Spectator Tagging Experiments to Understand the Structure of Matter

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

Abstract

How can we measure a sub-atomic particle which only comes into existence for an exceptionally short time and disappears before we can even detect it? This research aims to design innovative technology enabling us to do this, to push beyond current limits in our vital knowledge of the structure of matter.

We are on the brink of a transformation in our capabilities to observe the inner-dynamics of the nucleus, one of the main building blocks of our universe. 99.9% of the mass of the visible universe resides in atomic nuclei, which are composed of protons and neutrons (nucleons). Nucleons themselves have a composite structure, consisting of partons (quarks and gluons).

Hadrons are sub-atomic particles, including nucleons, which are bound together and interact by the fundamental strong interaction. This interaction is vital in many nuclear processes, for example chain reactions in burning stars, or nuclear reactors for energy. Quantum chromodynamics (QCD) is the theory describing the strong interaction. Understanding it will be key to answering some of the most pressing questions in nuclear physics, like "why don't quarks exist freely in Nature and why are they confined inside hadrons?" or "what is the origin of a hadron's mass?".

To understand QCD we must understand the structure of hadrons in terms of their partons. The arrangement of partons inside the nucleon is constantly changing, with hadrons continuously being created and destroyed inside it. About 20% of the time the nucleon exists in a virtual (very short-lived) state in which it is accompanied by a meson. Mesons are the simplest bound hadrons, comprising one quark and one anti-quark. They are the force mediators between nucleons, holding nuclei together, and are valuable virtual laboratories for QCD. Despite significant theoretical advances concerning their structure, experimental data are extremely sparse.

Through this research, UK scientists will lead experiments aiming to scatter high energy electrons from these virtual meson "clouds" of nucleons. This will shed light on the nucleon's elusive meson content and provide access to the composite structure of two different mesons - the pion and kaon. These mesons differ in their quark/anti-quark contents.

Scattering from the virtual meson cloud itself cannot be measured - the meson fragments during the scattering. To successfully select the correct scattering events, its existence must be inferred by measuring the corresponding nucleon recoiling from the interaction, in coincidence with the scattered electron. If the scattering took place from the meson cloud, the nucleon will travel in certain expected directions, with specific energies. This is spectator tagging and offers access to targets not easily found in Nature.

This research will optimise the design of the detector for the recoiling nucleons and operate it in the experiments. The detector will be filled with gas. When charged particles pass through it, a signal is created. The signals will be constantly recorded by fast electronics, to determine the directions and energies of the particles. This will be a ground breaking piece of technology. It must be capable of withstanding, and disentangling, extremely high rates of particles within its active volume (several millions of particles per second).

The experiments will be performed at the recently upgraded Jefferson Lab (USA), offering an unprecedented high intensity electron beam and opening the frontier to these rare scattering processes. The experiments will provide a gateway to a future landscape of spectator tagging experiments to study hadronic structure further. Techniques developed in this field also have potential impact in several applications which benefit society. For example in medical physics or nuclear waste decommissioning, where cutting edge particle detectors are instrumental, as well as knowledge of the detailed computer simulations required to study their implementation.

Publications

10 25 50
publication icon
Aguilar A (2019) Pion and kaon structure at the electron-ion collider in The European Physical Journal A

publication icon
Arrington J (2021) Revealing the structure of light pseudoscalar mesons at the electron-ion collider in Journal of Physics G: Nuclear and Particle Physics

publication icon
Boyd L (2021) Simulation of the response of the Solid State Neutron Detector for the European Spallation Source in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

publication icon
Chatagnon P (2021) First Measurement of Timelike Compton Scattering. in Physical review letters

publication icon
Contalbrigo M (2020) The CLAS12 Ring Imaging Cherenkov detector in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

publication icon
Rofors E (2021) Response of a Li-glass/multi-anode photomultiplier detector to collimated thermal-neutron beams in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

publication icon
Rofors E (2020) Response of a Li-glass/multi-anode photomultiplier detector to focused proton and deuteron beams in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

 
Description Nuclear Physics Advisory Panel
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
 
