Single spin asymmetries from a gluonic background in the Drell-Yan process
D. Boer, P. J. Mulders, O. V. Teryaev
TL;DR
This work shows that gluonic poles in twist-three hadronic matrix elements can produce single spin asymmetries in Drell–Yan that are indistinguishable from effects of time-reversal odd distributions, while preserving time-reversal invariance. By expressing DY through quark–gluon correlation functions and their equations of motion, the authors connect zero-momentum gluon poles to effective T-odd functions, $ ilde{f}_T^{eff}$ and $ ilde{h}^{eff}$, and derive the DY cross-section including intrinsic transverse momentum. A new gluonic-pole–induced asymmetry emerges from the $x=y$ projection of the quark–gluon correlator, alongside established asymmetries, and its existence depends on antisymmetric boundary conditions at light-cone infinity. The results clarify the origin of observed SSA in DY, highlight the role of boundary conditions and large-distance gluon fields, and stress the necessity of incorporating intrinsic $k_T$ at subleading order for a complete DY description.
Abstract
We discuss the effects of so-called gluonic poles in twist-three hadronic matrix elements, as first considered by Qiu and Sterman, in the Drell-Yan process. These effects cannot be distinguished from those of time-reversal odd distribution functions, although time-reversal invariance is not broken by the presence of gluonic poles. Both gluonic poles and time-reversal odd distribution functions can lead to the same single spin asymmetries. We explicitly show the connection between gluonic poles and large distance gluon fields, identify the possible single spin asymmetries in the Drell-Yan process and discuss the role of intrinsic transverse momentum of the partons.