of energetic neutrons to protons squeezed out during the compression stage of two colliding nuclides are sensitive to the isospin splitting.The elliptic flows of free nucleons are also to be promising observables for extracting the nucleon effective mass splitting.Further experimental measurements are being expected,in particular at the CSR-CEE platform in Lanzhou.Several observables are proposed for constraining the density dependence of symmetry energy,such as the transverse flow difference of neutrons and protons,double ratios of n/p and π-/π+,excitation functions of π-/π+ and K0/K+.展开更多
Understanding hadron structure within the framework of QCD is an extremely challenging problem. Our purpose here is to explain the model-independent consequences of the approximated chiral symmetry of QCD for two famo...Understanding hadron structure within the framework of QCD is an extremely challenging problem. Our purpose here is to explain the model-independent consequences of the approximated chiral symmetry of QCD for two famous results concerning the quark structure of the nucleon. We show that both the apparent success of the constituent quark model in reproducing the ratio of proton to neutron magnetic moments and the apparent success of the Foldy term in reproducing the observed charge radius of the neutron are coincidental. That is, a relatively small change of the current quark mass would spoil both results.展开更多
In the hydrogen molecular ion, the kinetic energy lowering of the electron is associated with its delocalization due to electron exchange between the two protons of the molecule. This decrease in the kinetic energy of...In the hydrogen molecular ion, the kinetic energy lowering of the electron is associated with its delocalization due to electron exchange between the two protons of the molecule. This decrease in the kinetic energy of the exchanged electron in the hydrogen molecular ion and the decrease in the dynamical mass of the two exchanged pions in the nucleon-nucleon interaction are at the origin of the attraction mechanism in the molecular covalent bonding and in the nuclear interaction. Based on this unitary approach of the attraction mechanism, the formulas of molecular potential and central nucleon-nucleon potential were derived. The decrease in the mass of the exchanged pions in the nucleon-nucleon bound state, actually means the decrease in the mass of the nucleons. This nucleon mass decrease could be a manifestation of the partial chiral symmetry restoration in nuclear matter.展开更多
A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed.Based on the new code,four commonly used parameter sets,SLy4,SkI2,SkM*and Gs are adopted in the ...A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed.Based on the new code,four commonly used parameter sets,SLy4,SkI2,SkM*and Gs are adopted in the improved quantum molecular dynamics model and the isospin sensitive observables,namely isospin transport ratios,single and double ratios of the yields of neutrons and protons are investigated.The isospin transport ratios are strongly sensitive to the slope of symmetry energy,and are not very sensitive to the nucleon effective mass splitting.On the other hand,the high energy neutrons and protons yields ratios from reactions at different incident energies provide a good observable to the momentum dependence of nucleon effective mass splitting.By comparing our calculations with the data,we find that the constrained L value(the slope of density dependence of symmetry energy) is about ~46 MeV when the Skyrme type interaction is considered in transport models,and the isospin diffusion data prefer to mn*>mp*,but it is not a strong constraint with deep χ2minimum.展开更多
A formula is derived for the central nucleon-nucleon potential, based on an analysis of the physical origin of the nucleon-nucleon attraction by pion exchange. The decrease of the dynamical mass of the interaction fie...A formula is derived for the central nucleon-nucleon potential, based on an analysis of the physical origin of the nucleon-nucleon attraction by pion exchange. The decrease of the dynamical mass of the interaction field, exchanged pion in this case, is the principal mechanism responsible for the nuclear attraction in a similar way that the decrease of the kinetic energy of the exchange electron in the diatomic molecule is directly responsible for the covalent molecular attraction. The minimum value of this central nucleon-nucleon potential and the position of the minimum are similar with the values reported in literature for a potential calculated by lattice QCD, which shares the features of the phenomenological nucleon-nucleon potentials. The Schrodinger equation with this central nucleon-nucleon potential was solved numerically for different values of the pion mass. The binding energy increases with the decrease of the pion mass. For masses higher than the real pion mass the nucleon-nucleon system is unbound. We discuss on the two pion exchange and hard core repulsion. The minimum value of the potential for two pion exchange is comparable with the minimum value of the CD Bonn potential. For a hard core radius of 0.5 fm the binding energy is equal to the deuteron binding energy.展开更多
