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 at CERN's Large Hadron Collider if one or other of the suggested deeper theories is correct, alongside interpretations of particle physics measurements without such theoretical prejudice. We must make sure that we optimise the analysis of the experiments there 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 technique of lattice QCD, which Glasgow has been instrumental in turning into a precision tool. Glasgow continues to lead progress and here we propose calculations that will predict more accurately how hadrons decay from one type to another via the weak force. The comparison with experiment will then allow us to push down uncertainties in the parameters of the weak force that allow for violations of symmetry between matter and antimatter. We also plan to calculate accurately the tiny effect of the strong force on the magnetic moment of the muon ahead of a new experimental determination of this quantity that aims to find out for sure whether it agrees with the Standard model or not.

The Glasgow team will also investigate theories that go beyond the Standard Model and test them with LHC data. The heaviest known particles, the Higgs boson and the top quark, are believed to be fundamental and can be harbingers of new dynamics. We must therefore undertake a comprehensive precision programme to measure their properties to the highest attainable precision. New physics may show up by subtly modifying these properties and we will devise ways of looking for these effects alongside other evidence for new physics. We will study particle properties by means of general, model-independent methods, which also make use of artificial intelligence to maximise sensitivity. This approach will enable us to connect our findings transparently with precise measurements of the aforementioned hadrons, which are sensitive to the presence of new particles and interactions. We will also examine specific new physics models, such as theories of Grand Unification, which unify the three forces together as one single force. We will determine how these exciting and fundamental theories affect the particle properties described above and thereby confront them with LHC observations. Experimental studies on the Higgs boson and top quarks are being led by the Glasgow ATLAS group and we will coordinate with them to uncover the fundamental truths of the universe.

The next few years will be a very exciting time for theoretical particle physics and Glasgow aims to be at the forefront of this work, preparing for the next Large Hadron Collider data taking runs.