Directed flow(v_(1))of the hypernuclei ^(3)_(Λ)H and ^(4)_(Λ)H have been observed in mid-central Au+Au collisions at√^(s)NN=3 GeV at RHIC.This measurement opens up a new possibility for studying hyperon–nucleon(Y...Directed flow(v_(1))of the hypernuclei ^(3)_(Λ)H and ^(4)_(Λ)H have been observed in mid-central Au+Au collisions at√^(s)NN=3 GeV at RHIC.This measurement opens up a new possibility for studying hyperon–nucleon(Y–N)interaction under finite pressure.In addition,multi-strangeness hypernuclei provide a venue to probe hyperon–nucleon–nucleon(Y–N–N)and even hyperon–hyperon–nucleon(Y–Y–N)interactions.Hypernuclei are important for making connection between nuclear collisions and the equation of state which governs the inner structure of compact stars.展开更多
The effect of confined one-gluon-exchange potential and instanton-induced interaction potential in the singlet(1S0)and triplet(3S1)channels for nucleon–nucleon interaction has been investigated in the framework of th...The effect of confined one-gluon-exchange potential and instanton-induced interaction potential in the singlet(1S0)and triplet(3S1)channels for nucleon–nucleon interaction has been investigated in the framework of the relativistic harmonic model using the resonating group method in the adiabatic limit with the Born–Oppenheimer approximation.The contributions of the different components of the interaction potentials have been analyzed.展开更多
In this paper we consider nucleons as tori, rotating with a constant angular velocity around the straight line passing through their mass centre (geometric centre) and perpendicular to their plane of rotation. We theo...In this paper we consider nucleons as tori, rotating with a constant angular velocity around the straight line passing through their mass centre (geometric centre) and perpendicular to their plane of rotation. We theoretically determine the corresponding potential energy and the force of interaction between pairs of nucleons, using our precise analytical formulas for the electrostatic interaction between two spheres with arbitrary radii and charges, which we derive using experimentally obtained results for the radii and the masses of the nucleons. From the values for binding energy found through our method, it follows that nuclear forces are electromagnetic in nature. In terms of magnitude of the force of interaction between proton and neutron, we obtain that Coulomb's forces are short-range. Our toroid model explains the experimental results not only for binding energy, but also for the radius, magnetic moment and the spin of the nuclei of atoms.展开更多
Nucleus-nucleus potentials are determined in the framework of double folding model for M3Y-Reid and M3Y- Paris effective nucleon-nucleon (NN) interactions. Both zero-range and finite-range exchange parts of NN inter...Nucleus-nucleus potentials are determined in the framework of double folding model for M3Y-Reid and M3Y- Paris effective nucleon-nucleon (NN) interactions. Both zero-range and finite-range exchange parts of NN interactions are considered in the folding procedure. In this paper the spherical projectile-spherical target system 16O+^2008Pb is selected for calculating the barrier energies, fusion cross sections and barrier distributions with the density-independent and density-dependent NN interactions on the basis of M3Y-Reid and M3Y Paris NN interactions. The barrier energies become lower for Paris NN interactions in comparison with Reid NN interactions, and also for finite-range exchange part in comparison with zero-range exchange part. The density-dependent NN interactions give similar fusion cross sections and barrier distributions, and the density-independent NN interaction causes the barrier distribution moving to a higher position. However, the density-independent Reid NN interaction with zero-range exchange part gives the lowest fusion cross sections. We find that the calculated fusion cross sections and the barrier distributions are in agreement with the experimental data after renormalization of the nuclear potential due to coupled-channel effect.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
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
With the development of radioactive beam facilities,studies concerning the shell evolution of unstable nuclei have recently gained prominence.Intruder components,particularly s-wave intrusion,in the low-lying states o...With the development of radioactive beam facilities,studies concerning the shell evolution of unstable nuclei have recently gained prominence.Intruder components,particularly s-wave intrusion,in the low-lying states of light neutron-rich nuclei near N=8 are of importance in the study of shell evolution.The use of single-nucleon transfer reactions in inverse kinematics has been a sensitive tool that can be used to quantitatively investigate the single-particle orbital component of selectively populated states.The spin-parity,spectroscopic factor(or single-particle strength),and effective singleparticle energy can all be extracted from such reactions.These observables are often useful to explain the nature of shell evolution,and to constrain,check,and test the parameters used in nuclear structure models.In this article,the experimental studies of the intruder components in lowlying states of neutron-rich nuclei of He,Li,Be,B,and C isotopes using various single-nucleon transfer reactions are reviewed.The focus is laid on the precise determination of the intruder s-wave strength in low-lying states.展开更多
