Birmingham Nuclear Physics Consolidated Grant 2016

Our proposed research has three broad themes that build upon our world leading areas of expertise. The first of these involves the study of high-energy nuclear collisions at the Large Hadron Collider, the world's highest energy particle accelerator. The aim of the ALICE experiment is to study nuclear matter, as it would have existed about a millionth of a second after the Big Bang when the Universe was so hot and so dense that nuclei did not exist. In its primordial state nuclear matter consists of its fundamental constituents (quarks and gluons) in a plasma state. We recreate this novel state of matter in our experiment and we are developing ways of studying these high-energy nuclear collisions to discover the properties of the quark-gluon plasma. This is technically challenging and the group has developed a sophisticated electronic trigger system that controls the experiment. The quark-gluon plasma has remarkable properties, such as an abundance of strange quarks and near-perfect fluidity. In this proposal, we are trying to determine whether size matters by finding the smallest drop of plasma that still retains these properties. We are using grazing collisions to explore the internal structure of nuclei at high energy. And we are looking at the debris of quarks and gluons that are sometimes scattered out of the collision, producing a shower of particles in our detector known as a jet, to study the conditions inside the plasma. We are also performing R&D into new detector technologies based on silicon pixel detectors in which the readout electronics is contained within the pixel. The second strand extends beyond the quark scale to the scale of nuclei. Here the challenge is to understand how the nature of the strong interaction plays out on the nuclear, rather than the sub-nucleon scale. Here the strong force is highly complex, which is manifest in correlations. These can be pairing correlations or correlations of higher order, which results in the formation of alpha-particle clusters. The geometric arrangement of clusters produces dynamical symmetries, which in turn gives a fingerprint of quantum mechanical states. The work performed by the Birmingham group has indicated the presence of a triangular arrangement of alpha particles in 12C. We propose to extend the techniques and ideas to a study of 16O that is predicted to be strongly influenced by a tetrahedral structure. What happens to alpha-particle clustering as particles are either added or removed from the cluster cores is extremely important as this is intimately connected with the structure of nuclei at the drip-lines. We will be studying a number of systems that will provide a deeper insight into phenomena such as nuclear molecules. Finally, we plan to develop an experimental programme to exploit gamma-ray beams to probe with great precision the structure of clustered nuclei via their electromagnetic properties. To-date this tool has provided us with some of the best insights into the structure of light nuclei and we plan to extend these studies to exotic cluster states above the cluster decay threshold. This programme will produce measurements to constrain state-of-the-art theory. This grant also recognises the importance of applying nuclear physics knowledge through a variety of applications. In the field of energy production using both nuclear fission and fusion there is a need for more precise measurements of a variety of nuclear reactions. We plan to use the University of Birmingham's MC40 cyclotron for nuclear data studies. Moreover, the cyclotron may be used to create a high radiation environment that mimics either reactor or decommissioning environments. We will develop a facility that will be used to test instrumentation and detection systems for use in such environments.