Novel effects in twist-three SSA

16th Workshop on High Energy Spin Physics

Anikin, I.V.^1 ; Teryaev, O.V.^1

Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna

141980, Russia^1

关键词: Direct photons;    Drell-Yan;    Drell-Yan process;    Gauge invariance;    Single-spin asymmetries;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/678/1/012056/pdf
DOI  :  10.1088/1742-6596/678/1/012056

来源: IOP

【 摘 要 】

We discuss the role of gluon poles and the gauge invariance for the hadron tensors of Drell-Yan and direct photon production processes with the transversely polarized hadron. These hadron tensors are needed to construct the corresponding single spin asymmetries. For the Drell-Yan process, we perform our analysis within both the Feynman and axial-type (contour) gauges for gluons. In both the Feynman and contour gauges, we demonstrate that the gauge invariance leads to the need of the new (non-standard) diagrams. Moreover, in the Feynman gauge, we argue the absence of gluon poles in the correlators ψγA+ψ related traditionally to dT(x,x)/dx. As a result, these terms disappear from the final QED gauge invariant Drell-Yan hadron tensor. For the direct photon production, by using the contour gauge for gluon fields, we find that there are new twist-3 terms present in the hadron tensor of the considering process in addition to the standard twist-3 terms.