CSR能区重离子反应中的介子产生

重离子反应中介子产生的观测对于认识重离子反应动力学和核物质性质具有重要的意义 .讨论了重离子反应中阈能附近介子产生的一些特点和研究现状 ,特别讨论了π介子产生和K+ 介子产生 .在我国兰州重离子冷却储存环上开展这方面的实验研究具有可能性 ,可望得到很有意义的结果 .及时开展这方面实验研究和相应的理论研究是必要的.It is important to measure meson productions in heavy ion collisions in order to understand the dynamics of heavy ion reactions and the properties of nuclear matter. In this paper we review the characteristic and present status of meson productions near the threshold energies in heavy ion collisions. Especially the pion and K + productions are discussed. We point out that it is meaningful and possible to carry out the experimental studies at the CSR. It is necessary to carry out timely the...     

在pA碰撞中K~±,η和ф介子的阈下产生

简要评述了在pA碰撞过程中K±,η和ф介子的阈下产生及其对应的物理含义。这些介子的阈下产生都可以在兰州CSR上实现,特别是通过pA碰撞实现ф介子的阈下产生还没有看到实验数据的报道。     

核物质中的π,K,ρ和η物理

介绍了入射能量约1AGeV时的重离子碰撞产生的介子物理,分析了SIS和Bevalac两个重离子加速器的实验数据中显示的介质效应,特别是手征对称性在有限密度时的部分恢复信号,指出了目前理论研究中存在的问题 ,最后讨论了兰州重离子加速器CSR可以进行的介子物理研究.The meson physics in heavy ion collisions around energy 1 A GeV is investigated. The experimental data at SIS and Bevalac on medium effects, especially on the signatures of chiral symmetry restoration at finite density are analyzed, and the related problems in the study are pointed out. Finally the possible meson physics at cool storage ring (CSR) is discussed.     

重离子碰撞中的介子——兰州重离子冷却储存环上可能实验的讨论

讨论了在兰州重离子加速装置冷却储存环上开展介子产生的实验研究的可能性和进行π和η介子产生研究的意义在 ＣＳＲ能量区域内, 核子可以激发为Δ和 Ｎ,因此, 在研究热密核物质的状态方程时, 考虑Δ和Ｎ自由度是重要的． 观察重离子碰撞中产生的介子可以提供热密核物质的状态方程, 从而可以提供核内物质分布以及 Ｎ在核物质中传播的信息． 建议建造一个测量介子的实验装置, 以开展该领域的研究.The possibilities for experimental study of meson production at Cooling Storage Ring (CSR) of Lanzhou are discussed. It is shown that the study of production of the pion and eta mesons at CSR is of significance. Nucleon can be excited to Δ and N * at CSR energy region. Therefore, it is important to consider the degree of Δ and N * in the study of the equation of states of hot and dense matter. The produced mesons in heavy ion collisions can provide information on...     

Photoproduction of Light Vector Meson in Relativistic Heavy Ion Collisions

We calculate the hard photoproduction of light vector meson from the fragmentation of photon in Pb Pb col- lisions. Using the perturbative quantum chromodynamics calculation, we rigorously derive the electromagnetic fragmentation production for p, co and Ф in relativistic nucleus-nucleus collisions by the photoproduction pro- cesses. It is shown that the differential cross section of photoproduction processes of light vector meson cannot be negligible in relativistic heavy ion collisions at Large Hadron Collider energies.     

Strangeness by Thermal Model Simulation at RHIC

The local temperature effect on strangeness enhancement in relativistic heavy ion collisions is discussed in the framework of the thermal model in which the K^＋ /h^＋ ratio becomes smaller with increasing freeze-out temperature. Considering that most strangeness particles of final-state particles are from the kaon meson, the temperature effect may play a role in strangeness production in hot dense matter where a slightly different temperature distribution in different areas could be produced by jet energy loss. This phenomenon is predicted by thermal model calculation at RHIC energy. The /Ф ratio in central Au＋Au collisions at 200GeV from the thermal model depends on the freeze-out temperature obviously when γs is different. It should be one of the reasons why strangeness enhancements of and Ф are different though they include two strange quarks. These results indicate that thermodynamics is an important factor for strangeness production and the strangeness enhancement phenomenon.     

中高能重离子碰撞的高能光子测量及相关物理

高能光子探测为研究中高能重离子碰撞的许多重要问题如核物质性质、韧致辐射、阈下和阈上中性介子产生等提供了机遇.简要回顾了近几年国外开展的中能与相对论重离子碰撞高能光子实验概况,并简要介绍了欧洲合作研制的高能光子探测器TAPS的基本构造.另外,用GEANT程序模拟计算了50—1000MeV光子在TAPS标准8×8阵列中的能量响应. The Measurement of energetic photon produced in intermediate energy and relativistic energy heavy ion collisions provides opportunities for investigating many interesting and sophisticated problems such as properties of nuclear matter under extreme condition, bremsstrahlung, neutral meson production both below and above the production threshold in free nucleon nucleon collision. The related experiments performed at GANIL and GSI as well as the structure of the popular used detector ...     

