Why build the Large Hadron Collider? - page 4
Keywords: Physics Report Large Hadron Collider Basic Introduction Grand Unified Theory Cosmic Rays Anti Matter Extra Dimensions String Theory Dark Matter Higgs Boson
By Jenny on 02/07/2009
Level: A Level (Year 13)
Page Number: 4 of 16 pages: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
in radius, and there were only 10 protons in each bunch, the chances of even one proton-proton collision taking place when two bunches met would be extremely small.
On the other hand, if each bunch had a billion-billion (1018) protons so that it was completely filled with protons, every proton from one bunch would collide with one from the other bunch, and you would get a billion-billion collisions per bunch crossing, however this would be extremely difficult and expensive to build.
The LHC operates between these two extremes; it has about a billion protons in each bunch producing a few collisions (up to 20) per bunch crossing.
These variables which control the amount of collisions depend on the design of the collider. They can all be combined into a single measurement called luminosity. Luminosity is defined as ‘the proportionality constant between the proton-proton collision rate and proton area’. In experimental particle physics, achieving high luminosity is as important as achieving high energy.
Not all collisions produce the same effects, and the types of collisions that the LHC was set up to study are extremely rare. So huge numbers of ordinary collisions have to be performed (why lots of is luminosity needed) just to see a few of the interesting ones.
The luminosity of the LHC is expected to be so large that as many as one billion total collisions may take place per second, and 10 to 100 collisions per second of these might be of potential scientific interest. Some of the most interesting types of collisions are so rare that they may only occur once every few hours or days. If the luminosity were ten times less they might be seen only once every few weeks, which would make their discovery much more difficult. Achieving this anticipated luminosity is therefore very important but represents an enormous technical challenge, requiring many new pieces of equipment to be specially designed and built (eg. the super conducting magnets and huge cryogenics system required to keep them cooled) which is very expensive.[1]
Guided by Magnets?
The high-energy protons are kept in their approximately circular orbits by the strong magnetic fields produced by the superconducting magnets.
In a magnetic field pointing vertically up, protons traveling to your right would feel a magnetic force towards you, and protons traveling to your left would feel a force away from you. To have the left-moving protons feel a force towards
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