Birmingham Nuclear Physics Group Consolidated Grant

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The atomic nucleus has recently seen its centenary. Over this time understanding of nuclei and their structure has evolved considerably. However, and perhaps surprisingly it is still not possible to calculate their structure with sufficient accuracy. The fundamental limitation is not only that the nucleus is a many body object, and the complexity that is a natural consequence, but the interaction is fundamentally yet to be understood. It is this interaction which generates all sorts of complex nuclear structures from clustering to halos, from spherical to deformed, from stable to unstable. In order to make more progress one has to understand how the nuclear strong interaction emerges from that at the sub nucleonic level, where quarks and gluons are the appropriate degrees of freedom. Growing the nuclear force from the Quantum Chromodynamic (QCD) level is the dominion of chiral effective field theory. This is one of a range of approaches which it is hoped will lead to understanding nuclei from first principles (ab initio). The Birmingham Nuclear Physics group's research spans the territory from the QCD to nucleonic and seeks to answer some of the central challenges of the subject. Through the collisions of nuclei at the highest possible energies yet created in the laboratory the group is exploring the quark-gluon plasma (QGP). This is a state of matter created when the energy in the collision is so high that the nucleons (protons and neutrons) melt into the quarks and gluons. This is believed to be precisely the phase of matter an instant after the big bang. These conditions are created in the laboratory for a fleeting moment and the challenge is to probe the matter in this phase before it dissociates. The Birmingham group are part of the ALICE collaboration at the LHC in CERN and have developed the sophisticated trigger, which selects key events in the millions of collisions in which the QGP is formed. Through our scientific leadership we have been able to get a feeling for the properties of the QGP. The challenge for the present grant is to go beyond the rather rudimentary understanding to provide a precise characterisation of its properties. This involves detailed measurements of particles as they are emitted from the QGP, for example measuring their survival probability as they cross the plasma. The aim to to reach a detailed understanding of this state of hadronic matter.The second strand reaches from the quark scale to the scale of nuclei. The ab initio calculations of nuclei are challenging and for many of them the limits lie close to mass 12. As a result much of the focus has fallen on carbon-12. The Birmingham group has led the development of the experimental understand of this nucleus and one particular quantum state - the Hoyle-state. This rather exotic state is not only believed to be constructed from three alpha-particles, but to be associated with the synthesis of carbon in stars. If the state did not exist nor would organic (carbon-based) life. Understanding its structure is fundamental to human existence. Not only has the group made a significant contribution to this understanding, but we are exploring the alpha-cluster correlations in a whole sequence of light nuclei. It is understanding these correlations which is key to testing the ab initio models and our understanding of the nuclear force. The group will perform a series of precision measurements to provide stringent tests of the best nuclear models to-date.The present application is a potentially high impact contribution to the development of our understanding of nuclear and hadronic matter.