393 research outputs found
Final State Interactions, T-odd PDFs & the Lensing Function
It has been suggested that under certain approximations the Sivers effect can
be described in terms of factorization of final state interactions and a
spatial distortion of impact parameter space parton distribution; that is a
convolution of the so-called lensing function and the impact parameter GPD .
In this approach the lensing function is calculated in a non-perturbative
eikonal model. This enables a comparison between the a priori distinct Sivers
function and the GPD which goes beyond the discussion of overall signs.Comment: 5 pages, 5 figures, misprints corrected: To appear in the Proceedings
of the 10th Conference on the Intersection of Particle and Nuclear Physics
(CIPANP 2009) San Diego, CA, 25-31 May 200
Probing Gluonic Spin-Orbit Correlations in Photon Pair Production
We consider photon pair production in hadronic collisions at large mass and
small transverse momentum of the pair, assuming that factorization in terms of
transverse momentum dependent parton distributions applies. The unpolarized
cross section is found to have azimuthal angular dependencies that are
generated by a gluonic version of the Boer-Mulders function. In addition, the
single-transversely polarized cross section is sensitive to the gluon Sivers
function. We present simple numerical estimates for the Boer-Mulders and Sivers
effects in diphoton production at RHIC and find that the process would offer
unique opportunities for exploring transverse momentum dependent gluon
distributions.Comment: 5 pages, 2 figures, minor changes, final version, to be published in
PR
Final state interactions and the Sivers function
The non-vanishing of naive T-odd parton distributions function can be
explained by the existence of the gauge link which emerges from the factorized
description of the deep inelastic scattering cross section into perturbatively
calculable and non-perturbative factors. This path ordered exponential
describes initial / final-state interactions of the active parton due to soft
gluon exchanges with the target remnants. Although these interactions are
non-perturbative, studies of final state interactions have been approximated by
perturbative one-gluon exchange in Abelian models. We include higher-order
gluonic contributions from the gauge link by applying non-perturbative eikonal
methods, incorporating color degrees of freedom in a calculation of the Sivers
function. In this context we study the effects of color by considering the FSIs
with Abelian and non-Abelian gluon interactions. We confirm the large QCD
scaling behavior of Sivers functions and further uncover the deviations for
finite . Within this framework of FSIs we perform a quantitative check of
approximate relations between T-odd TMDs and GPD which goes beyond the
discussion of overall signs.Comment: 5 pages, 6 figures, To appear in the proceedings of the 12th
International Conference on Meson-Nucleon Physics and the Structure of the
Nucleon (MENU 2010), May 31- June 4, 2010, Williamsburg VA, US
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