Phenomenology from Lattice QCD and Collider Physics

The Glasgow theory group has a strong reputation in studies of the subatomic world, and pushing forward our understanding of how it works. This is aimed at uncovering the fundamental constituents of matter and the nature of the interactions that operate between them. There are two approaches to this, and we will use both of them. One is to perform very accurate calculations within the theoretical framework of the Standard Model that we believe correctly describes the particles that we have seen so far and the strong, weak and electromagnetic forces of Nature. Discrepancies between these accurate calculations and what is seen in experiments will then point the way to a deeper theory that describes fundamental particle physics more completely. The second method is concerned with what we might see in LHC results, now appearing, if one of the suggested deeper theories is correct. We must make sure that we optimise the analysis of these experiments to learn as much as possible. Accurate calculations in the Standard Model have foundered in the past on the difficult problem of how to handle the strong force. This force is important inside particles that make up the atomic nucleus, the proton and neutron and a host of similar particles called hadrons produced in high energy collisions. The constituents of these particles are quarks, and they are trapped inside hadrons by the behaviour of the strong force. This 'confinement' of quarks makes calculations of the effect of the strong force on the physics of hadrons very challenging. It can be tackled, however, using the numerical techniques of lattice QCD. This method has been tested thoroughly by the Glasgow group in precision calculations of hadron masses and their comparison to experiment, and its current acceptance as a precision tool is based in no small part on their work. Glasgow continues to lead progress and here we propose further, harder calculations that will predict more details of how hadrons decay from one type to another via the weak force. The comparison of accurate results with experiment will allow us to constrain the parameters of the weak force that give rise to violations of symmetry between matter and antimatter. We plan to halve existing errors for these calculations and that will allow us to test the Standard Model very stringently. The Glasgow team will also investigate theories that go beyond the Standard Model and tests of them that can be done with LHC data. For example, we will provide phenomenological studies of possible physics signatures that could be seen at LHC and how they would distinguish between models. This includes studying new particles that would be present in some models with a view to establishing their properties. In particular we will develop methods for studying the physics of top quarks, which will be produced copiously at LHC. The top is the heaviest quark that we have seen, and it provides an exciting window into new physics. Experimental studies in this area are being led by the Glasgow ATLAS group and we will coordinate with them to provide ways of testing top quark properties in detail, including behaviour that could arise in beyond the Standard Model scenarios. We are also developing new methods for increasing the accuracy of how quarks and gluons affect scattering experiments, which is useful for LHC physics, but may in addition lead to insights in other theories besides QCD. The next four years will be a very exciting time for theoretical particle physics and Glasgow aims to be at the forefront of this work.