Nucleon-nucleon interactions in the double folding model for fusion reactions

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.

Probing the medium effect and isospin dependence of the in-medium nucleon-nucleon cross section in heavy ion collisions

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.

Charge Dependency of Strong Nuclear Force via Phase Shift Analysis of Nucleon-Nucleon Potential

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 i MeV to 350 MeV,the charge dependency of the strong nuclear 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.

Pade Expansion and Nucleon-Nucleon Scattering in Coupled Channels

We extend our Pade-aided analysis of the nonperturbative renormalization of nucleon-nucleon scatteringto the case of coupled channels.

Microscopic Three-Body Force Effect on Nucleon-Nucleon Cross Sections in Symmetric Nuclear Matter

We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetric nuclear matter at various densities, using the Brueckner Hartree-Fock approximation scheme with the Argonne Va4 potential including the contribution of microscopic three-body force. We investigate separately the effects of three-body force on the effective mass and on the scattering amplitude. In the present calculation, the rearrangement contribution of three-body force is considered, which will reduce the neutron and proton effective mass, and depress the amplitude of 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.

On the Mechanism of Nucleon-Nucleon Attraction by Pion Exchange

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.

A Universal Binding Mechanism in Molecular Covalent Bonding and Nucleon-Nucleon Interaction

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.

Binding Energy, Root Mean Square Radius and Magnetic Dipole Moment of the Triton Nucleus

The basis functions of the translation invariant shell model are used to construct the ground state nuclear wave functions of 3H. The used residual two-body interactions consist of central, tensor, spin orbit and quadratic spin orbit terms with Gaussian radial dependence. The parameters of these interactions are so chosen in such a way that they represent the long-range attraction and the short-range repulsion of the nucleon-nucleon interactions. These parameters are so chosen to reproduce good agreement between the calculated values of the binding energy, the root mean-square radius, the D-state probability, the magnetic dipole moment and the electric quadrupole moment of the deuteron nucleus. The variation method is then used to calculate the binding energy of triton by varying the oscillator parameter which exists in the nuclear wave function. The obtained nuclear wave functions are then used to calculate the root mean-square radius and the magnetic dipole moment of the triton.

In-medium nucleon-nucleon elastic cross-sections determined from the nucleon induced reaction cross-section data

Within the framework of the improved quantum molecular dynamics model, the medium modifications of the free nucleon-nucleon elastic cross-sections are investigated. By using various in-medium nucleon-nucleon elastic cross-sections in the model, the nucleon induced reactions on various targets are simulated, and the excitation functions of reaction cross-sections in the energy range from 25 MeV to 1 GeV are calculated. By comparing the calculations with the experimental data, the isospin, density, and momentum dependence of the medium correction factors of free nucleon-nucleon elastic cross-sections are determined.

Nucleon momentum distribution of 56Fe from the axially deformed relativistic mean-field model with nucleon-nucleon correlations

Nucleon momentum distribution(NMD), particularly its high-momentum components, is essential for understanding the nucleonnucleon(NN) correlations in nuclei. Herein, we develop the studies of NMD of 56Fe from the axially deformed relativistic mean-field(RMF) model. Moreover, we introduce the effects of NN correlation into the RMF model from phenomenological models basing on deuteron and nuclear matter. For the region k < kF, the effects of deformation on the NMD of the RMF model are investigated using the total and single-particle NMDs. For the region k > kF, the high-momentum components of the RMF model are modified by the effects of NN correlation, which agree with the experimental data. Comparing the NMD of relativistic and non-relativistic mean-field models, the relativistic effects on nuclear structures in momentum space are analyzed. Finally, by analogizing the tensor correlations in deuteron and Jastrow-type correlations in nuclear matter, the behaviors and contributions of NN correlations in 56Fe are further analyzed, which helps clarify the effects of the tensor force on the NMD of heavy nuclei.

Leading order relativistic chiral nucleon-nucleon interaction

Motivated by the successes of relativistic theories in studies of atomic/molecular and nuclear systems and the need for a relativistic chiral force in relativistic nuclear structure studies, we explore a new relativistic scheme to construct the nucleon-nucleon interaction in the framework of covariant chiral effective field theory. The chiral interaction is formulated up to leading order with covariant power counting and a Lorentz invariant chiral Lagrangian.We find that the relativistic scheme induces all six spin operators needed to describe the nuclear force. A detailed investigation of the partial wave potentials shows a better description of the;S——0 and;P;phase shifts than the leading order Weinberg approach, and similar to that of the next-to-leading order Weinberg approach. For the other partial waves with angular momenta J≥1, the relativistic results are almost the same as their leading order non-relativistic counterparts.

