通过J/Ψ→NM衰变研究N~*时的核子极点效应

研究了J／Ψ→pp^-π衰变过程中核子极点图的贡献，特别是由离壳效应带来的贡献．发现衰变宽度对形状因子是敏感的．在通过用J／Ψ→pp^-π衰变研究N^*时，核子极点图作为背景道的贡献是非常重要的；在通过J／Ψ→pp^-η和pp^-η研究N^*时，核子极点图的贡献可忽略不计；在通过J／Ψ→pp^-ω研究N^*时，核子极点图有明显的贡献． N-pole contributions, especially due to off shell effect, in J/Ψ→ NM decays are carefully studied. It is found that the decay width is sensitive to the form factor. The N pole contribution as a background is important in the J/Ψ→Nπ decay, ignorable in the J/Ψ→Nη and Nη' decays, and sizable in the J/Ψ→Nω decay.     

第二届国际中能物理会议在北京召开

第二届国际中能物理会议在北京召开第二届国际中能物理会议（ＩｎｔｅｒｎａｔｉｏｎａｌＳｙｍｐｏ－ｓｉｕｒｎｏｎＭｅｄｉｕｍＥｎｅｒｇｙ　Ｐｈｙｓｉｃｓ’９４）于１９９４年８月２２日至８月２６日在中国科学院高能物理研究所召开。这次会议是由中国科学院高能物...     

《中微子猎手》介绍

 自从中微子的概念被提出的一刻,物理学界一直被这个神秘的精灵所困扰。它最初是被迫引入的,"中微子之教父"泡利在建议存在这样一个"没法被实验观测"的粒子时说:"我做了一件可怕的事!"然而随着实验手段和理论研究的进展,我们对中微子的认识越来越深入,我们对它了解的越多,就越感到它的神奇。     

关于J/ψ辐射衰变产生胶球态的另一种机制

基于粲夸克偶素J/ψ质量大而寿命长的特征的物理内涵和对胶球态产生条件的理解,提出了J/ψ→Gb+γ过程产生胶球态的另一种机制,即认为胶球态Gb来自J/ψ中的组分粲夸克对c_con.(c_con.)分别转变为流粲夸克对c_{cur.(ccur.)时所发射的色八重态胶团对的融合,而余下的流粲夸克对再湮没为光子γ.通过用此模型的计算,讨论了ΓJ/ψ→Gb+γ与有关参数值的关系,并与J/ψ辐射衰变中通过两个末态胶子的强子化产生胶球的机制作出了对比.}     

核子的组分夸克模型与O+U→μμ+X过程

用核子的组分夸克模型计算了氧(O16)核和铀核(U235)中核子结构函数并讨论了200GeV/N的O+U→μμ+XDrell-Yan过程.与实验数据比较得到了相符的结果.指出各种核效应合在一起、对此过程的截面的最大影响可高达15%左右.因此在讨论诸如探索胶子夸克等离子出现问题而分析J/ψ压低现象时,原子核效应不可忽略.此外唯象学分析表明在这过程中表征微拢QCD修正效果的K因子似应随轻子对质量m的增大而缓慢减小,与QCD渐近自由直观想像和前人对此的有关分析相一致.     

N—N相互作用中自旋轨道耦合力的夸克模型

在夸克－夸克相互作用中考虑了单胶子交换的自旋轨道耦合力、由禁闭势导出的自旋轨道耦合力、由手征场σ交换提供的自旋轨道耦合力以及由双胶子交换提供的自旋轨道耦合力，从而可以统一地解释重子谱中的自旋轨道耦合效应及Ｎ－Ｎ散射中的各个分波的相移．     

跟着物理一起翱翔 介绍“粒子物理、核物理和宇宙学交叉学科前沿问题研讨会”系列会议

<正>2004年诺贝尔物理学奖得主威尔切克指出,我们期盼的物理黄金时代正在到来。19世纪末到20世纪初,随着量子论、相对论的相继出现,人类对自然界的理解也完成了一次飞跃,进入到崭新的层     

Possible heavy dibaryons

In the framework of the constituent quark model, the possible S-wave heavy dibaryon states with the c flavor are investigated. The factors which are responsible for the binding behavior of the dibaryon system are analyzed. It is shown that both the symmetry character of the system and the energy of interactions between interacting quarks are important for the binding behavior of the two-baryon system with the heavy flavor. As a result, seven possible candidates of heavy dibaryons with c flavor are predicted.     

Testing Bell inequality at experiments of high energy physics

Besides using the laser beam, it is very tempting to directly testify the Bell inequality at high energy experiments where the spin correlation is exactly what the original Bell inequality investigates. In this work, we follow the proposal raised in literature and use the successive decays J/ψ →γηc→ ∧∧ → pπ^- pπ^＋ to testify the Bell inequality. Our goal is twofold, namely, we first make a Monte-Carlo simulation of the processes based on the quantum field theory （QFT）. Since the underlying theory is QFT, it implies that we pre-admit the validity of quantum picture. Even though the QFT is true, we need to find how big the database should be, so that we can clearly show deviations of the correlation from the Bell inequality determined by the local hidden variable theory. There have been some critiques on the proposed method, so in the second part, we suggest some improvements which may help to remedy the ambiguities indicated by the critiques. It may be realized at an updated facility of high energy physics, such as BES III.     

Quark distributions in nuclei and nuclear effects on nucleon structure functions

Extended quark distribution functions are presented obtained by fitting a large amount of experimental data of the l-A DIS process on the basis of an improved nuclear density model. The experimental data of l-A DIS processes with A≥3 in the region 0.0010≤x≤0.9500 are quite satisfactorily described by using the extended formulae. Our knowledge of the influence of nuclear matter on the quark distributions is deepened.