在实际磁场中带电粒子径迹的模拟

本文介绍了在前冲谱仪中考虑实际磁场分布模拟带电粒子径迹的一种方法.从罗伦兹方程出发对实际磁场采用数值积分,得到动量精度为0.1%的带电粒子的模拟径迹.     

在实际磁场中带电粒子径迹的模拟

本文介绍了在前冲谱仪中考虑实际磁场分布模拟带电粒子径迹的一种方法.从罗伦兹方程出发对实际磁场采用数值积分,得到动量精度为0.1％的带电粒子的模拟径迹.     

运动带电粒子间的相互作用

运动带电粒子间的相互作用邓小玖（合肥工业大学合肥）众所周知，运动电荷之间如果只考虑洛仑兹力，牛顿第三定律一般不成立。然而若引进带电粒子在外磁场中的总动量户一ｍＧ十ａ二，其中ｑ二为被运动带电粒子带动的电磁场的动量’‘’，则广义力满足牛顿第三定律。如此处...     

带电粒子的动量分析和能量分析

本文介绍用磁分析器对带电粒子进行动量分析及用静电分析器对带电粒子进行能量分析的实验原理和方法.实验中用到高真空、离子源、磁场、高电压及小电流测量等方面的实验技术,可以对学生进行综合性的实验训练.一、基本原理 1.磁分析器 磁分析器是对带电粒子进行动量分析的仪器,它由直流电磁铁和真空盒组成.直流电磁铁包括磁轭、磁极和励磁线圈三部份(见图1).磁极和磁轭用工业纯铁做成,励磁线圈是用漆包线在铜骨架上绕制而成.两磁极面彼此平行,且呈60°扇形.放在两磁极之间的真空盒作为粒子的通道. 设速度为。的带电粒子进入磁感应强度为B的…     

在SIS／ESR上用FOPI装置研究重离子反应的中心碰撞

本文概括和讨论在SIS／ESR上用FOPI装置进行100－800MeV/uAu Au反应中心碰撞研究的首批实验结果：用高带电粒子多重性和低横动量方向相结合的双重选择标准，以及横－纵动量比研究了最中心碰撞事件；基于这些选择方法，首次得到了结团（中等质量碎片）发射的多重性和快度分布，清楚地观测到中等快度源；详细地研究了集体流与碰撞参数、碎片原子序数和入射能量的关系；首次在实验上发现方位分布对称的径向流和观测到垂直于反应平面的路子“挤出”效应；引入新的方法研究了定向边流的性质；首次用所有碎片和轻带电粒子来提取和确定反应的熵值；对实验数据与各种理论模型计算作了比较。     

正则动量面面观

对于带电粒子在磁场中的运动,一个很重要的概念是粒子的正则动量不同于它的机械动量,而这一点经常被忽视或者被混淆。本文从正则动量的基本定义出发,从经典的和量子的两方面分析了正则动量和机械动量的关系,指出正则动量才是基本的动力学变量。最后以磁镜装置为例说明了如何应用正则动量简明地给出问题的答案。     

均匀磁场中带电粒子的非定态波函数

取圆心坐标算符和初始机械动量算符为力学量完全集，给出均匀磁场中带电粒子的非定态波函数．     

负偏压射频放电过程的流体力学模拟

采用流体力学方法研究了负偏压射频放电的物理过程,计算了带电粒子密度及电场的时空分布,分析了在不同的近似条件下,离子动量平衡方程中各项的贡献。     

二氧化碳分子3σu轨道的电子动量谱测量

自从70年代实现（e,2e）电子动量谱测量以来,电子动量谱学获得了巨大的发展,成为探测物质结构的强有力的手段[1]。它可以分辨壳层来获得原子分子价壳层轨道的动量空间的电子密度分布,尤其是对低动量端的电子分布非常敏感。二氧化碳分子是一种典型的线性分子,对其结构的深入研究,具有相当的应用价值,尤其在环境保护领域。以前,CO2分子的电子动量谱曾被测量过三次[2-4],但由于能量分辨或动量分辨较低,研究结果不能令人满意。因此,用电子动量谱学的实验手段,进一步研究CO2分子,是非常有意义的。……     

北京谱仪Ⅱ上利用效率比方法进行μ鉴别的研究

北京谱仪Ⅱ的μ探测器的位置分辨和击中效率与带电粒子的动量和入射位置有关, 利用选取的宇宙线样本和强子样本对μ,探测器逐层进行了标度, 并利用构造的效率比函数在物理分析中有效地识别μ和强子.     

