Drell-Yan double-spin asymmetry A_{LT} in polarized p\bar{p} collisions: Wandzura-Wilczek contribution

TL;DR

This paper estimates the Wandzura-Wilczek contribution to the longitudinal-transverse spin asymmetry A_{LT} in polarized proton-antiproton Drell-Yan processes, suggesting measurable effects that can test twist-3 quark-gluon correlations.

Contribution

It provides the first realistic estimate of the Wandzura-Wilczek contribution to A_{LT} using empirical transversity data, guiding future spin experiments at GSI.

Findings

Large A_{LT} expected in proposed experiments.

A_{LT} exhibits a unique dependence on dilepton mass.

Results serve as a test for twist-3 quark-gluon effects.

Abstract

The longitudinal-transverse spin asymmetry A_{LT} in the polarized Drell-Yan process depends on the twist-3 spin-dependent distributions of nucleon. In addition to the contributions expressed as matrix element of the twist-3 operators, these distributions contain the so-called Wandzura-Wilczek part, which is completely determined by a certain integral of the twist-2 spin-dependent parton distributions. We demonstrate that the recently obtained empirical information on the transversity distribution allows a realistic estimate of the Wandzura-Wilczek contribution to A_{LT} for the case of polarized proton-antiproton collisions. In particular, our results in the Wandzura-Wilczek approximation indicate that rather large A_{LT} can be observed in the proposed spin experiments at GSI, and its behavior as a function of dilepton mass obeys novel pattern, compared with the other double-spin asymmetries A_{TT} and A_{LL}. Our results provide a guide for testing a signal of effects originating from the twist-3 operators associated with quark-gluon correlation.