Magnetic excitations for Ba isotopes are discussed within the nucleon-pair shell model trmicated iti the SDsubspace. With the SD pair determined by a surface-δ interaction, M1 transitions for 1344Ba are well fitted. ...Magnetic excitations for Ba isotopes are discussed within the nucleon-pair shell model trmicated iti the SDsubspace. With the SD pair determined by a surface-δ interaction, M1 transitions for 1344Ba are well fitted. The M1 andM3 transitions for 132Ba and 130Ba are also predicted. It is shown that the statement, the collective magnetic propertiesarc due to the orbital motion of nucleons, is approximately valid.展开更多
Using the most recent phase shift data for pp, nn, and np elastic scattering for different states (l=0.1....)in the energy range of 1 MeV to 350 MeV, the charge dependeney of the strong muclear force, is investigated....Using the most recent phase shift data for pp, nn, and np elastic scattering for different states (l=0.1....)in the energy range of 1 MeV to 350 MeV, the charge dependeney of the strong muclear force, is investigated. Our results indicate that although the charge independency holds in most of the energy range, such charge independency is broken in the particular energy range of 120 MeV to 200 MeV for all partial wave states considered here.展开更多
We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetricnuclear matter at various densities,using the Brueckner-Hartree-Fock approximation scheme with the Argonne V_(14)pote...We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetricnuclear matter at various densities,using the Brueckner-Hartree-Fock approximation scheme with the Argonne V_(14)potential including the contribution of microscopic three-body force.We investigate separately the effects of three-bodyforce on the effective mass and on the scattering amplitude.In the present calculation,the rearrangement contributionof three-body force is considered,which will reduce the neutron and proton effective mass,and depress the amplitudeof cross section.The effect of three body force is shown to be repulsive,especially in high densities and large momenta,which will suppress the cross section markedly.展开更多
Probing in-medium nucleon-nucleon (NN) cross section σ1/NN(α) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum-de...Probing in-medium nucleon-nucleon (NN) cross section σ1/NN(α) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum-dependent interaction (IMDI(T)). It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping R on the in-medium NN cross section α1/NN(α) in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of σ1/NN(α) in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R's in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of σ1/NN(α) because of adding a new judgement.展开更多
A set of new global phenomenological optical model potential parameters has been obtained in the mass range of target nuclei 220≤A≤260 with incident energies below 300 MeV, by simultaneously fitting the experimental...A set of new global phenomenological optical model potential parameters has been obtained in the mass range of target nuclei 220≤A≤260 with incident energies below 300 MeV, by simultaneously fitting the experimental data of 232Th and 23Su, and these potential parameters are analyzed and used to calculate the reaction cross sections, energy spectra and double differ- ential cross sections for p+232Th reaction. Comparison of calculated results using these potential parameters with available experimental data shows that the present form of global optical model potential could reproduce experimental data for both the neutron and the proton.展开更多
Using a new set of nucleon coupling constants CZll the properties of a proto neutron star are examined within the framework of the relativistic mean-field theory for the baryon octet system. It is found that the relat...Using a new set of nucleon coupling constants CZll the properties of a proto neutron star are examined within the framework of the relativistic mean-field theory for the baryon octet system. It is found that the relative number density of A,≡ , and ≡0 for CZll are all smaller than those for GL97 and for both CZ11 and GL97, ∑-∑0 and ∑+ do not appear. It is also found that the pressure and the maximum mass for CZll are all smaller than those for GL97. The maximum mass for CZ11 decreases by approximately 9 percent compared with that for GL97.展开更多
