Speaker
Prof.
Yuji Koike
(Department of Physics, Niigata University)
Description
We present a consistent framework for the twist-3 calculation for
the single transverse spin asymmetry (SSA). We prove that the consistent
use of the Ward identity for color gauge invariance is crutial to
obtain the factorization property and the gauge invariance of the
twist-3 single-spin-dependent cross section. This proof had been missed
in the previous literature. As an application, we present a complete
twist-3 cross section formula for SSA for semi-inclusive deep inelastic
scattering in terms of the complete set of the twist-3 quark-gluon
distributions which include all kinds of pole (soft-gluon-pole,
soft-fermion-pole and hard-pole) contributions. We will also make a
comment on the connection between the twist-3 approach and the
Sivers function approach to SSA. The detail is reported in our
recent paper Nucl.Phys.B763:198-227,2007 [HEP-PH 0610314].
Author
Prof.
Yuji Koike
(Department of Physics, Niigata University)
Co-author
Kazuhiro Tanaka
(Juntendo Univ.)