Nucleon properties and structure should be modified by short-range correlations(SRC)among nucleons.By analyzing SRC ratio data,we extract the mass of a nucleon in an SRC pair and the expected number of pn-SRC pairs in...Nucleon properties and structure should be modified by short-range correlations(SRC)among nucleons.By analyzing SRC ratio data,we extract the mass of a nucleon in an SRC pair and the expected number of pn-SRC pairs in deuterium,under the assumption that the SRC nucleon mass is universal for different nuclei.The nucleon mass of a two-nucleon SRC pair is m_(SRC)=852±18 MeV,and the number of pn-SRC pairs in deuterium is n^(d)_(SRC)=0.021±0.005.The mass deficit of the strongly overlapping nucleon can be explained by the trace anomaly contribution to the mass in QCD or alternatively by the vacuum energy in the MIT bag model.展开更多
From a Bayesian analysis of the electric dipole polarizability,the constrained energy of isovector giant dipole resonance,the peak energy of isocalar giant quadrupole resonance,and the constrained energy of isocalar g...From a Bayesian analysis of the electric dipole polarizability,the constrained energy of isovector giant dipole resonance,the peak energy of isocalar giant quadrupole resonance,and the constrained energy of isocalar gi-ant monopole resonance in 208Pb,we extract the isoscalar and isovector effective masses in nuclear matter at satura-tion density ρ0 as m^(*)_(s.0)/m=0.87^(+)_(-004) and m^(*)_(v.0)/m=0.78^(+006)_(-006),respectively,at 90%confdence level.The con-straints obtained on m^(*)_(d.0) and m^(*)_(v.0) lead to a positive isospin splitting of nucleon effective mass in asymmetric nuclear matter of isospin asymmetry σ at ρ0 as m^(*)_(n-p)/m=(0.20^(0.15)_(0.14)σ.In addition,the symmetry energy at the subsatura-tion density ρ^(*)=0.05 fm^(-3) is determined to be E_(sym)(ρ^(*))=16.7±1.3 MeV at 90%confidence level.展开更多
We have calculated the nucleon effective mass in symmetric nuclear matter within the framework of the Brueckner-Bethe-Goldstone (BBG) theory, which has been extended to include both the contributions from the ground...We have calculated the nucleon effective mass in symmetric nuclear matter within the framework of the Brueckner-Bethe-Goldstone (BBG) theory, which has been extended to include both the contributions from the ground-state correlation effect and the three-body force (TBF) rearrangement effect. The effective mass is predicted by including the ground-state correlation effect and the TBF rearrangement effect, and we discuss the momentum dependence and the density dependence of the effective mass. It is shown that the effect of ground state correlations plays an important role at low densities, while the TBF-induced rearrangement effect becomes predominant at high densities.展开更多
-The contributions of vacuum fluctuations to energy density in a weak momen-tum dependence of self-energy are calculated in Walecka model.After adjusting modelparameters and introducing momentum dependent form factors...-The contributions of vacuum fluctuations to energy density in a weak momen-tum dependence of self-energy are calculated in Walecka model.After adjusting modelparameters and introducing momentum dependent form factors at meson-nucleonvertices to reproduce the empirical nuclear matter saturation properties,Hartree-Fockresults including vacuum effects at low to moderate densities are similar to those in therelativistic Hartree approximation.展开更多
