Subject: Hi, I've got a question about isospin and quark generations:

Isospin was originally conceived as a defining quality to differentiate 
between protons and neutrons, but with the advent of quark-parton theory 
it became irrelevant to them and was instead adopted by the quarks to 
differentiate between U and D. Now, what I want to know is: how is it that 
the first generation has a special device solely to divide U from D, but 
with second and third generation quarks they can have such things as 
strangeness or topness, but no equivalent to isospin (strictly speaking, 
the second generation is considered to possess hypercharge, Y, but for 
some reason it isn't used to quite the extent that isospin, T3, 
is used)? I see no qualitative difference between them which would keep 
the higher mass quarks from requiring an arbitrarily constructed "isospin"-
like parameter just as the first generation does. If isospin is necessary, 
then so too should some equivalent be for the heavier quarks... say ortho-
spin and para-spin, (...hypercharge...) or something. Is there something 
I'm missing, perhaps a difference in some sort of presumed internal 
structure between that of light quarks and of heavy quarks?

Re: Hi, I've got a question about isospin and quark generations: