在大型强子对撞机上的CMS实验

LHC（large hadron collider）是目前世界上能量最高的强子对撞机.CMS(compact muon solenoid,中文译名是紧凑型缪子螺线管探测器)是LHC上的主要实验计划之一,其目标就是要寻找Higgs粒子或者超出标准模型的其他新粒子,探清自然界的电弱破缺机制,以及寻找暗物质.CMS实验位于高能量和高亮度的最前沿,是21世纪初人类认识微观世界最重要的物理实验之一.中国参加了这项国际合作,制作了部分μ子探测器、磁铁支架、电子学和地板等,目前转入物理研究工作,争取在物理研究中作出有显示度的贡献.文章简要介绍了CMS探测器以及CMS实验的目标和意义.     

大型强子对撞机上的CMS探测器

CMS探测器是大型强子对撞机(LHC)上的4个实验之一,它的设计思想是在质心能量为14TeV及积分亮度为1034cm-2s-1的条件下对质子-质子对撞进行研究.它的特点是非常紧凑,其μ子室几乎覆盖了4π立体角.另外,CMS探测器还有可提供超强磁场的超导磁铁和由超导磁铁环绕的径迹室以及电磁量能器和强子量能器.CMS探测器对于末态为电子、光子、特别是μ子的物理过程有很好的测量精度.     

大型强子对撞机上的CMS实验

CMS探测器是大型强子对撞机（LHC）上的四个实验之一,位于日内瓦附近的欧洲核子中心（CERN）法国一侧地下100米处。它的全称是“紧凑“子螺线管”（Compact Muon Solenoid）。     

大型强子对撞机上的CMS探测器

CMS探测器是大型强子对撞机（LHC）上的4个实验之一,它的设计思想是在质心能量为14TeV及积分亮度为1034 cm-2s-1的条件下对质子-质子对撞进行研究.它的特点是非常紧凑,其μ子室几乎覆盖了4π立体角.另外,CMS探测器还有可提供超强磁场的超导磁铁和由超导磁铁环绕的径迹室以及电磁量能器和强子量能器.CMS探测器对于末态为电子、光子、特别是μ子的物理过程有很好的测量精度.     

希格斯粒子及其实验寻找和发现

希格斯机制引入基本粒子物理的标准模型,解决了规范对称性自发破缺和粒子质量起源的问题,希格斯粒子成为粒子物理实验的最重要寻找目标。2012年大型强子对撞机(LHC)上的环状螺线管(ATLAS)和紧凑缪子螺线管(CMS)两个实验,分别以超过5倍标准偏差的统计显著性发现了与希格斯粒子性质一致的新粒子。     

希格斯粒子及其实验寻找和发现

希格斯机制引入基本粒子物理的标准模型,解决了规范对称性自发破缺和粒子质量起源的问题,希格斯粒子成为粒子物理实验的最重要寻找目标。2012年大型强子对撞机(LHC)上的环状螺线管(ATLAS)和紧凑缪子螺线管(CMS)两个实验,分别以超过5倍标准偏差的统计显著性发现了与希格斯粒子性质一致的新粒子。     

大型强子对撞机上的实验进展

大型强子对撞机的成功建成,使人类对微观世界的探索深入到了10^-18 m这样一个全新的领域。文章介绍大型强子对撞机上实验的最新进展。     

对撞机上寻找暗物质

大量的天文观测证实宇宙中存在暗物质。根据观测对暗物质性质的约束,目前最受关注的暗物质模型是弱作用重粒子模型。现在的暗物质探测实验也主要围绕这类暗物质粒子展开。文章介绍了探测弱作用重粒子的三种主要探测方法和各自的优缺点,特别介绍了在对撞机上探测暗物质的方法,并详细介绍了在大型强子对撞机(LHC)上寻找暗物质的最新结果及对暗物质粒子性质的最新限制。     

