Delta Particles vs Proton/Neutron: What's the Difference?

[alphali]

The quark composition of the Δ0 is the same as that of neutron but much heavier and the quark composition of Δ+ is the same as that of proton but also much heavier, so what is the difference between the delta particles and the proton and neutron and where did that extra mass come from?

 

[francesco85]

In my opinion, the difference lies in the fact that the spins of the quarks combine in such a way that in the case of protons and neutrons the total spin is 1/2, while in the case of the delta particles it is 3/2; this is a physically observable difference.
For what concerns the difference in mass, I'm not sure about what I'm going to say, but I think that it is due to some spin orbit coupling, or some interactions in the "effective nuclear" hamiltonian which involve the spin.

 

[Meir Achuz]

There is a spin-spin force that provides a positive energy for quarks with aligned spins, and a negative energy for spins in opposite alignment. All three quarks in the Delta have the same alignment, making it heavier than the proton.