Study of Elementary Particles Using OPAL Detector at LEP

LEP 使用 OPAL 探测器进行基本粒子研究

基本信息

批准号：
04044040
负责人：
KOBAYASHI Tomio
金额：
$ 12.8万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-04044040/
关键词：
CERN Electron-positron Collider LEP Z^0 boson the Standard Model Top Quark Higgs boson gamma lepton Bottom Quark 大型電子・陽電子衝突装置LEP Zﾟ粒子標準理論相互作用トップ・クォーク大統一理論

项目摘要

The OPAL experiment, in which we are participating, is one of the four major experiments at the CERN large electron-positron collider(LEP), which started operation in 1989 to study e^+e^- reactions in the vicinity of the Z^0 boson resonance. The performance of LEP has been improving year after year. The OPAL experiment has been also very successful, and we collected 770k Z^0 events(peak only)in 1992 and 730k Z^0 events(peak and off-peak)in 1993, respectively. The number of Z^0 events from the beginning of the experiment now amounts to more than 2 million events. Not only the number of events is increased, but also the data quality is much improved with newly introduced detector elements as well as with better understanding of the detector.The important results are listed below.1. The Z^0 mass was determined with the best precision, by reducing the ambiguity of the beam energy from 20 MeV to 6 MeV. The standard model was tested with the measurements of Z^0 properties (total decay width, partial decay widths, forward-backward asymmetries of lepton-pair and quark pair productions). The top quark mass was confirmed to be about 150 GeV. The grand unified theory was tested with the measured coupling constants of the electroweak and strong interactions.2. Two problems on gamma lepton were solved with the precise measurements of the branching fractions and the lifetime of gamma lepton.3. A variety of bottom quark properties (Z^0 partial decay width, forward-backward asymmetry of pair production, lifetimes of bottomed mesons and baryons, and oscillation of neutral bottomed meson)were measured with outstandingly good precision.4. The Higgs boson, elementary scalar particle in the standard model, is found to be heavier than 63 GeV. We obtained negative result on new particle with about 60 GeV mass, which had been suggested by the anomalous mass peak of two photons reported by the L3 group.

我们参与的蛋白石实验是Cern大型电子峰对撞机（LEP）的四个主要实验之一，该实验于1989年开始运行，研究了Z^0玻色子共振附近的E^+E^ - 反应。 LEP的表现逐年不断提高。蛋白石实验也非常成功，我们分别在1992年收集了770K Z^0事件（仅峰值）和1993年的730k Z^0事件（峰值和峰值）。从实验开始开始的Z^0事件的数量现在达到了200万以上。不仅事件的数量增加了，而且随着新引入的检测器元素以及对检测器的更好理解，数据质量也得到了很大的提高。重要的结果在下面列出。1。 Z^0质量是用最佳精度来确定的，通过将光束能量的歧义从20 MeV减少到6 MeV。用Z^0属性的测量值（总衰减宽度，部分衰减宽度，Lepton-Pair和Quark Pair Productions的前向不对称性）测试了标准模型。最高的夸克质量被确认约为150 GEV。大统一理论用电牵引和强相互作用的测得的耦合常数测试。2。用分支部分的精确测量和伽马·Lepton的寿命解决了伽马一体的两个问题。3。用非常好的精确度测量了多种底部夸克性能（z^0部分衰减宽度，成对产生的前向不对称性，底部介子和重子的寿命以及中性底部介子的振荡）。4。发现标准模型中基本标量粒子的希格斯玻色子比63 GEV重。我们获得了约60 GEV质量的新粒子的负结果，这是由L3组报告的两个光子的异常质量峰提出的。