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。     

欧洲大型强子对撞机LHC物理

对高能物理来说,2008年将是人们需要特别记住的一年。因为人们期待已久的在欧洲联合核子中心（CERN）建造的大型强子对撞机（LHC）及与其配套的探测器终在这一年的9月10日开始试运行了。从开始酝酿到定下LHC和与其配套的探测器的方案,再到建造的完成已有20多年的时间,其间克服了种种困难和挫折,终于在今年投入试运行。     

Beam-induced radiation in the compact muon solenoid tracker at the Large Hadron Collider

The intense radiation environment at the Large Hadron Collider, CERN at a design energy of $ \sqrt s $ \sqrt s = 14 TeV and a luminosity of 10³⁴ cm⁻² s⁻¹ poses unprecedented challenges for safe operation and performance quality of the silicon tracker detectors in the CMS and ATLAS experiments. The silicon trackers are crucial for the physics at the LHC experiments, and the inner layers, being situated only a few centimeters from the interaction point, are most vulnerable to beam-induced radiation. We have recently carried out extensive Monte Carlo simulation studies using MARS program to estimate particle fluxes and radiation dose in the CMS silicon pixel and strip trackers from proton-proton collisions at $ \sqrt s $ \sqrt s = 14 TeV and from machine-induced background such as beam-gas interactions and beam halo. We will present results on radiation dose, particle fluxes and spectra from these studies and discuss implications for radiation damage and performance of the CMS silicon tracker detectors.     

Large hadron collider physics program: Compact muon solenoid experiment

The LHC physics program at CERN addresses some of the fundamental issues in particle physics and CMS experiment would concentrate on them. The CMS detector is designed for the search of Standard Model Higgs boson in the whole possible mass range. Also it will be sensitive to Higgs bosons in the minimal supersymmetric model and well adapted to searches for SUSY particles, new massive vector bosons, CP-violation in B-system, search for subtructure of quarks and leptons, etc. In the LHC heavy ion collisions the energy density would be well above the threshold for the possible formation of quark-gluon plasma.     

Big Science and the Large Hadron Collider

The Large Hadron Collider (LHC), the particle accelerator operating at CERN, is probably the most complex and ambitious scientific project ever accomplished by humanity. The sheer size of the enterprise, in terms of financial and human resources, naturally raises the question whether society should support such costly basic-research programs. I address this question by first reviewing the process that led to the emergence of Big Science and the role of large projects in the development of science and technology. I then compare the methodologies of Small and Big Science, emphasizing their mutual linkage. Finally, after examining the cost of Big Science projects, I highlight several general aspects of their beneficial implications for society.     

B-physics results from the Large Hadron Collider

An overview of the first B-physics results from the LHC is presented, among which are various aspects of b production, rare B decays and CP violation.     

Physics results from the Large Hadron Collider

A brief review of the physics results of 2011 from experiments at the Large Hadron Collider is presented, first of all, the results of the search for the Standard-Model Higgs boson. Measurements of W- and Z-bosons, t- quark and the search for rare B-meson decays are in a good agreement with the Standard Model predictions in next-to-next-to-leading order (NNLO).     

Calculating the muon system response to background long-lived particles in the ATLAS detector at the Large Hadron Collider

An efficient method for constructing the background generator of the muon system for pp collisions in the ATLAS detector (Large Hadron Collider) is presented. The new method allows one to considerably reduce the number of simulations of secondary particles stopping up to thermal energies and to parameterize background particle fluxes. The correct choice of particles from parameterized fluxes allows one to simulate the muon system response in detailed geometry with the necessary statistical accuracy in reasonable time. The proposed method was developed and used to investigate the operation of the ATLAS muon trigger.     

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？文章介绍了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.     

Separation of signal and background events at the Compact Muon Solenoid of a Large Hadron Collider

A method for selection of hadronic jets based on the primary vertex of signal interaction is described; this method allows one to remove particles and jets from additional proton collisions and thus increase the efficiency of separation of the physically interesting signal.