6 research outputs found
Nucleon spin content and axial coupling constants in QCD sum rules approach
The review of current experimental situation in the measurements of the first
moment of spin dependent nucleon structure functions
is presented. The results of the calculations of twist-4
corrections to are discussed and their accuracy is estimated.
The part of the proton spin carried by quarks is calculated
in the framework of the QCD sum rules in the external fields. The operators up
to dimension 9 are accounted. An important contribution comes from the operator
of dimension 3, which in the limit of massless quarks is equal to the
derivative of QCD topological susceptibility . The comparison with
the experimental data on gives . The limits on and are found from selfconsistency of
the sum rule, \Sigma \ga 0.05, \chi' (0) \ga 1.6 \times 10^{-3} GeV^2. The
values of and are also determined
from the corresponding sum rules.Comment: Lecture at St.Petersburg Winter School on Theoretical Physics, Febr.
23-28, 1998 to be published in Proceedings, 14 pages, LaTeX 2e, 4 eps figures
included using epsf.st