slac-pub-2605 - SLAC - Stanford University

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perturbative or perturbative contribution dominates the structure functions
at x + 1 can thus be studied using spin and flavor correlations.
3. Form Factors and Hadronic Wavefunctions
Figure 3 illustrates the QCD predictions for Q‘F, given three different
initial wavefunction at QE = 2 GeV2 C261:
(a> 4(x,,Q,) = x1x2
(b) L$(x,,Q,) = 6(xi- l/2) (3.1)
(c) 4 (xi ,Q,) = (x1x2>
%
with representative values of the QCD scale parameter A2. In each case the
normalization is uniquely determined by (2.2); all curves ultimately converge
to the asymptotic limit (1.15). For Fig. 3, we have multiplied (1.14) by
(1+m2/Q2)-1 to allow a smooth connection with the low Q2 behavior suggested
P
by vector dominance models.
It
8251
+(X,,00)a8(Xi-l/21
0.1
-
-
p.01
i
5 10 20 40 80
II2 (GeV2) *..,.n
Fig. 3. QCD predictions for the
pion form factor assuming various
distribution amplitudes $(xi,QG)
at Qs = 2 GeV2 and various values
of the QCD scale parameter A2.
The data are from the analysis of
electroproduction e-p + e-+r'+n;
C. Bebek et al., Ref. C261.