K~＋核散射与核介质效应

近年来中能Ｋ＋核散射的研究引起人们相当大的兴趣。本文评述Ｋ＋介子作为原子核深部的最“干净”的强子探针呈现出的主要特点;总结了实验数据和理论结果之间存在的系统而严重的偏离;着重讨论了Ｋ＋核散射中传统和非传统核介质效应;最后指出：（１）不能简单地由Ｋ＋核子散射来解释Ｋ＋核散射;（２）Ｋ＋介子可能用来探测核内核子性质的变化,成为轻子或电磁探针的有益补充;（３）文内指出的问题要求在实验上和理论上做更多的工作。     

K~＋核散射与核介质效应

近年来中能Ｋ＋核散射的研究引起人们相当大的兴趣。本文评述Ｋ＋介子作为原子核深部的最“干净”的强子探针呈现出的主要特点；总结了实验数据和理论结果之间存在的系统而严重的偏离；着重讨论了Ｋ＋核散射中传统和非传统核介质效应；最后指出：（１）不能简单地由Ｋ＋核子散射来解释Ｋ＋核散射；（２）Ｋ＋介子可能用来探测核内核子性质的变化，成为轻子或电磁探针的有益补充；（３）文内指出的问题要求在实验上和理论上做更多的工作。     

200A GeV S+Au反应中光子产生的低横动量增强

用建立在LUND弦模型特别是PYTHIA事件产生器基础上的描写极端相对论性核-核碰撞的强子和弦级联模型--JPCIAE研究了入射能量为200A GeV的S+Au中心碰撞中光子产生.模型同时考虑了部分子QCD散射过程、强子末态相互作用以及强子衰变等光子产生反应道并作了协调处理.JPCIAE模型计算结果很好再现了WA93实验数据所呈现的低横动量增强效应.     

ee0A GeV S+Au反应中光子产生的低横动量增强

用建立在LUND弦模型特别是PYTHIA事件产生器基础上的描写极端相对论性核一核碰撞的强子和弦级联模型—JPCIAE研究了入射能量为200A GeV的S+ Au中心碰撞中光子产生.模型同时考虑了部分子QCD散射过程、强子末态相互作用以及强子衰变等光子产生反应道并作了协调处理.JPCIAE模型计算结果很好再现了WA93实验数据所呈现的低横动量增强效应.     

相对论重离子碰撞中的软探针和硬探针

简要回顾了高能核碰撞中夸克胶子等离子体的软探针和硬探针的一些最新进展，主要内容集中在相对论重离子对撞机和大型强子对撞机实验中各向异性集体流和喷注淬火的理论和唯象研究，对小系统中集体流的来源也做了简要的讨论。对于软探针，讨论了初态三维涨落和碰撞几何各向异性、相对论流体力学演化、末态各向异性集体流以及集体流的涨落、关联和纵向去关联等。通过与实验数据作系统的比较，可以探测重离子碰撞中夸克胶子等离子体的动力演化和各种输运性质。对于硬探针，集中讨论了部分子能量损失和喷注淬火对部分子味道的依赖性、重味夸克在夸克胶子等离子体中的强子化、整体喷注在核介质中的演化以及核介质对喷注的响应等。细致分析相关的观测量，可以帮助我们更全面地了解相对论核碰撞中喷注与核介质的相互作用以及重味粒子的生成。对于小系统，讨论初态和末态效应在解释小系统中轻强子和重味强子的集体流方面的贡献，这有助于我们理解大碰撞系统中集体流的起源成因。     

相对论性核-核碰撞中的弹核碎裂过程

本文概括了14.6AGeV,60AGeV,200AGeV~(16)O,14.5AGeV~(28)Si和200AGeV~(32)S与固定靶碰撞的弹核碎裂过程的主要实验结果,分析了弹核电磁离解截面与弹核和靶核电荷大小及弹核能量间的关系,核反应截面与弹核和靶核大小及弹核能量间的关系,得到了弹核碎片的电荷分布、横动量分布和发射角分布以及α粒子多重数分布等规律,讨论了弹核碎裂过程包括电磁离解与核反应碎裂的机制,还评述了相对论性核-核碰撞中弹核碎片的次级作用问题。     