Determination of the nucleon-nucleon interaction in the ImQMD model by nuclear reactions at the Fermi energy region

The nucleon-nucleon interaction is investigated by using the improved quantum molecular dynamic （ImQMD） model with three sets of parameters IQ1, IQ2 and IQ3, in which the corresponding incompressibility coefficients of nuclear matter are different. The charge distributions of fragments are calculated for various reaction systems at different incident energies. The parameters strongly affect the charge distributions and the fragment multiplicity spectrum below the threshold energy of nuclear multifragmentation. The fragment multiplicity spectrum for 238U＋197Au at 15 A MeV and the charge distributions for 129Xe＋12~Sn at 32 and 45 A MeV, and 197Au＋197Au at 35 A MeV are reproduced by the ImQMD model with the set of parameter IQ3. It is found that： 1） The charge distribution of the fragments and the fragment multiplicity spectrum are good observables for testing the model and the parameters. 2） The Fermi energy region is a sensitive energy region for studying nucleon-nucleon interaction.

A higher-dimensional model of the nucleon-nucleon central potential

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.

Study of nucleon-nucleon and alphanucleon elastic scattering by the Manning-Rosen potential

Although often used in molecular dynamics,in this work the Manning-Rosen potential is parameterized to compute the scattering phase shifts for the nucleon-nucleon and the alphanucleon systems by exploiting the standard phase function method.We obtain excellent agreement in phase shifts with the more sophisticated calculations up to partial waves l=2.

Renormalizability of leading order covariant chiral nucleon-nucleon interaction

In this work,we study the renormalization group invariance of the recently proposed covariant power counting in the case of nucleon-nucleon scattering[Chin.Phys.C 42(2018)014103]at leading order.We show that unlike the Weinberg scheme,renormalizaion group invariance is satisfied in the^(3)P0 channel.Another interesting feature is that the^(1)S0 and^(3)P1 channels are correlated.Fixing the relevant low energy constants by ftting to the^(1)S0 phase shiftsat T_(lab)=10 and 25 MeV with cutoff values∧=400-650 MeV,one can describe the 3 P1 phase shifts relatively well.In the limit of∧→∞,the^(1)S0 phase shifts become cutoff-independent,whereas the 3P1 phase shifts do not.This is consistent with the Wigner bound and previous observations that the 3P1 channel is best treated perturbatively.As for the^(2)P1 and^(3)S1-^(3)D1 channels,renormalization group invariance is satisfied.

原子核中的α团簇对核反应与相对论重离子碰撞的影响

团簇结构可以稳定存在于原子核的内部。研究原子核的α团簇结构及其影响在核物理与天体物理中是一个十分重要的课题。在过去几十年里,原子核的团簇结构效应在重离子核反应中有了较多的研究。本文主要总结了在核反应与相对论重离子碰撞中对原子核的α团簇结构效应的研究。例如,通过原子核的巨共振来研究原子核的团簇结构。通过核反应中的粒子(包括中子、质子以及光子)的发射与关联、集体流等研究原子核的团簇结构。进一步,我们把原子核的团簇效应延伸推广到相对论重离子碰撞中,比如,对集体流及其涨落、HBT(Hanbury Brown and Twiss)关联、多重性关联、双强子方位角关联、电磁场等的研究。

重离子碰撞中的同位旋效应

根据近年来利用同位旋相关输运理论在中能重离子碰撞同位旋效应研究方面的成果 ,并结合国际上在该问题上的进展 ,综合介绍和分析了中能重离子碰撞中的多重碎裂、原子核阻止和前平衡发射中子 -质子比的同位旋效应及其随入射道条件 :入射能量、碰撞参数、碰撞系统的质量 ,特别是随中子 -质子比的演化过程 .讨论了利用以上物理观测量在提取同位旋非对称核物质状态方程知识方面的可能性 ,并对其发展进行了展望 .

中能重离子碰撞中同位旋效应的灵敏探针

在重离子碰撞过程中， 基于重质量的弹核轰击轻质量靶核有大量中等质量碎片向前发射的逆运动学效应， 利用同位旋相关的量子分子动力学观察和研究了重离子碰撞过程中同位旋效应的灵敏性． 计算结果表明在所选能区， 中等质量碎片的多重性与带电粒子总数之间的关联是提取介质中核子核子碰撞截面的灵敏观测量， 而此时对称势的同位旋效应却不明显．

对液体空化机理的进一步探讨

针对当前液体空化机理的各种假设所存在的缺陷，应用热力学原理，对气泡核子作了进一步探讨，并得出在平面平衡的条件下，液体内部不可能稳定地存在纯蒸汽泡；在亲水性裂隙中气核是不可能稳定存在的；而在憎水性裂隙中气核是可以稳定存在的．还讨论了影响空化产生及发展的一些因素，在考虑固体表面糙度、水中杂质、含气量等因素后，用一个修正的空化数σ′１ 来作为衡量空化能否发生的依据，更为确切．这些论述，对气核假说的理论作了充实和完善．

高能不等核碰撞中的参与者数和二元核子核子碰撞数

采用核核碰撞的Glauber模型,给出了高能d核与Au核在不同对心碰撞中的参与者数与二元核子核子碰撞数,所得结果与RHIC PHOBOS合作组给出的结果相吻合.