Based on a theory of extra dimensional confinement of quantum particles [E. R. Hedin, Physics Essays, 2012, 25(2): 177], a simple model of a nucleon nucleon (NN) central potential is derived which quantitatively ...Based on a theory of extra dimensional confinement of quantum particles [E. R. Hedin, Physics Essays, 2012, 25(2): 177], a simple model of a nucleon nucleon (NN) central potential is derived which quantitatively reproduces tile radial profile of other models, without adjusting any free pa- rameters. It is postulated that a higher-dimensional simple harmonic oscillator confining potential localizes particles into three-dimensional (3D) space, but allows for an ewmescent penetration of the particles into two higtmr spatial dimensions. Producing an effect identical with the relativistic quan- tum phenolnenon of zitterbewegung, the higher-dimensional oscillations of amplitude h(mc) call be alternatively viewed as a localized curvature of 3D space back and forth into the higher dimensions. The overall spatial curvature is proportional to the particle's extra-dimensional ground state wave function in tile higher-dimensional harmonic confining potential well. Minimizing the overlapping curvature (proportional to the energy) of two particles in proximity to each other, subject to the constraint that for the two particles to occupy the same spatial location one of them must be excited into the 1st excited state of the harmonic potential well, gives the desired NN potential. Specifying only the imcleon masses, the resulting potential well and repulsive core reproduces the radial profile of several published NN central potential models. In addition, the predicted height of the repulsive core, when used to estimate the maximum neutron star mass, matches well with the best estimates from relativistic theory incorporating standard nuclear matter equations of state. Nucleon spin, Coulomb interactions, and internal nucleon structure are not considered in the theory as presented in this article.展开更多
Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei.As a future high energy nuclear physics project,an Electron-ion collider in China(EicC)...Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei.As a future high energy nuclear physics project,an Electron-ion collider in China(EicC)has been proposed.It will be constructed based on an upgraded heavy-ion accelerator,High Intensity heavy-ion Accelerator Facility(HIAF)which is currently under construction,together with a new electron ring.The proposed collider will provide highly polarized electrons(with a po-larization of 80%)and protons(with a polarization of 70%)with variable center of mass energies from 15 to 20 GeV and the luminosity of(2–3)×1033 cm^(−2)·s^(−1).Polarized deuterons and Helium-3,as well as unpolarized ion beams from Carbon to Uranium,will be also available at the EicC.The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region,including 3D tomography of nucleon;the partonic structure of nuclei and the parton interaction with the nuclear environment;the exotic states,especially those with heavy flavor quark contents.In addition,issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC.In order to achieve the above-mentioned physics goals,a hermetical detector system will be constructed with cutting-edge technologies.This document is the result of collective contributions and valuable inputs from experts across the globe.The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States.The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China.展开更多
基金Supported by National Natural Science Foundation of China(NSFC) projects (No.11175218)the Advancement Society of Young Innovation of Chinese Academy of Sciences
文摘Two different isospin splittings of nucleon effective mass in nuclear medium as the form of mn*>mp* and mn*<mp* have been implemented in an isospin and momentum dependent transport model.Their impacts on the isospin emission in heavy-ion collisions is investigated thoroughly.It is found that the yield ratios of energetic neutrons to protons squeezed out during the compression stage of two colliding nuclides are sensitive to the isospin splitting.The elliptic flows of free nucleons are also to be promising observables for extracting the nucleon effective mass splitting.Further experimental measurements are being expected,in particular at the CSR-CEE platform in Lanzhou.Several observables are proposed for constraining the density dependence of symmetry energy,such as the transverse flow difference of neutrons and protons,double ratios of n/p and π-/π+,excitation functions of π-/π+ and K0/K+.
基金国家自然科学基金,Department of Science and Technology of Guangxi Province of China
文摘Understanding hadron structure within the framework of QCD is an extremely challenging problem. Our purpose here is to explain the model-independent consequences of the approximated chiral symmetry of QCD for two famous results concerning the quark structure of the nucleon. We show that both the apparent success of the constituent quark model in reproducing the ratio of proton to neutron magnetic moments and the apparent success of the Foldy term in reproducing the observed charge radius of the neutron are coincidental. That is, a relatively small change of the current quark mass would spoil both results.