Φ Meson Production in Heavy Ion Collisions at RHIC

We present Φ meson production in Cu+Cu and Au+Au collisions measured by the STAR experiment at RHIC.The hadronic decay mode Φ→K~+K~- is used in the analysis.The yields for Φ meson in Cu+Cu and Au+Au collisions at a given beam energy are scaled by the number of participant.The N_(part) normalized Φ meson yields in heavy ion collisions over those from p+p collisions are larger than 1 and increase with collision energy.These results suggest that the source of enhancement of strange hadrons is related to the formation of a dense medium in high energy heavy ion collisions and can not be only due to canonical suppression of their production in smaller systems.We also present STAR results on the Φ meson elliptic flow υ_2 from 2~(1/SNN)=200 GeV Cu+Cu at RHIC.The elliptic flow in Cu+Cu system that has the similar relative magnitude and qualitative features as that in Au+Au system.The observations imply the hot and dense matter with partonic collectivity has been formed in heavy ion collisions at RHIC.However,eccentrality normalized υ_2,υ_2/(n_qε_(part)) is lower for Cu+Cu than for Au+Au collisions at 200 GeV.So this might indicate thermalization has not been reached in 200 GeV Cu+Cu collisions.     

K介子协变动力学及其准粒子模型的性质

简要综述了中高能重离子碰撞中K介子的产生及研究进展。重点介绍了K介子协变动力学模型, 并在此框架内分析了中高能重离子碰撞中K+介子以及与其伴随产生的Λ超子的集体流特征。 结果表明: 协变动力学模型能够很好地给出K+介子和Λ超子的微分直接流。 相对而言, 软势给出的集体流与实验值符合更好。同时, 通过对不同输运模型中K介子准粒子模型的基本属性进行对比分析, 明确了协变动力学模型中K介子准粒子模型的质量及能量随核物质密度的变化特征, 以及周围核子的运动对于K介子基本属性的影响。In the present paper, we briefly review the progress in the study of kaon production in heavy\|ion collisions at intermediate and high energies and introduce the covariant kaon dynamics model. The collective flows of positively charged kaon and the lambda hyperon associated produced with kaon are studied in the framework of the dynamics. It shows that the directed differential flow of K+ meson and Λ hyperon can be reasonably reproduced in the covariant kaon dynamics model. The calculated results with soft equation of nuclear matter are in better agrement with experimental data. Meawhile, a detailed comparison of the properites of different quasi\|particle models in various transport model and the influence of nucleon’s movement on the effective mass and energy of the quasi\|particle in the covariant kaon dynamics model are discussed.     

在RHIC的极限碎裂和Φ介子产生(英文)

利用强子和串级联模型LUCIAE研究了PHOBOS的极限碎裂等以及在PHIC进行的Au+Au碰撞中带电粒子多重性的经验标度规律. 对Φ介子的产生机制也通过与带电粒子多重性的比较进行类似的研究. 结果似乎表明在串级碎裂模型中带电粒子和Φ介子有共同的产生机制. 还讨论了PHOBOS经验标度规律的模型依赖性.The PHOBOS’s limiting fragmentation etc. three empirical scaling rules for charged multiplicity in Au+Au collisions at RHIC are investigated by ahadron and string cascade model LUCIAE. Similar studies are performed for the meson exploring its production mechanism via comparing with the charged multiplicity. The LUCIAE results for charged multiplicity are compatible with PHOBOS observations. However, for the  meson the three empirical scaling rules are either kept only or kept better in the LUCIAE calculations without reduction mechanism of the s quark suppression extra introduced for the strangeness in LUCIAE model. These results seem indicating a universal production mechanism for charged particle and  meson in string fragmentation regime. It is discussed that the PHOBOS’s empirical scaling rules are model dependent indeed.     

兰州CSR与高密核物理

讨论在兰州 Ｃ Ｓ Ｒ 上产生高密核物质的可能性以及在末态出现的相应信号． 估计了 Ｃ Ｓ Ｒ 所能达到的核物质密度, 分析了由于手征对称性部分恢复引起的强子阈下产生和强子流在 Ｃ Ｓ Ｒ 能区的特征． The possibility to produce highly dense nuclear matter at CSR of Lanzhou and the corresponding signals at final state are discussed. Especially, the maximum baryon density reached at CSR is estimated, and the subthreshold production and hadronic flow risen from the partial restoration of chiral symmetry at CSR energies are analyzed.     

