Are fractional quark charges imaginary or experimentally verified?

[elas]

Fundamental particles, electron and quarks; have charges in single units or thirds of a single unit.
Am I correct in believing that these are imaginary numbers and that there is no experimental proof that a 1/3 quark charge is actually 1/3 of the charge of an electron.

I ask this question because my books state that quarks were given there charge originally to fit in with the theory of sub-atomic particles, and this seems to have been accepted because it is not possible to conduct experiments to show the true relationship.

 

[Janitor]

Note the $$e_q$$ in equations (11) and (12) at this website on deep inelastic scattering of leptons and quarks. I believe experimental results agree well with this theory when you use the 1/3 and 2/3 charges for the various quarks.

http://www.nikhef.nl/pub/experiments/zeus/theses/andres_kruse/latex2html/node7.html

 

[elas]

Thanks Janitor, clearly Iwas mistaken.

 

[mathman]

Given the makeup of protons (2 up + 1 down) and neutrons (1 up and 2 down), their charges wouldn't work unless the charges were exactly 2/3 (up) and -1/3 (down). It is a simple linear algebra problem (2 eq. in 2 unknown).

 

[elas]

It is a simple linear algebra problem (2 eq. in 2 unknown).

Accept that you are correct and thanks for your reply.
My interest lies in doing what neither the Standard Model or string theory can do, that is to explain the underlying cause; that debate has to be conducted in the madhouse (Theory Developement forum).
I am entering a new subject in that forum that I hope you will visit because it refers to a new (mathematical) way of listing quarks that is totally different from current practice in that it links mass and charge together.

Now I have the required answer, I will close this forum with thanks to those who replied, regards, elas.