BESⅢ漂移室全长模型的建造及基于全长模型的BESⅢ漂移室电子学的测试

建造了BESⅢ漂移室全长模型. 在气体密封, 高压供给及前端电子学安装方面为BESⅢ漂移室的成功建造积累了经验. 另外, 在全长模型上对BESⅢ漂移室电子学进行了测试, 包括噪声, 漂移时间测量, 电荷测量, 以及电子学增益等方面. 测试的最终结果显示了BESⅢ漂移室电子学具有很好的性能, 能够满足它们的设计要求.     

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.     

BESⅢ RPC宇宙线测试系统

北京谱仪(BESⅢ)采用阻性板室(Resistive Plate Chambers)作为其muon探测器, 总使用面积达1200m². 为保证探测器的质量, 每一块阻性板室都要求通过宇宙线测试. 宇宙线测试系统使用3个流光管室作为其触发和寻迹系统, 其空间分辨可达2—3mm, 覆盖面积约4m², 测试系统可同时测量8块RPCs. 最后, 还报道了RPC的初次测试结果.     

Calibration of RPC-based muon detector at BESⅢ

The calibration algorithm for RPC-based muon detector at BESⅢ has been developed. The calibration method, calibration error and algorithm performance are studied. The primary results of efficiency and noise at layer, module and strip levels have been calibrated with cosmic ray data. The calibration constants are available for simulation and reconstruction tuning. The results of Monte Carlo and data are also compared to check the validation and reliability of the algorithm.     

Track reconstruction in the BESⅢ muon counter

The reconstruction algorithm for BESⅢ Muon Counter, MucRecAlg, is developed with the object-oriented language C++ in BESⅢ offline software environment. MucRecAlg consists of the following functions: to find track seeds either from extrapolation of tracks in the main drift chamber or from the fired strips in muon counter, to select fired strips associated to the candidate tracks, to fit the candidate tracks with a linear or quadratic function and to calculate other parameters of the tracks for muon identification. Monte Carlo samples are generated to check the performance of the reconstruction package, such as reconstruction efficiency, muon remaining rate and pion rejection rate, etc. The preliminary results show that the pion rejection rate is around 3%-4% while the muon remaining rate is better than 90% in 0.4-1.6 GeV/c momentum region, which meets the requirement as shown in the design report.     

BESⅢ track fitting algorithm

A track fitting algorithm based on the Kalman filter method has been developed for BESⅢ of BEPCⅡ.The effects of multiple scattering and energy loss when the charged particles go through the detector,non-uniformity of magnetic field (NUMF) and wire sag, etc., have been carefully handled.This algorithm works well and the performance satisfies the physical requirements tested by the simulation data.     

Lagrange multiplier method used in BESⅢ kinematic fitting

In this paper,the kinematic fitting with the Lagrange multiplier method has been studied for BESⅢ experiment.First we introduce the Lagrange multiplier method and implement kinematic constraints.Then we present the performance of the kinematic fitting algorithm.With the kinematic fitting,we can improve the resolution of track parameters and reduce the background.     

BES III漂移室边界场丝层补偿电压的研究

BESⅢ漂移室边界丝层单元存在着严重的X-T关系左右不对称问题, 模拟研究表明在边界场丝层上设置适当的补偿电压能很有效地减小这种不对称. 通过BESⅢ漂移室模型的束流测试验证了边界场丝层补偿电压方案对减小X-T关系左右不对称的有效性, 同时还研究了补偿电压对边界丝层单元空间分辨及dE/dx测量的影响.     

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.     

面向对象的BESⅢ探测器模拟系统

BESⅢ探测器的模拟软件包BOOST, 是基于Geant4开发的面向对象的模拟软件. BOOST全面地模拟了BESⅢ探测器的物质和几何结构, 给出了粒子在各个子探测器中的击中信息, 以ASCII码文件的形式输出原始数据和MC truth信息可供重建软件开发和物理分析使用, 初步结果显示BOOST的模拟是合理的.     