Transverse momentum spectra in high-energy nucleus-nucleus, proton-nucleus and proton-proton collisions

The transverse momentum distributions of final-state particles produced in nucleus-nucleus (AA), proton-nucleus (pA), and proton-proton (pp) collisions at high energies are investigated using a multisource ideal gas model. Our calculated results show that the contribution of hard emission can be neglected in the study of transverse momentum spectra of charged pions and kaons produced in Cu-Cu collisions at √s_NN=22.5 GeV. And if we consider the contribution of hard emission, the transverse momentum spectra of p and p produced in Cu-Cu collisions at √s_NN=22.5 GeV, K_s⁰ produced in Pb-Pb collisions at 158 A GeV, J/ψ particles produced in p-Pb collisions at 400 GeV and π⁺ , K⁺, p produced in proton-proton collisions at √s=200 GeV, can be described by the model, especially in the tail part of spectra.     

《原子核物理评论》2006年第23卷第1-4期总目次

第1期核物理在pA碰撞中K±,η和介子的阈下产生…………………………………………………………………………郭华等(1)非微扰QCD和核遮蔽效应对K因子的影响………………………………………………………………………智海素等(6)全同粒子维数与角动量耦合求和规则…………………     

J/ψ Production in Ultra-Peripheral pp Collisions through aTwo-Photon Process

Using the photon spectrum of a high energy charged patton, we investigate the J/ψ production via the two photon interaction mechanism in ultra-peripheral pp collisions. It is shown that the contributions from the direct electromagnetic and the corresponding fragmentation processes are meaningful for the J/ψ productions in ultra-peripheral pp collisions at LHC energy.     

3π强子物理和实验

在强子物理研究中,3π产生的理论和实验有非常重要的意义,是目前世界上很多大型实验设备的重要研究对象。3π强子物理包含丰富的物理内容,可以作为探索低能区强相互作用的有力工具。同时,3π产生过程是寻找奇特轻介子态的主要途径之一。另外,通过研究3π产生反应道还可以寻找“失踪”共振态和重子激发态之间的级联衰变。介绍了目前国际各大高能物理实验室的3π产生过程的实验、理论研究以及分波分析技术现状,重点介绍了美国杰弗逊国家实验室（Jefferson Lab,简称JLab）的CLAS（CEBAF Large Acceptance Spectrometer）实验上的3π反应过程。最后,指出了3π强子物理研究的意义和未来的研究方向。Three pion productions off nucleon are of significance in the research of hadron physics. Meanwhile it is the subject of many big experimental apparatus in the world. Due to the variety of three pion productions, it can be applied as an effective tool to study QCD in low energy region. Three pion productions is one of the main reactions in searching light exotic meson state. Moreover, it is possible to find out the "missing" baryon resonance and the cascaded decay process between baryon excited states. We introduce present experiments and theories of three pion productions as well as the partial wave analysis technique. The emphasis is on the CLAS (CEBAF Large Acceptance Spectrometer) experiment at JLab (Jefferson Lab). In the end, we point out the significance of studying the three-pion hadron physics at JLab.     

Rapidity dependence of hadron PT spectra in central Au＋Au collisions at √^SNN = 200 GeV

The transverse momentum spectra for identified hadrons at different rapidities in central Au＋Au collisions at √^SNN= 200 GeV are studied in a quark combination model. The results for PT spectra of π^±, K^±, p（p^-） and for the p/π ratios in a broader PT range at midrapidity agree well with the data. The transverse momentum spectra of pions, protons and antiprotons at various rapidities y - 1, η= 2.2 and y ≈ 3.2 are calculated and compared with the data.     

HBT参数对π源空间分布的敏感性研究(英文)

利用理想高斯源的两粒子关联函数，对单高斯源和双高斯源的两π介子HBT关联效应进行了研究，得出了相应的半径参数和A参数．结果表明，半径参数主要取决于高能重离子碰撞中多数π介子产生的中间区域；对产生π介子的边缘区域的空间分布形状不敏感．在边缘区域内产生的π介子主要影响A参数的变化．π介子源空间分布的非高斯形是导致λ参数减少的一个重要因素．The HBT radius parameters and the HBT λ-parameters of single Gaussian source and double Gaussian source are investigated by using two-pion correlation function in HBT intensity interferometry. It is indicated that the radius parameter is insensitive to the spatial shape of the edge zone of source and is mainly affected by the size of the central zone of pions emitted in high energy heavy-ion collisions. The pions produced at the edge of source influence the λ parameter. The non-Gaus...     

B→K0^＊（1430）K Decays in Perturbative QCD Approach

In this article, we calculate the branching ratios of B→K0^＊ （1430）K decays by employing the pertur-bative QCD （pQCD） approach at leading order. We perform the evaluations in the two scenarios for the scalar meson spectrum. We find that （i） The leading order pQCD predictions for the branching ratio Br（B^＋→K^＋K0^＊（1430）^0）are in good agreement with the experimental upper limit in both scenarios, while the pQCD predictions for other considered B→K0^＊（1430）K decay modes are also presented and will be tested by the LHC experiments; （ii） The annihilation contributions play an important role in these considered decays, for B^0→K0^＊（1430）^±K^± decays,for example,which are found to be （1-4）×10^-6.