BESIII飞行时间计数器束流实验的模拟研究

利用GEANT4软件包模拟了BESIII TOF模型束流实验,模拟结果和实验结果进行了比较,并解释了ESR膜作包装材料比用铝膜作包装时间分辨反而差的现象,以及5cm厚的闪烁体比4cm和6cm厚的闪烁体时间分辨好的实验结果。

BESIII离线系统和性能测试

本文介绍了BESIII离线数据处理软件系统的构成以及数据处理的主要流程;给出了利用工具软件TAU(Tuning and Analysis Utilities)对系统性能进行的测试结果,据此结果估算了BESIII实验所需的计算资源,并且与BESIII设计报告的相关部分进行比较,说明了BESIII计算机环境的设计基本满足BESIII离线数据处理的要求。

BESIII在线直方图软件的设计与实现

在线直方图软件是BESIII数据获取系统的重要组成部分。介绍了在线直方图软件的主要需求。通过对主要组件的设计和实现,描述了在分布式环境中如何产生、传输和收集直方图,还特别介绍了通过xml配置数据库实现的灵活简便易扩展的配置方式。

BESIIIΨ(3770)数据的BEPCII质心系束流能量刻度

截至2011年5月,BESIII探测器在BEPCII对撞机质心系能量3.773 GeV附近采集了2.9fb-1积分亮度的数据。对这些数据进行物理分析,需要对BEPCII的束流能量(Eb)进行刻度。用预期束流能量计算mKnπ的束流约束质量(mbc),拟合束流约束质量谱得到D介子质量(mD(fit))来刻度Eb。对全部Ψ(3770)数据进行了束流能量刻度,并检验刻度后的D介子质量和分辨(σD)。结果表明,用刻度后的束流能量得到的D介子质量更接近D介子的真实质量,且分辨得到进一步改善。

云计算在BESIII数据处理与分析中的应用

为适应BESIII实验数据的积累和资源需求的大幅增长,论文从性能评估、软件部署、用户使用、资源调度、数据管理等五个关键问题对BESIII数据处理与分析利用云计算资源展开研究,并通过BESIII分布式计算系统对云计算资源的整合实现了BESIII作业在云资源上的弹性调度和成功运行,这将为今后大规模应用奠定基础。

BESIII飞行时间探测器塑料闪烁体性能检测

北京谱议(BESIII)重大改造工程中飞行时间探测器所使用的各个塑料闪烁体需要严格测量和质量控制,包括机械尺寸、有效衰减长度和相对光产额。我们用宇宙线测量塑料闪烁体的衰减长度时,利用飞行时间探测器本身的时间信息重建出宇宙线的位置和方向,宇宙线在闪烁体上的光产额通过其两端光电倍增管的电荷信息来反应,这样测量的闪烁体的有效衰减长度统计量大、准确并且快速。检测结果表明,闪烁体的各项指标达到了的设计要求。

BESIII数据获取系统中VME机箱读出模型的设计及分析

本文着重介绍了应用于BESIII数据获取系统读出分支的读出模型的设计。文中简要介绍了北京谱仪系统及其数据获取系统对读出子系统的要求 ,并详细介绍了该模型的系统结构、数据处理流程和测试实验方法。本文特别介绍了在该模型设计过程中要实现的关键技术 ,最后对测试结果进行了分析和讨论。该模型最终实现了从电子学插件将数据读出、完成数据格式转换以及通过局域网将数据发送到读出计算机等功能。

BESIII MDC数据处理系统

北京谱仪III(BESIII)是北京正负电子对撞机II(BEPCII)上的一台大型通用磁谱仪,用于τ-粲物理实验研究。主漂移室(MDC)是BESIII上的主要探测器之一,用于测量带电粒子的位置,动量和粒子类型的鉴别。论文主要介绍了BESIII MDC事例重建系统,其中包括T0的计算,径迹重建和径迹拟合,数据离线刻度,dE/dx的重建和刻度等软件的原理、结构以及各软件包的主要性能。

