2012 Consolidated Grant Supplement

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The Particle Physics Research Group at the University of Edinburgh participates in the programme of research at the Large Hadron Collider in Geneva. The LHC is the most complex machine ever built, and creates conditions of energy density and temperature which existed at approximately 10^-12 seconds after the big bang when particles existed under very different conditions. With these conditions new particles can be created which we can study. At Edinburgh we are working in two different areas.In the first of these we work at the LHCb experiment. Prior to the 1960s, it had been thought that the laws of physics were symmetric under the combined operations of exchanging particle for anti-particle and reversing the parity of the particle. Under such conditions matter and anti-matter would behave in the same way. However, it was discovered that this symmetry was violated, and that matter does not behave in an identical way to anti-matter. In terms of the Standard Model (SM) of particle physics this is embodied in the phenomenon of CP violation arising through the CKM matrix. CP violation is essential to understanding the early universe. At early times there were equal amounts of matter and anti-matter. Under general assumptions of CPT symmetry and thermal equilibrium, this situation would have remained so as the universe expanded. During this expansion and cooling, matter and anti-matter would have annihilated into photons to leave a universe full of radiation, but no stars and galaxies. It was shown in 1967 by Sakarov that if three conditions were met, then it would be possible for a small imbalance of matter over anti-matter to accrue. This imbalance would be only 1 part in 10^9, but would be sufficient to explain the existence of the universe. These conditions demand that CP is violated in the laws of physics. Given this far-reaching link between particle physics and cosmology, experimenters have been seeking to understand this phenomenon for many years. The b-quark sector is the best place to further our understanding and this is domain of the LHCb experiment. LHCb is the next generation experiment to further these studies and will improve the accuracy of many measurements by orders of magnitude.In the second area we work at the ATLAS experiment. ATLAS is one of two detectors able to study a wide variety of particles created from the collision of protons, and can address fundamental questions. The most well know question is that of the origin of mass, and the most famous particle being sought is the Higgs boson. The Higgs is necessary because the beautiful symmetry (gauge symmetry) which underlies our understanding of particle interactions inherently demands that all particles are massless. This cannot be the case and the elegant solution put forward is now known as the Higgs mechanism. Discovery of the Higgs boson would be the proof that that this is true. Another area addressed by ATLAS is that of the search for supersymmetry whereby all particles we know of have a so called super-partner differing by one half unit of spin. If this proved to be true it would help solve many problems. One of its most important consequences would be a candidate for dark matter, which makes up about 25% of our Universe, and about which we know nothing.We are also working hard on the planning, design and development for the upgraded detectors at the LHC for around 2018. The intensity of the beans will be increased and the data rates recorded by the detectors will increase by orders of magnitude. This requires development of new detectors and electronics. In this grant application we request support for the Edinburgh Particle Physics Research Group, including academic staff and post-doctoral researchers to further all of these areas.