Quarks and gluons in hadrons and nuclei Page: 10 of 31
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S = 1 and I = 1 correlate
S = 0 and I = 0 correlate"
Thus the E0 and A0 which are distinguished by their u,d being I = 1 or 0 respec-
tively also have the u,d pair in spin = 1 or 0 respectively:
E0(u,d)1s - (ud)=.1S
A (ud) I=Os - (ud)S=OS
Thus, the spin of the A is carried entirely by the strange quark.
This is the source of the E-A mass difference. The f"i interaction acts be-
tween all possible pairs; thus
E [(u,d)ls]: <$-$>1 + s , (9)
A0 [(u,d)0s]: < (10)
(note <S-f> between a spinless diquark and anything vanishes; hence the absence of
(see p. 91 of Ref. 3). Further, if ms = mud, the E and A become mass degenerate,
and so in this limit
=$ ~ , -4 1.(12)
For unequal masses of u and s, the magnetic interaction scales as the inverse
mass. Hence finally
A0 ~ $-> (-3 }. (14)
Then with ms > mu, we find m > m as observed. Increasing ms/mu enhances the
effect (e.g., for the charmed analogues Ec[(u,d)c) and Ac[(u,d)c) the splitting
will be larger - again observed).
2.3. Color, the Pauli Principle, and Magnetic Moments
The electrical charge of a baryon is the sum of its constituent quark
charges. The magnetic moment is an intimate probe of the correlations between the
charges and spins of the constituents. Being wise, today we can say that the
neutron magnetic moment was the first clue that the nucleons are not elementary
particles. Conversely the fact that quarks appear to have g 2 suggests that
they are elementary (or that new dynamics is at work if composite).
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Close, F. E. Quarks and gluons in hadrons and nuclei, article, December 1, 1989; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1058782/m1/10/: accessed March 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.