Study of Elementary Particles Using OPAL Detector at LEP-II

欧洲核子研究中心的世界最高能量的e^+e^-对撞机LEP已于1989年开始运行。在1995年完成了非常成功的Z共振物理计划后，LEP于年开始了能量升级计划LEP 2。1996年，超过足以产生W玻色子对的碰撞能量。1997年LEP碰撞能量增加到183 GeV，1998年进一步推高到189.0eV。OPAL实验，我们一直在其中发挥主导作用，成功地收集了这一新能源地区的数据。为了充分利用这些数据，我们致力于了解探测器在高能下的性能，精确校准探测器，改进物理分析技术以获得测量精度和搜索灵敏度，并且我们还追求一些新的物理主题。已收集到约4000个W对事件。精确测量了产生截面、总W宽度和衰变分支比。W质量的精确测量，以及Z玻色子的精确结果，为标准模型的关键测试提供了信息。在W对事例数据样本增加的基础上，W质量测定的精度有了很大的提高.系统地研究了费米子对产生、Z对产生、单W产生和一般四费米子末态等标准模型过程。标准模型被发现在这个更高的能量区域工作得很好。希格斯玻色子是标准模型的一个关键元素，但尚未被发现，它的质量被发现比91 GeV.4重。对超对称粒子进行了修正，得到了改进的理论参数极限。

The world highest energy e^+e^- collider LEP at CERN has started its operation in 1989. After completion in 1995 of highly successful physics program at the Z resonance, LEP has started the energy upgrade program LEP2 in. 1996, exceeding the collision energy sufficient to produce the W boson in pair. In 1997 the LEP collision energy was increased to 183 GeV and further pushed up to 189 0eV in 1998. The OPAL experiment, in which we have been playing a leading role, has successfully collected data at this new energy region. In order to make full use of these data, we worked on understanding the detector performance at high energy, precise calibration of the detector, developments for improved physics analysis technique to gain precision of measurements and sensitivity for searches, and we also pursued a number of new physics topics.1. About 4000 W pairs events have been collected. The production cross-section, total W width and decay branching ratios were precisely measured. Accurate measurement of the W mass, together with the precision results of the Z boson, provides information for crucial tests of the Standard Model. Based on the increased data sample of W pair events, precision of W mass determination has been largely improved.2. Systematic investigations were made for varieties of Standard Model processes such as fermion pair production, Z pair production, single W production and general four-fermion final states. The Standard Model is found to work well at this higher energy region.3. The mass of the Higgs boson, which is a key element of the Standard Model yet undetected, is found to be heavier than about 91 GeV.4. Searches for Supersymmetric particles were performed and improved limits on the parameters in the theory have been obtained.