By using the chiral quark model and the quark delocalization colour screening model,the phase shifts of nucleonnucleon scattering for high partial waves are studied.The results of both the models are almost equivalent...By using the chiral quark model and the quark delocalization colour screening model,the phase shifts of nucleonnucleon scattering for high partial waves are studied.The results of both the models are almost equivalent.None of the quark models used have found any resonance-like structure in^(3)F_(2),^(3)F_(3),^(3)F_(4)and^(3)H_(4)partial waves.展开更多
The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree-Fock approximation. We particularly study the influences of the tensor...The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree-Fock approximation. We particularly study the influences of the tensor couplings of vector mesons ω and ρ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons w and p can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons ω and ρ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non- superfluid neutron star matter. However, when considering only the tensor coupling of vector meson ρ, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson ρ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.展开更多
Within the framework of a semiclassical Boltzmann-Uehling-Uhlenbeck (BUU) transport model, the high mo- mentum tail (HMT) effects of nucleon momentum distribution in the nucleus on the nucleon collective flows are...Within the framework of a semiclassical Boltzmann-Uehling-Uhlenbeck (BUU) transport model, the high mo- mentum tail (HMT) effects of nucleon momentum distribution in the nucleus on the nucleon collective flows are studied in semieentral Au+Au collisions. The HMT due to the isospin-dependent short-range correlations causes a smaller value of the collective flows. We find that the HMT effects on the nucleon collective flows are remarkable at beam energy of 300 MeV/nucleon and become weak as the incident beam energy increases. The results indicate that for the collective flow studies at intermediate energies, the HMT of nucleon momentum distribution in nucleus should be taken into account in transport models.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
The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance S11 (1535). Our analysis indi...The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance S11 (1535). Our analysis indicates that the constraints of the transition amplitude for the S11 resonance at the limit Q2 →∞ by QCD sum rule calculations are not applicable at a moderate Q2 range of 2.5 ~ 4 Ge V2 compared with the present available data if the contribution of S11 is dominant in the Q2 limit.展开更多
基金supported by supported in part by the National Natural Science Foundation of China(Nos.11890714,12147101)the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030008).
文摘Directed flow(v_(1))of the hypernuclei ^(3)_(Λ)H and ^(4)_(Λ)H have been observed in mid-central Au+Au collisions at√^(s)NN=3 GeV at RHIC.This measurement opens up a new possibility for studying hyperon–nucleon(Y–N)interaction under finite pressure.In addition,multi-strangeness hypernuclei provide a venue to probe hyperon–nucleon–nucleon(Y–N–N)and even hyperon–hyperon–nucleon(Y–Y–N)interactions.Hypernuclei are important for making connection between nuclear collisions and the equation of state which governs the inner structure of compact stars.
文摘The effect of confined one-gluon-exchange potential and instanton-induced interaction potential in the singlet(1S0)and triplet(3S1)channels for nucleon–nucleon interaction has been investigated in the framework of the relativistic harmonic model using the resonating group method in the adiabatic limit with the Born–Oppenheimer approximation.The contributions of the different components of the interaction potentials have been analyzed.
文摘In this paper we consider nucleons as tori, rotating with a constant angular velocity around the straight line passing through their mass centre (geometric centre) and perpendicular to their plane of rotation. We theoretically determine the corresponding potential energy and the force of interaction between pairs of nucleons, using our precise analytical formulas for the electrostatic interaction between two spheres with arbitrary radii and charges, which we derive using experimentally obtained results for the radii and the masses of the nucleons. From the values for binding energy found through our method, it follows that nuclear forces are electromagnetic in nature. In terms of magnitude of the force of interaction between proton and neutron, we obtain that Coulomb's forces are short-range. Our toroid model explains the experimental results not only for binding energy, but also for the radius, magnetic moment and the spin of the nuclei of atoms.