相对论性核—核碰撞中的弹核碎裂过程

本文概括了14.6AGeV,60AGeV,200AGeV~(16)O,14.5AGeV~(28)Si和200AGeV~(32)S与固定靶碰撞的弹核碎裂过程的主要实验结果,分析了弹核电磁离解截面与弹核和靶核电荷大小及弹核能量间的关系,核反应截面与弹核和靶核大小及弹核能量间的关系,得到了弹核碎片的电荷分布、横动量分布和发射角分布以及α粒子多重数分布等规律,讨论了弹核碎裂过程包括电磁离解与核反应碎裂的机制,还评述了相对论性核-核碰撞中弹核碎片的次级作用问题。     

核–核碰撞中喷注淬火导致的双强子产生压低

通过考虑喷注淬火效应,分析了相对论性高能重离子碰撞中双强子的产生.结果表明,喷注淬火压低了大不变质量谱和大横动量的双强子的产生.与质子–质子碰撞的情形类似,核–核的擦边碰撞(碰撞参数很大)产生的强子有很强的背靠背的关联.在核–核对心碰撞(碰撞参数很小)中,由于喷注穿过强作用物质导致的喷注淬火介质效应,产生的强子的背靠背的关联几乎消失.     

pp反应过程强子产生的不对称性

计算与分析了pp与p反应过程中轻味uds夸克的平均产生几率,得到它们与反应类型和反应能量的关系.进一步得出各种强子的相对产率,发现平均粒子产率,同位旋对称性,正反粒子多重数比例以及奇异抑制因子等,都与具体反应类型以及反应能量有关,特别得出pp反应中正反重子比率大于1 这与重离子碰撞实验结果非常吻合.     

pp(p)反应过程强子产生的不对称性

计算与分析了pp与pp反应过程中轻味uds夸克的平均产生几率, 得到它们与反应类型和反应能量的关系. 进一步得出各种强子的相对产率, 发现平均粒子产率, 同位旋对称性, 正反粒子多重数比例以及奇异抑制因子等, 都与具体反应类型以及反应能量有关. 特别得出pp反应中正反重子比率大于1, 这与重离子碰撞实验结果非常吻合.     

Identifying multiquark hadrons from heavy ion collisions

Identifying hadronic molecular states and/or hadrons with multiquark components either with or without exotic quantum numbers is a long-standing challenge in hadronic physics. We suggest that studying the production of these hadrons in relativistic heavy ion collisions offers a promising resolution to this problem as yields of exotic hadrons are expected to be strongly affected by their structures. Using the coalescence model for hadron production, we find that, compared to the case of a nonexotic hadron with normal quark numbers, the yield of an exotic hadron is typically an order of magnitude smaller when it is a compact multiquark state and a factor of 2 or more larger when it is a loosely bound hadronic molecule. We further find that some of the newly proposed heavy exotic states could be produced and realistically measured in these experiments.     

Heavy ion collisions at CMS and quark-gluon plasma

One of the most actual goals in high energy physics is reaching the state of deconfinement of hadronic matter and studying the properties of resultant quark-gluon plasma (QGP). Jet production, as well as other hard processes, is considered to be an efficient probe for formation of QGP in future experiments on heavy ion collisions at LHC.The Compact Muon Solenoid (CMS) is the general purpose detector designed to run at the LHC and optimized mainly for the search of the Higgs boson in proton-proton collisions. However, a good muon system and electromagnetic and hadron calorimeters with fine granularity gives the possibility to cover several important aspects of the heavy ion physics. The production of heavy quarkonia Γ, Γ′, Γ″ through their muon decay channel and the energy loss of hard jets, are valuable processes for studying the phase transition from the hadronic matter to the plasma of deconfined quarks and gluons.     

On chemical equilibrium in nuclear collisions

The data on average hadron multiplicities in central A+A collisions measured at CERN SPS are analysed with the ideal hadron gas model. It is shown that the full chemical equilibrium version of the model fails to describe the experimental results. The agreement of the data with the off–equilibrium version allowing for partial strangeness saturation is significantly better. The chemical freeze–out temperature of about 180 MeV seems to be independent of the system size (from S+S to Pb+Pb) and in agreement with that extracted in , and collisions. The strangeness suppression is discussed at both hadron and valence quark level. It is found that the hadronic strangeness saturation factor increases from about 0.45 for interactions to about 0.7 for central A+A collisions with no significant change from S+S to Pb+Pb collisions indicating that the strangeness enhancement in heavy ion collisions cannot be fully attributed to the increased system size. The quark strangeness suppression factor is found to be about 0.2 for elementary collisions and about 0.4 for heavy ion collisions independently of collision energy and type of colliding system. Received: 31 October 1997 / Published online: 26 February 1998     

