Recent experimental findings suggest that muons can be confined into beams appropriate for high-energy collisions, opening the door to novel physics. Researchers from Imperial College London led the investigation as part of the Muon Ionization Cooling Experiment. The results were published in the journal Nature Physics.
ISIS Neutron and Muon Beam facility. Image Credit: Imperial College
Particle accelerators are primarily used to investigate matter's composition through collisions; nevertheless, they are also employed in the production of silicon microchips, drug structural analysis, and cancer treatment.
More potent accelerators that use muons, the heavier cousins of electrons, have the potential to change the field completely. Present accelerators use protons, electrons, and ions. Because muon accelerators would be smaller and less expensive than current colliders, they could be constructed in the same locations and reach even greater energy.
One crucial technology needed for muon accelerators has now been shown to be successful through a fresh examination of a muon-beam experiment. This makes it possible to scale up a muon collider more quickly than other accelerator types that use various particles.
Our proof-of-principle is great news for the international particle physics community, who are making plans for the next generation of higher-energy accelerators. It is an important development towards the realization of a muon collider, which could fit into existing sites, such as FermiLab in the United States, where there is a growing enthusiasm for the technology.
Dr. Paul Bogdan Jurj, Study First Author, Department of Physics, Imperial College London
Powerful Particle Accelerators
The world's most potent particle accelerator, the Large Hadron Collider (LHC), smashes protons together at high energy. Scientists are interested in studying the new subatomic particles created by these collisions, such as the Higgs, other bosons, and quarks.
Building a considerably larger proton collider would be necessary to achieve higher-energy collisions and access new physics discoveries and applications. The LHC is designed like a ring with a circumference of 27 km, and a feasibility study is being conducted to construct a collider that is possibly nearly 90 km long.
However, other scientists are searching elsewhere for answers due to the significant expenditures and lengthy construction time required to establish such a collider. Alternatively, colliders that smash muons together are among the promising paths.
Muon colliders might achieve effective energy comparable to those suggested by the 90 km proton collider in a considerably smaller area since they would be more affordable and compact. However, to guarantee that the muons can collide frequently enough, technological advancement is required.
Marshalling Muons
The main issue has been getting the muons to gather in a compact enough area to generate a concentrated beam when they are accelerated. This is necessary to guarantee that they do not collide with the muon beam that is being propelled in the opposite direction around the ring.
Such a beam was previously created by the MICE collaboration by “cooling” the muons with magnetic lenses and materials that absorb energy. According to preliminary investigation, this was successful in moving muons toward the center of the beam.
The updated study examined this experiment's “shape” and spatial dimensions in further detail. The researchers demonstrated how the cooling had made the beam more “perfect” by reducing its size and facilitating the movement of the muons in a more ordered manner.
The Science and Technology Facilities Council (STFC) ISIS Neutron and Muon Beam facility at the STFC Rutherford Appleton Laboratory in the UK was used for the experiment. The team is currently collaborating with the International Muon Collider Collaboration to construct the next phase of demonstrations.
The clear positive result shown by our new analysis gives us the confidence to go ahead with larger prototype accelerators that put the technique into practice.
Ken Long, Professor and MICE Collaboration Spokesperson, Department of Physics, Imperial College London
Heading the MICE analysis team and currently spearheading the development of the muon cooling system for the Muon Collider at CERN, Dr. Chris Rogers is based at STFC's ISIS laboratory in Oxfordshire. He said: “This is an important result that shows the MICE cooling performance in the clearest possible way. It is now imperative that we scale up to the next step, the Muon Cooling Demonstrator, to deliver the muon collider as soon as possible.”
Journal Reference:
Bogomilov, M., et al. (2024) Transverse emittance reduction in muon beams by ionization cooling. Nature Physics. doi.org/10.1038/s41567-024-02547-4.