Collider Physics at the LHC

我的研究主要集中在对撞机物理，也就是人们期望在粒子加速器内部看到的东西。这样的实验已经使用了几十年，目前的机器（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））正在探测比以往更高的能量。为了了解在这些实验中发生了什么，详细的计算是必要的，以确定各种粒子是如何相互作用的。在大型强子对撞机中，质子碰撞在一起，产生一个非常高能量的局部集中，从中产生新的粒子。1995年首次发现的顶夸克就是这样一种粒子。这是我们目前对粒子物理学（称为标准模型）的描述中已知最重的粒子，它的许多特性仍然知之甚少。其行为的计算和测量很重要，主要有两个原因。首先，我们想完成我们对它的性质的理解。其次，人们强烈相信，在目前的标准模型之外，存在新的物理学，而大型强子对撞机将是发现这一点的关键。人们有充分的理由相信，这种新的物理学将会影响顶夸克的行为。因此，详细计算其目前所了解的性质，以及研究标准模型之外的各种理论如何影响其相互作用，是必要的任务。我大量参与了这些计算，这些计算最终以实验家使用的大型计算机程序的形式出现。大型强子对撞机的输出主要是由具有大量粒子的事件决定的。它们排列成准直的射流，每次事件中可能有许多这样的射流。原则上，这些喷流的性质可以用量子色动力学（QCD）理论来计算，量子色动力学是标准模型的一部分，它解释了共同构成质子的夸克和胶子的行为。然而，精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，用于计算包含许多射流的事件的性质，这种方法可以很快地应用于目前的计算能力。到目前为止，这项技术已经被应用到一个备受关注的过程中——希格斯玻色子的产生，这种粒子被认为是质量起源的原因。能够计算出希格斯粒子如何产生的特性，使我们能够有效地寻找这种粒子，并测量它的特性。

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.