How/why does spin affect properties of particles?

  • Thread starter Jarfi
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  • #1
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In supersymmetry, particles are said to have symmetric partners or something(dont remember what it was called) and those partners where exactly the same but they spun slower, so they had different properties, so why does different spin give different properties of particles?
 

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  • #2
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I think you have misunderstood the idea of Supersymmetry a little bit. The idea of a particle's "spin" is not a measure of how "fast" or "much" it spins, but rather is a quantum mechanical property of an particle which dictates the number of ways a particle can rotate about its axis. Each spin mode dictates a different Angular momentum and energy state, which are important concepts in QM. Particles with half-integer spin numbers (typically 1/2) are called "fermions" and include electrons, muons, protons, neutrons, neutrinos, etc. Particles with integer spin numbers (often 1) are called "bosons" and are force carrier such as the photon, gluon, W-, W+ and Z bosons. Two other bosons called the graviton and Higgs Boson are theorized but haven't been found. The theory of super-symmetry states that for ever fermion, there is an identical particle of opposite spin.

So, for example, the neutrino is a fermion, of spin number 1/2, Supersymmetry theorizes there is a particle of the exact same mass and charge, but instead of being a fermion of half integer spin, it is now a boson, of integer spin 1. This is called the "neutralino". Every fermion is supposed to have a similarly opposite-spin boson and vice-versa for the bosons. This neutralino would make a excellent candidate for Dark Matter, but alas, not supersymmetric particle have ever been found.

Different spin numbers effect many things, most basically, how a particle spins about its axis, but also dictates the sort of statistics we must use in order to do physics on large amounts of these particles, how particles interact with different energy states, etc. (example, an electron cannot share the same energy state with any other electron, which is seen in electron shells in atoms. However, photons, which are boson actually like to share energy states with other photons, and we can cram many of them into identical energy states, such as a Bose-Einstein condensate.
 
  • #3
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Hmm so if a particle spins in a different direction it changes its properties, but why?:eek:, sry dont really know much about physics, im still just an amateur noob:(
 
  • #4
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Hmm so if a particle spins in a different direction it changes its properties, but why?:eek:, sry dont really know much about physics, im still just an amateur noob:(
The word spin in quantum mechanics doesnt mean to literally spin, like a top. It is a property which, like soothsayer said,
Different spin numbers effect many things, most basically, how a particle spins about its axis, but also dictates the sort of statistics we must use in order to do physics on large amounts of these particles, how particles interact with different energy states, etc.
It is like any other property, be it charge, mass, angular momentum, etc.
 
  • #5
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So the spin of a particle is kind of like the particles state/how it behaves
 
  • #6
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Yep!

It's not *really* the angular momentum of a particle, or how it spins on its axis, it's more of an intrinsic property of a particle that we like to think of as a sort of spin. It's pretty weird quantum mechanical stuff, but it's just as fundamental to a particle as its mass or charge.

Here's a good site I found, With one little typo, the author mentioned photons have spin 0 when in fact they have spin 1, not that important for a gloss over of spin, but it changes things ;)

http://www.newton.dep.anl.gov/askasci/phy00/phy00562.htm
 
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  • #7
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Yep!

It's not *really* the angular momentum of a particle, or how it spins on its axis, it's more of an intrinsic property of a particle that we like to think of as a sort of spin. It's pretty weird quantum mechanical stuff, but it's just as fundamental to a particle as its mass or charge.

Here's a good site I found, With one little typo, the author mentioned photons have spin 0 when in fact they have spin 1, not that important for a gloss over of spin, but it changes things ;)

http://www.newton.dep.anl.gov/askasci/phy00/phy00562.htm


Great link, explains alot. Haha i tought they literally meant a spinning spere, but they dont even know what the spin in itself is just some kind of state of the particle, pretty cool how little we actually know about the world
 
  • #8
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pretty cool how little we actually know about the world
Indeed it is! It ensures this physics degree I'm getting wont be totally useless ;)
 

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