干涉截面对核子自旋结构函数的影响

利用非相对论和相对论夸克模型分别计算了干涉截面对极化核子自旋结构函数的影响.计算所得到的明显的作用为今后实验上抽取核子自旋结构函数提供了依据.     

Spin Cut-off Parameter of Nuclear Level Density and Effective Moment of Inertia

The spin cut-off parameter of the nuclear level density and effective moment of inertia for a large number of nuclei have been determined from analysis of the experimental data on S-wave neutron resonances and spins of low-lying levels. Contrary to claims made before, it is shown the spin cut-off parameter differs considerably from their corresponding rigid body values, and the energy dependence of the effective moment of inertia confirms the interacting fermion model prediction.     

超形变带自旋的比较指定

首次用Bohr-Mottelson公式和Harris公式同时指定A≈190区超形变带的带首自旋值.对大多数超形变带,用以上两种方法指定的自旋是一致的,而对部分超形变带则不一致.不能一致地指定自旋的和自旋指定不符合带首转动惯量系统学的超形变带,用带首转动惯量系统学或两类转动惯量系统学的方法重新指定其自旋.利用指定的自旋,拟合Bohr-Mottelson转动谱公式,研究了参数之间的关系,结果表明从Harris三参数公式导出的关系式更符合实验值.     

Nucleon Spin Structure Functions in the Resonance Region and the Duality

We discuss the nucleon spin structure function gl and the difference between the proton and neutrontargets gp1 - gn1 , based on quark model calculation. Quark-hadron duality for the nucleon spin structure function is alsoanalyzed. Effects of the △(1232) and Roper P11(1440) resonances on the spin structure function and on the differencegn1 - gn1 are mentioned. The results of different models for the Roper resonance are also addressed.     

A four quark-parton model analysis of recent high energy neutrino-nucleon scattering data

The data on neutrino (antineutrino), neutral and charged current cross-sections and theiry-distributions are analysed within the framework of the Weinberg-Salam theory and the quark-parton model incorporating charm. Other existing models are also compared. Interpretation of data appears easy in the case of models with charm whereas it is not so if charm is absent. Under some reasonable assumptions, the numerical values of the first moments of parton distribution functions are obtained. The sin² ϑ _W and other useful parameters are also determined for the various models.     

Finite-Size Scaling of the Domain Wall Entropy Distributions for the 2D ± J Ising Spin Glass

The statistics of domain walls for ground states of the 2D Ising spin glass with +1 and −1 bonds are studied for L × L square lattices with L ≤ 48, and p = 0.5, where p is the fraction of negative bonds, using periodic and/or antiperiodic boundary conditions. When L is even, almost all domain walls have energy E _dw = 0 or 4. When L is odd, most domain walls have E _dw = 2. The probability distribution of the entropy, S _dw , is found to depend strongly on E _dw . When E _dw = 0, the probability distribution of |S _dw | is approximately exponential. The variance of this distribution is proportional to L, in agreement with the results of Saul and Kardar. For E _dw = k > 0 the distribution of S _dw is not symmetric about zero. In these cases the variance still appears to be linear in L, but the average of S _dw grows faster than L. This suggests a one-parameter scaling form for the L-dependence of the distributions of S _dw for k> 0. PACS: 75.10.Nr, 75.40.Mg, 75.60.Ch, 05.50.+q     

高能强子化过程的自旋转移和轻子诱发反应中超子的极化

指出在轻子诱发反应中测量产生超子的极化是研究高能强子化过程自旋转移的理想途径.在总结这些反应产生的初始夸克或反夸克极化的基础上,给出了超子极化的计算方法.作为应用举例,给出了e⁺e^－湮没过程中LEP能量下各种超子的极化及与已有实验的比较.这些结果表明,测量各类超子的极化可作为检验不同的重子自旋结构图像,何者适用于高能碎裂过程的重要手段.     

Parton distributions,small-x physics and the spin structure of the nucleon

Several theoretical aspects in leading (1-loop) and higher (2-loop) order as well as various approaches of extracting leading twist-2 parton distributions from structure function measurements are discussed and summarized. Their implications for the small-x region (x⩽10⁻²) are analyzed and compared with alternative approaches where higher twist contributions (‘fans’) are added to the twist-2 LO terms in the evolution equations. The second part of these lectures deals with longitudinally polarized parton distributions related to the structure functiong ₁, in particular with various scenarios to explain the total spin structure of nucleons, including the gluon anomaly as well. Specific (realistic) tests for discriminating between these alternatives are discussed as well asx-dependent expectations, in particular for neutron targets in connection with the Bjorken sum rule. Furthermore, various theoretical expectations and sum rules for the transverse (chiral-even) structure functiong ₂ are presented and very recent developments of transverse chiral-odd (‘transversity’) distributions are briefly discussed.     

