424 research outputs found
Gluon poles and photon distribution amplitudes in Drell-Yan-like processes
We calculate the hadron tensor related to the photon-induced Drell-Yan
process, with incoming nucleon being transversally polarised. We predict the
new single spin asymmetry which probes gluon poles and which is expressed in
terms of photon (both chiral-odd and chiral-even) distribution amplitudes and
chiral-odd nucleon function stemming from the nucleon transverse polarization.Comment: 6 pages, 3 figures; Appendix has been adde
Non-factorized genuine twist 3 in exclusive electro-production of vector mesons
We present an analysis of genuine twist-3 quark contributions to the
amplitude of exclusive electro-production of transversely polarized vector
mesons. Using the formalism based on the momentum representation we calculated
all the genuine twist-3 terms of quark contributions to gamma_T^* --> rho_T
amplitude. We found that these terms can not be factorized owing to the
existence of the infrared divergencies in the amplitude of hard sub-processes.Comment: 4 pages. Talk presented by I.V. Anikin at European Workshop on the
QCD Structure of the Nucleon (QCD-N'02), Ferrara, Italy, 3-6 Apr 2002 (to
appear in Nucl. Phys. A, Proc. Suppl.
Constraining gluon poles
In this letter, we revise the QED gauge invariance for the hadron tensor of
Drell-Yan type processes with the transversely polarized hadron. We perform our
analysis within the Feynman gauge for gluons and make a comparison with the
results obtained within the light-cone gauge. We demonstrate that QED gauge
invariance leads, first, to the need of a non-standard diagram and, second, to
the absence of gluon poles in the correlators related traditionally to . As a result, these terms
disappear from the final QED gauge invariant hadron tensor. We also verify the
absence of such poles by analysing the corresponding light-cone Dirac algebra.Comment: 5 pages, 2 figures. The improved version. Accepted for publication in
PL
New contributions to gluon poles in direct photon production
We consider the direct photon production in two hadron collision with one of
the hadrons being transversely polarized. By using the contour gauge for gluon
fields, we find that there are new twist- terms present in the hadron tensor
of the considering process in addition to the standard twist- terms. In this
work, we demonstrate that the significance of these new terms are two-fold:
first, they are crucial to both the QED and QCD gauge invariance and, second,
their contributions to the hadron tensor are at least the same as those from
the standard ones. We also study the resuting effects which are responsible for
the universality breaking of the corresponding twist- parton distributions.Comment: 19 pages, 5 figure
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