Fermilab recently launched a new web site describing the idea of a muon collider. Why think about a future collider when we haven’t even started using the LHC yet? Because it takes a really long time to design and build one. The LHC was conceived a few decades ago, and the LHC project was approved in 1994, fifteen years ago. Also, Fermilab is soon going to shut down its Tevatron collider that has operated for almost 30 years, and is planning for its future.
I find the idea of a muon collider very intriguing. The idea is to collide positive and negative muons together, as opposed to colliding protons together as will be done at the LHC. A muon collider would be well suited to precise measurements, whereas the LHC is more of a discovery machine. This is because the protons colliding at the LHC are made of other particles called quarks and gluons, and it is those particles that actually collide in the LHC. So a collision of protons is really a collision of many quarks and gluons, which can be quite a messy thing to try to understand. A muon collider would collide muons only, so the collsions would be “cleaner” in the sense that there are fewer particles colliding at once. This makes understanding what happened in a collision easier to understand.
A muon collider would be a great tool for precisely studying whatever new particles are found at the LHC. Another option for a precise instrument is an electron collider, and there are proposals to build electron colliders as well. A muon collider has the advantage of being much smaller (a circle 2 km across instead of the proposed 30 or 50 km in a straight line proposed for electron colliders).
However, the technology necessary to build a muon collider is still being developed, whereas the technology needed to build an electron collider is already well advanced. But assuming we discover some interesting new particles at the LHC, building an electron or muon collider to follow up would be a great idea. So when will this happen? In the case of the muon collider, the schedule estimates I’ve seen currently put first collisions around 2028.