关于P的结构模型(部分子分布)的检验

用不同的P部分子模型计算了高能P+P(P)对撞中双重P交换对J/ψ产生过程的贡献.对以胶子为主的Ingelman-Schlein模型,高能时截面随能量s以Ins或In²S平稳增加.在TeV能区σ(S)～10²—10³nb.对于认为P类似于C=+1同位旋标量光子的Donnachie-Landshoff模型,截面随行为复杂些,而σ(S)值仅为1—3nb,比前者小2—3个量级.因此如果认为两模型采用的参数值可靠,则此过程是检验它们的有效方法.文章就此作了质疑式的简短讨论.     

自旋相干态变换和自旋-玻色模型的基于变分法的基态解析解

提出一种基于自旋相干态变换求解自旋-玻色模型基态的变分法, 并将其用于单原子模型, 得到旋波近似和非旋波近似情形下的解析基态能量和波函数, 特别是在光场与原子的弱、强耦合区域都与数值对角化结果符合得很好. 另外, 该方法也可以直接用于求解任意原子数的Dicke模型基态和相应的量子相变研究, 而通常基于Holstein-Primakoff变换的变分法, 原则上只适用于原子数趋于无穷的热力学极限情形. 关键词： 自旋相干态 变分法 J-C模型     

On Decay of Correlations for Unbounded Spin Systems with Arbitrary Boundary Conditions

We propose a method based on cluster expansion to study the truncated correlations of unbounded spin systems uniformly in the boundary condition and in a possible external field. By this method we study the spin–spin truncated correlations of various systems, including the case of infinite range simply integrable interactions, and we show how suitable boundary conditions and/or external fields may improve the decay of the correlations.     

An Analysis of the Proton Structure Function and the Gluon Distributions at Small x

Recently, we reported an analysis of Proton structure function at small x based on Taylor approximated DGLAP equations assuming a plausible relationship between the singlet and the gluon distributions. In this paper, we report a generalised version of the previous work. A corresponding study of the suggested gluon distribution is also made.The present generalised version of the model for the structure function results in a wider x range of phenomenological validity than the earlier one. A comparison of both the models of the proton structure function and the gluon distribution is made with exact result as well as with the Froissart saturated models of Block, Durand and Mckay.     

粗糙表面相关结构对远场散斑相位差统计性质的影响

假设弱散射体粗糙表面高度起伏服从高斯统计，在表面高度起伏分别服从高斯相关，指数相关，圆形相关的情况下，分析了由弱射体产生的远场高斯斑场相位差的条件统计分析。     

Ratio of Real to Imaginary for pp and (p)p Elastic Scatterings in QCD Inspired Model

We use the QCD inspired model to analyze the ratio of the real to the imaginary for pp and pp elastic scatterings. A calculation for the ratio of the real to the imaginary is performed in which the contributions from gluongluon interaction, quark-quark interaction, quark-gluon interaction, and odd eikonal profile function are included. Our results show that the QCD inspired model gives a good fit to the LHC experimental data.     

Study of Ratio of Proton Momentum Distributions with a Chiral Quark Model

The ratio between the anomalous magnetic moments of proton and neutron has recently been suggested to be connected to the ratio of proton momentum fractions carried by the valence quarks inside it. This moment fraction ratio is respectively evaluated by using constituent quark model and chiral quark model in order to check meson cloud effect. Our results show that the meson cloud effect is remarkable to the ratio of the proton momentum fractions, and therefore, this ratio is a sensitive test for the meson cloud effect as well as for the SU(6) symmetry breaking effect.     

Study of Topological Structure of Vacuum by Lattice QCD

Overlap fermions and improved 5Li cooling are compared, which exhibits that these two filter methods can produce similar structures. Then the overlap fermions and improved 5Li cooling are combined to calculate the topological charge and identify the structure of the vacuum. The results are consistent with instanton liquid model .     

Statistical Average of Spin Operators for Calculation of Three-Component Magnetization

When one wants to calculate all the three components of magnetization of Heisenberg model under random phase approximation, at least one of the components should be the solution of an ordinary differential equation. In this paper such an equation is established. It is argued that the general expressions of magnetization for any spin quantum number $S$ suggested before are the solution of the ordinary differential equation.     

Determinant formula for the partition function of the six-vertex model with a non-diagonal reflecting end

With the help of the F-basis provided by the Drinfeld twist or factorizing F-matrix for the open XXZ spin chain with non-diagonal boundary terms, we obtain the determinant representation of the partition function of the six-vertex model with a non-diagonal reflecting end under domain wall boundary condition.     

Statistics of Energy Levels and Zero Temperature Dynamics for Deterministic Spin Models with Glassy Behaviour

We consider the zero-temperature dynamics for the infinite-range, non translation invariant one-dimensional spin model introduced by Marinari, Parisi and Ritort to generate glassy behaviour out of a deterministic interaction. It is argued that there can be a large number of metastable (i.e., one-flip stable) states with very small overlap with the ground state but very close in energy to it, and that their total number increases exponentially with the size of the system.