Birmingham Nuclear Physics Group Consolidated Grant

Lead Research Organisation: University of Birmingham
Department Name: School of Physics and Astronomy

Abstract

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.

Planned Impact

The main beneficiaries of this research will be experimentalists and theorists working in the field of hot Quantum Chromodynamics and those working to understand the structure of light nuclei, from stability to the drip lines. They will directly benefit from the new insights that will arise out of this research and also the methodologies that are developed to deliver those insights. The results of this research will be disseminated in high impact journals, through conference talks and seminars so as to reach as wide an audience as possible. More broadly, this research is also of relevance to researchers in other fields, including astrophysics and cosmology. Some of the hardware developments related to the Birmingham design of the original ALICE trigger subsystem have already had impact, having being adopted by another experiment at CERN. Future developments that are foreseen in this proposal will potentially have relevance to a new generation of experiments planning to run in continuous data taking mode.

The experimental and analytical techniques employed by the group produce highly trained postgraduates who are in high demand in medical and nuclear related industries and elsewhere. The connection between pure, fundamental, and applied nuclear research is also significant. The recently formed Birmingham Centre for Nuclear Education and Research unites pure nuclear physics with applied research from materials, chemistry, geoscience, robotics and bioscience disciplines together with the nuclear industry. The skills and techniques provided by the pure science are key to the success of this Centre, also underpinning a significant portion of its educational programme. The group has strong links with the nuclear industry that goes back to the very beginning of the industry in the UK. We have recently established a new undergraduate programme in Nuclear Engineering and a postgraduate course in Nuclear Waste Management and Decommissioning. We engage with 20 of the UK's leading companies in the nuclear sector and have been instrumental in the development of policy regarding the future of the nuclear industry in the UK, informing the UK government. We have also exploited the MC40 cyclotron at Birmingham to develop a facility for the irradiation of materials that will be necessary for the design of a future generation of nuclear reactors. Building on our earlier policy work and recognising the important role that China will play in new nuclear build in the UK, contact has already been made with Chinese academics and nuclear power companies to explore areas of mutual interest regarding international policy in connection with future challenges of nuclear power.

A third strand revolves around the public understanding of science. The research that is outlined in this proposal has the potential to capture the imagination and to inspire a new generation of scientists. One part of the proposed research programme is involved in studying matter as it would have existed a fraction of a second after the Big Bang. This aspect is relevant to evolution of the early universe and the possible existence of (strange) quark matter stars. The other focuses on the Holye state in 12C, responsible for the synthesis of carbon in stars. Understanding the structure of the Hoyle state is a challenge that is relevant not only to nuclear science, but the origins of carbon based life itself. The Birmingham group has an extensive outreach programme, interacting with local schools and regional science centres and hosting events at the University. Aspects of our research has received coverage in national and international press. We recognise the importance of exploiting these opportunities to reach the widest possible audience

Publications

10 25 50
 
Description 1. The total multiplicity of particles produced in Pb-Pb collisions at the LHC scales with the number of participating nucleons, indicating that soft QCD processes are still largely responsible for particle production at LHC energies.
2. A mechanism to limit the growth of soft particle production, as provided by saturation-inspired models, is needed to reproduce the data.
3. Measurements of strange particle production as a function of transverse momentum provided insight into the hydrodynamic expansion of the quark-gluon plasma and the interplay between hadronisation from the bulk at low momentum and quark or gluon fragmentation at high momentum.
4. Studies of multi-strange baryon production in Pb-Pb collisions helped to determine the level of strangeness equilibration at LHC energies.
5. We observed strangeness enhancement as a function of multiplicity in p-Pb collisions, indicating the possibiloity of quark-gluon plamsa formation even in small systems at LHC energies.
6. Studies of ultra-peripheral Pb-Pb collisions revealed evidence of moderate gluon shadowing in the Pb nucleus at LHC energies.
7. By contrast, comparable studies in p-Pb collisions has not provided any evidence for the onset of saturation in the gluon density expected at low-x.
8. We have made a major contribution to the understanding of the structure of 12C above the alpha-decay threshold.
9. We have found clear evidence for the D3h, triangular 3-alpha, symmetry of the Hoyle state in 12C.
10. Provided some of the best evidence for the existence of the predicted 1/2+ first excited state in 9B.
11. Explored exotic molecular structures in the 14C nucleus finding evidence of a linear chain-like configuration.
12. We undertook the first resonant scattering experiment at the EXOTIC facility and found evidence for alpha-clustering in 28Mg that closely follow the signature split rotational bands predicted by microscopic models.
13. The extent of alpha clustering in calcium isotopes has been extracted by using wavelet analysis.
Exploitation Route This outcomes of this work are primarily of interest to researchers in the fields of high energy nuclear physics and nuclear structure. This work will be taken forward in future studies at the high luminosity LHC (Runs 3 and 4) and at new nuclear structure facilities such as ELI-NP and FAIR.
Sectors Education

 
Description Birmingham Nuclear Physics Consolidated Grant
Amount £1,466,551 (GBP)
Funding ID ST/P004199/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Public
Country United Kingdom
Start 10/2018 
End 09/2021
 
Description ALICE 
Organisation European Organization for Nuclear Research (CERN)
Department ALICE Collaboration
Country Switzerland 
Sector Public 
PI Contribution Support (maintenance and operation) of the Central Trigger Processor. Data Analysis.
Collaborator Contribution Access to an accelerator facility - the Large Hadron Collider. Provision of office space and central computing facility and network access. Access to shared data.
Impact Outputs are primarily through publications, listed in the relevant section of the form, which are the outcomes of collaborative research.
 
Description Catania 
Organisation University of Catania
Department Department of Physics and Astronomy
Country Italy 
Sector Academic/University 
PI Contribution Research collaboration on topics of common interest in nuclear structure - experimental techniques and experience
Collaborator Contribution Research collaboration on topics of common interest in nuclear structure - equipment
Impact Experimental measurements
Start Year 2014
 
Description RBI 
Organisation Ruder Boskovic Institute
Country Croatia 
Sector Public 
PI Contribution Joint experimental programme - experimentaql experience and scientific insight
Collaborator Contribution Research collaboration on topics of common interest in nuclear structure - experimental equipment/personel
Impact Publications
Start Year 2010
 
Description Multiple outreach activitives and public lectures to Schools, general public, teachers, and school children 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Professor Evans is involved in 20 to 25 outreach activities a year, mainly public lectures but also workshops, masterclasses, and summer schools.
All activities are physics based and most are related to the ALICE experiment in some way. The purpose of the activites are to inspire and encourage young people to take up physics (or other STEM subjects) at university.
Year(s) Of Engagement Activity 2015,2016,2017
URL http://www.birmingham.ac.uk/schools/physics/outreach/index.aspx
 
Description Nuclear Physics Master Class 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Master class for Year 12 students
Year(s) Of Engagement Activity 2016
 
Description Outreach Activities 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Numerous outreach activities - including talks and quizes
Year(s) Of Engagement Activity 2015