Development of the event generator for LHC including higher order corrections

开发大型强子对撞机事件发生器，包括高阶校正

基本信息

批准号：
14340081
负责人：
SHIMIZU Yoshimitsu
金额：
$ 5.12万
依托单位：
High Energy Accelarator Reseach Organization (2004)The High Energy Accelerator Research Organization (2002-2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The LHC(Large Hadron Collider) project at CERN is planned as the next-generation energy-frontier experiment. The LHC accelerator, which is a proton-proton colliding machine with the center-of-mass energy 14 TeV is under construction toward a beam commissioning in 2007. From Japan, more than hundred physicists participate to one of experimental groups (ATLAS collaboration), and are preparing for the coming experiments.One of physics motivations of the LHC experiments is to discover the Higgs particle, which is the only one missing ingredient in the standard model. In order to establish the model completely it is essential to find it and to investigate in details. It should be also important to search for new phenomena beyond the standard model through a tiny deviation of the experimental observations from theoretical predictions. Further not only for searching for new phenomena, but also performing precise measurement of parameters included in the standard model is another important iss … More ue of LHC.The background of the proton-proton colliding experiment must be completely predicted by QCD. This is, however, only 'in principle'. In fact it is very difficult task to make precise predictions because of an inherent feature of QCD. First of all, as QCD has a very large coupling constant, the convergence of perturbation series becomes very poor, or sometimes a perturbative calculation itself is meaningless. Moreover even in the region where the perturbation is applicable, there is no good renormalization point well defined experimentally. Then the lowest level(tree-level) calculation does not have any predictive power for the probability of the event rate. We need both higher-order perturbation and non-perturbative calculations for precise predictions of the background behavior.In this project we have established the method how to construct the event generator that includes the higher-order corrections based on the perturbative QCD. The key ingredients of calculation are as follows;1) Matrix Element I (lowest order),2) Matrix Element II (loop correction),3) Matrix Element III (real radiation),4) Loop Integration,5) Soft/Collinear Approximation,6) Parton-Shower model, 7) Matching between the matrix element and the parton shower.According to the study of above items, some simple examples of event generators (for Drell-Yan and prompt photon processes) have been constructed in this project. Now we are ready to calculate more complex processes like 'WIZ boson + jets'. Less

CERN 的 LHC（大型强子对撞机）项目计划作为下一代能源前沿实验 LHC 加速器是一种质心能量为 14 TeV 的质子对撞机，正在朝着光束方向建造。于 2007 年投入运行。来自日本的一百多名物理学家参加了其中一个实验小组（ATLAS 合作），并正在为即将到来的实验做准备。该项目的物理动机之一LHC实验的目的是发现希格斯粒子，它是标准模型中唯一缺失的一个成分，为了完整地建立模型，必须找到它并进行详细研究，寻找新的现象也应该很重要。通过实验观察与理论预测的微小偏差来超越标准模型，不仅是为了寻找新现象，而且对标准模型中包含的参数进行精确测量是LHC的另一个重要问题。质子-质子碰撞实验必须然而，这只是“原则上”的。事实上，由于 QCD 的固有特征，要做到精确的预测是非常困难的。扰动级数的收敛性变得很差，或者有时扰动计算本身毫无意义，而且即使在扰动适用的区域，也没有通过实验很好地定义好的重整化点，那么最低层（树级）计算也没有意义。有我们需要高阶扰动和非扰动计算来精确预测背景行为。在这个项目中，我们建立了如何构建包括高阶扰动的事件生成器的方法。基于微扰QCD的阶次校正。计算的关键要素如下：1）矩阵元素I（最低阶），2）矩阵元素II（环路校正），3）矩阵元素III（真实辐射），4）循环积分，5）软/共线逼近，6）Parton-Shower模型，7）矩阵元与parton喷淋之间的匹配。根据以上项目的研究，事件生成器的一些简单示例（对于Drell-Yan和提示）光子过程）已经在这个项目中构建完毕，现在我们准备计算更复杂的过程，例如“WIZ玻色子+喷流”。