Number say about the spin of a particle?

[MrPickle]

What does the number say about the spin of a particle?

Like for an quarks it's half, what does it mean by 1/2 spin?

 

[malawi_glenn]

It is invariance under rotation, the angle that leaves the state invariant. For a spin-1/2, we need 4pi (i.e. two revolutions)

http://en.wikipedia.org/wiki/Spin_(physics )

http://en.wikipedia.org/wiki/Angular_momentum#Angular_momentum_in_quantum_mechanics

http://en.wikipedia.org/wiki/Spin_quantum_number

 

[Meir Achuz]

What does the number say about the spin of a particle?

Like for an quarks it's half, what does it mean by 1/2 spin?

The number like 1/2 is the magnitude of the maximum z component of the spin angular momentum in units of hbar. That is, (1/2)hbar would this magnitude in whatever units you use for hbar.

 

[jtbell]

what does it mean by 1/2 spin?

It means that the particle has an intrinsic angular momentum with magnitude

$$|\vec S| = \sqrt {s(s+1)} \hbar =\sqrt{\frac{1}{2} \left(\frac{1}{2} + 1 \right)} \hbar$$

which works out to $9.14 \times 10^{-35}$ kg-m²/sec.