Heavy flavour hadron spectroscopy: An overview

A comprehensive overview and some of the theoretical attempts towards understanding heavy flavour hadron spectroscopy are presented. Apart from the conventional quark structure (quark, antiquarks structure for the mesons and three-quarks structure of baryons) of hadrons, multiquark hadrons the hadron molecular states etc., also will be reviewed. Various issues and challenges in understanding the physics and dynamics of the quarks at the hadronic dimensions are highlighted. Looking into the present and future experimental prospects at different heavy flavour laboratories like BES-III, CLEO-c, BaBar, Belle, LHC etc., the scope for theoretical extensions of the present knowledge of heavy flavour physics would be very demanding. In this context, many relevant contributions from the forthcoming PANDA Facility are expected. Scopes and outlook of the hadron physics at the heavy flavour sector in view of the future experimental facilities are highlighted.     

SPIN effects, QCD, and Jefferson Laboratory with 12 GeV electrons

QCD and Spin physics are playing important role in our understanding of hadron structure. I will give a short overview of origin of hadron structure in QCD and highlight modern understanding of the subject. Jefferson Laboratory is undergoing an upgrade that will increase the energy of electron beam up to 12 GeV. JLab is one of the leading facilities in nuclear physics studies and once operational in 2015 JLab 12 will be crucial for future of nuclear physics. I will briefly discuss future studies in four experimental halls of Jefferson Lab.     

Multiquark Production from Heavy Ion Collisions

In this talk, I will discuss the intrinsic differences between a compact multiquark state and a normal hadron or a hadronic molecule. Using the coalescence model, I will then show that these intrinsic differences lead to appreciable differences in the yields of these particles from a heavy ion collision depending on their assumed internal structure.     

在反应中的夸克对产生率、奇异抑制因子和重子介子比

利用夸克统计模型和强子产额的实验数据，研究了　反应中的夸克对产生率、奇异抑制因子和重子介子比，得到了这些量随能量的变化规律．     

Hadron production in relativistic nuclear collisions: thermal hadron source or hadronizing quark-gluon plasma?

Measured hadron yields from relativistic nuclear collisions can be equally well understood in two physically distinct models, namely a static thermal hadronic source vs. a time-dependent, nonequilibrium hadronization off a quark-gluon plasma droplet. Due to the time-dependent particle evaporation off the hadronic surface in the latter approach the hadron ratios change (by factors of ) in time. Final particle yields reflect time averages over the actual thermodynamic properties of the system at a certain stage of the evolution. Calculated hadron, strangelet and (anti-)cluster yields as well as freeze-out times are presented for different systems. Due to strangeness distillation the system moves rapidly out of the , plane into the -sector. Strangeness to baryon ratios prevail during a considerable fraction (50%) of the time evolution (i.e. -droplets or even -droplets form the system at the late stage: The possibility of observing this time evolution via two-particle correlations is discussed). The observed hadron ratios require MeV and MeV. If the present model is fit to the extrapolated hadron yields, metastable hypermatter can only be produced with a probability for . Received: 15 April 1997 / Revised version: 5 June 1997     

反质子引起的核反应中碎裂机制和粒子产生（英文）

基于兰州量子分子动力学（LQMD） 模型,系统研究了低能反质子引起的核反应中原子核碎裂机制和粒子产生。在LQMD输运模型中,考虑了反重子-重子、重子-重子和介子-重子碰撞可能产生的弹性散射、湮灭反应、电荷交换和非弹性散射。发展了并合模型,用于相空间构造初级碎片产生。处于激发态的碎片退激是基于统计模型描述。研究结果说明超子主要是由于奇异性交换产生;重碎片裂变会导致中等质量区域碎片产额增加;反质子引起的核反应有利于产生s=-2 和s=1 奇特超核,并给出了产生截面。Within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model, the nuclear fragmentation and particle production induced by low-energy antiprotons have been investigated thoroughly. Production of strange particles in the antiproton induced nuclear reactions is modeled within the LQMD model, in which all possible reaction channels such as elastic scattering, annihilation, charge exchange and inelastic scattering in antibaryon-baryon, baryon-baryon and mesonbaryon collisions have been included. A coalescence approach is developed for constructing the primary fragments in phase space. The secondary decay process of the fragments is described by the well-known statistical code. It is found that the strangeness exchange reactions dominate the hyperon production. A bump structure in the domain of intermediate mass for heavy targets appears owing to the contribution of fission fragments. It has advantage to produce heavier hyperfragments and hypernuclides with strangeness s = -2 (double-Λ fragments) and s = 1 (Λ-fragments) in antiproton induced reactions. The production cross sections are evaluated.