Quarks and gluons in hadrons and nuclei Page: 16 of 31
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
polarization is carried by quarks". This is a misinterpretation of Eq. (37). The
valence quarks are highly polarized (point (i) above); thus, the interpretation of
Eq. (37) is that something cancels or hides it. Candidates include a highly
polarized sea spinning opposite to the valence quarks, orbital angular momentum,
or gluon polarization.8-10
One can cancel out some charge weighting effects by looking at the difference
of proton and neutron for which
I( In = (Au-Ad) 6 , (38)
which is Bjorken's sum rule.5 The various gA in the baryon octet give information
on the differences of Au, Ad, and As which are summarized by a measured parameter
known as F/D. To extract the sum, eq, we need the proton integral (Eq. (36)) or
information on neutral current form factors
gA(vp +vp) = Au - Ad - As. (39)
I shall discuss this at the end of the talk. Preceding that, I shall discuss the
question of As, since the measured F/D and the measured Ip can be combined to ex-
tract a value for As. This appears to be substantial; EMC claiming that
As = -0.23 0.08. (40)
Implications and criticisms of this startling result will occupy the latter half
of this talk. First, I will discuss what we know about the (constituent) quark
polarization from static properties of the nucleon (magnetic moments, gA9/gV) and
review the extent to which the new insights do or do not require revision of this
3.1. Spin Polarization of Valence (Constituent) Quarks
In the constituent quark model where LZ = 0 the charges and the magnetic
moments of neutron and proton place the following constraints on the probabilities
for finding the flavors and spin correlations of "valence" quarks,
uv = 2dv v v (41)
The 56, LZ = 0 wave function of the nonrelativistic quark model (NRQM) satisfies
(41) but it is by no means unique. A hybrid state, where a gluon (JZ = 1) is
partnered by qqq in 70 (required by the Pauli principle for qqq in color 8) satis-
fies Eq. (41) for the coherent combination11 g(28+ 8) where the superscripts refer
to the 2S+1 of the net spin of the qqq system. The "valence quarks" here are
significantly depolarized relative to 56. One can also have a significant polar-
ized sea without destroying the magnetic moment relations. This is because
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Close, F. E. Quarks and gluons in hadrons and nuclei, article, December 1, 1989; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1058782/m1/16/: accessed March 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.