基金Project supported by the National Natural Science Foundation of China (Grant No 60572177)
文摘Nucleus-nucleus potentials are determined in the framework of double folding model for M3Y-Reid and M3Y- Paris effective nucleon-nucleon (NN) interactions. Both zero-range and finite-range exchange parts of NN interactions are considered in the folding procedure. In this paper the spherical projectile-spherical target system 16O+^2008Pb is selected for calculating the barrier energies, fusion cross sections and barrier distributions with the density-independent and density-dependent NN interactions on the basis of M3Y-Reid and M3Y Paris NN interactions. The barrier energies become lower for Paris NN interactions in comparison with Reid NN interactions, and also for finite-range exchange part in comparison with zero-range exchange part. The density-dependent NN interactions give similar fusion cross sections and barrier distributions, and the density-independent NN interaction causes the barrier distribution moving to a higher position. However, the density-independent Reid NN interaction with zero-range exchange part gives the lowest fusion cross sections. We find that the calculated fusion cross sections and the barrier distributions are in agreement with the experimental data after renormalization of the nuclear potential due to coupled-channel effect.
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.
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supported by the National Key R&D program of China(No.2018YFA0404403)National Natural Science Foundation of China(Nos.11775004,U1867214,and 11535004)
文摘With the development of radioactive beam facilities,studies concerning the shell evolution of unstable nuclei have recently gained prominence.Intruder components,particularly s-wave intrusion,in the low-lying states of light neutron-rich nuclei near N=8 are of importance in the study of shell evolution.The use of single-nucleon transfer reactions in inverse kinematics has been a sensitive tool that can be used to quantitatively investigate the single-particle orbital component of selectively populated states.The spin-parity,spectroscopic factor(or single-particle strength),and effective singleparticle energy can all be extracted from such reactions.These observables are often useful to explain the nature of shell evolution,and to constrain,check,and test the parameters used in nuclear structure models.In this article,the experimental studies of the intruder components in lowlying states of neutron-rich nuclei of He,Li,Be,B,and C isotopes using various single-nucleon transfer reactions are reviewed.The focus is laid on the precise determination of the intruder s-wave strength in low-lying states.
文摘Magnetic excitations for Ba isotopes are discussed within the nucleon-pair shell model trmicated iti the SDsubspace. With the SD pair determined by a surface-δ interaction, M1 transitions for 1344Ba are well fitted. The M1 andM3 transitions for 132Ba and 130Ba are also predicted. It is shown that the statement, the collective magnetic propertiesarc due to the orbital motion of nucleons, is approximately valid.
文摘Using the most recent phase shift data for pp, nn, and np elastic scattering for different states (l=0.1....)in the energy range of 1 MeV to 350 MeV, the charge dependeney of the strong muclear force, is investigated. Our results indicate that although the charge independency holds in most of the energy range, such charge independency is broken in the particular energy range of 120 MeV to 200 MeV for all partial wave states considered here.
基金supported by the Asia-Link project(CN/ASIA-LINK/008(94791))of the European Commissionin part by National Natural Science Foundation of China under Grant Nos.10775061,10505016,10575119,and 10175074+1 种基金the Knowledge Innovative Project of CAS under Grant No.KJCX3-SYW-N2the Major Prophase Research Project of Fundamental Research of the Ministry of Science and Technology of China under Grant No.2007CB815004
文摘We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetricnuclear matter at various densities,using the Brueckner-Hartree-Fock approximation scheme with the Argonne V_(14)potential including the contribution of microscopic three-body force.We investigate separately the effects of three-bodyforce on the effective mass and on the scattering amplitude.In the present calculation,the rearrangement contributionof three-body force is considered,which will reduce the neutron and proton effective mass,and depress the amplitudeof cross section.The effect of three body force is shown to be repulsive,especially in high densities and large momenta,which will suppress the cross section markedly.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No G2000077400), the Major Program of the National Natural Science Foundation of China (Grant Nos 10435080 and 105350101), the National Natural Science Foundation of China (Grant Nos 10447006 and 10575075), the CAS Knowledge Innovation Project Program (Grant No KJCX2-SW-N02).
