[kkylin]

It may be worth first understanding why g=2 (if you haven't before). This can be done on the basis of special relativity + quantum mechanics, i.e., the Dirac equation:

https://en.wikipedia.org/wiki/Dirac_equation

The "g" is the Lande g factor:

https://en.wikipedia.org/wiki/Land%C3%A9_g-factor

(As I recall nonrelativistic QM gives g=1.)

PS Not a physicist, but learned some of this at some point. Only ever learned about electrons, though; don't know how any of this translates to other particles.