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 BES 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 tra     

Simultaneous least squares fitter based on the Lagrange multiplier method

We developed a least squares fitter used for extracting expected physics parameters from the correlated experimental data in high energy physics. This fitter considers the correlations among the observables and handles the nonlinearity using linearization during the χ² minimization. This method can naturally be extended to the analysis with external inputs. By incorporating with Lagrange multipliers, the fitter includes constraints among the measured observables and the parameters of interest. We applied this fitter to the study of the m D⁰-D⁰ mixing parameters as the test-bed based on MC simulation. The test results show that the fitter gives unbiased estimators with correct uncertainties and the approach is credible.     

Study of the efficiency of event start time determination at BESⅢ

A method to estimate the efficiency of event start time determination at BESIII is developed.This method estimates the efficiency at the event level by combining the efficiencies of various tracks(e,μ,π,K,p,γ)in a Bayesian way.Efficiencies results and the difference between data and MC at the track level are presented in this paper.For a given physics channel,event start time efficiency and systematic error can be estimated following this method.     

五夸克态进展

对2003年和2004年强子物理研究中的热点——五夸克态,从实验进展和理论研究上进行了较为详细的介绍,对研究的现状进行了评价和展望,同时介绍了国内一些研究小组在五夸克态研究中做出的贡献.     

北京谱仪实验30年

<正>粒子物理的标准模型被认为是当前描述微观亚原子体系最成功的理论,它包括描述电弱相互作用的电弱统一理论和描述强相互作用的量子色动力学(QCD)两大部分。电弱统一理论虽然有些参数的测量精度尚需提高,但可靠性已经被大量精确的实验测量所验证;但QCD部分,尽管在高能量大动量转移下的计算已为实验事实所证实,但它在低能     

2018年粒子物理学热点回眸

 自从文明诞生之日起，人类便一直在探寻这个世界到底是由什么构成的，它又是以怎样的规律运转的。3000多年前的古中国，人们曾经认为世界是由金、木、水、火、土这5种元素组成。公元前6世纪，古希腊哲学家提出了物质是由基本粒子组成的猜测。1802年约翰·道尔顿正式提出所有物质是由原子组成的理论。到了20世纪，随着近代物理学的发展和技术的进步，人们逐渐具备了深入理解原子的能力，了解到原子是由更基础的粒子组成的，并且能够定量地研究其相互作用力。在人类文明史中，物质的基本组成及其相互作用始终是人类认知领域最前沿的问题，而粒子物理学便是当代物理学中研究这个基本问题的分支。     

HERMES实验上寻找五夸克粒子重建方法的研究

4种不同的事件重建方法被用来证实HERMES实验上, 从27.6GeV正电子轰击氘靶而产生的虚光子产物中,在衰变道pK0s→pπ+π－上寻找五夸克粒子Θ+时,所看到的K0sp不变质量谱1530MeV附近处的狭窄共振峰不是来自于特定重建方法的选择.