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Natural Science Forum / Physics / Particle Physics / January 2005Are all hadrons colourless?
Since the proton is comprised of quarks with colour charge, and the anti-proton is comprised of anti-quarks with anti-colour charge, shouldn't the proton have a net colour of colourless and the anti-proton have a net colour of anti-colourless (or black & white, to keep with the colour scheme). > Since the proton is comprised of quarks with colour charge, and the > anti-proton is comprised of anti-quarks with anti-colour charge, > shouldn't the proton have a net colour of colourless and the > anti-proton have a net colour of anti-colourless (or black & white, to > keep with the colour scheme). All observed hadrons are colorless by the nature of confinement and the running of the coupling constant for QCD. I suppose you could define colorless and anti-colorless, but it's vacuous in the same way that negative zero is vacuous. >Since the proton is comprised of quarks with colour charge, and the >anti-proton is comprised of anti-quarks with anti-colour charge, >shouldn't the proton have a net colour of colourless and the >anti-proton have a net colour of anti-colourless (or black & white, to >keep with the colour scheme). I hadn't thought of that before-- identifying baryon number with net color.  SignatureIrony: "Small businesses want relief from the flood of spam clogging their in-boxes, but they fear a proposed national 'Do Not Spam' registry will make it impossible to use e-mail as a marketing tool." http://www.bizjournals.com/houston/stories/2003/11/10/newscolumn6.html > >Since the proton is comprised of quarks with colour charge, and the > >anti-proton is comprised of anti-quarks with anti-colour charge, [quoted text clipped - 4 lines] > I hadn't thought of that before-- identifying baryon number with net > color. Doesn't really work though. Mesons and baryons are all colorless, but mesons have zero baryon number and (anti)baryons have a number of (-)1. In fact, baryon number and a color symmetric state should not be confused. Color obeys an SU(3) symmetry while baryon number conservation is a result of an U(1) symmetry and is something different! Besides, I like the way of thinking, that "anticolor" gives "black" instead of "white" (you're clearly a creative person! this is good!), but you lack one thing: what to do with mesons? Apart from that, there's also group theoretical arguments why there's only one type of singlet state, which we call "white". Kind regards, Annelies >>>Since the proton is comprised of quarks with colour charge, and the >>>anti-proton is comprised of anti-quarks with anti-colour charge, [quoted text clipped - 7 lines] > Doesn't really work though. Mesons and baryons are all colorless, but > mesons have zero baryon number and (anti)baryons have a number of (-)1. > Besides, I like the way of thinking, that "anticolor" gives "black" > instead of "white" (you're clearly a creative person! this is good!), > but you lack one thing: what to do with mesons? Apart from that, there's > also group theoretical arguments why there's only one type of singlet > state, which we call "white". > > Kind regards, > Annelies If a proton is considered to be white and an anti-proton to be black, then you could say quarks have a colour charge of 1/3 white and anti-quarks have a colour charge of 1/3 black. The meson is then made from an equal amount of black and white colour charge - creating grey. What properties would "grey charged" particles have? If they contained an equal amount of black and white charge, the charges would cancel each other out, making the grey charge a neutral one. This would then mean that the black and white charges were not neutral after all, and could be considered as positive and negative. This would give rise to hadrons having a positive, neutral, or negative net colour charge. :-) I like this kind of funny thinking about physics - but really, try not to loose yourself in "talking around", since there's a great deal of group theory involved here. All hadrons and antihadrons are "color singlet states". This has its consequences in the wave function of the hadron, that is: the "color part" of the wave function is antisymmetric. - which of course poses constraints on the other parts of the wave function! That "color singlet state" is what we call "white", but really, this is only a name! You could instead of calling it "color", try to find another name for it - but the main issue is that the quantum mechanical property stays the same. Maybe you want to try and find a book on SU(3) and its use in physics. It's a very interesting subject. You'll find a lot of them on Amazon, since the subject has been covered by a lot of authors! Still, even if I like to make some fun about the physics, you should try to avoid going "assuming" theoretical things without using some true theoretical arguments. Kind regards, Annelies >>Besides, I like the way of thinking, that "anticolor" gives "black" >>instead of "white" (you're clearly a creative person! this is good!), [quoted text clipped - 26 lines] > This would give rise to hadrons having a positive, neutral, or negative > net colour charge. > > >Since the proton is comprised of quarks with colour charge, and the > > >anti-proton is comprised of anti-quarks with anti-colour charge, [quoted text clipped - 6 lines] > Doesn't really work though. Mesons and baryons are all colorless, but > mesons have zero baryon number and (anti)baryons have a number of (-)1. If a proton is considered to be white and an anti-proton to