Why build the Large Hadron Collider? - page 3
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: 3 of 16 pages: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
to below 10K by a huge cryogenics system using superfluid helium.[cit iop] The cables will conduct current without resistance in their superconducting state. [1][3][5]
Overview of how the LHC works
Why so much energy?
7 TeV seems like a huge amount of energy, but the protons in the collider are made up of quarks and gluons, and the collisions between an individual quark or gluon from one proton and a quark or gluon from the other proton are of the most potential scientific interest.
On average, each quark carries only about 10% of the proton’s energy and each gluon even less. So typical quark-quark, quark-gluon, or gluon-gluon collision energies produced by the LHC are only a fraction of the proton’s collision energy of 14 TeV, about 1 TeV or less.
In a collision it is this energy that can be transformed into the masses of new particles, and as it is in the 0.1 to 1 TeV region that new particle masses are expected to lie, the huge amount of total proton energy is needed.[1]
How do they collide?
Colliding two proton beams travelling in separate circular beam pipes through oppositely directed magnetic fields would be difficult, so there are four collision points where there are no magnetic fields and the protons are moving in straight lines. At those points the two beams are brought together into a single vacuum pipe and allowed to collide head on.[1]
Why is so much new equipment required?
The protons come in roughly cylindrical bunches a few centimeters long and a few millionths of a meter in radius. The distance from one bunch to the next is 7.5 m. Since it takes light 25 nanoseconds to travel 7.5 m, and the protons are practically moving at the speed of light, head-on meetings between bunches at every collision point occur every 25 nanoseconds, or 40 million times per second.
If two bunches of protons meet head on, the number of collisions between protons from one beam and protons from the other might be ten, one, or zero. If the bunch size is fixed the number of collisions depends on how many protons there are in each bunch, and how big each proton is. Achieving a high rate of collisions requires small bunch size, many protons per bunch, and many bunch crossings in a set amount of time.
A proton has a radius of roughly about 10-15 meters. If the bunches were 10-6 meters
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