Kinematic Azimuthal Asymmetries and Lam-Tung Relation

TL;DR

This paper investigates the origin and validity of the Lam-Tung relation in Drell-Yan processes, analyzing how kinematic azimuthal asymmetries and QCD corrections influence its applicability and proposing generalizations for broader scenarios.

Contribution

It provides a new interpretation of the Lam-Tung relation as a kinematic azimuthal asymmetry and extends its applicability beyond the transverse virtual photon case.

Findings

Lam-Tung relation is linked to kinematic azimuthal asymmetries.

Radiative and power QCD corrections can violate the relation.

Generalized the relation for non-transverse virtual photons.

Abstract

The origin of Lam-Tung relation for the angular asymmetry of Drell-Yan dileptons is analyzed. The asymmetry constrained by this relation is shown to belongto the class of kinematic azimuthal asymmetries, emerging due to the deviation of the reference axis from the natural physical one. The validity and violation of Lam-Tung relation due to radiative and power QCD corrections is discussed. The relation is generalized to the case when the virtual photon is not the transverse oneand the possible applications are suggested.