A proton is composed of uud. Are the two up quarks paired up to cancel each other's spin or are one up quark and one down quark paired up?
I know the three quarks may only carry a small proportion of the total proton spin. But they still need to be aligned somehow.
I see the following figure on http://www.lns.mit.edu/nig/programs. It seems in most cases the two protons in He3 are paired up. Could the quarks in a nucleon work in a similar way?