BESIII上的重子形状因子（英文）

利用在2011~2013年BEPCII对撞机上的BESIII探测器收集的数据,测量了e^+e^-→pp在2.232 4~3.671 0GeV之间12个质心系能量点的截面.期待利用在2014年和2015年收集的更大的e^+e^-扫描数据样本做更进一步测量.通过标记和不标记初态辐射光子的方法,对pp珚形状因子进行了测量.利用BESIII的优良探测器表现,利用标记和不标记初态辐射光子的方法,对nn珔形状因子的测量进行了可行性研究.同时也一并报道了ΛΛ的形状因子的初步但不符合理论预期的结果,及利用在e^+e^-→Λ_cΛ_c阈值上收集的数据的预期.也期望BESIII能对其他超子的形状因子进行测量.

A Prototype of the Read-out Subsystem of the BESIII DAQ Based on PowerPC

This article describes the prototype of the read-out subsystem which will be subject to the BESIII data acquisition system. According to the purpose of the BESIII, the event rate will be about 4000 Hz and the data rate up to 50 Mbytes/sec after Level 1 trigger. The read-out subsystem consists of some read-out crates and a read-out computer whose function is to initialize the hardware, to collect the event data from the front-end electronics after Level 1 trigger, to transfer data fragments to the computer in online form through two levels of computer pre-processing and high-speed network transmission. In this model, the crate level read-out implementation is based on the commercial single board computer MVME5100 running the VxWorks operating system. The article outlines the structure of the crate level testing platform of hardware and software. It puts emphasis on the framework of the read-out test model, data process flow and test method at crate level. Especially, it enumerates the key technologies in the process of design and analyses the test results. In addition, results which summarize the performance of the single board computer from the data transferring aspects will be presented.

Prospects to study hyperon-nucleon interactions at BESIII

The prospects to study hyperon-nucleus/nucleon interactions at BESIII and similar e^(+)e^(-)colliders are analyzed in this paper.Utilizing the large quantity of hyperons produced by the decay of 10 billion J/■and 2.7 billion(3686)collected at BESIII,the cross sections of several specific elastic and inelastic hyperon-nucleus reactions can be measured via scattering between hyperons and nucleus in the dense objects of the BESIII detector.Subsequently,the cross sections of the corresponding hyperon-nucleon interactions can be extracted from further phenomenological calculations.The interactions between antihyperons and nucleus/nucleon,including scattering and annihilation,can also be studied using the method proposed in this study.The results will definitely benefit the realization of precise probes for hyperon-nuclei/nucleus interactions and establish constraints to study the potential of strong interaction,the origin of color confinement,a unified model for baryon-baryon interactions,and the internal structure of neutron stars.In addition,the desirable prospects of corresponding studies in the future Super Tau-Charm Factory(STCF)are discussed and estimated in this study.

Identification of deuterons at BESIII

The identification of deuterons with momenta in the range of 0.52−0.72 GeV/c is studied with specific ionization energy loss information using a data sample collected by the BESIII detector at center-of-mass energies between 4.009 and 4.946 GeV.Clean deuteron samples are selected using time of flight information.For all data samples,the deuteron identification efficiencies are higher than 95%,with a maximum difference of%between data and Monte Carlo simulation.This verifies the effectiveness of the deuteron identification method based on specific ionization energy loss and provides valuable information for future studies on processes involving deuterons in the final state at BESIII.

Study of BESIII trigger efficiencies with the 2018 J/ψ data

Using a dedicated data sample taken in 2018 on the J/ψpeak,we perform a detailed study of the trigger efficiencies of the BESIII detector.The efficiencies are determined from three representative physics processes,namely Bhabha scattering,dimuon production and generic hadronic events with charged particles.The combined efficiency of all active triggers approaches 100%in most cases,with uncertainties small enough not to affect most physics analyses.

