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LHC Season 2 Is About To Start Testing the Frontiers of Physics
An anonymous reader writes: The final preparations for the second run of the Large Hadron Collider (LHC) are in place. This week, it is expected to start taking new data with collisions at the record-breaking energy of 13 teraelectronvolts (TeV). There are a lot of expectations about this new LHC season. In one of CERN's articles, physicists tell of their hopes for new discoveries during the LHC's second run. "They speak of dark matter,supersymmetry, the Higgs boson, antimatter, current theory in particle physics and its limits as well as new theoretical models that could extend it."
On the other hand, if no new physics is discovered, could this be the Michelson–Morley experiment of the 2000s?
It could be "Shaka, when the walls fell!"
A valid question, and I like a well-turned metaphor ("it was a wine red sea"), but wasn't there a Star Trek episode essentially mocking that sort of usage?
When out president says something is "our Sputnik moment", the Tamarians would understand perfectly.
This could be "The river Temarc in winter!"
On the other hand, if no new physics is discovered, could this be the Michelson–Morley experiment of the 2000s?
That's probably very unlikely. Michelson-Morley was testing a prediction of the best understanding of light at the time. The non-observation of changes due to motion through the ether was clear evidence that the best understood theory for light was wrong.
Now we have found the Higgs the established model, called the Standard Model, has no more predictions to make: we have found it all. The problem is that there are some phenomena which the Standard Model cannot explain, like Dark Matter, and it relies on some amazing fine-tuning of parameters to have such a light Higgs (the odd of this happening by chance are about the same as winning a lottery 5-6 times in a row...and if someone did that nobody would believe it was simple luck!).
The solutions to these issues involve speculation by theorists and there are multiple candidates. Supersymmetry is probably the leading one but if we fail to see SUSY in the coming run then I, and a lot of my colleagues, will probably start to doubt it as the most likely explanation. However even then it might still be that SUSY is the explanation but at a higher energy scale that we can reach and just a more-than-minimal variety of it.
Personally the thing I expect the most for us to find is Dark Matter. this is based on two broad assumptions that cut across many different theoretical models: that Dark Matter interacts through the weak force and that it was thermally produced in the Big Bang. If these assumptions are correct then the mass of the Dark Matter particle has to be in reach of the LHC. However this is still far from any sort of guarantee: there are other models for Dark Matter out there with good motivation which we would not see e.g. axions.
You're right: the LHC beams are made up of separate bunches of protons. These bunches only collide at the 4 detectors. If they collided anywhere else, there wouldn't be anything to detect the products of the collision, so that collision would be a waste. Until the collision in the detectors, the protons moving in opposite directions are kept in separate beam lines: http://lhc-machine-outreach.we.... Here's a look inside the beam pipe: http://lhc-machine-outreach.we...
The time between collisions is 25 nanoseconds, meaning there is 25 feet between each bunch (light travels at about 1 foot per nanosecond). When two bunches collide, there are only 20-30 proton-proton collisions because the protons are so small compared to the size of the bunches. By the time the next bunches arrive at the collision point, the debris from the first collisions are completely gone from the original collision point (about 25 feet away in all directions).
http://lhc-machine-outreach.we...