Soft gluon corrections to double transverse-spin asymmetries for small-image dilepton production at RHIC and J-PARC Original Research Article

We calculate the double transverse-spin asymmetries, image, in transversely polarized Drell–Yan process at the transverse-momentum image of the produced lepton pair. We perform all-order resummation of the logarithmically enhanced contributions in the relevant Drell–Yan cross sections at small image, which are due to multiple soft gluon emission in QCD, up to the next-to-leading logarithmic accuracy. The asymmetries image to be observed in polarized experiments at RHIC and J-PARC are studied numerically as a function of image. We show that the effects of the soft gluon resummation to the polarized and unpolarized cross sections largely cancel in image, but the significant corrections still remain and are crucial for making a reliable QCD prediction of image. In particular, the soft gluon corrections enhance image considerably in the small image region compared with the asymmetry in the fixed-order image perturbation theory. We also derive a novel asymptotic formula which embodies those remarkable features of image at small image in a compact analytic form and is useful to extract the transversity image from the experimental data.