Nuclear Physics Consolidated Grant 21-24 - University of York

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The York Nuclear Physics Group is firmly positioned as one of the leading groups worldwide having recently expanded to a full complement of 14 academics with broad and connected research programmes encompassing hadron physics, nuclear structure, nuclear astrophysics, nuclear theory and applications-focussed work. Nuclear physics is one of the principal areas of research in the Department of Physics at York, where the group represents about 25% of the academic staff, and enjoys the strong support of the Department and the University in its continued development. The group carries out research in theoretical nuclear physics, as well as experimental nuclear physics which it conducts at leading facilities in Europe, North America and Japan. This consolidated grant will support the group's activities in the period 2021-2024. To explain the context of our research, we have to describe the system we are working on - the atomic nucleus. The atoms forming our visible universe each contain an atomic nucleus, comprised of light (up, down) quarks which manifest as the familiar three-quark groupings of protons and neutrons (together known as nucleons) in a many-body quantum mechanical system. There are many open questions regarding how these nucleons arrange themselves in the nucleus: What happens when the nucleons overlap in violent collisions? Are the strong forces between nucleons the same for different combinations (pn and pp)? What is the role of three-nucleon forces? Do heavy nuclei have a "neutron skin"? These are all topics that our research will address through theoretical developments and an ambitious experimental programme at a wide range of facilities worldwide. The range of nuclei we observe today, from light to heavy elements, was created by nuclear reactions within stars and by the violent collisions of dense stellar objects such as neutron stars. Our research addresses fundamental gaps in our knowledge of the nuclear reactions forming these nuclei in stars by reproducing these reactions here on earth, in the laboratory. We are also probing the underlying nuclear science of neutron stars. There is a lot to learn about neutron stars, it is not even established what is inside! Our group will lead investigations into the exciting possibility that a new form of matter, a hexaquark containing six quarks, could play a pivotal role. At even smaller distance scales, we will also challenge the question of where the mass of the nucleus comes from. We know this arises from the masses of the constituent protons and neutrons. However only ~2% of this comes from the mass of the three quarks making up the nucleon. Exploring this murky quantum world through experiments at world-leading facilities will cast more light on the origins of mass.