文摘In the hydrogen molecular ion, the kinetic energy lowering of the electron is associated with its delocalization due to electron exchange between the two protons of the molecule. This decrease in the kinetic energy of the exchanged electron in the hydrogen molecular ion and the decrease in the dynamical mass of the two exchanged pions in the nucleon-nucleon interaction are at the origin of the attraction mechanism in the molecular covalent bonding and in the nuclear interaction. Based on this unitary approach of the attraction mechanism, the formulas of molecular potential and central nucleon-nucleon potential were derived. The decrease in the mass of the exchanged pions in the nucleon-nucleon bound state, actually means the decrease in the mass of the nucleons. This nucleon mass decrease could be a manifestation of the partial chiral symmetry restoration in nuclear matter.
基金Supported by National Natural Science Foundation of China(NSFC) projects (Nos.11075215,10875031,11005022,11005155 and 11275052)973 Program of China(No.2013CB834404)National Science Foundation(Grants No.PHY-0606007)
文摘A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed.Based on the new code,four commonly used parameter sets,SLy4,SkI2,SkM*and Gs are adopted in the improved quantum molecular dynamics model and the isospin sensitive observables,namely isospin transport ratios,single and double ratios of the yields of neutrons and protons are investigated.The isospin transport ratios are strongly sensitive to the slope of symmetry energy,and are not very sensitive to the nucleon effective mass splitting.On the other hand,the high energy neutrons and protons yields ratios from reactions at different incident energies provide a good observable to the momentum dependence of nucleon effective mass splitting.By comparing our calculations with the data,we find that the constrained L value(the slope of density dependence of symmetry energy) is about ~46 MeV when the Skyrme type interaction is considered in transport models,and the isospin diffusion data prefer to mn*>mp*,but it is not a strong constraint with deep χ2minimum.
文摘A formula is derived for the central nucleon-nucleon potential, based on an analysis of the physical origin of the nucleon-nucleon attraction by pion exchange. The decrease of the dynamical mass of the interaction field, exchanged pion in this case, is the principal mechanism responsible for the nuclear attraction in a similar way that the decrease of the kinetic energy of the exchange electron in the diatomic molecule is directly responsible for the covalent molecular attraction. The minimum value of this central nucleon-nucleon potential and the position of the minimum are similar with the values reported in literature for a potential calculated by lattice QCD, which shares the features of the phenomenological nucleon-nucleon potentials. The Schrodinger equation with this central nucleon-nucleon potential was solved numerically for different values of the pion mass. The binding energy increases with the decrease of the pion mass. For masses higher than the real pion mass the nucleon-nucleon system is unbound. We discuss on the two pion exchange and hard core repulsion. The minimum value of the potential for two pion exchange is comparable with the minimum value of the CD Bonn potential. For a hard core radius of 0.5 fm the binding energy is equal to the deuteron binding energy.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB34030301)the National Science Foundation China(11305007)。
文摘Nucleon properties and structure should be modified by short-range correlations(SRC)among nucleons.By analyzing SRC ratio data,we extract the mass of a nucleon in an SRC pair and the expected number of pn-SRC pairs in deuterium,under the assumption that the SRC nucleon mass is universal for different nuclei.The nucleon mass of a two-nucleon SRC pair is m_(SRC)=852±18 MeV,and the number of pn-SRC pairs in deuterium is n^(d)_(SRC)=0.021±0.005.The mass deficit of the strongly overlapping nucleon can be explained by the trace anomaly contribution to the mass in QCD or alternatively by the vacuum energy in the MIT bag model.
基金Supported in part by the National Natural Science Foundation of China(11905302,11625521)National SKA Program of China(2020SKA0120300)。
文摘From a Bayesian analysis of the electric dipole polarizability,the constrained energy of isovector giant dipole resonance,the peak energy of isocalar giant quadrupole resonance,and the constrained energy of isocalar gi-ant monopole resonance in 208Pb,we extract the isoscalar and isovector effective masses in nuclear matter at satura-tion density ρ0 as m^(*)_(s.0)/m=0.87^(+)_(-004) and m^(*)_(v.0)/m=0.78^(+006)_(-006),respectively,at 90%confdence level.The con-straints obtained on m^(*)_(d.0) and m^(*)_(v.0) lead to a positive isospin splitting of nucleon effective mass in asymmetric nuclear matter of isospin asymmetry σ at ρ0 as m^(*)_(n-p)/m=(0.20^(0.15)_(0.14)σ.In addition,the symmetry energy at the subsatura-tion density ρ^(*)=0.05 fm^(-3) is determined to be E_(sym)(ρ^(*))=16.7±1.3 MeV at 90%confidence level.
