在大型强子对撞机上探索物质本源的大型重离子实验

欧洲核子研究中心的大型重离子实验探测器(ALICE),利用2008年开始运行的大型强子对撞机(LHC),将核物质加热到太阳中心温度的几十万倍,研究在高温高密的极端环境下生成的新物质形态(夸克胶子等离子体或夸克物质)的性质.这样的实验有可能从本源上探索:强作用力如何支配物质结构?夸克作为强作用力的基本量子,如何禁闭于质子和中子内部?夸克作为物质的基本组成单元,质量从何而来?文章介绍在大型强子对撞机上探索物质本源的大型重离子实验,内容包括:强作用力与夸克模型、渐进自c由与夸克禁闭、重离子碰撞与夸克物质、LHC上的ALICE实验、连通夸克和宇宙.     

High pt and photon physics with ALICE at LHC

ALICE,A Large Ion Collider Experiment,is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma （QGP） and phase transition.High-transversemomentum photons and neutral mesons from the initial hard scattering of partons can be measured with ALICE calorimeters,PHOS （PHOton Spectrometer） and EMCAL （ElectroMagnetic CALorimeter）.Combing the additional central tracking detectors,the γ-jet and π 0-jet measurements thus can be accessed.These measurements offer us a sensitive tomography probe of the hot-dense medium generated in the heavy ion collisions.In this paper,high p T and photon physics is discussed and the ALICE calorimeters capabilities of high-transverse-momentum neutral mesons and γ-jet measurements are presented.     

高能重离子碰撞间歇行为的系统研究

本文用阶乘矩方法分析了几种入射能量(14.6,60,200A GeV)下氧、硅和硫离子诱导乳胶核反应和硫离子与金靶相互作用过程的间歇行为.利用EMU01组的实验数据发现,在赝快度间隔1—0.1范围内,这几种核反应过程都有间歇性.间歇指数随入射能量和末态相对论带电粒子平均多重数的增加而减少,随靶核质量的增加而增加.在实验误差范围内,观察到间歇指数随射弹核质量的增加有上升趋势.     

ALICE光子谱仪前端电子学系统的性能研究

首先讨论了ALICE光子谱仪前端电子学的物理需求, 介绍了光子谱仪前端电子学测试系统. 采用该系统对光子谱仪前端电子学系统板(FEE)进行了检测, 检测表明现行设计的前端电子学系统板的物理性能已达到了ALICE实验的预期物理目标.     

UrQMD模型中对质心能量7.7~62.4 GeV下正反粒子椭圆流的差异研究(英文)

利用UrQMD-3.3p1 模型模拟了在质心能量√sNN = 7.7, 11.5, 19.6, 27, 39 和62.4 GeV 的Au+Au 碰撞,在中心快度区域分析了质子,π+,K+ 以及它们相应的反粒子的椭圆流。分析了粒子与相应的反粒子的v2 差值随横动量pT 的变化。分析结果表明,在UrQMD 模型中在整个BES 能区K- 的v2 值大于K+ 的。在能区7.7 ~ 62.4GeV π+ 和π-的v2(pT) 值几乎相同。然而实验上在低能区7.7, 11.5 和19.6 GeV, 在所考察的pT 值范围内v2(π-)大于v2(π+)。能清楚看到在UrQMD模型中在整个BES 能区反质子的v2 大于质子的,这与实验结果相反。理论结果与实验数据相反,表明我们还需要不断深化对重离子碰撞的强耦合性和输运过程的非平衡性的理解。     

大型强子对撞机LHC上的ALICE实验

 ALICE 大型离子对撞机实验(A Large Ion Collider Experiment)是欧洲核子中心(CERN) 的大型强子对撞机LHC 上的4 个主要国际合作项目之一。合作组包括36 个国家的132 个研究单位的约1200 位物理学家、工程师和技术工人。其中包括约200 多研究生。中国原子能科学研究院、华中师范大学和华中科技大学参与了ALICE国际合作。     

重离子耗散碰撞激发函数的涨落

综述了重离子耗散碰撞激发函数中截面涨落现象的实验与理论研究的现状． The present status of the studies on the cross section fluctuation phynomeno in dissipative heavy ion collisions (DHIC) is reviewed, especially for the fluctuation characteristics and the theoretical deuelopment.     

用阶乘矩技术提高相对论重离子碰撞实验数据样本中QGP事件比例的方法

在相对论重离子碰撞中形成QGP时,与之相伴随的有一些非QGP背景事件.把末态(方位角、快度)二维相空间中阶乘矩剧烈上翘的消失与一些普遍认为的QGP信号(如K/π比的上升)联系起来讨论,提出了一种从实验数据中挑选候选的QGP事件的方法.用Mont–Carlo模拟表明,这种方法有效地提高了挑选出来的子样本中QGP事件的信噪比.     

