PROJECTS and ACTIVITIES within the PARTICLE PHYSICS DEPARTMENT
Much of our current understanding of elementary particle physics is embodied in the so-called 'Standard Model', which describes the phenomena of particle physics in terms of `matter' and `force' particles. The matter particles are the quarks and leptons which come in three 'generations' with very different masses. The force particles include the 'gauge bosons' which mediate the three forces that determine elementary particle interactions; 'gluons' for the strong force, the 'W and Z bosons' for the weak force and 'photons' for the electromagnetic force.
Whilst this standard model describes much particle physics, it is far from complete relying on a relatively large number of input parameters. It also raises a great number of questions. Why are there just three generations of quarks and leptons? What is the mechanism by which mass is generated and is it connected with the hitherto undetected particle - the 'Higgs Boson'? Our experiments now show that neutrinos have masses - so how are neutrino masses related to the quark and lepton masses?
The aim of the experiments carried out in the particle physics department, in collaboration with colleagues from UK universities, is to answer some of these and related questions. The experiments are located at different research institutes around the world:
- CERN European Laboratory for Particle Physics (located in Geneva, Switzerland)
- Fermilab Fermi National Accelerator Laboratory (located near Chicago)
- SURF Sanford Underground Research Facility (South Dakota, USA)
- J-PARC Japan Proton Accelerator Research Complex (Tokai, Japan)
- ILL Institut Laue Langevin (located in Grenoble, France)
In addition, experiments are carried out underground at the SOUDAN mine in Minnesota, USA and at the Boulby mine in Yorkshire, UK. Some further information about the facilities and the individual experiments is given below, together with references to relevant papers and web addresses. Research students will work in one of these groups, under the supervision of a senior research physicist. The project will be chosen in discussion with the student and the supervisors. More detailed information is given later in the section "Details of Studentships".
The Large Hadron Collider (LHC) is currently the highest energy accelerator and the world's largest scientific instrumentation at CERN in Geneva, Switzerland. Up to the end of 2018 protons were collided head-on, each proton in each bunch in each of the two colliding beams having an energy of 6500 GeV. In 2012 proton collisions with beam energies of 3500 GeV and 4000 GeV allowed us to discover the Higgs boson, which was the last missing piece of our underlying theory, the Standard Model (SM). Currently, we are searching for new phenomena beyond the SM and carry our high-precision SM measurements and also already prepare the experiments for future running periods. At RAL we are involved with the two general purpose detectors (ATLAS and CMS) as well as with LHCb.
The next Dark Matter experiment LZ, situated at SURF in South Dakota, USA, will be conducted deep underground to reduce backgrounds due to cosmic rays. SURF will also host the next-generation long-baseline neutrino experiment, DUNE, scheduled to start data-taking in the mid-2020s. The near detector and neutrino beamline are at Fermilab, USA, giving a baseline of 1300 km from the target to the far detector.
Tokai to Kamioka (T2K) is a neutrino oscillation experiment using the existing Super-Kamiokande experiment as the far detector. It is located in Kamioka on the west coast of Japan directly in the path of a muon-neutrino beam generated 295 km away at the J-PARC facility in Tokai. The construction of the next generation neutrino oscillation experiment Hyper-Kamiokande is foreseen in 2020. Hyper-Kamiokande (Hyper-K) is a water Cherenkov detector centred on a huge underground tank containing 300,000 tonnes of water, with a sensitive volume about a factor of 10 larger than its predecessor Super-Kamiokande (Super-K). Like T2K, the experiment will be located in Kamioka and use a neutrino beam at the J-PARC facility in Tokai.
OTHER UNDERGROUND and NON-ACCELERATOR EXPERIMENTS
Some testing for LZ, for example screening of some of the detector material for radioactivity, is carried out at Boulby, UK. Testing for The Neutron EDM experiment is making high sensitivity measurements on neutrons from the reactor at ILL, Grenoble, France. Work is also ongoing for research and development into a possible next-generation neutron EDM experiment. All these experiments are looking for physics outside the standard model.