Nuclear Physics Consolidated Grant 2020

Lead Research Organisation: University of Liverpool
Department Name: Physics

Abstract

The majority of visible mass of the universe is made up of atomic nuclei that lie at the centre of atoms. Nuclear physics seeks to answer fundamental questions such as: "How do the laws of physics work when driven to the extremes? What are the fundamental constituents and fabric of the universe and how do they interact? How did the universe begin and how is it evolving? What is the nature of nuclear and hadronic matter?" The aim of our research is to study and measure the properties of atomic nuclei and hot nuclear matter in order to answer these questions.
For exotic nuclear systems lying far from stability we will explore how the nucleus prefers to rearrange its shape, which can be a sphere, rugby ball, etc. and how it stores its energy among the possible degrees of freedom. We will study the properties of the very few cases where nuclei can assume the shape of a pear, that may be key in understanding why the universe has a matter-antimatter imbalance. We will explore in the region of the proton and neutron drip lines, which are the borders between bound and unbound nuclei and are relevant to understanding how atomic nuclei are synthesised in stars. Nuclei beyond the proton drip line have so much electrical charge that they are highly unstable and try to achieve greater stability through the process of proton emission. We will investigate how this process is affected by the nucleus' shape and structure, and make precision measurements of these fundamental properties using lasers. No one yet knows just how many neutrons and protons can be made to bind together. We will study the heaviest nuclei that can be made in the laboratory and determine their properties which will allow better predictions to be made for the "superheavies". We will also investigate how the properties of nuclei develop as we make them spin faster and faster, determining the precise nature of ultra-high spin states in heavy nuclei, just before the nucleus breaks up due to fission.
Nuclear matter can exist in different phases, analogous to the solid, liquid, gas and plasma phases in ordinary substances. By varying the temperature, density or pressure, nuclear matter can undergo a transition from one phase to another. In extreme conditions of density and temperature (about 100 thousand times more than the temperature at the heart of the sun!), a phase transition should occur and quarks and gluons (of which the protons and neutrons are made) should exist in a new state of matter called the Quark-Gluon Plasma. By colliding nuclei together at high energies at the Large Hadron Collider at CERN, we will study properties of this new state of matter. Such information is not only important for nuclear physics but also to understand neutron stars and other compact astrophysical objects.
This programme of research will employ a large variety of experimental methods to probe many aspects of nuclear structure and the phases of strongly interacting matter, mostly using instrumentation that we have constructed at several world-leading accelerator laboratories. The work will require a series of related experiments at a range of facilities in order for us to gain an insight into the answers to the questions posed above. These experiments will help theorists to refine and test their calculations that have attempted to predict the properties of nuclei and nuclear matter, often with widely differing results. The resolution of this problem will help us to describe complex many-body nuclear systems and better understand conditions in our universe a few fractions of a second after the big bang.

Planned Impact

Nuclear physics research and technology development has had a huge beneficial influence in our Society. Through low-carbon energy production, radiation detection for national security or environmental monitoring and cancer diagnosis and treatment in modern healthcare, the applications emerging from nuclear physics are numerous.


Recent high-profile scientific discoveries include:

- An electronic transition was located in nobelium, making Z=102 the heaviest element for which optical spectroscopy has been performed. This observation was published in Nature and we subsequently measured the ionisation potential with high precision and have begun to extract moments and radii of different isotopes (leading to 2 PRLs).

- Following the publication in Nature of its discovery that 224Ra is pear-shaped, the Liverpool group has now established that the radon isotopes 224Rn and 226Rn do not possess static pear shapes in their ground states, so they are not promising candidates to have measurable atomic electric dipole moments. This work was publicised in Nature Communications, CERN Courier, Phys.org, Science Daily and Scienmag.

- The presence of two different topologies in light Hg isotopes that coexist and mix at low excitation energy has been firmly established for the first time through our programme of complementary experiments. The laser spectroscopy results published in Nature Physics were compared with the largest Monte-Carlo shell model calculations ever performed, providing insights into the microscopic origins of shape coexistence.

- In a paper published in Nature Physics, the ALICE collaboration reported novel phenomena observed in proton collisions at the LHC. Until then enhanced strangeness production had been observed only in collisions of heavy nuclei, and was considered as a manifestation of the primordial state of matter called the quark-gluon plasma. ALICE's new and unexpected measurements indicate that this phenomenon may now have been observed in smaller and simpler systems as well. This discovery opens up an entirely new dimension for the investigation of the strongly-interacting matter from which our universe emerged.


The University of Liverpool has significant industrial engagement programmes that support knowledge exchange and the development of future REF returnable impact cases with a focus on nuclear measurement techniques and instrumentation. Industrial collaborators include AWE, Mirion, Kromek, Ametek, John Caunt Scientific, Metropolitan Police, MoD, National Nuclear Laboratory, Rapiscan, Sellafield Ltd. and a large number of NHS Trusts.


The University Department of Physics is one of only three national training providers for the Modernising Scientific Careers Clinical Science (Medical Physics) MSc, funded by the NHS. This provides a unique opportunity to build collaborative research and Continuing Professional Development partnerships within the Healthcare sector.


Beyond satisfying human curiosity around the workings of nature, pure research in nuclear physics has also tremendous societal impact. The University of Liverpool has an excellent track record in public engagement and outreach in a subject that has a natural fascination for the public. Indeed, it fulfils the important role of educating the public in nuclear radiation and its wider aspects, both positive and negative and is important to drive interest in the study of STEM subjects. Nuclear Physicists are frequently invited to share their knowledge and talk about their research at schools, science festivals and community groups.


The University of Liverpool hosts the state-of-the-art Central Teaching Laboratory (CTL) facility. The CTL has a dedicated laboratory for Nuclear Physics and radiation measurements. The CTL holds schools and outreach activities on a regular basis with University support, such as the Science Jamborees for 300 Cubs, Beavers and Brownies.

Publications

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