What Is the Difference Between Color Neutral and Colorless in Quantum Physics?

[humsafar]

Basics on Quantum Physics...

I have Two basic Questions which I need an easy, simple answer...

First is...What is Spin of a particle? any simple way to define it?

 

[Fredrik]

There's no simple way to define it. The complete answer can be found in the theory of representations of groups.

You should probably tell us what you have studied already. Have you studied any quantum mechanics yet? Linear algebra?

 

[Tac-Tics]

Spin is a fundamental degree of freedom in a particle. You can ask where a particle is moving. You can ask what its momentum is. You can ask its spin along an axis.

Experimentally, spin is related to magnetism. If you shoot a beam of electrons through a non-uniform magnetic field, you'll see that the beam splits into exactly two beams.

Classically, it was reasoned that this phenomenon is due to electrons rotating about their own axis. Thus, it's called "spin".

Spin is also the same phenomenon that causes polarization in light.

Spin is a quantum property, so it's kinda funny. A fun little experiment (and the one I remember most vividly from high school physics) is this:

Take two photographic filters (http://en.wikipedia.org/wiki/Photographic_filter).

Hold the first up to your eye. Put the second one in back of it and slowly rotate it.

The amount of light that goes through depends on the rotation. If the filters are aligned properly, 50% of the light goes through. If you rotate it 90º, suddenly, the filters block 100% of the light. Rotate it another 90º, and you're back to 50%.

Here's the weird part. Rotate them so that all the light is blocked. Now take a third filter at a 45º angle to the others. Put it in between. What happens?

(Well, if you filter out ALL the light, then filter out some MORE, you've stilled filtered out ALL the light... right?)

The amazing thing is that by adding that third filter, suddenly, light gets through again!

 

[alxm]

Try the search function too, there have been quite a few threads on "What is spin?" and similar.

 

[humsafar]

Ok i got my answer...

My second question is that i read some notes on QCD from the website of hyperphysics, they say there are two main states of colors in hadrons or mesons (color neutral and colorless), colorless means color and anticolor being on same particle (let's say pion0), how does it differ from color neutral? Please give detailed and simple worded answer like Post#3 if possible...