Final cooling scheme for muon colliders: a door opener for future discovery machines

Discovering unknown phenomena in particle physics – one of the most essential aspects of high energy physics, requires optimizing and developing high energy particle accelerators, for new discoveries. To be able to reach high particle energies (TeV) at all, new accelerators are needed that are larger and come with high financial costs. For this reason, it is very relevant to develop energy efficient and economic accelerators while continuing progress in that area. One of the most important goals is not only produce Higgs bosons on a much larger scale than it is possible so far, but also generate completely unknown particles. This will allow us to determine the mass of these particles and is likely to give us a glimpse of the physics beyond the Standard Model and therefore opening new doors for groundbreaking discoveries. Since the publication of the European Strategy for Particle Physics in 2020, it is known that scientists are further working on creating a concept of a new muon accelerator led by CERN.Advantage of this technology include that muons are leptons and therefore convert the entire center of mass energy to create new particles during collisions, which would not be possible in collisions with hadrons. This makes the lepton accelerator to a precision and discovery machine at high energies. Further, muons are 200 times heavier than electrons. As a result, bremsstrahlung and synchotron radiation may be neglected, which in turn cannot be done with electron accelerations. Nevertheless, the muon beam creates a high emittance after its creation, which drives the divergence of the beam. The only feasible way to reduce or cool this emittance within the very short lifetime of the muon is based on the principle of ionization cooling. Past studies have not achieved optimal final emittance values. Therefore, this work aims at gradually cooling the emittance of the muons beam by means of specific absorbers inside very high magnetic fields before it is finally accelerated to several TeV. As a result, the final cooling system should provide muon beams with the optimal properties required by the muon collider design.