相对论核模型和EMC效应

本文认为原子核是保持重子数守恒的若干核子和反核子的复合系统,在核内有过剩的π介子担负核子或反核子间交换作用.这些过剩π介子和反核子内的部分子带走一定动量分额,从而可解释x中间区EMC效应的主要特征.考虑到遮蔽-反遮蔽效应和费米运动后,计算了多种原子核的EMC效应,在0相似文献   

核子与原子核的奇异性产生和重味产生

本文简要评述中高能强子散射和电磁散射实验中原子核的奇异性产生与重味产生,并重点介绍该领域近年新实验结果和对奇异性产生反应机制的新认识。实际上,自上世纪70年代起已通过强子反应和光核反应开始了奇异性产生的研究工作。由于近年来SATURNE和COSY（强子探针）以及ELSA和JLab（电磁探针）的发展,提供了大量高精度的奇异性产生方面的实验数据,使人们能够深入研究奇异性产生的碰撞机制,进而研究重子谱与超核物理。本文评述奇异性产生在实验和理论两方面的新进展,包括核靶与核子靶两种情况,以及它们与核结构和强子结构研究的联系。本文最后对重味产生反应也进行适当介绍。     

介绍一种“π凝聚”的理论模型

一、引言 π分子是一种基本粒子,属介子旅.根据据所带电荷为 、 、0,可分为π ,π-,πu三种π介子π介子的自旋转为零,宇称为负,同位旋为1,静止质量为139, 物理MeV,寿命为10-8see.它在核物理中占有十分突出的地位.自从1935年日本　川秀树提出了核力介子理论以来,现在一般都认为,核子-核了间的相互作用是通过π分子来传递的。在原子核内存在着瞬时出现的π介子,与自由π介子不同,它不满足的质能关系式,因此说它是“虚”的π介子. 最近几年,有不少理论物理工作者[1]在探讨这样一个问题:在原子核内是否有真实的自由π介子存在?他们考虑的基点…     

我国物质结构研究的大型实验平台(续)——原子核科学与技术实验设施

我们现在从基本粒子来到原子核的层次。核物理是一门重要的基础研究领域,核技术在能源等诸多方面有着广泛的应用。为了深入开展核物理的研究,科学家发明了加速器,用高能量的粒子束流作为"炮弹",打开原子核的奥秘。为了开发蕴藏在原子核内部的巨大能量,科学家发明了反应堆,建成了核能发电站,并研究更安全、更有效的核能装置,造福于人类。从20世纪30年代中子的发现起,人们就知道原子核主要是由质子和中子构成的。随着研究的深入,核物理研究的前沿又推进到放射性核束物理、核天体物理、重子物理、超核、超     

核物理中的π介子

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 ...     

奇时间(time-odd)分量对41Ca性质的影响

发展了包括奇时间(time-odd)分量的三轴形变的RMF理论模型, 采用包含σ和ω介子自相互作用以及微观质心修正的PK1有效相互作用, 自洽考虑了由于奇A核中的未配对的核子对时间反演不变性的破坏所导致的重子流, 以⁴¹Ca为例, 研究了奇时间分量对重子流以及原子核性质的影响.     

原子与原子核的新形态——介子原子和介子核

 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。     

夸克平均场模型的有限核及超核研究

夸克平均场模型采用组分夸克模型描述重子,已被用于研究有限核及超核的性质.介子平均场直接与核子内的组分夸克相互作用,从而改变了核介质内重子的性质.夸克平均场模型能够给出令人满意的球型核及超核的性质,该模型也预言了核介质中核子体积的膨胀及核子有效质量的降低.     

基于相对论Hartree-Fock理论的原子核壳结构性质研究

一直以来，原子核壳结构是原子核物理研究的重点关注内容。特别是随着近年来新一代放射性核束装置和探测技术的蓬勃发展，丰中子原子核中新的壳结构及其演化与形成机制等成为核物理关注的热点之一。在基于核力介子交换图像建立的相对论Hartree-Fock 理论框架下，本工作以Ca同位素、双幻核 208Pb、超重核以及极端丰中子核为例，综述丰中子原子核中新的壳结构形成机制，高角动量态赝自旋对称性恢复与介质中核力吸引-排斥平衡，赝自旋对称性恢复/破缺与原子核壳结构、新奇现象等研究工作，并着重关注了与原子核新壳结构形成、赝自旋对称性恢复以及新奇现象等密切相关的交换(Fock)项效应。     

反质子物理

本文介绍反质子与核子和与原子核碰撞后各种物理现象．它与核子的散射获得的位势是吸引势和吸收型,与核的光学势是强吸收到．湮没后产生众多的介子和重子．以及在高能下湮没产生奇特性粒子、带粲的介子、重子．并探索获得混杂子、在核中存在反质子、其它新粒子的可能性． In this paper several physical phenomena of antiproton-nucleon and antiproton-necleus collision are discussed. The potential obtained from p-N scattering is attraction and absorption type. The optical potential of nucleus is strong absorption type. The annihilation happens after pp collision and thenproduces many kinds of meson, hadron, even produce some exotic particle and charmonium at high energy pp anihilation. Posibilities to find hybrids, antiproton and other particles in nucleus are also explored.     

The strangeness of dense baryonic matter

Particle production in heavy-ion collisions is sensitive to the reaction dynamics and to the conditions inside the dense and hot fireball. In particular, experimental data on strangeness production at SIS energies, together with their theoretical interpretation based on microscopic transport theory,p permit to explore fundamental aspects of modern nuclear physics: the determination of the nuclear equation-of-state at high baryon densities and the properties of hadrons in dense nuclear matter. Experimental data and theoretical results will be reviewed.     

