Understanding Spin: Subatomic Particle Properties & Measurements

[atom888]

I have a few questions with spin. Actually, quite a alot.

1)What I know is proton and electron have spin. What subatomic particle doesnt' have spin?
2)What is spin?
3)Are they a physical thing for particles?
4)How did scientist measure it?
5)What is up and down spin mean?
6) why is it 1/2 instead of other value?
7) What are the actual interaction between same and different spin?
8) can we speed up or slow down the spin? If so, how?
9) does it take or give energy if spin can be change?

I apologize if the thread already exist. I could have go read wiki but I don't think they have all the answer. Besides... it's solid stuffs in here. lol Thx

 

[malawi_glenn]

1) proton is not an elementary particle, whereas the electron is. But for example the $K_0^*$ has spin zero. The pion is also a composite particle, which belongs to the meson family. You can look on wiki -> "Hadrons" and then "Baryons" and "Mesons". and Scalar mesons and so on. But spin for composite particles is not really the same as the spin concept for elementary particles.

2) Intrinsic spin is an intrinsic degree of freedom that a particle posess.

3) what do you mean by "a physical thing"? It is not just a mathemetical concept, one can measure the spin of particles.

4) Youn search on wiki for 'spin', there is a historical introduction to it. It has to

5) The projection of the spin vector on an reference vector. For each value on S, you can have 2S+1 different projections.

6) spin does not have to be 1/2, it can be 1 or 3/2 etc. The main point is that only integer and half-integer values are allowed. The derivation can be found in almost any QM textbook, e.g Sakurai - modern quantum mechanics.

7) The interaction is due to the coupling of magetic and electic moments and so on. Orbital motion and spinning motion of electric charges in the classical world gives rise to electromagnetic interactions. One can use the same analogy when one introduces orbital and spin- angular momentum in QM.

8) The thing is that spin in QM has nothing to do with particles moving in cirular orbits, as planets moving around the sun. It has nothing to do with that, so one can not "make the electron spin slower around its own axis" since it does not spin around its own axis in the first place.

9) Depends on the physica system. Generally, if you apply a magnetic field on atoms, then the different electrons will occupy an energy state that is most energetically favourble. And since the spin has to do with the magnetic interaction, the electrons with spin up will occupy a different energy state than an electron with spin down. Serach for "stark effect" and "zeeman effect"

 

[sir-pinski]

1) As far as we know, all subatomic particles have spin. This includes protons, electrons, neutrons, and even smaller particles like quarks and gluons.
2) Spin is a fundamental property of particles that describes their intrinsic angular momentum. It is not the same as the physical spinning motion we are familiar with in everyday objects.
3) Yes, spin is a physical property of particles. It is one of several properties that describe the behavior and characteristics of subatomic particles.
4) Scientists measure spin using various techniques, including scattering experiments and measurements of magnetic moments.
5) Up and down spin refer to the direction of the particle's spin. It is often visualized as a spinning top, with the up direction being the axis of rotation and the down direction being opposite to the axis of rotation.
6) The value of spin is determined by the type of particle. For example, electrons have a spin of 1/2, while protons and neutrons have a spin of 1/2 or 3/2.
7) Particles with the same spin can interact with each other through the strong, weak, and electromagnetic forces. Particles with different spin can also interact, but the strength of the interaction may vary.
8) The spin of a particle cannot be directly sped up or slowed down. However, it can be affected by external forces, such as magnetic fields.
9) Changing the spin of a particle does not necessarily require energy. In some cases, it may release or absorb energy, but this depends on the specific interaction and the energy levels of the particles involved.