Collider Physics at the LHC

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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.