Collider Physics at the LHC

我的研究主要集中在对撞机物理学上，也就是人们希望在粒子加速器内看到的东西。这样的实验已经使用了几十年，目前的机器(例如即将在日内瓦附近的欧洲核子研究中心的大型强子对撞机(LHC))正在探测比以往任何时候都更高的能量。为了了解在这些实验中发生了什么，有必要进行详细的计算，以确定所涉及的各种粒子如何相互作用。在大型强子对撞机中，质子相互碰撞，形成局部的高能量集中，由此产生新的粒子。其中一个这样的粒子是所谓的顶夸克，于1995年首次被发现。这是我们目前对粒子物理学(称为标准模型)的描述中已知的最重的粒子，它的许多性质仍然知之甚少。计算和衡量它的行为很重要，主要有两个原因。首先，我们想要完成我们对其属性的理解。其次，人们强烈认为，在目前的标准模型之外存在着新的物理学，而大型强子对撞机将在揭示这一点上发挥关键作用。我们有强烈的理由相信，这种新的物理学将影响顶夸克的行为。因此，按照目前所理解的对其性质的详细计算，以及调查超越标准模型的各种理论想法如何影响其相互作用，是必要的任务。我在很大程度上参与了这些计算，这些计算最终采取了实验者使用的大型计算机程序的形式。大型强子对撞机的输出是由含有大量粒子的事件主导的。它们排列在准直的喷嘴中，在每个事件中都可能有许多这样的喷嘴。原则上，这些喷流的性质可以用一种叫做量子色动力学(QCD)的理论来计算，这是标准模型的一部分，解释了共同构成质子的夸克和胶子的行为。然而，要准确地进行这些计算是极其困难的。我参与了一种新的近似方法的开发，用于计算包含许多喷流的事件的性质，该方法在目前的计算能力下是快速适用的。到目前为止，这项技术已经被应用于一个备受关注的过程--希格斯玻色子的产生，这是一种被认为是质量起源的粒子。能够计算希格斯粒子是如何产生的性质，使我们能够有效地搜索这种粒子，并测量它的性质。

My research focuses predominantly on collider physics, namely what one expects to see inside a particle accelerator. Such experiments have been in use for many decades, and current machines (such as the forthcoming Large Hadron Collider (LHC) at CERN, near Geneva) are probing higher energies than ever before. In order to understand what happens in these experiments, detailed calculations are necessary in order to determine how the various particles involved interact. In the LHC, protons are collided together to create a localised concentration of very high energy, out of which new particles emerge. One such particle is the so-called top quark, first discovered in 1995. This is the heaviest known particle in our current description of particle physics (known as the Standard Model), and many of its properties are still poorly understood. The calculation and measurement of its behaviour are important for two main reasons. Firstly, we would like to complete our understanding of its properties. Secondly, it is strongly believed that new physics exists beyond the current Standard Model, and that the LHC will be pivotal in uncovering this. There are strong motivations for believing that this new physics will affect the behaviour of the top quark. Thus, detailed calculation of its properties as presently understood, together with investigation of how various ideas for theories beyond the Standard Model have an impact on its interactions, are necessary tasks. I am heavily involved in these calculations, which ultimately take the form of large computer programs used by experimentalists. The output of the LHC is dominated by events which have lots of particles. These arrange themselves in collimated jets, and there can be many of these in each event. In principle the properties of these jets can be calculated using a theory called Quantum Chromodynamics (QCD), the part of the Standard Model that explains the behaviour of the quarks and gluons which collectively make up protons. However, it is extremely difficult to carry out these calculations exactly. I have been involved in the development of a new approximate method for calculating the properties of events containing many jets, which is fast to apply with present computing power. This technique has so far been applied to a process of high topical interest - the production of a Higgs boson, a particle thought to be responsible for the origin of mass. Being able to calculate the properties of how the Higgs is produced allows us to efficiently search for this particle, as well as measure its properties.