THE MUON COLLIDER* (Sandro's Snake)

In the quest for the Higgs bosons, a muon collider may be conceived as the experimental device more affordable and more feasible than electron-positron or very large hadron colliders, like NLC, CLIC, SSC and LHC. Muons have a mass ten times lighter than protons and are therefore easier to be steered on circular trajectories. On the other side their mass is a hundred times heavier than electrons and their motion is considerably less affected by the synchrotron radiation. Muons are elementary lepton particles, with no internal structure. Like the electrons, they have obvious advantages over the hadron counterpart when they are used as the main projectiles for the production of the Higgs bosons. Moreover, because of their larger mass, they are also better suited than the electrons themselves, due to a considerably larger propagator constant. Unfortunately, muons do not exist in nature and they have to be produced with the only technique we know these days: impinging an intense beam of protons on a target. This will cause muon production, but with a very large volume of the phase space. Like in the case of the production of antiprotons, in order to make the beam of some use for the subsequent collisions, muons also have to be collected and cooled to a sufficiently high intensity and small beam dimensions, before they can be accelerated and injected in the collider proper. To make the situation more complicated, there is also the fact that muons are intrinsically unstable particles with a very short lifetime. Accumulation, cooling, acceleration and all other required beam manipulations are then to be executed extremely fast if one requires that a large fraction of the particle beam survives to the collision point. This paper describes a feasibility study for the design of a muon collider. Recognized the fact that the particle lifetime increases linearly with the energy, we have adopted a scheme where steps of cooling and acceleration are