The proton's spin: A quark model perspective Page: 6 of 14
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significant polarized sea without destroying the magnetic moment relations.
This is because
P' 2Au-Ad+(-2Ai+Ad+RA )'
where R = md/ms = 3/5. The electrical neutrality of
contribution. A detailed fit is made in Ref. 12.
The (gAgV) for the octet of baryons also relate
abilities such as
-Au -Ad +-Ad,
kgy v v v
the sea tends to shield its
to the spin polarized prob-
where we used Eq. (9). Thus immediately
Adv - -0.25; Auv W 1.
In the 56 NRQM one would have3)
Ad - -1/3; Au - 4/3; Au + Ad = 1,
and the entire spin polarization comes from the quarks. However, from Eq.
we see that
Au + Ad = 3/4, (14)
and so, in advance of the EMC data, only naive "quarkists" would have expected
100% for Aqv. Anyone who worked with four-component spinors, of which the MIT
bag is a specific model example, knew that the "orbital dilution" in the lower
components played an essential role.13) In fact, the Aqv expectation is even
less than Eq. (14). When one makes a best fit to all of the baryon octet gA V'
Aqv (= 3F-D) = 0.55 0.10. (15)
Note the appearance of F and D which summarizes the gA/V. This parameter will
appear later. Note that many analyses of the polarization data use2,6,10,15)
F/D a 0.63 (Ref. 16). However, this value fitted a value of the neutron life-
time that we now know to have been incorrect.17,18) The correct current
value19-25) is lower than 0.63 and is dependent upon assumptions about SU(3)
The earliest predictions for the deep inelastic polarization asymmetry in
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Close, F. E. The proton's spin: A quark model perspective, article, January 1, 1989; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1059459/m1/6/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.