Why are protons used to create Higgs particles at CERN? Can anyone please explain the concepts very simply? (How to explain this to a layman?)
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3 Answers
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Charges doing circles emit radiation which slows them because they lose energy. The emited energy is proportional to the mass of the particle, thus in a circular accelerator it is better to use more massive stuff.
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$\begingroup$ shouldn't it be inverse proportional? $\endgroup$– NoldigCommented Mar 26, 2015 at 10:49
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$\begingroup$ @Noldig why should it be the case? $\endgroup$ Commented Mar 26, 2015 at 10:56
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Before the proton collider there existed the electron positron collider, LEP. The center of mass energies explored were not enough , the highest about 204 GeV was not enough for the discovery of the 125GeV Higgs together with the necessary other particles to conserve the quantum numbers though a search was made..
As the other answer says the smaller the mass of the projectiles the greater the energy loss at high energies, so the project changed into LHC, in the same tunnel protons accelerated which could go to TeV energies and scan a larger energy range. In retrospect it might have been possible to boost the energies even with energy losses of the electron/positron beams, as 114 is very close to 125, but as the mass of the Higgs could have been anyplace from 114GeV to 1000 it was thought wiser to go to a higher energy proton proton machine.
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In addition to what has already been answered, one of the advantages of proton colliders with respect to $e^+ e^-$ colliders in the context of the Higgs searches, is that you can explore a very wide range of possible Higgs masses, roughly up to 1 TeV. The reason is that the proton is a composite object, and what is involved in the collision are not the protons themselves but one of their elementary constituents (so called partons: quarks, anti-quarks and gluons). And there is always a probability to pick-up a parton having a large fraction of the proton energy and hence, large masses can be probed. This probability is a function of the fraction energy and of the type of partons. It is called Parton Distribution Function, or PDF in short. For $e^+ e^-$ collider the beam energy set up the energy available for the collision. For proton colliders, the beam energy set up the maximum energy available for the collision, but the PDF allows to explore a wide range of mass up to this limit.
