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Understanding spin in bosons

  1. The detection of spin in Hadrons and Leptons is done through magnetism, a spin 1/2 particle has two states in a magnetic field, an up particle goes up, a down particle goes down. A spin 1 particle has three states, an up/up goes up, a up/down stays straight and a down/down goes down. A spin 3/2 particle has 4 states, the up/up/up goes up a lot, the up/up/down goes up a bit, the up/down/down goes down a bit, a down/down/down particle goes down a lot.

    What about the bosons? Wiki says the higgs is a 0 spin particle and the z/w/photon particles are spin 1.

    Is this just theory or has it been experimentally shown?

    Photons don't react to a magnetic field so what does it mean experimentally, what do people see?

    How can people be so sure that a z-particle is spin 1? Are there specific effects that can be measured that show this?
     
  2. jcsd
  3. Chronos

    Chronos 9,951
    Science Advisor
    Gold Member

    The concept of spin is complicated. You should focus on that.
     
  4. Simon Bridge

    Simon Bridge 14,950
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    You can look up the particles to see how their spins have been worked out.

    Virtual particle spins are deduced from the interaction products.
    Photon spin manifests, among other things, in polarization effects.
     
  5. ZapperZ

    ZapperZ 29,890
    Staff Emeritus
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    http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.110.081803

    Please take note that in physics, when something has been claimed to be verified or discovered, we very seldom base that on only one characteristic! We often have to verify several different properties. In this case, the Higgs was verified not just with a value for its mass, but also with many other properties that were predicted from the Standard Model. It is why had to build the LHC.

    As has been mentioned, you CAN look up the experimental verification of other particles in the Standard Model so far.

    Zz.
     
  6. Your second example of a particle with spin 1 is a boson (all particles with integer spin are bosons) so I guess you have answered your own question there. The question you should have asked instead is how can we tell the spin of neutral particles. That includes bosons such as the photon and fermions such as the neutrino as well and excludes fermions such as the electron and bosons such as the W as well.

    Yes, it's easier to figure out the spin of charged particles. It is also easier to see them at all. But there are indirect (and harder) ways to figure out the properties of neutral particles.
     
  7. mfb

    Staff: Mentor

    You can do this Stern-Gerlach experiment with a nuclei and electrons, but it is not useful for most unstable particles.

    A common way to measure spin of unstable particles is an angular analysis of their decay products. Spin-0 particles will emit their decay products in all directions (in their rest frame) with the same probability, particles with non-zero spin show different patterns.

    Another test is the production mechanism. If a particle is produced by a virtual photon, for example, it will have spin 1 (with the J/psi as the most prominent example), as the photon spin. For the photon, you can use classical electromagnetism to show it has to have spin 1.
     
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  8. Correct me if I am wrong, but doesn't the circular polarization of a single photon correspond to its spin?
     
  9. mfb

    Staff: Mentor

    That is its spin orientation, not its particle property "spin 1". And that is the classical way to show the spin, right.
     
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