BESⅢ端盖TOF探测器的研制

针对BESⅢ端盖TOF的研制方案, 设计和制作了特殊构型的闪烁探测器. 研究了光电倍增管(R5924)和塑料闪烁体(BC404, BC408, EJ204)的性能. 测量了几种包装材料对单个闪烁探测器模块光收集和本征时间分辨的影响. 使用800MeV实验电子束对探测器模块的测量结果显示, 采用EJ204和BC404晶体其时间分辨小于80ps; 采用ESR材料包装可获得较大的输出信号, 提高了探测器的性能.     

Tuning of the cosmic-ray test system of the BESⅢ drift chamber

The BESⅢ drift chamber and its subsystems need a cosmic-ray test after the chamber construction to check the chamber construction quality,testing the joint operation of the whole system and the performance of the chamber.The noise performance,drift time and charge measurements,and the scanning of channels were examined specifically.The preliminary results of the test indicate that the whole system works well.     

A photon conversion finder at BESⅢ

A photon conversion finder (PCF) based on track information from the main drift chamber (MDC) of the Beijing Spectrometer (BES0) at the Beijing Electron Positron Collider (BEPC/) is developed. The validation of the PCF is done by reconstructing π⁰ and measuring the branching fraction of J/ψ →γη'. Using the developed PCF tool, we mapped the materials from the interaction point through the BEPCII beam pipe up to the inner wall of the MDC.     

Online data quality monitoring system at BESⅢ

The online Data Quality Monitoring (DQM) tool plays an important role in the data recording process of HEP experiments. The BESⅢ DQM collects data from the online data flow, reconstructs them with offline reconstruction software and automatically analyzes the reconstructed data with user-defined algorithms. The DQM software is a scalable distributed system. The monitored results are gathered and displayed in various formats, which provides the shifter with current run information that can be used to identify problems quickly. This paper gives an overview of the DQM system at BESⅢ.     

BESⅢ μ探测器阻性板模型室的性能研究

对基于酚醛树脂的阻性板室(RPC)进行研究. 通过改进的表面处理工艺, 开发了一种新的阻性板材料, 并在不同温度下对多块样板的电阻率进行了测量. 对比了基于此新型阻性板的不同电阻率RPC模型室的探测效率、计数率和暗电流. 利用¹³⁷Cs γ源和实验束流研究了流光模式RPC的抗辐照性能. 结果表明此新型阻性板RPC满足BESⅢ μ探测器的要求.     

BESⅢ上的ηc物理

介绍了当前对η_c衰变的研究状况,即理论上还不能很好的描述η_c的衰变机制,实验上也需要更大的样本对η_c衰变进行深入的研究.基于在BESⅢ上预期一年所能获取的J/ψ和ψ′事例数,集中讨论了在BESⅢ上可进行的η_c物理的研究.主要包括η_c衰变到不同末态分支比的测量,新衰变模式的寻找,质量和宽度的精确测量以及稀有衰变的寻找,并对η′_c衰变的研究也做了简单讨论     

BESⅢ上奇特态的寻找

介绍了对奇特态质量及其衰变性质的理论研究，对奇特态候选者的实验研究现状也做了详细讨论. 并分析了理论预言和实验观测之间存在的不一致性. 从实验的角度上，对在BESⅢ上通过J/y 衰变寻找奇特态的几个过程做了讨论.     

Monte Carlo study on the low momentum μ-π identification of the BESⅢ EM calorimeter

The BESⅢ detector has a high-resolution electromagnetic calorimeter which can be used for low momentum μ-π identification.Based on Monte Carlo simulations, μ-π separation was studied.A multilayer perceptron neural network making use of the defined variables was used to do the identification and a good μ-π separation result was obtained.     

Lagrange multiplier method used in BESⅢ kinematic fitting

In this paper,the kinematic fitting with the Lagrange multiplier method has been studied for BESⅢ experiment.First we introduce the Lagrange multiplier method and implement kinematic constraints.Then we present the performance of the kinematic fitting algorithm.With the kinematic fitting,we can improve the resolution of track parameters and reduce the background.