Quarks in a meson, antibaryon, baryon

[Lori15]

Hi

I have just started an intro physics course - it has very little maths, explaining as much as possible in words.

I am having trouble with understanding the relationship between colour charges and quarks and how they are formed to create hadrons.

I understand that the colour charge must be neutral - so can a red quark can combine with an antired quark regardless of whether it is a anti-redtop quark, or anti-red bottom quark etc in order to create a neutral colour.

I would have thought that you would have to know the combination of electric charges possible in a meson and then be able to check it against the possible colour combinations...?

Any help appreciated.

Thanks
L

 

[malawi_glenn]

I don't understand your question.

 

[marlon]

Hi

I would have thought that you would have to know the combination of electric charges possible in a meson and then be able to check it against the possible colour combinations...?

Thanks
L

Why ?

marlon

 

[mathman]

I would have thought that you would have to know the combination of electric charges possible in a meson and then be able to check it against the possible colour combinations...?

The general rule is that the result be color neutral. For mesons, this means any color and its anti-color. For baryons this means one red, one green, and one blue. (There are theories involving more than these numbers in combination - not in an ontro course.) All charge combinations are allowed.

 

[_Mayday_]

Wait a minute. Are all quarks allocated colours and what do the colour represent? Do all fundamental partcles like leptons also have colours?

 

[marlon]

Wait a minute. Are all quarks allocated colours and what do the colour represent? Do all fundamental partcles like leptons also have colours?

Only quarks have a colour charge. These colours are basically quantum numbers that arise from the symmetry inherent to the strong interaction.
Leptons do not have a colour charge because they do not interact via the strong interaction.

If you want some general info, go here : http://pdg.web.cern.ch/pdg/particleadventure/frameless/strong.html

marlon

 

[Lori15]

Why ?

marlon

I was trying to understand whether you could have as a possible combination an antired anticharm quark and a red down quark in a meson - alternatively - the combination antired anticharm quark and a blue quark is unacceptable as this does not make a neutral colour.
But I wondered if all quarks can have any colour charge - perhaps some combinations wouldn't be allowed because of the allowed electric charges in a meson. But looking at it now I can see that as a meson is composed of quark/antiquark then it doesn't matter whether it is a u,p,c,s,t,or b quark because as long as it paired with its anticolour it doesn't matter what flavour of the six quarks you choose. I think I was allowing myself to get confused about the electric charges.

Thanks for your help

 

[pam]

I was trying to understand whether you could have as a possible combination an antired anticharm quark and a red down quark in a meson

It is a bit more complicated than that. You have to have a linear combination
(r,ar)+(b,ab)+(g-ag). Otherwise each meson would be threefold color degenerate.

 

[Lori15]

It is a bit more complicated than that. You have to have a linear combination
(r,ar)+(b,ab)+(g-ag). Otherwise each meson would be threefold color degenerate.

I haven't got that far in my course yet - in fact I don't think it goes that far at all - but I think I get the gist of what you mean - I think the point was to encourage thinking on what are possible and not possible combinations regardless of anything else.

Thanks
L

 

[Vanadium 50]

I think the fact that you are missing is that color (red-ness, etc.) and flavor (down-ness, charm-ness, etc.) are independent.