BESIII测量X_(c J)→ηη’的蒙特卡罗研究

基于BOSS软件框架,利用BESIII合作组产生的400 M单举ψ(3686)事例,研究在BESIII探测器上实现测量到X_(c J)→ηη’分支比的可能性.以无信号事例的单举ψ(3686)样本为背景样本,以纯信号蒙特卡罗事例为信号样本,控制信号事例,在分别假设观测到X_(c J)→ηη’衰变过程信号显著水平为3σ和5σ的情况下,得到该过程对应的分支比.

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.

Measurements of the center-of-mass energies of e^(+)e^(-)collisions at BESIII

During the 2016-17 and 2018-19 running periods,the BESIII experiment collected 7.5 fb of e^(+)e^(-)collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV.These data samples are primarily used for the study of excited charmonium and charmoniumlike states.By analyzing the di-muon process e^(+)e^(-)→(γISR=FSR)μ^(+)μ^(-),we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV.Through a run-by-run study,we find that the center-of-mass energies were stable throughout most of the data-collection period.

The offline data quality monitoring of the BESIII end cap TOF system

Purpose The end cap time of flight(TOF)at Beijing spectrometer was upgraded with multi-gap resistive plate chamber technology in order to improve the particle identification capability in 2015.The offline data quality monitoring is a critical aspect of the data processing chain aiming at providing data with good quality for physics analyses.Methods An offline data quality monitoring tool for upgraded end cap TOF has been developed to provide feedback about the functioning and performance of detector hardware and data processing chain.Results Detector information and reconstructed time-of-flight characteristics of charged tracks are filled into plots using full Bhabha events reconstruction results,and then,these plots are used to assess the operational conditions of the detector and the quality of the data by the experts.Conclusion This paper is describing the design and the content of performance of the offline data quality monitoring of end cap TOF and the data quality performance achieved during last 2 years’physical data taking.

BESIII上ψ(3686)→X(pp)φ衰变的Monte Carlo研究

在BOSS软件框架下,利用BESⅢ实验组产生的4(3686)单举Monte Carlo数据样本通过对衰变过程ψ(3686)→X(pp^-)φ的研究,分析了pp^-的质量阈值增强X(pp^-)在BESⅢ探测器上实现测量的可能性.以无信号事例的单举ψ(3686)样本为背景样本,以纯信号Monte Carlo事例为信号样本,控制信号事例,假设观测到质量阈值增强的信号统计显著水平为3σ和5σ,在这两种情况下,分别给出了所研究过程的衰变分支比.

Number of J/ψ events at BESIII

Using inclusive decays of J/ψ aprecise determination of the number of J/ψ events collected with the BESIII detector was performed.For the two data sets taken in 2009 and 2012,the numbers of J/ψ events were recalculated to be(224.0±1.3)×10^(6) and(1088.5±4.4)×10^(6),respectively;these numbers are in good agreement with the previous measurements. For the J/ψ sample taken in 2017-2019,the number of events was determined to be(8774.0±39.4)×10^(6).The total number of J/ψ events collected with the BESIII detector was determined to be(10087±44)×10^(6),where the uncertainty is dominated by systematic effects,and the statistical uncertainty is negligible.

Study of cluster reconstruction and track fitting algorithms for CGEM-IT at BESIII

Considering the effects of aging on the existing Inner Drift Chamber （IDC） of BESIII, a GEM-based inner tracker, the Cylindrical-GEM Inner Tracker （CGEM-IT）, is proposed to be designed and constructed as an upgrade candidate for the IDC. This paper introduces a full simulation package for the CGEM-IT with a simplified digitization model, and describes the development of software for cluster reconstruction and track fitting, using a track fitting algorithm based on the Kalman filter method. Preliminary results for the reconstruction algorithms which are obtained using a Monte Carlo sample of single muon events in the CGEM-IT, show that the CGEM-IT has comparable momentum resolution and transverse vertex resolution to the IDC, and a better z-direction resolution than the IDC.