Edinburgh Nuclear Physics Group Consolidated Grant Proposal

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The research programme aims at understanding the processes that forge the elements in stars and the big bang and obtaining a deeper understanding of nuclear matter. This requires remarkable experiments underground that let us study reactions at the very low energies occurring in stars such as the sun, and with beams of radioactive nuclei to understand the reactions that take place in explosive events such as supernovae which occur at higher temperatures and involve unstable isotopes. The astrophysical origin of the elements heavier than iron remains a particular mystery - they may for example be produced in thermally pulsing stars, supernovae and merging neutron stars. Fusion reactions with neutrons play a vital role in producing these elements but we do not understand these reactions, and the properties of radioactive isotopes produced by them, well enough. We will study reactions with neutron beams and study the properties of highly neutron-rich nuclei existing very far from stability. The nature of matter in neutron stars themselves remains a mystery. These are like large nuclei but bound by the gravitational force rather than the strong force. We will perform measurements of the neutron skin which forms on the surface of nuclei with intense high energy photon beams. The neutron skin is a mini laboratory for neutron star matter and by accurately measuring its properties we can access new information on neutron star structure and cooling mechanisms. The nature of matter inside neutron star cores is a great mystery, and it has been suggested that matter containing strange quarks may be present - a remarkable hypothesis. Our experiments will test the nature of nuclear matter for the conditions found in neutron stars. There is evidence that quarks can exist as a group of 6, a hexaquark, and may even be present inside neutron stars and influence their properties. This is not something found in textbooks but the theory of the strong force, quantum chromo dynamics, allows this exotic possibility. We will perform experiments to provide stronger evidence for the existence of the hexaquark and probe its properties.