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.

LEP 实验中观察到瞬发光子产生过程。我们已经检查了 e^+e^-*qqgamma 过程，包括单环 QCD 校正。这项研究是由日本小组和法国小组使用不同的正则化方法完成的。在LEP实验中，观察到两个轻子和两个光子的事件，这被怀疑是一种新现象。利用GRACE系统，该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^^-gammaamma的截面，无论事件是否发生是基于高阶 QED 相互作用的传统方法。虽然实验信号超出了上述背景预期，但由于实验争议，其来源仍不确定。利用GRACE系统，我们对高能e^下三粒子和四粒子最终态的过程进行了系统计算。 +e^-实验，例如LEPH、JLC等。强耦合常数的估计是通过研究帕顿簇射模型NLLjet的实验数据并通过包括恢复在内的解析计算来完成的。QED的公式完成了parton喷淋，使得对任意基本过程进行高阶QED校正成为可能。针对单环振幅开发的数值方法也扩展到多环情况。开发了一种新的符号处理系统。具有收缩粒子物理计算中出现的表达式的功能。研究了包括超粒子产生在内的一些过程，并显示了未来对撞机中预期的可能信号。为了有效地执行相空间积分，一种新的方法研究了数值积分的方法。