Final Report for OJI grant. Page: 4 of 7
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
0.1
o E142(SAC)
o 754 [MAC,
008 * UERMES[D-)Y
A E99777[(J A(1232) position
S <Q2>=10GeY I
0.06 - <Q2>=1 74e
" <Q2> =26GeYt
0.04 - 00>
0.02 -
A 3He
-0.02 - I
-0.04 -
-0.06 - IJ
-0.08
0.1
0 0.2 0.4 0.6 08 1
Figure 2: Preliminary data for AiHe versus x from Jefferson Lab experiment E-01-012 at four values
of Q2 from 1.0 to 3.6 GeV2, along with world data. Though the data follow the general trend of
the DIS fit, they tend to undershoot the DIS fit at higher x.
are dominated by the interaction of the virtual photon with a single, non-interacting quark. This
is known as a leading twist (twist-2) contribution, and it is this simple picture that allows one to
interpret gi in the parton model as a weighted sum over the individual quark distribution functions.
In gi, higher-order (higher-twist) contributions from soft gluon exchange or quark-mass effects are
suppressed relative to the twist-2 contribution. These higher-twist contributions are not suppressed
in g2.
Wandzura and Wilczek [13] have exploited the fact that the twist-2 contribution is present in
both gi and 92 to write an expression for the twist-2 part of 92, in terms of gi,
24W(x Q2) = -g(x,Q2) +11 91(X/Q)dX' (3)
Next-to-leading order fits [14, 15] to the precise world data on gi allow one to accurately calculate
gtw. By making precise measurements of 92(X, Q2) and subtracting gtw, one can isolate the higher
twist contributions to 92. This feature of 92 provides a unique opportunity to quantify the size of
the higher-twist contributions.
Wolfgang Korsch (Univ. of Kentucky) and Averett were co-spokespersons for experiment E-
97-103 [16], which made a precision measurement of the Q2 dependence of g2 in the deep-inelastic
region. Longitudinally polarized electrons were scattered inclusively from a transversely polarized
3He target at five values of Q2 in the range 0.58 to 1.36 GeV2, and fixed x - 0.2. Analysis and
final publication of these results was completed during the course of this grant. William and Mary
graduate student Kevin Kramer was supported by Averett's DOE grant and received his Ph.D.
from this experiment.
Figure 3 shows our data for g2 as a function of Q2 along with calculations of g2W from the
BB [14] and AAC03e [15] NLO analyses. The data are more than 5ar above zero, and at lower
Q2, show a systematic positive deviation from gzW, which we interpret as evidence for non-
zero higher-twist contributions. In the OPE, the twist-2 and twist-3 contributions to 92 enter at
the same order in Q2, with additional higher-twist contributions suppressed by powers of 1/Q.
Assuming these additional higher-twist contributions are small, we expect the quantity 92 - 92W
to be constant as a function of Q2. When compared to g2 W from BB, a fit to our data gives4
Upcoming Pages
Here’s what’s next.
Search Inside
This report 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 Report.
Averett, Todd. Final Report for OJI grant., report, October 13, 2006; United States. (https://digital.library.unt.edu/ark:/67531/metadc884120/m1/4/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.