共查询到20条相似文献,搜索用时 46 毫秒
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在强子层次上,原子核或强子物质的基本组元是核子和介子.弄清这些强子的结构,并由基本原理出发研究它们的性质,是当代核物理的重要课题.在各种介子中,π介子是最轻且最重要的介子.关于自由空间中π介子的结构与性质、核介质内π介子的性质、π 核子相互作用与π 核相互作用等问题,始终受到相当多的关注.π介子在核物理中的作用直接联系着手征对称性,汤川秀树关于π介子的最初概念已经大大发展了.有清楚的实验证据表明,核内存在π介子的集体模式,这种集体模式与以前观测到的所有核集体运动模式截然不同.拟对π 核物理的研究现状及值得进一步研究的主要问题予以简要评述. At the hadronic level, nucleons and mesons are constituents of nuclei and hadronic matter. Understanding the structures of hadrons, finding the physics of how the properties of these particles arise from the first principle, are major interests in modern nuclear physics. Among mesons, the lightest and most important one is certainly the pion, thus it is no accident that its structure, properties (both in free space and in nuclear matter) and interactions with nucleons and nuclei have gotten considerable ... 相似文献
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本文计算了π介子单电荷交换机制对传递重中微子的0νββ衰变振幅的贡献,并与以前的π介子双电荷交换机制下的计算结果进行了比较,我们发现:对此衰变有重要贡献的π介子自由度只是π介子双电荷交换机制. 相似文献
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本文基于最重要的"硬"产生机制,计算了Z0衰变产生Bc(或Bc)介子并伴有c(或c)和b(或b)两个重夸克喷注的产生率.指出在LEP上的下一次取数据中将产生出足够数目的Bc(或Bc)介子的性质成为可能. 相似文献
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研究了核介质中π介子衰变常数fπ 随核介质密度 ρ变化的规律 ,指出了随着核密度的增加fπ 逐渐减小。在正常核物质密度 ρ0 (=0 .17fm3 )时 ,fπ 减小百分之三十三左右。这对于研究核物质中介子动力学和相对论重离子碰撞中夸克胶子等离子体相变都是十分重要的。 相似文献
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pp^-→π^0π^0 η飞行湮没过程是寻找π^0π^0η系统中的胶球和π^0η系统中的J^pc为1^- 的奇特态粒子的极佳过程,采用相对论张量分波分析方法给出该过程的分波分析理论公式,并对该过程进行了一些蒙特卡罗模拟研究。 相似文献
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研究了200A GeV S+S和S+Ag碰撞中K、π介子产生的量子统计效应, 并和实验结果进行了比较;理论计算再现了实验结果.获取的freeze-out温度约为110MeV,重子密度约为0.05ρ0. 相似文献
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S. A. Bulychev A. E. Kudryavtsev V. V. Kulikov M. A. Martem’yanov V. E. Tarasov W. J. Briscoe I. I. Strakovsky 《Physics of Atomic Nuclei》2017,80(9):1549-1552
The reaction γn → π0n is investigated both theoretically and experimentally as an important step toward determining the electromagnetic coupling constants of the N* and Δ* resonances [1]. We analyze the data on the collisions of γ quanta with energies between 200 and 800 MeV with a deuterium target collected by the A2 experiment in Mainz, Germany. These complement the data for neutral-pion photoproduction on protons obtained by the same experiment [2]. 相似文献
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Varlachev V. A. Dudkin G. N. Krechetov Yu. F. Manatskov V. I. Padalko V. N. Tryasuchev V. A. Shuvalov E. N. 《Russian Physics Journal》2003,46(9):874-882
Results of an experiment on the search for the emission of 0 mesons in neutron-induced fission of 235U nuclei based on the detection in coincidence of two -quanta from the 0-meson decay performed with the nuclear reactor developed at the Scientific-Research Nuclear Physics Institute at Tomsk Polytechnic University are described. The experimental setup comprised two erenkov spectrometers of total absorption for the detection and measurement of -quantum energy placed in two coaxial horizontal channels of the nuclear reactor. Water filters placed in the channels were used to protect the detectors from -, -, and neutron fluxes. To reject the cosmic radiation, scintillation counters of large area, operating in anticoincidence mode, were placed above each spectrometer. The experimentally measured limitation on the probability of neutral pion emission in neutron-induced fission of nuclei was established 4.1·10–11 with a 90% confidence level. The energy spectrum of -quanta from the active reactor zone was measured in the range 32–65 MeV. The parameters of the spectrum deviated from the results of theoretical calculations and from the experiment performed with the nuclear pulse reactor developed at the Joint Institute for Nuclear Research (Dubna). 相似文献
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Physics of Atomic Nuclei - In this paper after a historical introduction I discuss ideas of a pion softening and pion condensation in a dense nuclear matter, in particular in neutron stars, and a... 相似文献
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Fissilities induced by the absorption ofπ ? at rest in nuclei ranging from rare earth region to Uranium are evaluated by means of the Exciton Model. The theoretical results satisfactorily reproduce the experimental findings provided the ratioa f/an is greater than unity and equal to 1.1. 相似文献
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We explore the interplay between the few-body aspects of few-pion states and the many-body aspects of their quark structure. We show for a schematic quasispin model similar to the Nambu–Jona-Lasinio model how one can derive rather accurately the pion–pion scattering length from the excitation spectrum in a box. 相似文献
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Olgierd Dumbrajs 《Fortschritte der Physik》1981,29(10):487-494
The concept of the pion-nucleus coupling constants is discussed. Methods of their determination are reviewed. These include: forward dispersion relations, extrapolation of differential cross sections to the poles in the angular variable, analysis of data on electromagnetic form factors with the use of the PCAC and CVC hypotheses, pion photoproduction at threshold and low-ernergy theorems. Our present knowledge of the pion coupling to the He, Li, Be, C, N and O nuclei is summarized. 相似文献