重离子碰撞中发射核子的多重性

在激子模型中,考虑了多次发射效应和它与态间跃迁的耦合,计算了重离子碰撞中非平衡发射粒子的多重性,并与实验做了比较.     

25MeV/u40Ar+115In反应中前中角区碎片发射研究

从25MeV/u⁴⁰Ar+¹¹⁵In反应前中角区出射碎片的能谱、角分布和Z电荷分布出发,讨论了碎片发射机制随出射角和核电荷数Z的渐进变化;用改进的量子分子动力学(MQMD)模型研究了碎片角分布及Z电荷分布,理论计算和实验值整体上符合较好,但在前角区MQMD模型低估了碎片的产额,在中角区对于Z接近弹核的碎片,理论计算比实验值偏高;碎片产物的角分布及Z电荷分布还与统计模型GEMINI进行了比较,发现在前角区平衡蒸发的成分所占比例很小,中角区所占的比例有所增加,但仍然 关键词：     

Measuring beauty production in Pb-Pb collisions at the LHC via single electrons in ALICE

We present the expected ALICE performance for the measurement of the p _t-differential cross section of electrons from beauty decays in central Pb-Pb collisions at the LHC. for the ALICE Collaboration Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

Photon multiplicity measurements: From SPS to RHIC and LHC

Results from the photon multiplicity measurements using a fine granularity pre-shower photon multiplicity detector (PMD) at CERN SPS are discussed. These include study of pseudorapidity distributions of photons, scaling of photon multiplicity with number of participating nucléons, centrality dependence of 〈p _T〉 of photons, event-by-event fluctuations in photon multiplicity and localised charged-neutral fluctuations. Basic features of the PMD to be used in STAR experiment at RHIC and in ALICE experiment at LHC are also discussed.     

Collision geometry and particle production in high energy heavy ion collision experiments

An overview of research status of soft physics in high energy heavy-ion collision experiments and recent experimental results are presented. This paper includes four parts: 1) Theoretical predictions of quark-gluon plasma and introduction for high energy heavy ion collision experiments. 2) Experimental status on collision     

Proton-proton physics with the ALICE muon spectrometer at the LHC

ALICE, the dedicated heavy-ion experiment at the LHC, has also an important proton-proton physics program. The ALICE muon spectrometer will be presented and the corresponding physics analysis will be reviewed. A particular emphasis will be placed on heavy-flavor measurement. (for the ALICE Collaboration) The text was submitted by the author in English.     

Prospects for strangeness measurement in ALICE

The study of strangeness production at LHC will bring significant information on the bulk chemical properties, its dynamics, and the hadronization mechanisms involved at these energies. The ALICE experiment will measure strange particles from topology (secondary vertices) and from resonance decays over a wide range in transverse momentum and shed light on this new QCD regime. These motivations will be presented as well as the identification performance of ALICE for strange hadrons. (for the ALICE Collaboration) The text was submitted by the author in English.     

High pt and photon physics with ALICE at LHC

ALICE,A Large Ion Collider Experiment,is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma (QGP) and phase transition.High-transversemomentum photons and neutral mesons from the initial hard scattering of partons can be measured with ALICE calorimeters,PHOS (PHOton Spectrometer) and EMCAL (ElectroMagnetic CALorimeter).Combing the additional central tracking detectors,the γ-jet and π 0-jet measurements thus can be accessed.These measurements offer us a sensitive tomography probe of the hot-dense medium generated in the heavy ion collisions.In this paper,high p T and photon physics is discussed and the ALICE calorimeters capabilities of high-transverse-momentum neutral mesons and γ-jet measurements are presented.     

Anisotropic flow of Pb+Pb s_(NN)~(1/2)= 5.02 TeV from a multi-phase transport model

Anisotropic flow is an important observable in the study of the quark-gluon plasma that is expected to be formed in heavy-ion collisions. With a multiphase transport(AMPT) model we investigate the elliptic(v_2),triangular(v_3), and quadrangular(v_4) flow of charged particles in Pb+Pb collisions at s_(NN)~(1/2)= 5.02 TeV. We then compare our flow results with the published ALICE flow results. We find our AMPT simulated results are consistent with ALICE experimental data.     

Low-<Emphasis Type="Italic">p</Emphasis><Subscript>T</Subscript> proton-proton physics at low luminosity at LHC

This review of low-p _T proton-proton physics at low luminosity at the large hadron collider (LHC) should cover all LHC experiments, but in practice, is mainly related to ALICE, for reasons which will be explained. However, the relevance to other LHC experiments is clear, as low-p_T. phenomena represent an important component of the background to their high-p_T. phenomena which needs to be calibrated. The ALICE collaboration will study proton-proton collisions as part of their heavy-ion programme, where most signals are relative to the proton-proton system. In addition, the ALICE detector’s unique acceptance at low p_T as well as its unique particle identification capability will make it possible to carry out a program of genuine proton-proton physics complementary to those of other LHC experiments.