基金Supported by National Natural Science Foundation of China (11175219,10875151,10740420550)Major State Basic Research Developing Program of China (2007CB815004)+2 种基金Knowledge Innovation Project of Chinese Academy of Sciences (KJCX2-EW-N01)Chinese Academy of Sciences Visiting Professorship for Senior International Scientists (2009J2-26)CAS/SAFEA International Partnership Program for Creative Research Teams (CXTD-J2005-1)
文摘We have calculated the nucleon effective mass in symmetric nuclear matter within the framework of the Brueckner-Bethe-Goldstone (BBG) theory, which has been extended to include both the contributions from the ground-state correlation effect and the three-body force (TBF) rearrangement effect. The effective mass is predicted by including the ground-state correlation effect and the TBF rearrangement effect, and we discuss the momentum dependence and the density dependence of the effective mass. It is shown that the effect of ground state correlations plays an important role at low densities, while the TBF-induced rearrangement effect becomes predominant at high densities.
文摘-The contributions of vacuum fluctuations to energy density in a weak momen-tum dependence of self-energy are calculated in Walecka model.After adjusting modelparameters and introducing momentum dependent form factors at meson-nucleonvertices to reproduce the empirical nuclear matter saturation properties,Hartree-Fockresults including vacuum effects at low to moderate densities are similar to those in therelativistic Hartree approximation.
文摘Based on a theory of extra dimensional confinement of quantum particles [E. R. Hedin, Physics Essays, 2012, 25(2): 177], a simple model of a nucleon nucleon (NN) central potential is derived which quantitatively reproduces tile radial profile of other models, without adjusting any free pa- rameters. It is postulated that a higher-dimensional simple harmonic oscillator confining potential localizes particles into three-dimensional (3D) space, but allows for an ewmescent penetration of the particles into two higtmr spatial dimensions. Producing an effect identical with the relativistic quan- tum phenolnenon of zitterbewegung, the higher-dimensional oscillations of amplitude h(mc) call be alternatively viewed as a localized curvature of 3D space back and forth into the higher dimensions. The overall spatial curvature is proportional to the particle's extra-dimensional ground state wave function in tile higher-dimensional harmonic confining potential well. Minimizing the overlapping curvature (proportional to the energy) of two particles in proximity to each other, subject to the constraint that for the two particles to occupy the same spatial location one of them must be excited into the 1st excited state of the harmonic potential well, gives the desired NN potential. Specifying only the imcleon masses, the resulting potential well and repulsive core reproduces the radial profile of several published NN central potential models. In addition, the predicted height of the repulsive core, when used to estimate the maximum neutron star mass, matches well with the best estimates from relativistic theory incorporating standard nuclear matter equations of state. Nucleon spin, Coulomb interactions, and internal nucleon structure are not considered in the theory as presented in this article.
文摘Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei.As a future high energy nuclear physics project,an Electron-ion collider in China(EicC)has been proposed.It will be constructed based on an upgraded heavy-ion accelerator,High Intensity heavy-ion Accelerator Facility(HIAF)which is currently under construction,together with a new electron ring.The proposed collider will provide highly polarized electrons(with a po-larization of 80%)and protons(with a polarization of 70%)with variable center of mass energies from 15 to 20 GeV and the luminosity of(2–3)×1033 cm^(−2)·s^(−1).Polarized deuterons and Helium-3,as well as unpolarized ion beams from Carbon to Uranium,will be also available at the EicC.The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region,including 3D tomography of nucleon;the partonic structure of nuclei and the parton interaction with the nuclear environment;the exotic states,especially those with heavy flavor quark contents.In addition,issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC.In order to achieve the above-mentioned physics goals,a hermetical detector system will be constructed with cutting-edge technologies.This document is the result of collective contributions and valuable inputs from experts across the globe.The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States.The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China.