Drell–Yan double-spin asymmetry ALT in polarized pp¯ collisions: Wandzura–Wilczek contribution

The longitudinal-transverse spin asymmetry A L T 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 L T for the case of polarized proton–antiproton collisions. In particular, our results in the Wandzura–Wilczek approximation indicate that rather large A L T 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 T T and A L L . Our results provide a guide for testing a signal of effects originating from the twist-3 operators associated with quark–gluon correlation.