Experimental Particle Physics at the University of Edinburgh

The Edinburgh Experimental Particle Physics group is currently working in three different running experiments and we are also working on several future projects. The ATLAS experiment at the Large Hadron Collider (LHC): ATLAS is one of two detectors able to study a wide variety of particles created from the collision of protons at the highest energies ever created, and it addresses fundamental questions. The most well known is that of the origin of mass. The beautiful 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. The discovery of the Higgs boson has verified this, and now we must measure its properties in great detail. Another area addressed by ATLAS is the search for new heavy particles such as new heavy Higgs like particles or supersymmetric particles, which are predicted in models trying to address shortcomings of the Standard Model, such as why their is dark matter. The LHCb experiment at the LHC. Prior to the 1960s, it had been thought that 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. This is embodied in the phenomenon of CP violation and is essential to the understanding of the early universe. Shortly after the big bang there were equal amounts of matter and anti-matter. During 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, including CP violation, were met, then it would be possible for a small imbalance of matter over anti-matter to accrue, which would be sufficient to explain the existence of the universe. LHCb measures differences (CP violation) in behaviour of particles and antiparticle with at least one b or anti-b quark and searches for very rare decays of these particles, which could be affected by heavy unobserved particles. The LUX experiment, which is the current world-leading apparatus searching for dark matter. It is well known that some 27% of the Universe is comprised of Dark Matter - that is matter of some form which does not interact in a way which produces radiation, or other easy to observe signatures. There are many theoretical candidates and resolution of this mystery must include the direct detection of our own galactic dark matter. Thermal production of Weakly Interacting Massive Particles in the early universe naturally results in the correct dark matter abundance today, and most supersymmetry models mentioned earlier contain such particles. Many other well-motivated theories also invoke particles that may be searched for. We are also working hard on the design, development and construction of the upgraded detectors at the LHC for around 2020. The intensity of the beams will be increased and the data rates recorded by the detectors will increase by orders of magnitude. This requires building new detectors for precisely measuring trajectories of longlived particles, for measuring Cherenkov photons to deterimene their speed, and faster and more powerful simulation, and new ways to handle the massive data rates. We are also constructing the LUX-ZEPLIN project, expected to dominate direct searches for dark matter in the next decade. We work on simulations, control systems for the 10 tonnes of liquid xenon, and analysis. We have recently started an activity neutrino physics by joining the Hyper-K experiment to be constructed in Japan. One of the most interesting fact of nature is that there are only three species of neutrinos, which until recently were thought to be massless. It is important to measure precisely the "mixing" between the species and to search for CP violation in neutrinos.