文摘Probing in-medium nucleon-nucleon (NN) cross section σ1/NN(α) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum-dependent interaction (IMDI(T)). It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping R on the in-medium NN cross section α1/NN(α) in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of σ1/NN(α) in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R's in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of σ1/NN(α) because of adding a new judgement.
基金supported by the China Ministry of Science and Technology (No. 2007CB209903)National Basic Research Program of China(973 Program)
文摘A set of new global phenomenological optical model potential parameters has been obtained in the mass range of target nuclei 220≤A≤260 with incident energies below 300 MeV, by simultaneously fitting the experimental data of 232Th and 23Su, and these potential parameters are analyzed and used to calculate the reaction cross sections, energy spectra and double differ- ential cross sections for p+232Th reaction. Comparison of calculated results using these potential parameters with available experimental data shows that the present form of global optical model potential could reproduce experimental data for both the neutron and the proton.
基金Project supported by the Natural Science Foundation of Anhui Province of China (Grant No. 1208085MA09)the Science Research Program of Institutions of Higher Education of Anhui Province of China (Grant No. KJ2012Z297)the Fundamental Research Funds for the Central Universities (Grant No. SWJTU12ZT11)
文摘Using a new set of nucleon coupling constants CZll the properties of a proto neutron star are examined within the framework of the relativistic mean-field theory for the baryon octet system. It is found that the relative number density of A,≡ , and ≡0 for CZll are all smaller than those for GL97 and for both CZ11 and GL97, ∑-∑0 and ∑+ do not appear. It is also found that the pressure and the maximum mass for CZll are all smaller than those for GL97. The maximum mass for CZ11 decreases by approximately 9 percent compared with that for GL97.
基金Supported by the National Science Foundation of China under Grant Nos 10775072 and 10947160the Research Fund for the Doctoral Program of Higher Education of China under Grant No 20070319007.
文摘By using the chiral quark model and the quark delocalization colour screening model,the phase shifts of nucleonnucleon scattering for high partial waves are studied.The results of both the models are almost equivalent.None of the quark models used have found any resonance-like structure in^(3)F_(2),^(3)F_(3),^(3)F_(4)and^(3)H_(4)partial waves.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11447165,11373047 and 11265009the Youth Innovation Promotion Association of Chinese Academy of Sciences under Grant No 2016056
文摘The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree-Fock approximation. We particularly study the influences of the tensor couplings of vector mesons ω and ρ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons w and p can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons ω and ρ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non- superfluid neutron star matter. However, when considering only the tensor coupling of vector meson ρ, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson ρ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.
基金Supported by the Fundamental Research Funds for the Central Universities under Grant No lzujbky-2014-170the Research Fund for the Doctoral Program of Higher Education of China under Grant No 20120211120002the National Natural Science Foundation of China under Grant Nos 11205075 and 11375076
文摘Within the framework of a semiclassical Boltzmann-Uehling-Uhlenbeck (BUU) transport model, the high mo- mentum tail (HMT) effects of nucleon momentum distribution in the nucleus on the nucleon collective flows are studied in semieentral Au+Au collisions. The HMT due to the isospin-dependent short-range correlations causes a smaller value of the collective flows. We find that the HMT effects on the nucleon collective flows are remarkable at beam energy of 300 MeV/nucleon and become weak as the incident beam energy increases. The results indicate that for the collective flow studies at intermediate energies, the HMT of nucleon momentum distribution in nucleus should be taken into account in transport models.
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.
文摘The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance S11 (1535). Our analysis indicates that the constraints of the transition amplitude for the S11 resonance at the limit Q2 →∞ by QCD sum rule calculations are not applicable at a moderate Q2 range of 2.5 ~ 4 Ge V2 compared with the present available data if the contribution of S11 is dominant in the Q2 limit.