Double transverse-spin asymmetries in Drell-Yan processes with antiprotons

We present next-to-leading order predictions for double transverse-spin asymmetries in Drell-Yan dilepton production initiated by proton-antiproton scattering. The kinematic region of the proposed PAX experiment at GSI: 30≲s≲200GeV2 and 2≲M≲7GeV is examined. The Drell-Yan asymmetries turn out to be large, in the range 20-40%. Measuring these asymmetries would provide the cleanest determination of the quark transversity distributions.