排序方式: 共有12条查询结果,搜索用时 15 毫秒
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普通原子核由质子和中子组成。随着实验和理论研究的发展,人们认识到还存在着另外一类奇特的原子和原子核--介子原子和介子核。这些新形态的原子和原子核在自然界中是很难找到的,原因是它们的寿命很短。只有在实验室中才能观测到这些奇特的原子和原子核,所以一直不太被人们了解。然而近年来,新的实验现象和新的理论分析使人们对介子原子和介子核有了新的认识。我们在介绍介子原子和介子核之前,首先对介子作一个简单的介绍。介子跟核子一样都是参与强相互作用的粒子,各种介子都是由一个正夸克和一个反夸克组成的两夸克系统。不同的介子由不同的夸克组成。 相似文献
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简要介绍和评述了近几年来中高能核物理中一些受关注的问题,重点介绍了核子电磁形状因子和K^-介子与原子核相互作用势强度问题。 Several problems in intermediate and high energy nuclear physics have attracted considerable attention in these years: (1) Nucleon electromagnetic form factors. There is a systematic difference between the recently measured data from high energy polarized electron-nucleon scattering experiments and the previous Rosenbluth results. (2) The strength of K^- nucleus optical potentials. It varies qualitatively from different analyyses on K^- nucleus interactions. In this paper, the above problems are discussed and reviewed briefly. 相似文献
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简要评述超核物理学近几年的发展,包括常规超核和非常规超核两个方面.对于包含通常超子的常规超核,重点介绍近来在日本KEK完成的一批超核实验及其理论分析.对其中关于超子杂质效应和超子平均自由路程等实验测量结果进行了理论分析,得到一些有意义的结果.并对奇异数为S=-2的Ξ超核的结构和性质进行了若干研究.对于包含C夸克或B夸克的其他味超核,以及可能的包含pentaquark的θ+超核也做了适当的介绍. Progress and recent status of experimental and theoretical investigations on hypernuclear physics are briefly reviewed, including conventional hypernuclear physics and unconventional hypernuclear physics. We introduce the recent progress of hypernuclear experiments in KEK, Japan and the studies of fine structure in γ-ray spectroscopy of Λ hypernuclei. The spin-flip transition between the ground-state spin doublet of light hypernuclei has been observed and the transition energy provides important.. 相似文献
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A chiral quark-model approach is extended to the study of the
$\bar{K}N$ scattering at low energies. The process of
$K^-p\rightarrow \Sigma^0\pi^0$ at $P_K\lesssim 800$ MeV/c (i.e. the
center mass energy $W\lesssim 1.7$ GeV) is investigated. The
$\Lambda(1405)S_{01}$ dominates the reactions over the energy region
considered here. Around $P_K\simeq 400$ MeV/c, the
$\Lambda(1520)D_{03}$ is responsible for a strong resonant peak in
the cross section. Our analysis suggests that there exist
configuration mixings within the $\Lambda(1405)S_{01}$ and
$\Lambda(1670)S_{01}$ as admixtures of the
$[\textbf{70},^2\textbf{1},1/2]$ and
$[\textbf{70},^2\textbf{8},1/2]$ configurations. The
$\Lambda(1405)S_{01}$ is dominated by
$[\textbf{70},^2\textbf{1},1/2]$, and $\Lambda(1670)S_{01}$ by
$[\textbf{70},^2\textbf{8},1/2]$. The non-resonant background
contributions, i.e. $u$-channel and $t$-channel, also play important
roles in the explanation of the angular distributions due to
amplitude interferences. 相似文献
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A chiral quark-model approach is employed to study theˉ KN scattering at low energies.The processes of Kˉp → Σ 0 π 0,Λπ 0 andˉ K 0 n at P K 800 MeV/c (i.e.the center mass energy W 1.7 GeV) are investigated.The analysis shows that the Λ(1405)S 01 dominates the processes Kˉp → Σ 0 π 0,ˉ K 0 n in the energy region considered here.Around P K 400 MeV/c,the Λ(1520)D 03 is responsible for a strong resonant peak in the cross section of Kˉp → Σ 0 π 0 andˉ K 0 n.To reproduce the data,an unexpectedly large coupling for Λ(1520)D 03 to KN is needed.In contrast,the coupling for Λ(1670)S 01 to KN appears to be weak,which could be due to configuration mixings between Λ(1405)S 01 and Λ(1670)S 01 .By analyzing Kˉ p → Λπ 0,evidences for two low mass S-wave states,Σ(1480)S 11 and Σ(1560)S 11,seem to be available.With these two states,the reaction Kˉp →ˉ K 0 n can also be described well.However,it is difficult to understand the low masses of Σ(1480)S 11 and Σ(1560)S 11 .The s-channel amplitudes for Kˉp → Λπ 0 are also larger than the naive quark model expectations.The non-resonant background contributions,i.e.t-channel and/or u-channel,also play important roles in the explanation of the angular distributions due to amplitude interferences. 相似文献
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