Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Quarks in a meson, antibaryon, baryon

  1. Mar 8, 2008 #1

    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.

  2. jcsd
  3. Mar 8, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    I dont understand your question.
  4. Mar 8, 2008 #3
    Why ?

  5. Mar 8, 2008 #4


    User Avatar
    Science Advisor

    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.
  6. Mar 8, 2008 #5
    Wait a minute. Are all quarks allocated colours and what do the colour represent? Do all fundamental partcles like leptons also have colours?
  7. Mar 8, 2008 #6
    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 [Broken]

    Last edited by a moderator: May 3, 2017
  8. Mar 9, 2008 #7

    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
  9. Mar 9, 2008 #8


    User Avatar

    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.
  10. Mar 9, 2008 #9

    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.

  11. Mar 9, 2008 #10

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2017 Award

    I think the fact that you are missing is that color (red-ness, etc.) and flavor (down-ness, charm-ness, etc.) are independent.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook