The Physics of Nuclei, Nuclear Matter and Nucleosynthesis Report of the Nuclear Physics Advisory Panel 13 November 2009 Report of Nuclear Physics Advisory Panel The physics of Nuclei, Nuclear Matter and Nucleosynthesis Contents 1. Nuclear Physics in the 21 st Century ................................................................2 2. International Context ......................................................................................4 3. The UK Scientific Programme ........................................................................4 3.1 Science Questions..................................................................................5 3.2 Nuclear Astrophysics/What are the Origins of the Elements? .................5 3.3 What is the Nature of Nuclear Matter? ....................................................7 3.4 How do the properties of hadrons and the quark-gluon plasma emerge from fundamental interactions? ..........................................................................8 4. Structure of the Community ............................................................................9 5. Modus Operandi and Funding ......................................................................10 6. Current Programme......................................................................................10 7. Current and Future Projects .........................................................................13 7.1 AGATA .................................................................................................13 7.2 NuSTAR ...............................................................................................13 7.3 PANDA.................................................................................................14 7.4 ISOL UK ...............................................................................................15 7.5 JLAB upgrade.......................................................................................15 7.6 ELENA..................................................................................................16 8. Future Programme .......................................................................................17 8.1 Funding and Priorities...........................................................................19 8.2 FAIR funding.........................................................................................23 8.3 Balance of Programme (Projects : Exploitation)....................................23 9. Nuclear Theory.............................................................................................24 10. Societal Benefits of Nuclear Physics Research ............................................24 11. Process ........................................................................................................25 11.1 Panel Membership................................................................................26 Appendix 1: Exploitation Facilities ........................................................................27 Appendix 2: Examples of Highlights of the UK Research Programme ..................28 A2.1 Nuclear isomers in superheavy elements as stepping stones towards the island of stability...............................................................................................28 A2.2 Role of the ∆ inside the nucleus and components of the matter distribution involved in nuclear excitations..........................................................................28 A2.3 Nuclei at extreme spins; breaking through the spin barrier.......................29 A2.4 The Quark-Gluon Plasma (QGP) .............................................................29 A2.5 Study of Exotic Nuclei Using Knockout Studies........................................30 A2.6 Nuclear Molecules....................................................................................30 A2.6 Nuclear Shape Coexistence.....................................................................31 A2.7 Cosmic Gamma-ray Emission..................................................................31 A2.7 The nuclear Magic of Tin..........................................................................32 Report of Nuclear Physics Advisory Panel The physics of Nuclei, Nuclear Matter and Nucleosynthesis 1. Nuclear Physics in the 21 st Century Modern nuclear physics addresses fundamental issues relating to matter created within 10 -5 s of the big bang and matter in exotic astrophysical environments such as neutron stars. It explores the emergent properties of matter from the basic interactions between quarks in baryons and mesons, to the shell structures of heavy nuclei such as uranium and how such nuclei may be synthesised in supernovae explosions. It therefore connects intimately with basic research in Particle Physics and Astrophysics, and is highly pervasive technologically. As a discipline it represents 99.9% of the mass of the visible universe. Understanding the nature of strongly interacting nuclear matter stands as one of the most challenging and most important scientific quests. This ambitious venture aims at building a fundamental description of nucleons starting with the individual quarks and gluons and ending with a description of nuclei and their structure. On the nuclear scale, this ab-initio approach sets out with a description of the nucleon- nucleon interaction and ultimately offers the possibility to accurately predict the structure of any nucleus. Most current models of nuclei use effective (as opposed to fundamental) interactions whose parameters are tuned to reproduce properties of stable nuclei in their ground-states. It has been found that the best tests of these models and their underlying assumptions has been to measure nuclear properties at the extremes; of stability (the drip-lines), of charge (superheavy nuclei), excitation and angular momentum. It is in these paradigms that the predictions diverge and will also form the ultimate tests of the ab-initio approaches. It is the pushing back of our knowledge of nuclei at such limits which acts as a driver for future UK research. Remarkably, descending from an apparently chaotic many-body problem, the nucleus can be described in terms of rather simple degrees of freedom, where nucleons move in non-chaotic orbits governed by their average interaction with all other constituents of the nucleus. Correlations between nucleons are manifest in pairing or ultimately rotational or vibrational modes where all nucleons act coherently. These simple modes are reflected in underpinning symmetries, which provide a characteristic experimental signature. At the limits of existence new structural modes have been observed, e.g. halo nuclei which possess a large volume of neutron Figure 1. Modified Segré Chart (A. Richter INPC 2004). Nuclear Physics extends from understanding the properties of the proton and neutron within QCD, the nature of the Quark- Gluon Plasma, the interaction of nucleons motivated by QCD, the structure of light nuclei using ab- initio approaches which include two- body and three-body nucleon- nucleon forces through to the structure and dynamics of complex many-body systems. The UK is tackling all of these questions. matter with a compact core. Such systems provide sensitive tests of nucleon-nucleon correlations. In the future it is likely that even more exotic structures will be found. Understanding the forces and symmetries driving these transitions and their connection to the strong interaction is of central importance. = 2 = Report of Nuclear Physics Advisory Panel The physics of Nuclei, Nuclear Matter and Nucleosynthesis At the sub-nuclear level, surprisingly, the structures of the proton and neutron remain unfixed. Whilst most textbooks would suggest a simple system composed of 3 spin 1/2 quarks, experimentally this is found to be far from the truth – only 30% of the proton arises from the spin of the quarks. The remainder is a ferment of gluons and virtual particles, which conspire together with the quark orbital motion to give a spin of 1/2 – how remains a mystery. New experiments with improved sensitivity are being developed to answer such questions. This challenge of describing nucleons within the framework of Quantum Chromodynamics (QCD) complements that of understanding the nucleus from the interaction of the constituent nucleons. The most extreme test of nuclear matter occurs when nuclei collide at energies at which the energy density reaches 0.7 GeV/fm3 (5 times normal nuclear matter density). At such densities the nucleons dissolve into their quark constituents, undergoing a phase transition. This provides a laboratory test of the nature of matter a short instant after the Big Bang. A description of such a phase of strongly- interacting matter within QCD remains a challenge, as does its experimental characterisation. Extremes of matter also occur in the cataclysmic death-throes of stars: supernovae. It is here that half of the elements above iron are synthesised, but exactly how is unknown. Generically the mechanism is referred to as the r-process, which encapsulates a series of rapid neutron-capture reactions. However, the question of the site of the r-process and if there is a single r-process, or many, remains to be answered. These reaction rates are so fast that the path proceeds through nuclei which are so neutron-rich, exotic, that they are not naturally occurring. It is only now that we are just beginning to synthesise them in the laboratory and accurately determine their properties. This endeavour