Theory without experimental support is just philosophy
No, It is just a theory. Supergravity is not philosophy. Any way, I meant to say that experimental physics is not a business of mine. And I do not find it interesting to talk about the various lepton-nucleon DIS experiments.
Color is indeed based upon experimental evidence -- for example, the lack of qq hadrons mentioned in another thread.
The introduction of the colour degree of freedom "was" based purely on theoretical ground, without it the (3/2)^{+} decuplet baryon wavefunctions would violate Pauli principle. This is why it was called the colour
hypothesis. The story here is similar to that of the neutrino hypothesis. Do you see what I meant by theoretical "facts"; we know "it" is there even though experiment does not show "it".
At that time, there was no experiment that led us to the introduction of colours.
The absence of
qq hadron does not mean or imply that quarks carry colour. However, if the quark does carry colour, then the absence of
qq means that colour is a hidden degree of freedom, i.e. coloured hadrons are not observable. This is why (after the introduction of colour) it was "
assumed":
"
only colour-singlets are observable"
But what is it about colour that makes it a hidden degree of freedom? I wish, I know the answer. It seems that the colour-singlet conjecture is not derivable from the mathematical tools of the theory.
We still do not know why the quarks can not
confine themselves in a bound state of
coloured hadrons like qq. But we know why we do not know: the exact form of q-q potential (which we do not know) should be able to rule out such bound-states. That is if, it is meaningful to talk about such thing as the "exact q-q potential".
We
now know several
direct pieces of experimental evidence which support the colour hypothesis. The first comes from the analysis of the \pi^{0} lifetime (as discussed by many textbooks), this is "wrong" by roughly a factor N^{2}=9 without the inclusion of colour. Further support comes from measurements of:
R_h = \sigma ( e^{+}e^{-} \rightarrow hadrons) / \sigma (e^{+}e^{-} \rightarrow \mu^{+} \mu^{-})
with the inclusion of the colour factor 3, the calculations shows
R = 11/3 in reasonable agreement with the data.
I was having a little trouble understanding how this fit in with the conventional picture of hadron structure that jtbell described.
I thought my statement was clear and simple
do you simply mean what you said in your last post, that there is a non-negligible probability of finding the proton in the five-quark configuration due to the sea of virtual pairs?
O Yes, this is what I meant, and this is (it seems) exactly how jtbell understood my statement.
regards
sam