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B Particle of M=0, Q=1, S=1/2, Confined?

  1. Jan 1, 2017 #1
    Hypothetically, could we have a mass-less electrically charged particle of spin 1/2 confined by a hypothetical potential so that at large distance scales the particle looked like localized massive charged particle of spin 1/2? I'm thinking of a mass-less charged particle that does some kind of speed of light random walk.

    Is it possible to interpret electrons this way?

  2. jcsd
  3. Jan 1, 2017 #2


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    Coincidentally, this is not too far away from how the Higgs mechanism works. There is no confining potential, but the interactions with the background Higgs field. And the "random walk" is a quantum random walk with the particle passing all possible states with different amplitude. Without the Higgs field, the electron would be massless.

    However, it is generally simpler to include the mass part of the Lagrangian in the free part when doing perturbation theory.
  4. Jan 1, 2017 #3
    Can I build on that picture in the following way. In 3 dimensional momentum space plot a very large number of momentum vectors that represents the possible values of momentum this mass-less particle can take. Let all the momentum vectors with a positive (negative) component of momentum in the z direction have right-handed helicity (left-handed helicity), or momentum vectors in the upper half of momentum space are right-handed and momentum vectors in the lower half of momentum space are left-handed.

    With such an assignment do I get a particle that is spin up?

    Notice if we rotate the above picture 180 degrees about the x or y axis we get spin down?

    A rotation of the above picture 90 degrees around the y axis gives us 50% spin in +x and 50% spin in -x?

  5. Jan 1, 2017 #4


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    The proton is also an interesting system in that context: tiny masses of the quarks (charged with spin 1/2), confined by QCD, leading to a much larger mass. The proton spin is very complex, and not simply the sum of spins of its valence quarks.
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