The proton's spin: A quark model perspective Page: 4 of 14
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:
However, it d.'es not seem to be widely appreciated that the F/D of Ref. 16
was much constrained by an outdated value of the neutron lifetime, and that Ref.
16 chose "to omit from (their) fit the neutron decay correlation (which yields)
9A - 1.?58 0.009, which differs significantly from the result 1.239 0.009
required by the neutron lifetime measurements". The value accepted as correct
todayl8) differs by some 30 from the old value, and this, together with other
data on hyperon beta decays,16,18,19) shows that F/D is much smaller than the
old value. Flavor symmetry breaking causes a spread in values of F/D, depending
on which partial set of data one uses; indeed, the symmetry breaking even calls
into question the utility of the F/D parameter, 20) and so Refs. 17 and 21 set up
their analyses without direct reference to F/D. Translating their work into
F/D, one finds that the value subsumed in Ref. 17 is F/D - 0.56 consistent with
that implicit in Ref. 21 and, within errors, with the fitted value in Ref. 22.
Reference 23 obtained an even smaller value of F/D - 0.545 0.02. Recent
improvements in the En beta decay data, in particular, may raise F/D to 0.58
(Ref. 24), but nowhere as high as the 0.63 used previously.
The magnitudes for As implied by these values for F/D are
F/D - 0.548 0.01 + As - -0.12 0.06 Ref. 23 (19)
F/D - 0.58 0.01 + As - -0.15 0.08 Ref. 24. (20)
Thus we see that the magnitude of the (negative) strange polarization may
be only half as big as that previously assumed. The QCD-corrected value of the
Ellis-Jaffe sum rule falls from 0.19 (the cited value when F/D - 0.63) to 0.17
if F/D - 0.56, thereby reducing the statistical significance of the much-
advertised failure of this sum rule.
What independent information exists on As? Elastic neutrino-proton scat-
tering can, in principle, probe this quantity,32) and a fit to these data give
As - -0.15 0.09.
Note that this agrees with the revised value in the present paper arising from
the smaller F/D and the revised EMC integral (Ref. 29).
One should also be aware that the neutrino experiment is also consistent
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. The proton's spin: A quark model perspective, article, January 1, 1989; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1059459/m1/4/: accessed March 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.