Double-spin asymmetry $A_{LT}$ in open charm production

TL;DR

This paper calculates the gluon contribution to the double-spin asymmetry in open charm production at RHIC using a collinear twist-three approach, providing a gauge-invariant formula for the first time.

Contribution

It introduces the first calculation of gluon contributions to A_{LT} in open charm production, using a gauge-invariant, factorized formula derived via Ward-Takahashi identities.

Findings

Provides a systematic way to analyze three-gluon correlations

Derives a gauge-invariant formula for A_{LT}

Enables combined analysis with single-spin asymmetries

Abstract

In the collinear twist-three approach, we calculate for the first time the gluon contribution to double (longitudinal-transverse) spin asymmetry A_{LT} for open charm production in proton-proton collisions measurable at RHIC. Utilizing the Ward-Takahashi identity for the non-pole part of the hard scattering amplitude, we derive a factorized, gauge invariant formula for the asymmetry. The result may be combined with the previous studies of single-spin asymmetry in the same channel and allows for a systematic analysis of three-gluon correlations inside a transversely polarized nucleon.