2
$\begingroup$

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?

enter image description here

$\endgroup$
  • 1
    $\begingroup$ On the wiki, you can find exotic baryons differing from the proton/neutron only that they have +++ spin configuration. This results a highly unstable particle with spin 3/2, decaying in the order of $10^{-20} s$ to a proton/neutron. $\endgroup$ – peterh - Reinstate Monica Sep 2 '16 at 19:29
  • $\begingroup$ @peterh The Delta baryons could probably be considered as a case where the three quarks are not paired at all. That is why they have spin 3/2. $\endgroup$ – Fan Sep 2 '16 at 19:35
-1
$\begingroup$

The wave function of a proton is $2|u\uparrow u\uparrow d\downarrow\rangle-|u\uparrow u\downarrow d\uparrow\rangle-|u\downarrow u\uparrow d\uparrow \rangle$... So the probability of having u paired up with d is 2/3, and that of having u paired up with u is 1/3.

| cite | improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.