Quarks and gluons in hadrons and nuclei Page: 19 of 31
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reflect the dynamics that binds the quarks to form hadrons, and are determined by
a light cone nucleon wavefunction. The constituent quark structure functions
q(x/y, Q2) are adapted from Altarelli et al.36 together with Carlitz and Kaur's
ansatz37 for the spin of soft valence partons within a polarized constituent
This picture of partons convoluted within constituents generates some effec-
tive LZ * 0 but not enough to account for the spin deficit claimed by EMC. The
data seem to fall below the model systematically for x c 0.1. If these small x
data survive further experiments, then it seems that polarization of the sea (not
included in Ref. 35) must be allowed for. This naturally leads to the question of
whether there are polarized strange quarks in the proton.
3.2. Polarized Strange Quarks?
One exciting possibility is that the EMC data imply a large polarization of
strange quarks and/or antiquarks within the proton. If true, this could have sig-
nificant consequences. In particular, it could modify earlier analyses of elec-
troweak parity violation in deuterium where Campbell et al. argue,15 the polarized
strange quarks could give contributions that dominate over electroweak radiative
corrections. An extreme claim has appeared in the literature that the large value
for As is in conflict with perturbative QCD. If true, this would be devastating.
This claim comes about, in part, because an incorrect value of F/D has been used
in the analyses. It is this parameter, and its implications for es, that I will
Given the integral, Ii, of the polarized structure function gi(x,Q2), one
extracts As (including new QCD corrections)
I x xQz- 1 (gA\9f-1 cr5(Q2) 3f+1l + s4
Ip f dxg(xQ2) - V f+1 - i f+1' (4)
where f F/D with as(Q2) = 0.27, gA/gV = 1.254 0.006 and Ip = 0.126 0.022. A
feeling for the sensitivity of As to f can be gauged from the approximate relation
As = (f-0.40) 0.07. (49)
The widely used value, following the much-quoted fit of Ref. 16 has been
F/D = 0.63 0.02 + as = -0.23 * 0.09. (50)
If the sea is flavor-independent, then Eq. (50) summarizes the widely accepted
interpretation of the EMC polarized structure function data where a significant
negative polarization of the sea cancels out the positive polarization of the
This value w"ras based on the original value for Ip quoted by EMC,2 namely Ip =
0.116 0.022. However, the revised value,29 Ip = 0.126 0.022, reduces the
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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/m1/19/: accessed March 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.