be black, then you could say quarks have a colour charge of 1/3 white and anti-quarks have a colour charge of 1/3 black. The meson is then made from an equal amount of black and white colour charge - creating grey. What properties would "grey charged" particles have? If they contained an equal amount of black and white charge, the charges would cancel each other out, making the grey charge a neutral one. This would then mean that the black and white charges were not neutral after all, and could be considered as positive and negative. This would give rise to hadrons having a positive, neutral, or negative net colour charge. > > > >Since the proton is comprised of quarks with colour charge, and > the [quoted text clipped - 16 lines] > anti-quarks have a colour charge of 1/3 black. The meson is then made > from an equal amount of black and white colour charge - creating grey. Well, except that's now how color charge works at all. Color charge is given the labels R,G,B because there are three kinds of charges and an SU(3) symmetry between them. The only ways to get "white" are RGB or RantiR,BantiB,GantiG. It is quite wrong to say that quarks have a white color charge. The whole point is that the growth of the QCD coupling constant at long range confines all colored objects into colorless bunches. > What properties would "grey charged" particles have? > [quoted text clipped - 7 lines] > This would give rise to hadrons having a positive, neutral, or negative > net colour charge. As I have explained above, this is wrong. If hadrons had some net color charge, then they would be bound together just as quarks are bound together and you'd never see them. That doesn't happen. >Well, except that's now how color charge works at all. >Color charge is given the labels R,G,B because there are [quoted text clipped - 4 lines] >coupling constant at long range confines all colored >objects into colorless bunches. >As I have explained above, this is wrong. If hadrons had >some net color charge, then they would be bound together >just as quarks are bound together and you'd never see them. >That doesn't happen. Thinking in an artistic sense for a moment, black, white and grey are not classesd as colours - but as colourless shades. I got myself a bit confused there for a moment. Black, white, and grey charged hadrons would all be colourless. Baryons would be colourless white. Anti-baryons would be colourless black. Mesons would be colourless grey. Mesons being grey, would decay into black and white particles. In the case of the pion, these particles would be the muon which would be white, and the muon anti-neutrino which would be black The white muon would decay into a white muon neutrino, a white electron, and a black electron anti-neutrino. The above pion decay process showed the electron to be white and the electron anti-neutrino to be black. This would then require the W boson to be grey. When a white neutron decays into a white proton, it creates a grey W boson, which in turn decays into a white electron and black anti-neutrino. This model does more than identify baryon number. It shows the conservation of baryon number, baryon to lepton transformation, and conservation of lepton number - all from the colour charge of the quarks, which is conserved. > >Well, except that's now how color charge works at all. > >Color charge is given the labels R,G,B because there are [quoted text clipped - 23 lines] > case of the pion, these particles would be the muon which would be > white, and the muon anti-neutrino which would be black > The white muon would decay into a white muon neutrino, a white > electron, and a black electron anti-neutrino. [quoted text clipped - 9 lines] > conservation of lepton number - all from the colour charge of the > quarks, which is conserved. Except that it's not really related to color charge at all. How would a black or a grey particle transform under SU(3)? A singlet is a singlet, which means white is the only kindof colorless there is. No idea, you tell me! What's SU(3)? what's a singlet? What do you mean by transform? If you can tell me what your background is in mathematics and physics, then I can have a look to see what book I should recommend you about the subject! Kind regards, Annelies > No idea, you tell me! > What's SU(3)? what's a singlet? What do you mean by transform? > If a proton is considered to be white and an anti-proton to be black, > then you could say quarks have a colour charge of 1/3 white and > anti-quarks have a colour charge of 1/3 black. That's the Baryon number. More precisely, the quantum number permitted by quantum field theory would be (Baryon - Lepton). This is what plays the analogous role of "brightness" in color space (color charge is, then, saturation, the 2 dimensions of the SU(3) charge are the "chromaticity coordinates"). Electrons have B-L = -1; that's what I called "black" in the table I presented. Positrons +1 ("white"); protons +1, anti-protons -1. > What properties would "grey charged" particles have? There's no force (yet) known that corresponds to or contains the quantum number B-L. If there were, it would satisfy either the Maxwell or Proca equations, the latter giving you, in effect, a static field of the form exp(-kr)/r^2. Like charges would repel, unlike charges attract. It would show up as a '5th force' or would be confused with an extra [anti-]gravitational force. So, undoubtedly, you will find something searching under "5th force", "baryon number", "anti-gravity" or combinations thereof. The mesons would be neutral. |
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