Erratum: Scale dependence of twist-three contributions to single spin asymmetries [Phys. Rev. D 80, 114002 (2009)]

We explore the possibility to construct higher-twist parton distributions in a nucleon at some low reference scale from convolution integrals of the light-cone wave functions (WFs). To this end we introduce simple models for the four-particle nucleon WFs involving three valence quarks and a gluon with total orbital momentum zero, and estimate their normalization (WF at the origin) using QCD sum rules. We demonstrate that these WFs provide one with a reasonable description of both polarized and unpolarized gluon parton densities at large values of Bjorken variable x > 0.5. Twist-three parton distributions are then constructed as convolution integrals of qqqg and usual three-quark WFs. The cases of the polarized structure function g_2(x,Q^2) and single transverse spin asymmetries are considered in detail. We find that the so-called gluon-pole contribution to twist-three distributions relevant for single spin asymmetry vanishes in this model, but is generated perturbatively at higher scales by the evolution, in the spirit of GRV parton distributions.Comment: 22 pages, 11 figure

We reexamine the scale dependence of twist-three correlation functions relevant for the single transverse spin asymmetry in the framework of collinear factorization. Evolution equations are derived for both the flavor-nonsinglet and flavor-singlet distributions and arbitrary parton momenta. Our results do not agree with the recent calculations of the evolution in the limit of vanishing gluon momentum. Possible sources for this discrepancy are identified.

We carry out the first complete calculation of kinematic power corrections ~t/Q(2) and ~m(2)/Q(2) to the helicity amplitudes of deeply virtual Compton scattering. This result removes an important source of uncertainties in the quantum chromodynamics predictions for intermediate momentum transfers Q(2) ~ 1-10 GeV(2) that are accessible in the existing and planned experiments. In particular, the finite-t corrections are significant and must be taken into account in the data analysis.

We carry out the first complete calculation of kinematic power corrections ∼ t/Q 2 and ∼ m 2 /Q 2 to several key observables in Deeply Virtual Compton Scattering. The issue of convention dependence of the leading twist approximation is discussed in detail. In addition we work out representations for the higher twist corrections in terms of double distributions, Mellin-Barnes integrals and also within a dissipative framework. This study removes an important source of uncertainties in the QCD predictions for intermediate photon virtualities Q 2 ∼ 1-5 GeV 2 that are accessible in the existing and planned experiments. In particular the finite-t corrections are significant and must be taken into account in the data analysis.