Compressed baryonic matter—experiments at GSI and FAIR

Experiments on strangeness production in nucleus-nucleus collisions at SIS energies address fundamental aspects of modern nuclear physics: the determination of the nuclear equation-of-state at high baryon densities and the properties of hadrons in dense nuclear matter. Experimental data and theoretical results will be reviewed. The planned “Compressed Baryonic Matter” (CBM) experiment at the future Facility for Antiproton and Ion Research (FAIR) aims at the exploration of the QCD phase diagram at the highest baryon densities. This includes the search for the deconfinement and chiral phase transition and for the QCD critical endpoint. Possible observables and the experimental setup will be discussed. The text was submitted by the author in English.     

Baryon yields, isospin effects and strangeness production in elementary hadronic interactions

New NA49 data from hadron+proton and hadron+Pb interactions are used to extract detailed information on projectile isospin effects and baryon, baryon pair and strangeness production. Consequences for the interpretation of hadron production and strangeness enhancement in nuclear collisions are discussed.     

Phase transition of the baryon-antibaryon plasma in hot and dense nuclear matter

We investigate the presence of thermodynamic instabilities in a hot and dense nuclear medium where a phase transition from a gas of massive hadrons to a nearly massless baryon, antibaryon plasma can take place. The analysis is performed by requiring the global conservation of baryon number and zero net strangeness in the framework of an effective relativistic mean field theory with the inclusion of the Δ(1232)-isobars, hyperons and the lightest pseudoscalar and vector meson degrees of freedom. Similarly to the low density nuclear liquid-gas phase transition, we show that such a phase transition is characterized by both mechanical instability (fluctuations on the baryon density) that by chemical- diffusive instability (fluctuations on the strangeness concentration). It turns out that, in this situation, phases with different values of antibaryon-baryon ratios and strangeness content may coexist.     

Hadron and nuclear physics with inverse compton gamma-rays at SPring-8

A new facility for GeV γ-ray beams in an energy range of 1.5–2.4 GeV has been constructed for developing hadron physics at SPring-8. GeV γ-rays are produced via the inverse Compton scattering process, and are used to study the sub-nucleonic structure of nucleon via the productions of φ and K⁺ mesons. The recent experimental results to observe φ and K⁺ mesons are discussed to look for the physics in relation to strangeness quarks in baryon resonances. A new beam line for MeV γ-rays at SPring-8 to give new possibilities for the studies of the weak-strong coupling effects in nuclear mediums through the observation of parity violation is also discussed.     

Properties of Strange Matter in a Model with Effective lagrangian

The strange hadronic mater with nucleons,Λ-hyperons and Ξ-hyperons is studied by using an effective nuclear model in a mean-field approximation.The density and strangeness fraction dependence of the effective baryon masses as well as the saturation properties and stabilities of the strange hadronic matter are discussed.     

奇异强子物质的有效模型描述

把 FST模型推广到包含奇异性的情形,并在平均场近似下用它来研究含有核子、Λ超子和Ξ超子的奇异强子物质的性质.讨论了有效重子质量对介质密度和奇异数含量的依赖性以及奇异强子物质的饱和性和稳定性. The strange hadronic matter with nucleon, Λ hyperon and Ξ hyperonis was studied by using an effective model in a mean field approximation. The density dependence of the effective baryon masses as well as the saturation properties and stabilities of the strange hadronic matter were discussed. The result indicates a quite large strangeness fraction range where the multi hyperon nuclear matter is stable against particle emission. In the large strangeness fraction region the Ξ component dominates...     

Strangeness nuclear physics

An overview of strangeness nuclear physics is given, focussing on spin dependent effects in Λ hypernuclei, on the ΛN → NN weak interaction in Λ hypernuclei, on the density dependence of the Σ nuclear potential and on double strangeness physics. A special emphasis is placed on the recent proposal to study experimentally Ξ⁻ atoms.     

Flavored exotic multibaryons and hypernuclei in topological soliton models

The energies of baryon states with positive strangeness, or anticharm (antibeauty), are estimated in the chiral soliton approach, in the “rigid oscillator” version of the bound-state soliton model proposed by Klebanov and Westerberg. Positive strangeness states can appear as relatively narrow nuclear levels (Θ-hypernuclei), and the states with heavy antiflavors can be bound with respect to strong interactions in the original Skyrme variant of the model (SK4 variant). The binding energies of antiflavored states are also estimated in the variant of the model with a sixth-order term in chiral derivatives added to the Lagrangian to stabilize solitons (SK6 variant). This variant is less attractive, and nuclear states with anticharm and antibeauty can be unstable relative to strong interactions. The chances of obtaining bound hypernuclei with heavy antiflavors increase within the “nuclear variant” of the model with a rescaled model parameter (the Skyrme constant e or e′ decreased by a out 30%), which is expected to be valid for baryon numbers greater than B ～ 10. The rational map approximation is used to describe multiskyrmions with a baryon number of up to about 30 and to calculate the quantities necessary for their quantization (moments of inertia, sigma term, etc.).     

Progress in p-shell A hypernuclear spectroscopy

The strangeness nuclear physics is an important branch of nuclear physics. The spectroscopic study of A hypernuclei has been used as a tool for investigating the A-N interaction as well as probing the nuclear interior structure. In this paper some high-lights and open questions in the spectroscopic study of p-shell A hypernuclei are presented.