Structure of Quarks

[Ewen]

I'll keep this simple mainly because my understanding of thia field is very small and I'm running the risk of trying to describe things in my own words that'll ultimately confuse you!

 

Basically my question is this. If a quark is elementary, what makes them "appear" in 6 different forms? In my head I see that if two "things" are different, it is because they have differing constituents. Something that is elementary doesnt have constituents?

 

I'm sorry for the unusual way of wording this question but I've only got the tip of my toe in this particular area and this is a question that's been bugging me. I'm sure it's a simple answer that I'm just not picking up on. Any comments would be wonderful.

[goodyhi11]

If a quark is elementary, what makes them "appear" in 6 different forms?

 

The reason why they appear in 6 different forms is each quark contains different energy or power. For instance C quark has 1.5Gev, but S quark has 90eV.

[Ewen]

And that's the only difference? The only constituent of a quark is its energy?

[Severian]

No - they have more differences.

 

This comes back to the thread the other day about how do you define a particle. Is a quark just a quark or should we say 'down quark' and 'up quark' etc? Really up and down quarks are past of the same isospin doublet. Think of it as a vector with two entries - the upper entry we call the up quark while the lower we call the down quark. We distinguish them in this way because they have different values of 'isospin'. (Technically the up and down quarks are different fundamental representations of SU(2).)

 

But really there are three different colors of quark: red, green and blue. So there are 3 up quarks and 3 down quarks. (Tehnically, each of these is a different representation of SU(3).)

 

Then there are 3 copies of this repaeted at hight mass - we call these generations. So totalling it all up we have 2x3x3=18 different quarks! Although only 6 different names since we class the different colors as the 'same particle'. Goodyhi11 is partly right in that the reason that we don't call the different colored quarks as different articles is because they have the same mass, and we are a bit prejudiced about mass.

 

We still don't understand why they have different masses....

 

A side not: even though the quark is classically point-like, since it have a color charge it will have a constant cloud of gluons around it, so in terms of observations the quark has structure (as does the photon, electron etc).

[Daecon]

From my (somewhat limited) knowledge of String theory, each of the six quarks is like a tiny tiny almost point-like string, each resonating or vibrating at a slightly different frequency, to give these six distinctive flavours or colours, or whatever term you use to tell them apart.

[Nicholas]

The structure of matter is all I have taken from string theory.

That matter has structure.

That one thing alone is of value!

 

Beyond that I say its nonsense.

[Ewen]

From my (somewhat limited) knowledge of String theory, each of the six quarks is like a tiny tiny almost point-like string, each resonating or vibrating at a slightly different frequency, to give these six distinctive flavours or colours, or whatever term you use to tell them apart.

That pretty much sums it up. Thank you