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Study of New Phenomena by the Collider LEP at CERN

CERN 的 LEP 对撞机研究新现象

基本信息

批准号：
03041087
负责人：
SHIMIZU Yoshimitsu
金额：
$ 4.48万
依托单位：
National Laboratory for High Energy Physics (KEK)
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03041087/
关键词：
Electron-positron annihilation Standard model in particle physics Radiative corrction in electro-weak theory QCD parton shower Automatic calculation of Feynman amplitude Higgs particle Supersymmetric model 深非弾性散乱 QCDパ-トンシャワ-超対称性粒子自動計

项目摘要

The prompt photon production process is observed in LEP experiments. We have examined the process e^+e^-*qqgamma including one-loop QCD correction. This research is done using different regularization method by Japanese group by French group.In LEP experiments, events with two leptons and two photons are observed, which are suspected to be a new phenomenon. By use of GRACE system, the system to generate Feynman diagrams and to generate matrix elements for a corresponding process,we have calculated the cross section for e^+e^-*ll^^-gammagamma in electro-weak theory, whether the events are conventional ones based on the higher order QED interaction. Though the experimental signal exceeds the above background expectations, the origin of these is still uncertain due to the experimental controversy.Using the GRACE system, we have done systematic computation of the processes with three- and four-particle final states in high energy e^+e^- experiments, e.g., LEPH, JLC and so forth.The estimation of the strong coupling constant is done by studying experimental data by the parton shower model NLLjet and by the analytic calculation including resummation.The formulation of QED parton shower is done, so that the decoration of higher order QED correction for an arbitrary elementary process becomes possible.The numerical method developed for one-loop amplitude is also extended to multi-loop case.A new system for the symbolic manipulation is developed It has the feature to contract the expressions which appear in the calculation in particle physics.Some processes including the production of the super-particles are studied and the possible signal expected in the future colliders is shown.To execute the phase space integration efficiently, a new method for the numerical integration is investigated.

在LEP实验中观察到了瞬发光子产生过程。我们研究了包含单圈QCD修正的过程e^+e^-*qqgamma。本文的研究是由日本和法国的研究小组分别采用不同的正则化方法进行的，在LEP实验中，观测到了两个轻子和两个光子的事例，这被怀疑是一种新的现象。本文利用GRACE系统（生成费曼图和相应过程的矩阵元的系统），计算了电弱理论中e^+e^-*ll^-γ射线的截面，无论这些事例是否是基于高阶QED相互作用的常规事例。利用GRACE系统，我们对高能e^+e^-实验中的三粒子和四粒子末态过程进行了系统的计算，例如：LEPH，JLC等，通过部分子簇射模型NLLjet对实验数据的研究，以及包括重算在内的解析计算，估算了强耦合常数，给出了QED部分子簇射的公式，从而使对任意基元过程的高阶QED修正的修饰成为可能，并将单圈振幅的数值方法推广到多圈振幅，本文介绍了一种新的符号操作系统，它具有压缩粒子物理计算中出现的表达式的特点。研究了包括超粒子产生在内的一些过程，并给出了未来对撞机可能出现的信号。为了有效地进行相空间积分，研究了一种新的数值积分方法。