北京谱仪触发判选系统的模拟

介绍了北京谱仪(BES)触发判选系统的模拟程序,并用实验数据对其正确性作了验证.运用该程序,首次用BES的蒙特卡罗(Monte Carlo)数据从系统角度直接给出了触发判选效率,所得结果与实验方法测定的触发效率相一致,说明触发判选系统符合BES物理取数的要求.该模拟软件可以用来完备BES的Monte Carlo程序库,并可为今后触发系统的研究提供参考数据.     

Study of BESⅢ MUC offline software with cosmic-ray data

Cosmic-ray data of 90 M events have been collected and used for calibration, alignment as well as detector tuning. A special tracking algorithm for the BESⅢ muon counter is developed and verified with Monte-Carlo simulation and then further confirmed with the cosmic-ray data. The obtained strip resolutions are in good agreement with the design values. A new alignment approach for the BESⅢ muon counter is confirmed with the cosmic-ray data and proposed to be used in future analysis of experimental data.     

北京谱仪触发效率的测量

介绍了用实验测量北京谱仪触发判选系统触发效率的方法．着重介绍触发条件表的设置，事例选择和触发效率的计算，给出各触发条件和不同类型事例的触发效率．     

Development and Application of Fast Monte Carlo Simulation Method for Beijing τ-Charm Factory (BTCF)

Based on the existing concept design and the expected performance of the detector at the future τ-charm factory,a fast Monte Carlo simulation program package using the BES software frame and data structure has been devcloped.Vadous important and/or interesting physics issues have been simulated by using this method,and a series of important physics results have been got.The design idea,the program frame,and the advantages of this method have been described.One can conclude that this Monte Carlo simulation method can greatly save CPU and disk space,and is specially suitable for BES users.The physics results obtained from the simulation demonstrate that it is essential to build the BTCF.     

A TRIGGER SCHEME FOR COSMIC RAY EXPERIMENT WITH A SAMPLE-AND-HOLD SYSTEM

This paper presents a trigger scheme which has been used in a cosmic ray experiment with a sample-hold readout system.The experiment shows that this trigger scheme can fully collect the whole output signals of the wire chamber for the random cosmic ray events and get rid of the problem of signal loss caused by the delay of sampling gate.Some disscussions about using this scheme for cosmic ray test of BES are also provided.     

An extended segment pattern dictionary for a pattern matching tracking algorithm at BESⅢ

A pattern matching based tracking algorithm, named MdcPatRec, is used for the reconstruction of charged tracks in the drift chamber of the BESⅢ detector. This paper addresses the shortage of segment finding in the MdcPatRec algorithm. An extended segment construction scheme and the corresponding pattern dictionary are presented. Evaluation with Monte-Carlo and experimental data show that the new method can achieve higher efficiency for low transverse momentum tracks.     

Neutron response calculation on the basis of variable track etch rates along the secondary particle trajectories in CR-39

The calculation of the response of CR-39 detectors exposed to neutrons is of high importance for their dosimetric application. A computer code system has been developed for this purpose. Whereas the generation of secondary charged particles is carried out using non-analogue Monte-Carlo techniques with variance reduction the simulation of the track formation process is treated without any free parameter starting from the etch rate ratio V(REL) only. Results are given for the contribution of recoil protons to the response as a function of the neutron energy and angle of incidence. Furthermore, the influence of an external radiator has been studied. The comparison of the calculated values with experimental data confirm the reliability of the track etch model applied.     

Event generators at BESⅢ

We present a brief remark and introduction to event generators for tau-charm physics currently used at BESⅢ,including KKMC,BesEvtGen,Bhlumi,Bhwide,Babayaga and inclusive Monte-Carlo event generators.This paper provides basic information on event generators for BESⅢ users.     

Monte Carlo tuning for the BESⅢ time-of-flight system

Using experimental data, Monte Carlo tuning is implemented for performance parameters associated with the scintillation counters and readout electronics of the BESⅢ time-of-flight (TOF) system, as part of the full simulation model. The implementation of the tuning is described for simulations designed to reproduce the performance of a number of TOF system parameters, including pulse height, hit efficiency, time resolution, dead channels and background. In addition, comparisons with experimental data are presented.     

THE COSMIC RAY DATA ANALYSIS OF μ-COUNTER ARRAY IN BES

By analysing the cosmic ray data of μ-counter array in BES,we obtained informations on the threshold for identifying signal and noise,the detection efficiency of single wire layer,the particle detection efficiency,and the location resolutions in z direction and in γ-φ plane for μ-counter array.The comparison between eexperimental data and Monte-Carlo simulation showed good agreement.     

磁场对水系统内能影响的MC计算机模拟方法研究

用Monte-Carlo计算机模拟方法,通过对一个含有64个水分子的三维体系在磁场作用时内能变化的计算,定量评估了磁场强度及温度对磁处理效应的影响。研究发现:水的内能与外加磁场强度的关系曲线是一条多极值曲线;水-水径向分布函数伴峰的高度与磁感应强度也具有多极值特征;计算机模拟结果与实验结果基本一致,计算机模拟确实是从分子水平研究磁处理机理的有效方法。     

Primary Vertex Fitting in BES

In this paper,the principle of primary vertex fitting of BES has been described. Some modifications to the original program are made and the vertex distributions for the experimental data of Run462—961 are presented.     

