paper

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

arXiv:hep-ph/0703079 · doi:10.1016/j.nuclphysb.2007.04.022

Abstract

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

26 pages, 12 figures, typos corrected, references added, version to appear in Nucl. Phys. B

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