Search for New Particles and Study of Interactions between Particles with "OPAL" Detector at Electron Position Collider "LEP".

我们参与的OPAL实验是欧洲核子研究中心（CERN）大型正负电子对撞机（LEP）的四个实验之一，该实验于1989年8月开始运行，旨在研究Z^0共振附近的正负电子反应。我们在1989年成功记录了30k个Z^0事件，从实验开始就有了许多令人兴奋的发现。在接下来的几年里，越来越多的Z^0事件（1990年17万事件，1991年40万事件）被收集起来，以获得更精确和更有意义的结果。其中最重要的发现，我们已经获得：1。精确测定Z^0属性（质量、总宽度、部分宽度等）验证了标准模型的有效性.基本粒子只有三代。这极大地限制了宇宙起源的各种模型。希格斯粒子是标准模型中必不可少的基本标量粒子，其质量大于51 GeV。顶夸克是标准模型中的第六个夸克，其质量可能在100 GeV到180 GeV之间。没有新的粒子，如超对称（SUSY）伙伴，存在到Zo能量区域。精确测定τ轻子和底夸克的性质，它们作为Z^0粒子的衰变产物被大量观测到。这些数据进一步表明了标准模型的有效性。精确测定了强相互作用的耦合常数。量子色动力学（QCD）的理论被广泛地以各种方式检验。研究了大统一理论。最简单的SU（5）模型已被证明与我们的实验数据不符，而SUSY SU（5）模型看起来最有希望.随着LEP在Z^0共振下的持续运行，到1993年底将收集到数百万个Z^0事例，这将使我们能够寻找标准模型可能的破缺.

The OPAL experiment, in which we are participating, is one of the four experiments at the large electron-positron collider at CERN (LEP) which started operation in August 1989 to study electron-positron reactions in the vicinity of the Z^0 resonance. We successfully recorded 30k Z^0 events in 1989, which led to numerous exciting findings from the beginning of the experiment. In the following years more and more Z^0 events (170k events in 1990 and 400k events in 1991) were collected to obtain yet more precise and significant results. Among the most important findings we have obtained are :1. Precise determinations of Z^0 properties (mass, total width, partial widths, etc.) which verified the validity of the standard model.2. There are only 3 generations of the elementary particles. This significantly constrained various models of the origin of the universe.3. The Higgs particle, elementary scalar particle essential in the standard model, is heavier than 51 GeV.4. The mass of the top quark, the sixth quaxk in the standard model, probably lies between 100 GeV and 180 GeV.5. No new particles, such as supersymmetric (SUSY) partners, exists up to the Zo energy region.6. Precise determination of the properties of the tau leptons and the bottom quarks, which were abundantly observed as decay products of the Z^0 particle. These data further signify the validity of the standard model.7. The coupling constant of the strong interaction was precisely determined. The theory of the Quantum Chromodynamics (QCD) was extensively examined in various ways.8. Grand Unified Theories were examined. The simplest SU (5) model proved not in accordance with our data, instead the SUSY SU (5) model looks most promising.As LEP keeps running at the Z^0 resonance, several millions of Z^0 events will be collected by the end of 1993, which will enable us to look for possible breakings of the standard model.