DOI 10.1007/s100520000429
An estimate of higher twist
at small
xB and low Q2 based upon a Saturation Model
J. Bartels1 - K. Golec-Biernat1,2 - K. Peters1
1 II. Institut für Theoretische Physik,
Universität Hamburg, Luruper Chaussee 149,
22761 Hamburg
2 Institute of Nuclear Physics,
Radzikowskiego 152, 31-342 Krakow, Poland
Received: 20 March 2000 / Published online: 9 August 2000 - © Springer-Verlag 2000
Abstract
We investigate the influence of higher twist corrections to deep inelastic
structure functions in the
low-Q2 and small-x HERA region. We review the general features of the
lowest-order QCD diagrams which contribute to twist-4 at small-x, in
particular the sign structure of longitudinal and transverse structure
functions which offers the possibility of strong cancellations in
F2.
For a numerical analysis we perform a twist analysis of the saturation
model
which has been very successful both in describing the structure function and
the DIS diffractive cross section at HERA. As the main conclusion, twist
4 corrections are not small in FL or FT but
in
F2=FL + FT they almost cancel. This indicates the limitation
on the use of the DGLAP formalism at small x and Q2.
We point out that FL analysis needs
a large twist-4 correction. We also indicate the region of validity
of the twist expansion.
Copyright Società Italiana di Fisica, Springer-Verlag 2000