Description UKRI ECR forum member
Geographic Reach National 
Policy Influence Type Participation in a national consultation
 
Description University of Glasgow Lord Kelvin/Adam Smith (LKAS) Award
Amount £100,000 (GBP)
Organisation University of Glasgow 
Sector Academic/University
Country United Kingdom
Start 09/2019 
End 09/2024
 
Description Binding Blocks Collaboration 
Organisation University of York
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution Participation in events by researchers and research students; knowledge exchange; resource sharing; training of personnel partaking in events.
Collaborator Contribution Participation in events by researchers, research students and undergraduate students; knowledge exchange; resource sharing; training of personnel partaking in events.
Impact Several of outreach activities as noted in engagement outputs.
Start Year 2019
 
Description The Jefferson Lab Hall A,Super BigBite Spectrometer and Tagged Deep Inelastic Scattering Collaborations 
Organisation Thomas Jefferson National Accelerator Facility
Country United States 
Sector Public 
PI Contribution Knowledge exchange; simulation and analysis software development; proposal submission; detector installation and commissioning; data taking; experiment spokesperson duties; time served in Hall A Coordinating Committee (organising of paper reviews, collaboration meetings etc).
Collaborator Contribution Knowledge exchange; access to and provision of experimental equipment and accelerator facilities; storage of and access to data; data taking; proposal submission; co-authorship.
Impact TBD
Start Year 2019
 
Description EIC related interview on Jefferson Lab website 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Discussed my research into the Electron Ion Collider, and my role within the collaboration, in a written online interview which was featured on the webpage and social media account of the Jefferson Laboratory national accelerator facility in USA, increasing awareness of the research and award within the user community of the facility and the wider general public.
Year(s) Of Engagement Activity 2021
 
Description Jefferson Lab Newsletter 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This award was highlighted in the weekly newsletter of the international Jefferson Laboratory, increasing awareness of the research and award within the user community of the facility.
Year(s) Of Engagement Activity 2019
 
Description Outreach talk at IOP London 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact The research associated with this award was presented in the form of a roughly 1hr duration talk to roughly 30 members of the general public as part of a large-scale nuclear physics public outreach event held at the Institute of Physics premises in London.
Year(s) Of Engagement Activity 2020
 
Description Participation in online forum Q&A as part of nuclear physics masterclass 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Participated in answering questions posted by school pupils on an online forum running as part of an online Nuclear Physics Masterclass organised and ran by Binding Blocks from the University of York. The forum was available to the full number of participants in the online masterclass and more than one third of the participants were highly engaged and completed the material. Feedback received during the forum conversations including increased interest and understanding in nuclear physics.
Year(s) Of Engagement Activity 2020
URL https://www.york.ac.uk/physics/public-and-schools/secondary/binding-blocks/
 
Description Research fortnight interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Interview about the research activities related to the award was given to Research Fortnight. The article was made available on the Research Professional website.
Year(s) Of Engagement Activity 2019
 
Description Scattering activity stand at IOP nuclear physics open exhibition 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact A self explanatory hands-on exhibit explaining particle scattering experiments in nuclear physics was installed as part of a wider nuclear physics exhibition at the IOP building in London running for just under two weeks duration.
Year(s) Of Engagement Activity 2020
 
Description Scattering in nuclear physics stand exhibited during IOP family day 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact An interactive stand explaining particle scattering in nuclear physics experiments and how we can "see the unseen" was demonstrated during a dedicated Family Day related to nuclear physics at the IOP building in London.
Year(s) Of Engagement Activity 2020
 
Description Teacher training event at University of Glasgow 
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 Organised and hosted a CPD event at University of Glasgow. The research topic involved with this award was discussed with teachers and STEM ambassadors during the event. During this event, a public engagement toolkit which may be used to explain the research involved with this award was also demonstrated to the participants and offered to them as a future resource for classrooms or STEM ambassador activities. Several other nuclear-physics related activities which could be available for lending too were also presented, including the Binding Blocks lego chart of radio isotopes.
Year(s) Of Engagement Activity 2020