Birmingham Nuclear Physics Group Rolling Grant Application

The nucleus, despite its popular perception, is a highly complex quantum body. It is often represented in text books as a static collection of spheres; a view driven by the atomic perspective where all that really matters is the mass of the nucleus and its charge. On the contrary, the nucleus is a highly dynamic system where nucleons move with velocities approaching a fraction of the speed of light; meaning that relativistic effects are non-negligible. Moreover, the location of the nucleon is not well defined, only the probability of finding a nucleus at a given point. Each nucleon is confined within its own probability field (orbital) and thus the interaction between nucleons is governed by their overlap. One might anticipate that despite this complexity the calculation of the interactions and thus the binding energy, mass, shape and moments (electric and magnetic) should still be a tractable problem. However, what prevents such a realisation is that the nature of the interaction between nucleons remains to be fully understood, in particular the nature of correlations which exist inside nuclei. Furthermore, the nuclear force is a manifestation of colour forces, which act to bind quarks inside nucleons. This transition from nucleonic to quark degrees of freedom remains to be understood. What is more, it is not completely clear how the properties of the nucleon is comprised from its constituent quarks and gluons. The understanding of the formation of the chemical elements requires an understanding of nuclei and nuclear processes. The cooking of elements in the life-cycle of stars, both in their main burn phase and their eventual death (novae or supernovae) is one of the eleven key questions posed by the US Academy of Science. One of the most important of these processes is the synthesis of 12C through the portal of the Hoyle state - a quantum state which enhances the capture rate of 4He by 8Be by 10^8. This state is so important, that if it did not exist, then neither would human kind. It is believed that this state must have a very unusual (cluster) structure, and to demonstrate this is of great importance. Before nuclei were sythesised, protons and neutrons must have been formed. This process would have occurred a fraction of a second after the Big Bang, before which matter would have consisted of a plasma of quarks and gluons, and other fundamental particles. One of the most exciting goals of modern physics is to explore this new state of matter, and moreover to study its transition to normal nuclear matter. This becomes possible with the world's largest and most powerful particle accelerators, giving us the chance to study the physics near the beginning of the universe. The Birmingham group is engaged in a research programme which is aimed at addressing many of these questions. The relativistic heavy-ion group, through their research programme at RHIC (STAR) and the LHC (ALICE) are colliding nuclei at very high energies in an attempt to create the quark gluon plasma, and then to measure its transition into normal nuclear matter using complex detector systems. The charged particle group is focussed on the study of the structure of light nuclei and understanding the correlations between nucleons which manifest themselves as clusters inside the nucleus. In particular the search for linear arrangements of clusters has been a dream for over 40 years. The group will also attempt to pin down the nature of the Hoyle state. The laser spectroscopy work measures fundamental properties of nuclei, such as their shape and moments crucial for developing a detailed understanding of what the nucleons are doing inside the nucleus. Many of these nuclei feature in the so-called r-process, which takes place in neutron fluxes in supernovae which are apparently 10^9 higher than in stars. This work provides an important link between nuclear science and cosmology and promises to lead to a deeper understanding of the origins of our universe.