When telling high school kids what I am doing, I compare the experiments done at the LHC with colliding two trains with cargo. After the collision, you examine the debris to find out where the trains were going. (I have a very suggestive movie to support this story.) In colliding protons, we collide two “bags” of fundamental particles. Only considering the clean-ness of the collisions, it would be much better to collide electrons on their anti-particles positrons. As was done at LEP. Unfortunately, electrons radiate of energy when they are forced around a corner, and the LHC is a circle, so they need to follow a curved path. Protons radiate far less, so they can reach higher energies.
At these high energies, we hope to see all kinds of New Physics. But: it is going to be hard to study the characteristics of the new processes. Because the collisions are so messy. So some people are already anticipating on the construction of a new collider. An electron-positron collider at energies in the same range as the LHC. This collider will need to be straight (in jargon: linear), and large to reach the high energies. Last Friday one of the other fifteen Lucie’s working at CERN gave a talk at Nikhef about CLIC. Lucie Linssen is leading the linear collider detector R&D group, so is an real expert. It was a very interesting talk, I like R&D. But it made me wonder.
The LHC is not producing any collisions at 14 TeV any time soon. The detectors are working very well, but at the low frequencies of incoming cosmics. Birds fly in and out the accelerating complex. I do not doubt that the LHC will run, I bet my PhD on it. But don’t we need to focus now? What need do we have for a new accelerator if LHC finds nothing, or everything? And how do we know that another collider is the only answer after the LHC?
On the other hand: No guts, no glory. That today’s ambition is the future’s reality is only interesting if the ambitions are set high. And if we learned one thing from the LHC it could be that we do not get the New Knowledge without effort and ambition.