北京谱仪端盖簇射计数器的能量分辨及其模拟研究

利用北京谱仪Ｊ／、Ｄｓ能量下端盖簇射计数器（ＥＳＣ）内的ｅ＋ｅ－末态事例，研究了电子簇射在ＥＳＣ中单个计数管的脉冲幅度分布、击中单元总数分布和各读出层的击中单元数分布、沉积能量分布和总沉积能量的分布；得到能量分辨约为２２％在ＳＯＢＥＲ程序框架的基础上采用双高斯分布描述单计数管脉冲幅度谱，ＥＧＳ４描述电磁簇射，考虑了三维磁场分布，完成了ＥＳＣ蒙特卡罗模拟程序，模拟结果与实验数据符合很好。     

基于VHTRC的棱柱式高温气冷堆核设计程序验证北大核心CSCD

高温气冷堆是国际公认的固有安全性高的反应堆堆型。针对高温气冷堆包覆颗粒燃料引入的燃料组件的双重非均匀性以及棱柱式堆芯布置的非均匀性和强空间耦合效应,提出基于蒙特卡罗均匀化-确定论输运方法的RMC-SaraGR程序系统作为棱柱式高温气冷堆的核设计程序。基于日本棱柱式高温气冷堆临界实验装置VHTRC基准题,针对此套核设计程序系统开展了均匀化模型研究和初步验证。研究结果表明,基于蒙特卡罗均匀化方法,采用全堆模型、合适的能群结构和分区方式产生组件群常数,并经过超级等效均匀化方法进行等效均匀化修正,可以保证堆芯多群均匀计算具有较高的计算精度。     

强流电子束产生和传输的数值模拟

本文采用SLAC-226程序计算了1.5MV强流电子束在二极管内的加速过程以及出阳极后的传输过程。高亮度二极管的设计是高效率自由电子激光的关键技术之一。本工作的目的就是通过1.5MV注入器的数值模拟,为寻找优化的二极管结构设计提供一种有效的数值方法。程序考虑了外加电磁场和电子束自身空间电荷和自生磁场效应。我们讨论了外加磁场的各种构形以及它们对束流品质的影响,计算结果与国外EBQ程序计算结果和实验结果进行了比较,证明本工作的结果是可靠的。SLAC-226程序可以为直线感应加速器的设计提供参考数据。     

北京谱仪中的初级顶点拟合

本文介绍了初级顶点拟合的基本原理，对原有程序作了一些修改，给出了部分实验事例的初级顶点分布.     

AMS02电磁量能器三维重建

研究了AMS02电磁量能器簇射三维重建, 发展出一个新的三维重建程序, 并用 蒙特卡罗模拟以及2002年束流测试数据对其进行了检验．该程序应用两次方向 重建、结合光纤衰减修正、横向以及纵向能量泄漏补偿, 完整地对事例进行了 重建, 得到了较为理想的能量分辨率和角度分辨率．     

Introduction of the Trigger System and the Measurement for Trigger Efficiency at L3+Cosmics Experiment

The trigger process of L3+Cosmics experiment at CERN is introduced briefly. Also we checked whether the settings of L3+Cosmics trigger system by simulation are correct or not and introduced a method on trigger efficiency calculation. To get trigger efficiency for μ spectrum measurement, an experimental data sample, which includes events passing the trigger set to measure the μ spectrum and not passing, is needed. Then L?3+C trigger process is simulated with these events in this sample to know how many events should pass the trigger. By checking a trigger bit recorded in the experimental data, one can know how many events passed the trigger in hardware in these simulated events. The ratio then determines the trigger efficiency for μ spectrum measurement. And the systematic error is analyzed. The results on trigger efficiency have been used to the measurement of μ spectrum.     

Interfacial and co-existence properties of the Lennard-Jones system at the triple point

A molecular dynamics simulation of the three phases of the Lennard-Jones system in co-existence is reported. The triple-point properties are compared with bulk-phase Monte-Carlo results, with experimental data on argon, and with the results of a preliminary simulation of this system.

Thermodynamic properties of the crystal-liquid and liquid-vapour interfaces are reported and difficulties in calculating interfacial excess properties are discussed. The crystal-liquid and liquid-vapour interfacial tensions are in accord with previous predictions.

It is suggested that the direct simulation of co-existing phases is a potentially practical route to the phase diagram if the thermodynamic equations of state of the individual phases are known.     

Energy Resolution and Its Simulation for the ESC of BES

With data collected by the Beijing Spectmmeter (BES) in the J/ψ,ψ′, and D_s energy region, a lot of e⁺e^－ final state evenb are selected in the solid angle region covered by the endcap shower counters (ESC). Some characteristics of the ESC are analysed, such as the spectrnun of pulse height for, a single counter cell, the hit nwnbers in the ESC and in every reading layer of the ESC, the shower energies deposited in the ESC and in every layer of the BSC. The energy resoiudon of the ESC in obtained to be about 22%/E(GeV) Based on the odginal frame of SOBER, a Monte Carlo simulation program for the ESC is developed with a dual Gaussian pulse height spectrtun of the single counter cell. The electromagnetic cascades are calculated by the EGS4 package and a three-dimension magnetic field in the BES is included. The simulation results agree with experimented data well.