Hunt for Exotic Particles: Dibaryons

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Physics and Astronomy

Abstract

The vast majority of the "mass" of visible matter around us is in fact not really mass. It arises from the interaction energy of the components of the proton and neutron, the quarks and gluons. Because of Einstein's famous equivalence of mass and Energy (E=mc^2) the violent interactions of these subatomic particles can generate mass. For the matter around us on Earth and the matter visible in the stars of the night sky these mass generation mechanisms are much more relevant than the mass arising from the recently discovered Higgs, which accounts for less than 1% of the mass of the atomic nucleus. The mechanism of how quarks and gluons are confined into the bound systems of nucleons, which are the building blocks of the nuclei around us, is not well established. The basic theory of how they interact (Quantum Chromo Dynamics or QCD) has been proposed for some time, but how QCD manifests at the scale of the nucleon or other hadrons is not well understood. It is one of the biggest unsolved scientific problem in modern physics.
Based on the QCD theory describing how quarks interact (specifically color confinement) one expects that there should be many possible bound states of quarks and gluons. Until very recent years the zoo of bound systems comprised only baryons (qqq) and mesons (qqbar). However in addition the gg and ggg glueball states, tetra-quark systems and possibly pentaquark states are not ruled out by the basic principles of QCD. The field has been revolutionized by the recently discovered system Zc(c cbar d ubar). The race is on to establish the other exotic beasts of QCD which will give a totally new constraint and perspective on the nature of strongly interacting matter. I lead one of the most promising future directions to further our knowledge of the nature of matter, the hunt for dibaryons - mysterious six-quark states.
The possibility of exotic dibaryonic states was first proposed by F. Dyson in 1964, just half a year after the Gell-Mann's publication of the quark model. However, this topic received particular attention only after Jaffe's proposal of the so-called H-dibaryon, a uuddss state. I recently led research which has established the existence of a particle made from 6 quarks - the d* dibaryon: a uuuddd state. This is one of the biggest results in the field of strongly interacting matter in the past decade and provides a new window to investigate our understanding of QCD. This exotic object has a high angular momentum, with all six quarks in the ground state having their spins aligned. This d* resonance was investigated in reactions of proton beams on nuclei by the WASA collaboration, largely under my leadership, and is part of an ongoing program. I wish to lead a completely new research branch to investigate this object using beams of high energy photons and electrons to search for it's sister particles. These are the crucial missing piece of the jigsaw needed to unambiguously establish the new exotic particle. I will also establish how the new dibaryon particle interacts with the photon and the electron - it's electromagnetic properties. This will allow the size of the dibaryon to be constrained, enabling the genuine dibaryon with all 6 quarks tightly packed to be distinguished from a molecular-type object with two packages of 3 quarks each.
The new field of dibaryon physics will have major impact on a wide range of research areas including primordial nucleosynthesis, star dynamics, dark matter searches and the nature of quark confinement.

Publications

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Related Projects

Project Reference Relationship Related To Start End Award Value
ST/L00478X/1 31/03/2015 30/06/2018 £427,124
ST/L00478X/2 Transfer ST/L00478X/1 01/07/2018 30/03/2020 £153,476
 
Description pn-system with aligned spins known as deuteron is bound by 2.2 MeV. A mirror pn state - "demon deuteron" is unbound by 66keV. If the "demon deuteron" would be bound, only neutron stars and black holes would exist in our universe. In addition to d* dibaryon (bound by 80 MeV) we searched for the mirror state - "demon d*" and found it unbound.
Exploitation Route Neutron stars dynamics, early universe hydrodynamics, matter formation.
Sectors Other

URL http://www.sciencedirect.com/science/article/pii/S0370269316305561
 
Title High acceptance neutron polarymetry 
Description Method allow the measurement of neutron polarisation in very large angular range and neutron energy ranges. Will be applied for the main measurements proposed in grant application to be performed in summer 2016. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact Many baryon resonance decays have neutron in the final state, measuring polarisation of the outgoing neutron allow determination of the resonance properties. Verification of the method will be performed at upcoming summer 2016 beamtime. 
 
Title high acceptance neutron detection and reconstruction 
Description Develop a method of reliable use of detected neutrons in high acceptance calorimeter at Mainz for many-body reactions. 
Type Of Material Improvements to research infrastructure 
Year Produced 2015 
Provided To Others? Yes  
Impact Use of detected neutrons instead of treating them as "unidentified particles" allows strong background suppression in reactions where neutrons are involved. Use of Kinematical Fit detected neutrons further improve detector resolution providing better accuracy in particle spectroscopy. 
 