Study of charged and neutral multiplicities associated with large transverse momentum π0's in proton-proton collisions

A streamer chamber detector surrounding an intersection region of the CERN ISR was triggered on large transverse momentum π⁰'s by means of an array of lead-glass counters. The directions of all charged particles and photons converted in lead-oxide plates inside the streamer chamber were measured. Data were taken at c.m.s. energies of 45, 53 and 63 GeV around two production angles of the high-p_Tπ⁰ (90° and 53°). The total charged multiplicity associated with large transverse momentum π⁰'s is presented for the first time. Associated photon multiplicities are given for different phase-space regions. The data are compared with two extreme models, a simple jet model and a cluster model which describes normal inelastic events. The cluster model agrees much better with the data.     

Geodesic Structure of Static Charged Black Hole Solutions in 2 + 1 Dimensions

Geodesics structure of static charged black holes for dilaton gravity is constructed. In particular, circular and radial geodesics for charged and uncharged test particles are studied. Various possibilities are discussed for range of parameters for the black hole and the test particles. The orbits of the particles with angular momentum are presented.     

Aging effect in the BESIII drift chamber

As the main tracking detector of BESIII, the drift chamber provides accurate measurements of the position and the momentum of the charged particles produced in e+e-collisions at BEPCII. After six years of operation, the drift chamber is suffering from aging problems due to huge beam-related background. The gains of the cells in the first ten layers show an obvious decrease, reaching a maximum decrease of about 29% for the first layer cells. Two calculation methods for the gain change(Bhabha events and accumulated charges with 0.3% aging ratio for inner chamber cells) give almost the same results. For the Malter effect encountered by the inner drift chamber in January 2012, about 0.2% water vapor was added to the MDC gas mixture to solve this cathode aging problem.These results provide an important reference for MDC operating high voltage settings and the upgrade of the inner drift chamber.     

Angular momentum transport produced by shear flow driven drift waves in a collisional magnetoplasma

A shear flow instability in a nonuniform partially ionized magnetoplasma has been investigated and the angular momentum transport of charged particles caused by drift waves has been estimated. The angular momentum transport of the electrons and ions is not equal because the system is not conservative. The present investigation should help to understand the origin of fluctuations and associated parallel momentum transport of charged particles in nonuniform laboratory and astrophysical plasmas with sheared ion flow.     

Diffractive and nondiffractive components of the multiplicity distribution in pp collisions

Topological cross sections for diffractive and nondiffractive components in pp collisions are deduced on the basis of a dynamical model proposed earlier to explain the multiplicity distribution of charged particles. The model has an important prediction for the angular and momentum distributions of charged particles in diffractive events.     

Some examples of associated charged particle multiplicities in proton-proton collisions at 19 GeV/c

19 GeV collisions in the CERN 2 meter hydrogen bubble chamber have been investigated for the number of prongs associated with an observed p, Λ, π^? or K_s⁰ with specified cms momentum components. For p and Λ the associated charged particles have been classified according to their longitudinal direction relative to the observed p and Λ     

Angular correlations in proton-proton collisions producing a high transverse momentum π0

In an experiment at the CERN ISR, a streamer chamber detector surrounding one of the intersection regions was triggered on large transverse momentum π⁰'s by means of an array of lead-glass counters. The directions of charged particles and γ rays converted in lead-oxide plates inside the streamer chamber were measured. Data were taken at c.m. energy of √s = 53 GeV at two production angles of the high p_Tπ⁰ (90° and 53°). They indicate an enhancement of particles mostly in the hemisphere opposite to the π⁰. In the 53° data, a shift of this enhancement towards rapidities opposite to the rapidity of the π⁰ and confined to a ±30° azimuthal region around the collision plane is observed. In addition, a short-range angular correlation is evidenced between the high p_Tπ⁰ and the other collisions products (photons or charged particles). Two-particle correlations between charged particles produced in association with the high p_Tπ⁰ are found similar to those     

Heavy ion reactions at 75–100 MeV/nucleon

Energy and momentum component distributions of singly and doubly charged particles in¹⁶O-emulsion nucleus interactions at 75–100 MeV/n are presented. The parallel momentum distributions show larger shifts than at 2 GeV/n, indicating emission from systems with mean velocities ≈0.06 c relative to the parent nuclei. Particles with intermediate rapidities have, on the average, larger transverse momenta than particles with large rapidities. The charged particle multiplicity in peripheral collisions is the same at 0.1, 0.2 and 2 GeV/n, while the difference in multiplicity for central collisions is pronounced.     

Dynamical derivation of momentum diffusion coefficients at collisions of relativistic charged particles

An expression has been obtained for the diffusion tensor of particles in the momentum space on the basis of the dynamics of particles motion. The general equations have been used to determine the rms momentum spread at collisions of relativistic charged particles at times shorter than the time of randomization of particles motion and at greater times when motion is completely random.