Probing the three-gluon correlation functions by the single spin asymmetry in p^\uparrow p\to DX

We study the single transverse-spin asymmetry for the inclusive open-charm production in the pp-collision, p^\uparrow p\to DX, induced by the three-gluon correlation functions in the polarized nucleon. We derive the corresponding twist-3 cross section formula in the leading order with respect to the QCD coupling constant. As in the case of the semi-inclusive deep inelastic scattering, ep^\uparrow\to eDX, our result differs from the previous result in the literature. We also derive a "master formula" which expresses the twist-3 cross section in terms of the gg\to c\bar{c} hard scattering cross section. We present a model calculation of the asymmetry at the RHIC energy, demonstrating the sensitivity of the asymmetry on the form of the three-gluon correlation functions.Comment: 25 pages, 7 figures. Final version to appear in PRD. Some changes in the section of numerical calculation include

Transverse single spin asymmetry in the Drell-Yan process

We revisit the transverse single spin asymmetry in the angular distribution of a Drell-Yan dilepton pair. We study this asymmetry by using twist-3 collinear factorization, and we obtain the same result both in covariant gauge and in the light-cone gauge. Moreover, we have checked the electromagnetic gauge invariance of our calculation. Our final expression for the asymmetry differs from all the previous results given in the literature. The overall sign of this asymmetry is as important as the sign of the Sivers asymmetry in Drell-Yan.Comment: 9 page

Highlight of Dubna-SPIN97 Workshop

A summary of the Workshop on High Energy Spin Physics (Dubna-SPIN97), Dubna, 7-12 July 1997, is given.Comment: Latex, sprocl.sty included, 8 pages. Talk at 13-th Internat. Symposium on High Energy Spin Physics, Protvino, 8-12 Sept 1998. Will appear in Proceedings (World Sci. PC). A misprint in title is correcte

Three-gluon contribution to the single spin asymmetry in Drell-Yan and direct-photon processes

We derive the single-spin-dependent cross section for the Drell-Yan lepton-pair production and the direct-photon production in the $pp$-collision induced by the twist-3 three-gluon correlation functions in the transversely polarized nucleon in the leading order with respect to the QCD coupling constant. Combined with the contribution from the twist-3 quark-gluon correlation functions in the literature, this completes the twist-3 cross section for these processes. We also present a model calculation of the asymmetry for the direct photon production at the RHIC energy, demonstrating the sensitivity of the asymmetry to the form of the three-gluon correlation functions. In particular, we show that the asymmetry in the backward direction of the polarized nucleon is determined by the small-$x$ behavior of the correlation functions.Comment: 15 pages, 3 figure

Dihadron fragmentation functions for large invariant mass

Using perturbative Quantum Chromodynamics, we compute dihadron fragmentation functions for a large invariant mass of the dihadron pair. The main focus is on the interference fragmentation function H_1^{\open}, which plays an important role in spin physics of the nucleon. Our calculation also reveals that H_1^{\open} and the Collins fragmentation function have a closely related underlying dynamics. By considering semi-inclusive deep-inelastic scattering, we further show that collinear factorization in terms of dihadron fragmentation functions, and collinear factorization in terms of single hadron fragmentation functions provide the same result in the region of intermediate invariant mass.Comment: 4 pages; issue with layout fixe

Universal Structure of Twist-3 Soft-Gluon-Pole Cross Sections for Single Transverse-Spin Asymmetry

We prove that twist-3 soft-gluon-pole (SGP) cross section for single spin asymmetries (SSA) is determined by a certain ``primordial'' twist-2 cross section up to kinematic and color factors in the leading order perturbative QCD. In particular, for the processes in which the partonic hard scattering occurs among massless partons, the invariance of the ``primordial'' partonic cross section under scale transformation leads to remarkable simplification of the SGP cross section, reproducing compact form that was recently observed for pion production $p^\uparrow p\to \pi X$ and direct-photon production $p^\uparrow p\to \gamma X$.Comment: 5 pages in LaTex. 2 figures. Minor modifications in the tex

Hadronic Dijet Imbalance and Transverse-Momentum Dependent Parton Distributions

We compare several recent theoretical studies of the single transverse spin asymmetry in dijet-correlations at hadron colliders. We show that the results of these studies are all consistent. To establish this, we investigate in particular the two-gluon exchange contributions to the relevant initial and final state interactions in the context of a simplifying model. Overall, the results confirm that the dijet imbalance obeys at best a non-standard or "generalized" transverse-momentum-dependent factorization.Comment: 13 pages, 3 figure

Partonic Pole Matrix Elements for Fragmentation

A model-independent analysis of collinear three-parton correlation functions for fragmentation is performed. By investigating their support properties it is shown, in particular, that the so-called partonic pole matrix elements vanish. This sheds new light on the understanding of transverse single spin asymmetries in various hard semi-inclusive reactions. Moreover, it gives additional strong evidence for the universality of transverse-momentum-dependent fragmentation functions.Comment: 4 pages, 2 figures; minor changes, matches journal versio

The chirally-odd twist-3 distribution e(x)

Properties of the nucleon twist-3 distribution function e(x) are reviewed. It is emphasized that the QCD equations of motion imply the existence of a delta-function at x=0 in e(x), which gives rise to the pion-nucleon sigma-term. According to the resulting ``practical'' DIS sum rules the first and the second moment of e(x) vanish, a situation analogue to that of the pure twist-3 distribution function $\bar{g}_2(x)$.Comment: 19 pages, 3 figures, new references and figures adde