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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实验中观察到快速光子产生过程。我们检查了过程e^+e^-*qqgamma，包括单回路QCD校正。日本和法国的研究小组分别采用了不同的正则化方法。在LEP实验中，观察到两个轻子和两个光子的事件，这被怀疑是一种新的现象。利用GRACE系统生成费曼图并生成相应过程的矩阵元素，计算了电弱理论中e^+e^-*ll^ - γ γ的横截面，无论事件是否基于高阶QED相互作用的常规事件。虽然实验信号超出了上述背景预期，但由于实验上的争议，这些预期的来源仍然不确定。利用GRACE系统对LEPH、JLC等高能e^+e^-实验中三粒子和四粒子终态过程进行了系统计算。通过研究部分子阵雨模型NLLjet的实验数据和包括恢复在内的解析计算，对强耦合常数进行了估计。给出了QED部分子簇的公式，从而使对任意初等过程进行高阶QED修正成为可能。单回路振幅的数值计算方法也推广到多回路情况。提出了一种新的符号处理系统，它具有将粒子物理计算中出现的表达式进行缩合的特点。研究了包括产生超粒子在内的一些过程，并给出了未来对撞机可能产生的信号。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。