Particle Physics: From the Early Universe to the Large Hadron Collider

Particle physics is all about understanding the elementary building blocks of nature and their interactions. Over the years, physicists have developed the Standard Model of particle physics, which is extremely successful in describing a very wide range of natural phenomena from things as basic as how light works and why atoms form through to the complicated workings inside stars and the synthesis of nuclei in the first few minutes after the Big Bang. However, we know that the Standard Model is not the whole story for it leaves many questions unanswered. Our proposal focuses on these unanswered questions and the way that scientists hope to address them in the coming years using experiments like the Large Hadron Collider (LHC) or observations like those that will be made using the Planck satellite. At the LHC, physicists are searching for the Higgs boson, which represents our current best guess as to what is responsible for the origin of mass. They are also searching for a whole host of new particles such as those predicted by supersymmetry. If supersymmetry is discovered then it offers the hope also to explain the origin of the Dark Matter that makes up a large fraction of the material that is known to exist in the Universe. The scientists in our consortium will explore the theory of supersymmetry and dark matter. We will use data from experiments like the LHC to identify which of the many possible variants of supersymmetry are allowed by the data and to suggest new ways to explore those models in experiments. Any 'new physics' produced at the LHC will be produced as a result of smashing two protons into each other and that means they will be produced in a complicated environment, probably in association with 'jets' of other particles. Members of our consortium will explore how we can make use of these jets to learn more about the associated new physics: the better we understand the environment in which new physics occurs, the more we are able to learn about the new physics itself. This is a complicated business that often necessitates computer simulations of particle collisions. Our members are experts in these simulations and have plans on how the make them more accurate, which is necessary if we are to make the most of the exciting data from the LHC. The Standard Model of particle physics is also deficient when it comes to explaining the early history of the Universe, when it was hot and dense. The evidence is now very strong that the history began with an era of accelerating expansion, called inflation. We are experts on inflation and its consequences. Inflation makes the Universe featureless, except for quantum fluctuations which somehow grow, causing the density of matter and energy in the Universe to vary with position. These initially small variations grow to become observable effects. One effect is the formation of the billions of galaxies that populate the night sky. Another effect is to leave a tiny imprint on the cosmic microwave background radiation (CMB), a faint hum of microwave radiation in which the earth is bathed. The CMB will be studied in exquisite detail by the Planck satellite, which was launched in 2009. We hope to be at the forefront of interpreting the Planck data in the hope of pinning down which of the various theories of the early universe are ruled out and which remain viable. The deficiencies of the Standard Model extend still further for it does not explain the amount nor even the existence of ordinary matter. Our scientists will use this to constrain possible physics beyond the Standard Model and to do that they need to master the dynamics of the Universe shortly after the end of inflation. Last but not least, we hope to understand better the mysterious 'Dark Energy' that drives the current and future acceleration of the Universe: perhaps it is because Einstein's theory of gravity is not quite right and that is something we will explore.