Birmingham Nuclear Physics Consolidated Grant 2023

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Our proposed research has two 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 and is entirely responsible for it. 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.What happens in stars: the cooking pots of the Universe and how the structure of the nuclei involved in these reactions influences the formation of elements is at the centre of Theme 2's research portfolio. From red-giant stars which burn helium to some of the most explosive events known, such as X-ray bursts and supernovae - out-shining galaxies, albeit for a short time - the structure of nuclei play a pivotal role. The interplay between neutrons and protons within the nucleus can have a very significant impact on such astrophysical processes. One manifestation of the nuclear force is the observation of clustering in which protons and neutrons clump together inside larger nuclei, for example into alpha particles (two protons and two neutrons). The strong force is highly complex, which makes theoretical predictions formidable, so our research makes extremely precise measurements of how light nuclei interact. By detecting all the fragments of such collisions we can rebuild the nuclear system from which they originated to reveal detailed properties and also measure how quickly nuclei will combine together in stellar environments. These results can then be used to improve models of these colossal energy-release events taking place and that have led to the abundance of elements we find on earth. Finally, we are developing an experimental programme to exploit gamma-ray and neutron beams. Gamma rays allow the structure of nuclei to be probed with great precision through their electromagnetic properties. Conversely, uncharged neutrons are capable of transmuting elements even at low energies and reveal information about the most important matter-producing reactions in the Universe. This is possible due to Birmingham's new high-intensity neutron facility which is able to mimic what happens in the stars in our laboratory.