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Study of Elementary Particles Using OPAL Detector at LEP-II

使用 LEP-II OPAL 探测器进行基本粒子研究

基本信息

批准号：
11694058
负责人：
MORI Toshinori
金额：
$ 11.9万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11694058/
关键词：
CERN LEP-II OPAL experiment Leadglass calorimeter Standard Model W boson Higgs boson Supersymmetry

项目摘要

The world highest energy e+e- collider LEP at CERN has started the energy upgrade program LEP2 after the completion in 1995 of its highly successful physics program at the Z resonance, to the energy above the threshold of W pair production. LEP has progressively updated the highest energy record. In 1999 the collision energy reached at 202 GeV, higher than originally anticipated, and was further pushed up in 2000 to 209 GeV after every efforts to gain energy had been made. The OPAL experiment successfully collected data at these new energies. In order to make full use of these data, efforts have been made for understanding the detector performance, precise calibration, development of physics analysis to gain precision and sensitivity to searches, and analyses of new physics topics have been purseed.In 1999-2000, OPAL collected about 8000 W pair events. The production cross-section and W decay branching ratios have been accurately measured. Precise determination of the W boson mass, together with the precision results of Z boson, allows crucial tests of the Standard Mode. The increased data sample allows the accuracy of such measurements to be further improved.Systematic studies have been made for variety of Standard Model processes, such as fermion-pair production and boson-pair production. The Standard Model is found to work well at these new energy region. Constraints on various models of new physics have been obtained.The most exciting thing with higher energy is a possible discovery of new particles. Higgs boson has been searched for, but no clear evidence has been found in the OPAL data alone. The Standard Model Higgs boson is found to be heavier than about 110 GeV.Effort to gain sensitivity by combining results of four LEP experiments is being pursued. Searches for Supersymmetric particles have been performed. Limits on the parameters in the theory have been largely improved.OPAL has published about 60 scientific papers in these two years.

欧洲核子研究中心（CERN）的世界上能量最高的电子对撞机LEP在1995年完成其非常成功的Z共振物理计划后，开始了能量升级计划LEP2，使能量超过W对产生的阈值。LEP逐步更新了最高能量记录。1999年，碰撞能量达到202 GeV，高于最初的预期，并在2000年进一步推高到209 GeV，之后尽一切努力获得能量。OPAL实验成功地收集了这些新能量的数据。为了充分利用这些数据，OPAL在了解探测器性能、精确定标、发展物理分析以提高探测器的精度和灵敏度以及分析新的物理课题等方面进行了努力。精确测量了产生截面和W衰变分支比。W玻色子质量的精确测定，以及Z玻色子的精确结果，允许标准模式的关键测试。随着数据样本的增加，测量的准确性进一步提高。人们对标准模型中的各种过程，如费米子对产生和玻色子对产生，进行了系统的研究。标准模型被发现在这些新的能源区工作得很好。对新物理的各种模型的约束已经得到了。最令人兴奋的事情与更高的能量是一个可能的新粒子的发现。希格斯玻色子一直在寻找，但仅在OPAL数据中没有发现明确的证据。标准模型的希格斯玻色子被发现比约110 GeV重。正在努力通过结合四个LEP实验的结果来获得灵敏度。对超对称粒子进行了量子化学计算。OPAL在这两年中发表了约60篇科学论文。