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Particle constituents - very confused

  1. Sep 16, 2008 #1
    Hi, I was hoping someone could shed light on my confusion.

    I understand that a neutron decays into a proton, electron and neutrino. However I also read that a neutron isn't actually made from them. I don't quite understand this. However I shall try...

    Would I be correct in saying that when particles collide and produce other particles, this doesn't mean that these child particles are actual constituents of the parent particles they came from? It really comes down to how energetic these particles are upon impact, as to what resultant particles are emitted. Low energy collisions emit one set of child particles, whereas a higher energy collision will emit a different set of child particles. So in fact the neutron could decay into something else if the 'energy' was set high enough.

    Further to this I was thinking about the LHC. Prior to its upgrade the LEP collided leptons, however now it is a hadron collider. The LEP was fundamental in establishing the mass of the W/Z boson. So essentially lepton collisions produced bosons. This confuses me as I thought leptons can't be further divided into other fundamental particles. The experiment leads me to believe that bosons can arise from leptons. I think this is where I am getting confused.

    I am driven to make the conclusion that given any two random particle streams (whether they be both bosons, fermions, hadrons or a combination or whatever particle), that the collision will result in whatever particle(s) you desire, given high enough energies. Is this correct?

    So why upgrade the LEP to a LHC? If my line of thought is correct, can't you just increase the energy of the electron/positron collision to energies sufficient enough to create a higgs boson (as the LEP creates bosons)? Or does it require more energy for the LEP to generate a higgs boson, as opposed to the LHC? (i.e. cost of this energy differential would out-scale the cost of the LHC upgrade)

    Thanks for any help!

    phyzzy :smile:
    Last edited: Sep 16, 2008
  2. jcsd
  3. Sep 16, 2008 #2


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    Correct, it's easier to think about the particles being totally destroyed (turned into energy) and then the energy being used to make whatever new particles are needed to add upto the same total amount of energy. There are also other rules to conserve charge / spin etc before and after the collision. Think of it as making change, a $5 bill isn't made of dimes / quarters / pennies but you can convert it into them!

    Bosons are another class of particles. A photon is a boson so you could collide an electron and an anti electron and just end up with a pair of photons.

    Protons are 2000 times heavier than electrons but have the same charge, so if you accelerate them through the same voltage you get 2000 times as much energy!
    Or another way of thinking about it, you can built a machine with 2000 times lower voltages than if you used electrons ( I know it's a rather simplified picture of the LHC)
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