Description A2 collaboration (Crystal Ball, Mainz[Germany]) 
Organisation Johannes Gutenberg University of Mainz
Country Germany 
Sector Academic/University 
PI Contribution 1) Analysis of the data 2) Detector maintenance and running (shift) 3) Construction of new detector components (Start construction of new polarymeter and particle identification detector as proposed in grant application)
Collaborator Contribution Detector maintenance, calibration, accelerator maintenance, target maintenance
Impact 1) New insight into nuclear and particle physics. 2) High quality polarisation measurements 3) Baryon spectroscopy
 
Description A2 collaboration (Crystal Ball, Mainz[Germany]) 
Organisation National Institute for Nuclear Physics
Department National Institute for Nuclear Physics - Pavia
Country Italy 
Sector Academic/University 
PI Contribution 1) Analysis of the data 2) Detector maintenance and running (shift) 3) Construction of new detector components (Start construction of new polarymeter and particle identification detector as proposed in grant application)
Collaborator Contribution Detector maintenance, calibration, accelerator maintenance, target maintenance
Impact 1) New insight into nuclear and particle physics. 2) High quality polarisation measurements 3) Baryon spectroscopy
 
Description A2 collaboration (Crystal Ball, Mainz[Germany]) 
Organisation Ruhr University Bochum
Country Germany 
Sector Academic/University 
PI Contribution 1) Analysis of the data 2) Detector maintenance and running (shift) 3) Construction of new detector components (Start construction of new polarymeter and particle identification detector as proposed in grant application)
Collaborator Contribution Detector maintenance, calibration, accelerator maintenance, target maintenance
Impact 1) New insight into nuclear and particle physics. 2) High quality polarisation measurements 3) Baryon spectroscopy
 
Description A2 collaboration (Crystal Ball, Mainz[Germany]) 
Organisation University of Basel
Country Switzerland 
Sector Academic/University 
PI Contribution 1) Analysis of the data 2) Detector maintenance and running (shift) 3) Construction of new detector components (Start construction of new polarymeter and particle identification detector as proposed in grant application)
Collaborator Contribution Detector maintenance, calibration, accelerator maintenance, target maintenance
Impact 1) New insight into nuclear and particle physics. 2) High quality polarisation measurements 3) Baryon spectroscopy
 
Description A2 collaboration (Crystal Ball, Mainz[Germany]) 
Organisation University of Bonn
Country Germany 
Sector Academic/University 
PI Contribution 1) Analysis of the data 2) Detector maintenance and running (shift) 3) Construction of new detector components (Start construction of new polarymeter and particle identification detector as proposed in grant application)
Collaborator Contribution Detector maintenance, calibration, accelerator maintenance, target maintenance
Impact 1) New insight into nuclear and particle physics. 2) High quality polarisation measurements 3) Baryon spectroscopy
 
Description A2 collaboration (Crystal Ball, Mainz[Germany]) 
Organisation University of Glasgow
Department Physics and Astronomy Department
Country United Kingdom 
Sector Academic/University 
PI Contribution 1) Analysis of the data 2) Detector maintenance and running (shift) 3) Construction of new detector components (Start construction of new polarymeter and particle identification detector as proposed in grant application)
Collaborator Contribution Detector maintenance, calibration, accelerator maintenance, target maintenance
Impact 1) New insight into nuclear and particle physics. 2) High quality polarisation measurements 3) Baryon spectroscopy
 
Description Hall-B (Clas, Clas-12, [JLab, USA]) 
Organisation JLab
Sector Private 
PI Contribution 1) Data analysis 2) Simulations 3) Construction of new detector components
Collaborator Contribution 1) Data analysis 2) Simulations 3) Construction of new detector components
Impact 1) New spectroscopy data 2) Baryon and meson spectroscopy 3) high-energy photon beams
 
Title High acceptance polarimeter 
Description High acceptance polarimeter 
Type Of Technology Detection Devices 
Year Produced 2016 
Impact High acceptance polarimeter can be used in precise experiment where the polarisation measurements of high energy ejectiles are required. Can be used for the next generation experiments of physics beyond Standard Model. 
 
Title Particle Identification Detector for the Crystal Ball collaboration, Mainz 
Description New Particle Identification Detector. 
Type Of Technology Detection Devices 
Year Produced 2016 
Impact Compact design, complex shape, adiabatic lightguides, 3D printed shapes for compactness. 
 
Description 18th STFC UK Postgraduate Nuclear Physics Summer School 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact STFC UK Nuclear physics summer school for the 1-2year PhD students in Lancaster. 3 Lectures on hadron physics with emphasis on my research techniques and recent progress in multi-quark systems.
Year(s) Of Engagement Activity 2015
URL http://personal.ph.surrey.ac.uk/~cb0023/npschool/npschool/Lecturers.html
 
Description Organisation of the "Exotic hadron spectroscopy" workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Co-Organiser of the "Exotic Hadron Spectroscopy" workshop. The aim of the workshop was to bring together the nuclear and particle physics communities to discuss experimental searches for exotic hadronic resonances (tetra, penta, hexaquarks etc); the latest data analysis methods used; the theoretical interpretation of these states and the potential for future searches at current experimental facilities (CERN, JLab, Mainz).
Year(s) Of Engagement Activity 2016
URL https://higgs.ph.ed.ac.uk/workshops/exotic-hadron-spectroscopy
 
Description Organisation of the "Exotic hadron spectroscopy workshop 2017" 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Co-Organiser of the "Exotic Hadron Spectroscopy" workshop. The aim of the workshop was to bring together the nuclear and particle physics communities to discuss experimental searches for exotic hadronic resonances (tetra, penta, hexaquarks etc); the latest data analysis methods used; the theoretical interpretation of these states and the potential for future searches at current experimental facilities (CERN, JLab, Mainz). It was very successful in 2016. It was decided to make it annual. EHS Workshop-2017 was organised in Dec. 2017.
Year(s) Of Engagement Activity 2017
URL https://higgs.ph.ed.ac.uk/workshops/exotic-hadron-spectroscopy-2017